Robust adsorption of Direct Navy Blue-106 from textile industrial effluents by bio-hydrogen fermented waste derived activated carbon: Equilibrium and kinetic studies

S. Kanchi; K. Bisetty; Gopalakrishnan Kumar; M.I. Sabela

doi:10.1016/j.arabjc.2013.11.050

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Original Article

10 (

2_suppl

); S3084-S3096

doi:

10.1016/j.arabjc.2013.11.050

Robust adsorption of Direct Navy Blue-106 from textile industrial effluents by bio-hydrogen fermented waste derived activated carbon: Equilibrium and kinetic studies

S. Kanchi^{^a,⁎}, K. Bisetty^{^a,⁎}, Gopalakrishnan Kumar^{^b}, M.I. Sabela^{^a}

a Department of Chemistry, Durban University of Technology, P.O. Box 1334, Durban 4000, South Africa

b Department of Environmental Engineering and Science, Feng Chia University, Taichung, Taiwan, ROC

⁎Corresponding authors. Tel.: +27 31 3733004/2311. suvardhank@gmail.com (S. Kanchi), bisettyk@dut.ac.za (K. Bisetty)

Received: 2013-7-12, Accepted: 2013-11-27, Published: 2013-05-01

Disclaimer:
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.

Peer review under responsibility of King Saud University.

Abstract

The developed bio-hydrogen fermented waste activated carbon (BHFW-AC) has proven to be a cost effective, highly efficient and eco-friendly adsorbent, an alternative (low cost) source of AC for the removal of Direct Navy Blue-106 (DNB-106). This study investigated the feasibility of BHFW at low temperature (100 °C) using chemical carbonization treatment with H₃PO₄ for 24 h. The parameters pH, temperature, initial dye concentration and contact time have been optimized by batch experiments to increase the adsorption efficiency of the BHFW-AC. Interestingly, the batch adsorption equilibrium data followed the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich models with the Langmuir isotherm providing the best fit to the equilibrium data. On the other hand, the kinetic data followed closely the pseudo-second-order rate kinetic model. Besides, the thermodynamic study showed that the adsorption was a spontaneous endothermic process.

Keywords

Bio-hydrogen fermented waste-activated carbon (BHFW-AC)

Direct Navy Blue-106 (DNB-106)

Adsorption

Activated carbon (AC)

Textile wastewater

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1 Introduction

Direct Navy Blue-106 with chemical name [6,13-dichloro-3,10-bis (phenylamino)-disodium salt] is shown in Fig. A1. Dye effluent pollution is a main concern due to its toxicity to many life forms. The discharge of these effluents from the textile, leather, paper and plastic industries into the environment is of concern for both toxicological and esthetical reasons (Metivier-Pignon et al., 2003; Ravikumar et al., 2005). According to the statistical survey (Lee et al., 2006) more than seven hundred thousand tones of dye related toxic materials are produced from several varieties of commercial dyes. Nowadays the greatest challenge facing the environmental scientists in the world is the de-colorization of dye waste water from the textile industries using various treatment protocols such as adsorption, chemical coagulation, disinfection, filtration and oxidation (Chu and Ma, 2000; Peter and Freeman, 1996; Tunay et al., 1996 ). Among these, adsorption has become a well-known separation technique for the removal of pollutants as well as having the potential of regeneration, recovery and recycling of the adsorbent materials.

Different treatment methodologies such as coagulation, precipitation, sedimentation, ultra filtration, ozonation, oxidation and reverse osmosis have been applied in the removal of dye molecules from wastewaters. However, adsorption is considered as a superior technique comparatively with other traditional treatment methods due to its availability, simplicity of design, high efficiency, ease of operation and ability to treat dyes in a more concentrated form (Bulut and Aydın, 2006). In recent years, this has prompted a growing research interest in the production of AC from renewable and cheaper precursors which are mainly industrial and agricultural by-products, for the application of wastewater treatment. The removal of organic color by adsorption on to agricultural residues has recently become a subject of considerable interest. The reported studies include sawdust (Poots et al., 1976), hardwood (Asfour et al., 1985), bagasse pith (McKay et al., 1987a,b), rice husk and bark (McKay et al., 1987a,b; Long Lin et al., 2013), maize cob (El-Geundi and Nassar, 1987), and banana pith (Namasivayan et al., 1993), date pits (Girgis and El-Hendawy, 2002), fire woods and pistachio shells (Wu et al., 2005), cassava peel (Rajeshwarisivaraj et al., 2001), groundnut shell (Kannan and Sundaram, 2001), oil palm fiber (Tan et al., 2007), bamboo (Hameed et al., 2007), coconut husk (Tan et al., 2008), agricultural by-products (Baccar et al., 2013), jatropha curcas pods (Palanivel et al., 2012) and agricultural waste [coffee grounds, melon seeds and orange peels] (Djilania et al., 2012) for the removal of various dyes.

Though many cost effective adsorbents have been studied for the decolorization process, studies on the BHFW as an economical and eco-friendly adsorbent for dye removal have not yet been fully explored. Utilization of this waste for the treatment of wastewater is a win–win strategy because it not only converts the waste into a useful material, but it also prevents on-site burning of the waste and saves on disposal costs.

Accordingly, the aim of this work was to evaluate the potential of BHFW-AC as a low-cost adsorbent for the removal of a DNB-106 from textile industrial effluents. DNB-106 was chosen as a target contaminant to characterize the adsorptive properties of BHFW-AC as it is a common dye used in textile industries. However, several parameters that affect the adsorption include pH, temperature, initial concentration of dye and contact time has to be optimized. Additionally, models to fit the adsorption equilibrium and kinetic data were also formulated in this study. Moreover, the thermodynamic parameters obtained for the present system were based on isotherm data.

2 Experimental

2.1

2.1 Reagents

All chemicals were of analytical grade reagents and doubly distilled deionized water was used throughout the experiment. A stock solution of 1000 mg L⁻¹ was prepared by dissolving the appropriate amount of DNB-106 (Sun well Chemicals Co., LTD, China) in 500 mL and make up with 1000 mL distilled water. The spiked wastewater of DNB-106 was prepared by dissolving 40 mg of NaCl and 40 mg of Na₂SO₄ crystal in 1000 mL containing 150 mg L⁻¹ of DNB-106. The pH measurements were made using a Metrohm pH meter and the test solutions were adjusted using reagent grades of dilute HCl (0.1 N) and NaOH (0.1 N). The concentration of DNB-106 in the samples was determined by UV–vis Spectrophotometer (Unico, 2800). Agitation of adsorbent–adsorbate was carried out in a thermostatic shaking assembly (Firstek, Taiwan).

2.2

2.2 Bio-hydrogen fermented biomass

Prof. Chiu-Yue Lin (Department of Environmental Science and Engineering, Feng Chia University, Taichung, Taiwan) and his team are working on production of bio-hydrogen from water hyacinth, an aquatic weed commonly available on the surface of ponds in Taiwan. After bio-hydrogen fermentation, the solid material remained is known as bio-hydrogen fermented waste (BHFW). The procurement and characteristics of BHFW are shown in Fig. 1 and Table 1, respectively.

Procurement scheme for BHFW and its derived AC (BHFW-AC).

Table 1 Characteristics of BHFW.

TS^⁎ (% w/w)	VS^⁎ (% w/w)	TCOD^⁎ (g g⁻¹ TS)	Total carbohydrate^⁎ (mg hexose equivalent g⁻¹ TS)	Cellulose^⁎ (%)	Hemi cellulose^⁎ (%)	Lignin^⁎ (%)	Elementary analysis wt% (dry-basis)^⁎				C/N ratio^⁎
TS^⁎ (% w/w)	VS^⁎ (% w/w)	TCOD^⁎ (g g⁻¹ TS)	Total carbohydrate^⁎ (mg hexose equivalent g⁻¹ TS)	Cellulose^⁎ (%)	Hemi cellulose^⁎ (%)	Lignin^⁎ (%)	C	H	N	S	C/N ratio^⁎
78.6	65.4	14.2	522.2	23.1	24.2	18.4	36.8	9.7	3.1	4.3	11.9

⁎ Tested by dried biomass, TS = total solids; VS = volatile solids; TCOD = total chemical oxygen demand.

2.3

2.3 Preparation of BHFW-AC

BHFW was chosen as precursor for the production of activated carbon via a single step chemical carbonization using H₃PO₄. In the present study, 90 g of crushed BHFW was soaked completely in 120 mL of 70% H₃PO₄ solution and agitated slightly for 2 h to ensure the penetration of H₃PO₄ throughout the material. Then, the mixture was heated at 80 °C for 1 h and left overnight at room temperature for appropriate wetting and impregnation of the precursor. The impregnated mass was dried in an air oven at 80 °C overnight, then, admitted into the reactor (ignition tube), which was then placed in a tubular electric furnace open from both ends. The temperature was raised at the rate of 50 °C per 10 min until the desired temperature was reached. The carbonization process was carried out at 500 °C for 80 min in limited air. The product was thoroughly washed with warm (70 °C) distilled water until pH of the solution become neutral. Finally, the BHFW-AC was dried at 110 °C for 24 h and sieved to different particle sizes and kept for further use. The characteristics of BHFW-AC are shown in Table 2.

Table 2 Characteristics of BHFW-AC.

Parameter	Value
Ash (%)	6.32
Density (g mL⁻¹)	1.75
Percentage of moisture	2.41
CEC (m mol g⁻¹)	2.70
pH_pzc	3.42
Yield (%)	96.0

Textural properties
S_BET (m² g⁻¹)	1242.00
Mesopore volume (mL g⁻¹)	0.620
Mesopore area (m² g⁻¹)	450.32
Micropore volume (mL g⁻¹)	0.324

2.4

2.4 Characterization of BHFW-AC

The elemental analysis of BHFW-AC was performed using EA1108 (Carlo-Erba). The surface morphology of BHFW-AC was studied by scanning electron microscopy using Hitachi S3000H model. FTIR analysis of BHFW-AC was carried out in the range of 500–4500 cm⁻¹ by Digilab FTS3500, Japan, with KBr pellets. The resulting AC was then characterized with respect to its pore structure and surface area using nitrogen adsorption/desorption at −196 °C using a gas sorption analyzer (Quantachrome, NOVA 1000e series, USA).

2.5

2.5 Adsorption capacity studies

Batch experiments were carried out to test the adsorption capacity of DNB-106 on the BHFW-AC. The experiments were carried out in a 250 mL Erlenmeyer flask by mixing 100 mL of dye solution in a range of 50–550 mg L⁻¹ initial concentrations. Approximately, 0.1 g of AC with size of 200 μm was added into the flask and the pH was carefully adjusted between 2.0 and 10.0 by adding a small amount of either 0.1 N HCl or 0.1 N NaOH solutions. The dye solutions were stirred using a mechanical magnetic stirrer at 313 K. The optimum pH was determined to be 6.0 and used throughout the experiments. The temperatures were also varied (313, 323 and 333 K), to determine the adsorption equilibrium time and the maximum removal of DNB-106 from aqueous solutions. All samples were filtered prior to triplicate analysis in order to minimize interference of the carbon fines with the analysis. The concentrations of DNB-106 in the supernatant solutions before and after adsorption were determined using a double beam UV–vis Spectrophotometer and the amount of adsorption at equilibrium, q_e (mg g⁻¹), was calculated by the following equations:

(1)

q_{e} = \frac{(C_{0} - C_{e}) V}{W}

(2)

(%) Removal = \frac{(C_{0} - C_{e})}{Ce} \times 100

where C₀ and C_e (mg L⁻¹) are the liquid-phase concentrations of DNB-106 at initial and equilibrium, respectively. V (L) is the volume of the solution and W (g) is the mass of dry adsorbent used.

2.6

2.6 Desorption studies

The DNB-106 loaded AC was separated by filtration, using Whattman filter paper No. 42 and the filtrate was used for the investigation of the desorption capacity of BHFW-AC. Then, BHFW-AC was washed with doubly distilled deionized water to remove the un-adsorbed DNB-106. Desorption studies were carried out using several such AC samples and were agitated in doubly distilled deionized water followed by 0.1 N NaOH/HCl. The desorbed DNB-106 in the colloidal solution was separated by centrifugation and analyzed as described above.

3 Result and discussion

3.1

3.1 Characterization of BHFW-AC

3.1.1

3.1.1 Porosity of BHFW-AC

Porosity of the AC was identified using the standard nitrogen adsorption procedure (Wang et al., 2005). In Fig. 2, the nitrogen adsorption isotherm analysis of BHFW-AC revealed the presence of microporosity which was considerably developed to mesoporosity as the carbon activation on BHFW progressed.

N2 adsorption–desorption isotherms at −196 °C of BHFW-AC.

According to the Horvath-Kawazoe method, the pore size distribution for the BHFW-AC substantiates the amount of pores in the microporous range, with the average pore diameter of approximately 3.4 nm as illustrated in Fig. 3. The maximum differential volume was obtained at 0.19 nm of the pore width.

Horvath-Kawazoe pore size distributions of BHFW-AC.

3.1.2

3.1.2 SEM and FTIR of BHFW-AC

Fig. 4a–c shows the SEM images of the BHFW-AC and adsorption of DBN-106 on the BHFW-AC. Many large pores like snake holes were observed clearly on the surface of the AC (see Fig. 4b). The well-developed pores had led to the large surface area and porous structure of the activated carbon. Fig. 5 displays the FTIR spectra obtained for the prepared AC. A sharp pointed absorption band at 3400 cm⁻¹ was observed due to –OH groups (Puziy et al., 2002) present in BHFW-AC. The peak at 2355 cm⁻¹ corresponds to the $C ≡ O$ stretching vibration probably due to the incorporation of the heteroatoms (in this case, oxygen atom from enriched carbon dioxide atmosphere during the activation process) at the edge of the aromatic sheet or within the carbon matrix (Tan et al., 2007). The broader peak observed at 1616 cm⁻¹ corresponds to the $C ⚌ C$ stretching vibrations in aromatic rings. The broader band at 1085 cm⁻¹ has been assigned to the C–OH stretching vibrations of alcohols and phenols, thus confirming the presence of the OH groups in the BHFW-AC. The peak at 789 cm⁻¹ corresponds to C–H out of plane bending toward the region of benzene derivatives.

SEM images of (a) BHFW (b) BHFW-AC before adsorption (c) BHFW-AC after adsorption.

3.2

3.2 Optimization of adsorption parameters

3.2.1

3.2.1 Effect of pH

pH plays a vital role in the removal of DNB-106 onto the AC from textile waste effluents. It was observed that the adsorption was highly dependent on the pH of the solution which affects the surface charge of the adsorbent and the degree of ionization of the adsorbate. At lower pH more protons are available; thereby decreasing the electrostatic attractions between the positively charged dye anions and the positively charged adsorption sites consequently, leading to an ionic repulsion between the positively charged surface and the cationic dye molecules thereby reducing the adsorption of dye. When the pH of the solution was increased, the positive charges on the solution interface decreased and the adsorbent surface appeared negatively charged. This is justified by the linear relationship between pH 2.0–6.0 and the % removal of DNB-106 removal (Fig. 6). The higher adsorption capacity obtained at higher pH values was due to the abundance of OH^- ions, therefore increasing the electrostatic attractions between the positively charged dye anions and the negatively charged adsorption sites. At the pH >6.0, the % of DNB-106 removal remained constant and consequently chosen as an optimum value for this study.

Effect of pH on adsorption of DNB-106 onto BHFW-AC.

3.2.2

3.2.2 Effect of contact time and initial dye concentration

Rapid adsorption was observed within 3 h, thereafter a steady increase of DNB-106 was adsorbed for less than an hour to a constant value of 245 mg g⁻¹. The total time was set to 4 h to ensure adequate equilibration during adsorption and kinetic studies. The amount of DNB-106 dye adsorbed per unit mass of BHFW-AC carbon increased with increasing dye concentration ranging from 250 to 550 mg L⁻¹. Maximum dye was obtained from the solution within 10 h after the start of every experiment. Thereafter, the concentration of DNB-106 in the liquid phase remained constant. In the process of the dye adsorption, the dye molecules initially have to first encounter the boundary layer effect and then they have to diffuse from the boundary layer film onto the adsorbent surface and then finally diffuse into the porous structure of the adsorbent. For higher initial concentrations no significant changes on the equilibrium time were observed. The uptake of the dye removal vs time curves shown in Fig. 7 is single, smooth and continuous leading to saturation, suggesting the possibility of monolayer coverage of DNB-106 on the outer surface of the BHFW-AC (Low et al., 1993).

Effect of initial concentration of DNB-106 sorption onto BHFW-AC.

3.2.3

3.2.3 Effect of particle size

From the earlier reports (Preeti et al., 2007) it is obvious that a decrease in particle size of BHFW-AC, results in an increase of the adsorption capacity of DNB-106. This was due to the fact that the smaller particles contain larger surface area and hence more DBN-106 removed at equilibrium state is depicted in Fig. 8. This was due to the low driving force per unit surface for mass transfer in case of smaller particles when compared to larger particles in the solution (Ozacar and Sengil, 2002).

Effect of particle size on the sorption of DNB-106 onto BHFW-AC.

3.2.4

3.2.4 Effect of temperature

Fig. 9 shows that increasing the amount of adsorbed DNB-106 with temperature from 313 to 333 K, increases the adsorption capacity of BHFW-AC, demonstrating the dependence of adsorption capacity on temperature. Once the pores on the surface of BHFW-AC have adsorbed the DNB-106 molecules, it will hold back the successive entrance of DNB-106 molecules at the opening of the pores (see the snake holes shelter pores in Fig. 4b). The rate of intra-particle diffusion of adsorbate into the pores will be intensified with an increase in temperature due to the endothermic processes (Guo et al., 2003). Thus, the adsorption increases with temperature.

Effect of temperature on the sorption of DNB-106 onto BHFW-AC.

3.3

3.3 Equilibrium modeling

The adsorption isotherm represents how the molecules are distributed between the liquid and solid phases when the adsorption process reaches an equilibrium state. The isotherm data were analyzed by fitting them to the different isotherm model an important step, could be used for design adsorption behavior of BHFW-AC (Garg et al., 2004). In the present study, the obtained equilibrium data for the adsorption of DNB-106 on to BHFW-AC were analyzed by considering Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm models. These were calculated using the least-squares fitting method. Langmuir isotherm equation in a linear form (Namasivayam and Arasi, 1997) represented as:

(3a)

q_{e} = \frac{Q_{m} {bC}_{e}}{(1 + {bC}_{e})}

(3b)

on linearization : \frac{C_{e}}{q_{e}} = \frac{C_{e}}{Q_{m}} + \frac{1}{Q_{m} b}

where q_e and C_e are the equilibrium concentrations of dye molecules in the adsorbed and liquid phases in mmol g⁻¹ and mmol L⁻¹, respectively. Q_m and b are Langmuir constants which are associated with adsorption capacity and adsorption energy respectively calculated using equations 3a-b and data are presented in Table 3. It was calculated by plotting slope and intercepts linearly; C_e/q_e vs C_e (see Fig. 10a). The R² value of 0.999 indicated that the adsorption data of DNB-106 on to the BHFW-AC at all three temperatures studied were best fitted to the Langmuir isotherm model. Langmuir isotherm can also be expressed in terms of a dimensionless constant of the separation factor or equilibrium parameter, R_L, defined as:

(4)

R_{L} = \frac{1}{1 + {bC}_{0}}

where b and C₀ are the Langmuir constant and initial concentration of dye molecule respectively. The R_L value indicates the shape of isotherm (Namasivayam and Arasi, 1997). R_L value between 0 and 1 indicates favorable adsorption, while R_L > 1, R_L = 1, and R_L = 0 indicate unfavorable, linear, and irreversible adsorption isotherms. The value of R_L was found to be 0.007 at 313 K, and this again confirmed that the Langmuir isotherm model fits well for adsorption of DNB-106 onto the BHFW-AC under the conditions used in this study.

Table 3 Langmuir, Freundlich, Temkin and Dubinin–Radushkevich isotherm model for adsorption of DNB-106 onto BHPW-AC.

Isotherms	Parameters/values			Temperature K
Isotherms	Q₀ (mg g⁻¹)	b (L⁻¹ mg)	R²	Temperature K
Langmuir	280.16	0.46	0.999	313
	335.71	1.73	0.999	323
	387.00	0.64	0.999	333

	K_F (mg g⁻¹) (L mg⁻¹)^1/ⁿ)	1/n	R²
Freundlich	93.15	0.32	0.832	313
	139.40	0.31	0.628	323
	133.58	0.28	0.667	333

	A (L/g)	B	R²
Temkin	26.75	35.69	0.897	313
	91.24	41.29	0.740	323
	38.16	50.38	0.819	333

	q_s (mg g⁻¹)	E	R²
Dubinin–Radushkevich	277.42	1310.18	0.997	313
	371.12	2255.26	0.835	323
	297.75	2376.21	0.426	333

(a) Langmuir (b) Freundlich (c) Temkin (d) Dubinin–Radushkevich model curves for adsorption of DNB-106 onto BHPW-AC at various temperatures.

Pure empirical form of Freundlich isotherm equation is $q_{e} = k_{f} C_{e}^{1 / n}$ which explains the adsorption of dye molecule onto heterogeneous system (Haghseresht and Lu, 1998). Linear form of Freundlich isotherm equation is:

(5)

\log q_{e} = \log K_{f} + \frac{1}{n} \log C_{e}

where q_e and C_e are the equilibrium concentrations of dye molecules in the adsorbed and liquid phases which are expressed in mmol g⁻¹ and mmol L⁻¹, respectively, whereas k_f and n are the Freundlich constants which are associated with the sorption capacity and intensity, respectively. These two values are calculated from the intercept and slope by plotting log q_e vs log C_e (Fytianos et al., 2000; Hosseini et al., 2003) as shown in Fig. 10b and the data are summarized in Table 3.

The Temkin isotherm is expressed as

(6)

q_{e} = \frac{RT}{b} \ln (K_{T} C_{e}) = B_{1} \ln (K_{T} C_{e})

where constant B₁ = R_T/b (heat of adsorption), R = Universal gas constant (J mol⁻¹ K⁻¹), T = Temperature (K), b = Variation of adsorption energy (J mol⁻¹) and K_T = Equilibrium binding constant (L mg⁻¹). A plot of q_e vs ln C_e is shown in Fig. 10c and values obtained corresponding to the constants K_T and B together with the R² values are shown in Table 3.

The Dubinin–Radushkevich (D–R) isotherm approach assumes that there is a surface area where the adsorption energy is homogeneous as shown in Fig. 10d. The D–R isotherm is expressed as:

(7)

q_{e} = Q_{m} \exp (- K {[RT \ln (1 + \frac{1}{Ce})]}^{2}) = Q_{m} \exp (- K ε^{2})

where ε (Polanyi potential) = RT ln (1 + 1/Ce), Q_m is the D–R constant, K denotes the average mean free energy related to sorption of dye per mole of the sorbate when it is transferred to the surface of the solid from infinity in the solution and this energy can be represented using the following relationship:

(8)

E = \frac{1}{\sqrt{2 K}}

Overall, on correlating the data in Table 3 obtained from all four adsorption isotherm models, the Langmuir isotherm model yielded the best fit with the highest R² value at all temperatures compared to the other three models. Confirmation of the experimental data into Langmuir isotherm equation indicated the homogeneous nature of BHFW-AC surface, i.e., each DNB-106 molecule/BHFW-AC adsorption had equal adsorption activation energy. These results also demonstrated the formation of monolayer coverage of dye molecule at the outer surface of BHFW-AC.

3.4

3.4 Kinetic modeling

Adsorption kinetics of DNB-106 on the surface of BHFW-AC was studied by employing pseudo-first-order, pseudo-second-order and Weber and Morris models. The pseudo-first-order equation (Langergren and Svenska, 1898) is expressed as:

(9)

\ln (q_{e} - q_{t}) = \ln q_{e} - k_{1} t

where q_e and q_t are the amounts of DNB-106 adsorbed (mg g⁻¹) at equilibrium and at time t (h), respectively, and k₁ (h⁻¹) was the rate constant of adsorption. Values of k₁ at 313 K were calculated from the plots of ln (q_e − q_t) vs t as shown in Fig. 11a for various initial concentrations of DNB-106. The R² values obtained were relatively small and the experimental q_e values are not in agreement with the calculated values obtained from the linear plots (see Table 4). The pseudo-second-order equation (McKay et al., 1987a,b) at equilibrium state of adsorption can be expressed as

(10)

\frac{t}{q_{t}} = \frac{1}{k_{2} q_{e}^{2}} + \frac{1}{q_{e} t}

where k₂ (g mg⁻¹ h) is the rate constant of second-order equation. The linear plot of t/q_t vs t at 313 K yielded R² values >0.999 for all DNB-106 concentrations as shown in Fig. 11b. It also showed a good agreement between the experimental and the calculated q_e values (see Tables 4 and 5), indicating the feasibility of this model to describe the adsorption process of DNB-106 on to BHFW-AC.

(a) Pseudo first order (b) pseudo second order models for the sorption of DNB-106 on to the BHFW-AC at 313 K.

Table 4 Correlation of pseudo-first-order and pseudo-second-order models for different initial DNB-106 concentrations at 313 K.

Initial concentration (mg L⁻¹)	q_e, exp (mg g⁻¹)	q_e, cal(mg g⁻¹)	K₁ (h⁻¹)	R²	SSE (%)
Pseudo-first-order
50	51.05	11.46	0.820	0.630	40.14
150	89.01	17.06	0.930	0.680	72.50
250	192.51	98.26	0.770	0.950	94.81
350	258.24	160.94	0.410	0.840	97.86
450	271.83	165.34	0.420	0.850	107.05
550	277.72	153.32	0.380	0.750	124.96

Pseudo-second-order
50	51.05	51.25	0.660	0.9990	0.36
150	89.01	88.95	0.730	0.9980	0.21
250	192.51	198.07	0.090	0.9990	5.71
350	258.24	240.09	0.070	1.0000	18.30
450	271.83	251.99	0.060	0.9990	19.99
550	277.72	245.89	0.080	1.0000	31.98

Table 5 Correlation of intra-particle diffusion model for different initial DNB-106 concentrations at 313 K.

Initial concentration (mg L⁻¹)	q_e, exp (mg g⁻¹)	Intraparticle diffusion
Initial concentration (mg L⁻¹)	q_e, exp (mg g⁻¹)	q_e cal (mg/80 g)	K_p (mg g⁻¹ h^1/2)	R²	SSE (%)
50	51.05	52.80	0.820	0.880	1.65
150	89.01	91.07	0.980	0.950	1.96
250	192.51	234.77	17.60	0.990	42.15
350	258.24	306.53	31.80	0.990	48.19
450	271.83	316.01	30.54	0.970	44.07
550	277.72	294.72	21.52	0.940	16.89

To test the diffusion mechanism between dye molecule and BHFW-AC, an intra-particle diffusion model proposed by Weber and Morris (Weber and Morris, 1962) has been used and the amount adsorbed is given by

(11)

q_{t} = k_{p} t^{1 / 2}

where k_p (mg g⁻¹ h^1/2), the intra-particle diffusion rate constant, is obtained from the slope of the straight line of q_t vs t^1/2 as shown in Fig. 12. In the first stage, instantaneous adsorption was seen which results in the sharper portion in the graph (see Fig. 12). As intra-particle diffusion was the rate limiting step, the second stage of adsorption was steady and gradual. Finally, in the third stage adsorption reaches to equilibrium state where intra-particle diffusion process becomes slow due to the extremely low adsorbate concentrations left in the solutions. In Fig. 12, it can be seen clearly that the line did not pass through the origin due to the difference in the mass transfer rate between initial and final stages of adsorption (Mohanty et al., 2005).

Intra-particle diffusion model for the sorption of DNB-106 onto the BHFW-AC.

By using the sum of squared errors (SSE, %) model, the validity of three kinetic models such as pseudo-first-order, pseudo-second-order and Weber and Morris intra-particle diffusion models was verified based on the following equation:

(12)

SSE = \frac{\sqrt{\sum {(q_{e}, \exp - q_{e},cal)}^{2}}}{N}

where N = number of data points.

The lower the values of the sum of squared errors, the better is the fitted model for the adsorption of dye molecule on the surface of prepared activated carbon. The obtained analytical data of SSE for three models tabulated in Tables 4 and 5 show that the pseudo-second-order kinetic model yielded the lowest SSE values which are agreeable with the R² values obtained earlier. This proves that the adsorption of DNB-106 on the BHFW-AC carbon can also be best described by the pseudo-second-order kinetic model which was based on the chemi-sorption equilibrium that predicted the performance throughout the studies as being a rate controlled process (Tseng and Tseng, 2005).

3.5

3.5 Adsorption thermodynamics

Energy cannot be lost or gained in an isolated environment due to change in entropy as per thermodynamic laws (Kumar and Kumaran, 2005). Thermodynamic studies reveal the changes taking place in standard enthalpy (ΔH⁰), standard entropy (ΔS⁰) and standard free energy (ΔG⁰) due to transmission of unit mole of solute from solution onto the solid–liquid interface. The values of ΔH⁰ and ΔS⁰ were expressed using the following equation:

(13)

\ln K_{d} = \frac{Δ S^{0}}{R} - \frac{Δ H^{0}}{RT}

where R = universal gas constant (8.314 J/mol K), T = absolute temperature (K) of the solution and K_d = distribution coefficient which can be calculated as:

(14)

K_{d} = \frac{C_{Ae}}{C_{e}}

where C_Ae (mg L⁻¹) and Ce (mg L⁻¹) are the amount adsorbed on solid at equilibrium and the equilibrium concentration respectively. The values of ΔH⁰ and ΔS⁰ were calculated from the slope and intercept of plot drawn between ln K_d and 1/T (see Fig. 13). ΔG⁰ can be calculated using the below expression:

(15)

Δ G^{0} = - RT \ln K_{d}

Graph of ln Kd vs 1/T at various initial concentrations of DNB-106.

From Table 6 the positive value of ΔH⁰ indicated the endothermic nature of the adsorption mechanism. The highest monolayer sorption efficiency of DNB-106 on the BHFW-AC increased from 152.17 to 443.10 mg g⁻¹ with an increase in temperature of the solution from 313 to 333 K (see Table 3). This noteworthy result could explain the endothermic nature of the adsorption phenomenon. The positive value of ΔS⁰ indicated the desirability of the BHFW-AC for DNB-106 and enhancing the randomness at the solid–solution interface during the adsorption process. The negative value of ΔG⁰ revealed the possibility and spontaneous nature of the adsorption with a high preference of DNB-106 onto the surface of BHFW-AC.

Table 6 Thermodynamic parameters for adsorption of DNB-106 onto BHPW-AC.

Initial concentration (mg L⁻¹)	ΔG⁰(J/mol)
Initial concentration (mg L⁻¹)	ΔH⁰ (J/mol)	ΔS⁰ (J/mol)	313 K	323 K	333 K
50	12914.65	82.59	−11926.50	−13021.60	−12654.15
150	32582.25	150.00	−1262.15	−14587.00	−14688.85
250	73840.47	287.32	−1684.55	−16158.50	−17867.55
350	115947.57	405.56	−6214.68	−14505.80	−12112.65
450	70055.11	250.64	−3722.15	−6364.14	−6516.26
550	46893.13	168.48	−2618.06	−2465.18	−3854.79

3.6

3.6 Desorption studies of DNB-106 from the surface of BHFW-AC

Desorption studies were carried out with various concentrations of HCl over the range of 0.05 to 0.2 M for 1 h to retain the DNB-106 into the desorption medium from the surface of BHFW-AC. The adsorbate concentration at the equilibrium state C_ad (mg L⁻¹) was calculated by taking the difference between the initial and equilibrium concentration (C₀ − C_e) of the analyte. The used up BHFW-AC was separated as per aforesaid procedure in Section 2.6. The sample was dried in a vacuum oven at 40 °C for 1 h and was then agitated by adding dilute HCl using mechanical shaker with 150 rpm. It indicates that desorption efficiency increased up to 95% with a gradual increase in the concentration of HCl up to 0.15 M. Beyond this concentration desorption remains constant as depicted in Fig. 14. The desorbed DNB-106 concentration was measured using expression:

(16)

(%) Desorption = \frac{Cad}{Cde} \times 100

Effect of HCl concentration on the desorption of DBN-106 from the BHFW-AC.

3.7

3.7 Comparison study of BHFW-AC with previously reported adsorbents

The sorption capacity of DNB-106 by BHFW-AC at 313 K ranging from 50 to 550 mg g⁻¹ was comparable to AC available in the market and some other adsorbents prepared from agricultural waste reported in earlier studies as shown in Table 7. Due to its high surface area (1242 m²g⁻¹), adsorption capacity, cost effectiveness of BHFW-AC it can be considered as a reliable and alternative activated carbon for the removal of DNB-106 from textile industrial effluents. Preparation of BHFW-AC was highly economical (estimated cost for the preparation of AC for the present experiment including transportation of raw material, electrical charges and chemicals used was only NT$ 135 or US$ 4.56) which stands best among the reported AC in the literature (Emna et al., 2011; Saban Tanyildizi, 2011; Wenhong et al., 2011; Li et al., 2010; Hamdi et al., 2009; Khaled et al., 2009 ).

Table 7 Comparison of BHFW-AC with reported ACs in the literature.

ACs	Analyte	Adsorption isotherm models	Kinetic models	Surface area (m² g⁻¹)	References
Untreated clay	Reactive Red-120	Langmuir, Freundlich	Pseudo first order, pseudo second order, Elovich equation and Intraparticle diffusion equation	–	Emna et al. (2011)
Pea nut hull	Reactive Black-5	ANOVA Quadratic model	Pseudo first and second order	–	Saban Tanyildizi (2011)
Paper mill sewage sludge	Reactive Red-24	–	–	280.01	Wenhong et al. (2011)
Polymer loaded bentonite	Acid scarlet GR and Acid Dark 2G	Langmuir, Freundlich	–	–	Li et al. (2010)
Bagasee pith	Rhodamine-B	Langmuir, Freundlich, Temkin, Harkins-Jura and Halsey equations	Pseudo first order, pseudo second order, Elovich equation and Intraparticle diffusion equation	522.70	Hamdi et al. (2009)
Orange peel	Direct N Blue-106	Langmuir, Freundlich, Koble-Corrigan, Redlich-Peterson, Temkin and Dubinin–Radushkevich	Pseudo first order, pseudo second order, Elovich, Intraparticle diffusion equation	–	Khaled et al. (2009)
BHFW-AC	Direct N Blue-106	Langmuir, Freundlich, Temkin and Dubinin–Radushkevich	Pseudo first order, pseudo second order, Intraparticle diffusion equation	1242.00	This study

4 Conclusion

The developed AC from BHFW is a unique adsorbent for the removal of DNB-106 from industrial textile effluents over a wide range of concentrations. The surface area of the BHFW-AC was porous with well developed snake hole like pores as shown in the corresponding SEM images. Hence, DNB-106 is found to adsorb robustly on the surface of the BHFW-AC. Among all the adsorption isotherm models, the equilibrium data, was best described by the Langmuir isotherm showing a maximum monolayer adsorption surface area of 1242 mg g⁻¹ at 313 K. The kinetics of the adsorption followed the pseudo-second-order kinetic model. Furthermore, the results of thermodynamic studies showed a positive ΔH⁰ value, which indicated the endothermic nature of the adsorption process. The positive ΔS⁰ value showed the enhanced randomness at the solid–liquid interface during the adsorption mechanism. Due to the spontaneous nature of adsorption of DNB-106 onto the surface of BHFW-AC, the ΔG⁰ values were negative. Overall, this investigation showed that AC derived from BHFW was efficient, for the removal of DNB-106 from textile waste effluents, thus demonstrating a worthy alternative for the commercially available activated carbon.

Acknowledgments

The authors gratefully acknowledge Taiwan’s National Science Council (NSC-99-2221-E-035-017-MY3, NSC-100-2811-E035-002), Taiwan’s Bureau of Energy (Grant No. 99-D0204-3), Feng Chia University (FCU-10G27101), Durban University of Technology and National Research Foundation of South Africa for the financial support to carry out this research.

References

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[Google Scholar]
McKay G., El-Geundi M., Nassar M.M., . External mass transport processes during the adsorption of dyes onto bagasse pith. Water Res.. 1987;22:1527-1533.
[Google Scholar]
McKay G., Ramprasad G., Mowli P., . Desorption and regeneration of dye colors from low-cost materials. Water Res.. 1987;21:375-377.
[Google Scholar]
Metivier-Pignon H., Faur-Brasquet C., Cloirec P.L., . Adsorption of dyes onto activated carbon cloths: approach of adsorption mechanisms and coupling of ACC with ultrafiltration to treat coloured wastewaters. Sep. Purif. Technol.. 2003;31:3-11.
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[Google Scholar]
Ozacar M., Sengil I.A., . Adsorption of acid dyes from aqueous solutions by calcinated aluminite and granular activated carbon. Adsorption. 2002;8:301-308.
[Google Scholar]
Palanivel Sathishkumar, Mani Arulkumar, Thayumanavan Palvannan, . Utilization of agro-industrial waste jatropha curcas pods as an activated carbon for the adsorption of reactive dye Remazol Brilliant Blue R (RBBR) J. Clean Prod.. 2012;22:67-75.
[Google Scholar]
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Poots V.J.P., McKay G., Healy J.J., . The removal of acid dye from effluents using natural adsorbents-II wood. Water Res.. 1976;10:1067-1070.
[Google Scholar]
Preeti S.N., Singh B.K., Siddarth N., . Equilibrium, kinetic and thermodynamic studies on phenol sorption to clay. J. Environ. Prot. Sci.. 2007;1:83-91.
[Google Scholar]
Puziy M., Poddubnaya O.I., Martinez-Alonso A., Suarez-Garcia F., Tascon J.M.D., . Synthetic carbons activated with phosphoric acid. I. Surface chemistry and ion binding properties. Carbon. 2002;40:1493-1505.
[Google Scholar]
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[Google Scholar]
Ravikumar K., Deebika B., Balu K., . Decolourization of aqueous dye solutions by a novel adsorbent: application of statistical designs and surface plots for the optimization and regression analysis. J. Hazard. Mater.. 2005;B122:75-83.
[Google Scholar]
Saban Tanyildizi M., . Modeling of adsorption isotherms and kinetics of reactive dye from aqueous solution by peanut hull. Chem. Eng. J.. 2011;168:1234-1240.
[Google Scholar]
Tan I.A.W., Hameed B.H., Ahmad A.L., . Equilibrium and kinetic studies on basic dye adsorption by oil palm fibre activated carbon. Chem. Eng. J.. 2007;127:111-119.
[Google Scholar]
Tan I.A.W., Hameed B.H., Ahmad A.L., . Optimization of preparation conditions for activated carbons from coconut husk using response surface methodology. Chem. Eng. J.. 2008;137:462-470.
[Google Scholar]
Tseng R.L., Tseng S.K., . Pore structure and adsorption performance of the KOH-activated carbons prepared from corncob. J. Colloid Interface Sci.. 2005;287:428-437.
[Google Scholar]
Tunay O., Kabdasli I., Eremektar G., Orhon D., . Colour removal from textile waste water. Water Sci. Technol.. 1996;34:9-16.
[Google Scholar]
Wang S., Zhu Z.H., Coomes A., Haghseresht F., Lu G.Q., . The physical and surface chemical characteristics of activated carbons and the adsorption of methylene blue from wastewater. J. Colloid Interface Sci.. 2005;284:440-446.
[Google Scholar]
Weber, W.J., Morris, J.C., 1962. Proceedings of the International Conference on Water Pollution Symposium, vol. 2, Pergamon, Oxford, pp. 231–266.
Wenhong Li., Qinyan Yue., Peng Tu., Zuohao Ma., Baoyu Gao., Jinze Li., Xing Xu., . Adsorption characteristics of dyes in columns of activated carbon prepared from paper mill sewage sludge. Chem. Eng. J.. 2011;178:197-203.
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Appendix A.

(Fig. A1).

Structure of Direct Navy Blue-106 (DNB-106).

Show Sections

[1] Asfour H.M., Fadali O.A., Nassar M.M., El-Geundi M.S., . Equilibrium studies on adsorption of basic dyes on hardwood. J. Chem. Technol. Biotechnol. A. 1985;5:21-27.
[Google Scholar]

[2] Baccar R., Blanquez P., Bouzid J., Feki M., Attiya H., Sarra M., . Modeling of adsorption isotherms and kinetics of a tannery dye onto an activated carbon prepared from an agricultural by-product. Fuel Process. Technol.. 2013;106:408-415.
[Google Scholar]

[3] Bulut Y., Aydın H., . A kinetics and thermodynamics study of methylene blue adsorption on wheat shells. Desalination. 2006;194:259-267.
[Google Scholar]

[4] Chu W., Ma C.W., . Quantitative prediction of direct and indirect dye ozonation kinetics. Water Res.. 2000;34:3153-3160.
[Google Scholar]

[5] Djilania Chahrazed, Zaghdoudi Rachida, Modarressi Ali, Rogalski Marek, Djazi Fayçal, Lallam Abdelaziz, . Elimination of organic micropollutants by adsorption on activated carbon prepared from agricultural waste. Chem. Eng. J.. 2012;189–190:203-212.
[Google Scholar]

[6] El-Geundi M., Nassar M.M., . Colour removal from textile effluents by adsorption techniques. Water Res.. 1987;25:271-273.
[Google Scholar]

[7] Emna Errais, Joelle Duplay, Fadila Darragi, Inès M'Rabet, Amelie Aubert, Fabienne Huber, Gilles Morvan, . Efficient anionic dye adsorption on natural untreated clay: kinetic study and thermodynamic parameters. Desalination. 2011;275:74-81.
[Google Scholar]

[8] Fytianos K., Voudrias E., Kokkalis E., . Sorption-desorption behavior of 2,4-dichlorophenol by marine sediments. Chemosphere. 2000;40:3-6.
[Google Scholar]

[9] Garg V.K., Moirangthem A., Kumar R., Gupta R., . Basic dye (methylene blue) removal from simulated wastewater by adsorption using Indian rosewood sawdust: timber industry waste. Dyes Pig.. 2004;63:243-250.
[Google Scholar]

[10] Girgis B.S., El-Hendawy A.A., . Porosity development in activated carbons obtained from date pits under chemical activation with phosphoric acid. Microporous Mesoporous Mater.. 2002;52:105-117.
[Google Scholar]

[11] Guo Yupeng, Yang Shaofeng, Wuyou Fu, Qi Jurui, Li Renzhi, Wang Zichen, Hongding Xu., . Adsorption of malachite green on micro- and Mesoporous rice husk-based active carbon. Dyes Pig.. 2003;56:219-229.
[Google Scholar]

[12] Haghseresht F., Lu G., . Adsorption characteristics of phenolic compounds onto coal- reject-derived adsorbents. Energy Fuels. 1998;12:1100-1107.
[Google Scholar]

[13] Hamdi M.H. Gad, Ashraf A. El-Sayed, . Activated carbon from agricultural byproducts for the removal of Rhodamine-B from aqueous solution. J. Hazard. Mater.. 2009;168:1070-1081.
[Google Scholar]

[14] Hameed B.H., Din A.T.M., Ahmad A.L., . Adsorption of methylene blue onto bamboo-based activated carbon: kinetics and equilibrium studies. J. Hazard. Mater.. 2007;141:819-825.
[Google Scholar]

[15] Hosseini M., Mertens S.F.L., Ghorbani M., Arshadi M.R., . Asymmetrical Schiff bases as inhibitors of mild steel corrosion in sulphuric acid media. Mater. Chem. Phys.. 2003;78:800-806.
[Google Scholar]

[16] Kannan N., Sundaram M.M., . Kinetics and mechanism of removal of methylene blue by adsorption on various carbons—a comparative study. Dyes Pig.. 2001;51:25-40.
[Google Scholar]

[17] Khaled Azza, El Nemr Ahmed, El-Sikaily Amany, Abdelwahab Ola, . Removal of Direct N Blue-106 from artificial textile dye effluent using activated carbon from orange peel: adsorption isotherm and kinetic studies. J. Hazard. Mater.. 2009;165:100-110.
[Google Scholar]

[18] Kumar K.V., Kumaran A., . Removal of methylene blue by mango seed kernel powder. Biochem. Eng. J.. 2005;27:83-93.
[Google Scholar]

[19] Langergren S., Svenska B.K., . Zur theorie der sogenannten adsorption geloester stoffe. Veternskapsakad Handlingar. 1898;24(4):1-39.
[Google Scholar]

[20] Lee J.W., Choi S.P., Thiruvenkatachari R., Shim W.G., Moon H., . Evaluation of the performance of adsorption and coagulation processes for the maximum removal of reactive dyes. Dyes Pig.. 2006;69:196-203.
[Google Scholar]

[21] Li Qian, Yue Qin-Yan, Yuan Su, Gao Bao-Yu, Sun Hong-Jian, . Equilibrium, thermodynamics and process design to minimize adsorbent amount for the adsorption of acid dyes onto cationic polymer-loaded bentonite. Chem. Eng. J.. 2010;158:489-497.
[Google Scholar]

[22] Lin Long, Zhai Shang-Ru, Xiao Zuo-Yi, Song Yu, Ana Qing-Da, Song Xiao-Wei, . Dye adsorption of mesoporous activated carbons produced from NaOH-pretreated rice husks. Bioresour. Technol.. 2013;136:437-443.
[Google Scholar]

[23] Low K.S., Lee C.K., Heng L.L., . Sorption of basic dyes by Hydrilla verticillata. Environ. Technol.. 1993;14:115-124.
[Google Scholar]

[24] McKay G., El-Geundi M., Nassar M.M., . External mass transport processes during the adsorption of dyes onto bagasse pith. Water Res.. 1987;22:1527-1533.
[Google Scholar]

[25] McKay G., Ramprasad G., Mowli P., . Desorption and regeneration of dye colors from low-cost materials. Water Res.. 1987;21:375-377.
[Google Scholar]

[26] Metivier-Pignon H., Faur-Brasquet C., Cloirec P.L., . Adsorption of dyes onto activated carbon cloths: approach of adsorption mechanisms and coupling of ACC with ultrafiltration to treat coloured wastewaters. Sep. Purif. Technol.. 2003;31:3-11.
[Google Scholar]

[27] Mohanty K., Das D., Biswas M.N., . Adsorption of phenol from aqueous solutions using activated carbons prepared from Tectona grandis sawdust by ZnCl₂ activation. Chem. Eng. J.. 2005;115:121-131.
[Google Scholar]

[28] Namasivayam C., Arasi J.S.E., . Removal of Congo red from wastewater by adsorption onto waste red mud. Chemosphere. 1997;34:401-417.
[Google Scholar]

[29] Namasivayan C., Kanchana N., Yamuna R.T., . Waste banana pith as adsorbent for the removal of rhodamine-B from aqueous solutions. Waste Manage.. 1993;13:89-95.
[Google Scholar]

[30] Ozacar M., Sengil I.A., . Adsorption of acid dyes from aqueous solutions by calcinated aluminite and granular activated carbon. Adsorption. 2002;8:301-308.
[Google Scholar]

[31] Palanivel Sathishkumar, Mani Arulkumar, Thayumanavan Palvannan, . Utilization of agro-industrial waste jatropha curcas pods as an activated carbon for the adsorption of reactive dye Remazol Brilliant Blue R (RBBR) J. Clean Prod.. 2012;22:67-75.
[Google Scholar]

[32] Peter A.T., Freeman H.S., . Physico-Chemical Principles of Color Chemistry. London: Blackie Academic and Professional; 1996.

[33] Poots V.J.P., McKay G., Healy J.J., . The removal of acid dye from effluents using natural adsorbents-II wood. Water Res.. 1976;10:1067-1070.
[Google Scholar]

[34] Preeti S.N., Singh B.K., Siddarth N., . Equilibrium, kinetic and thermodynamic studies on phenol sorption to clay. J. Environ. Prot. Sci.. 2007;1:83-91.
[Google Scholar]

[35] Puziy M., Poddubnaya O.I., Martinez-Alonso A., Suarez-Garcia F., Tascon J.M.D., . Synthetic carbons activated with phosphoric acid. I. Surface chemistry and ion binding properties. Carbon. 2002;40:1493-1505.
[Google Scholar]

[36] Rajeshwarisivaraj S., Sivakumar P., Senthilkumar V., Subburam K., . Carbon from Cassava peel, an agricultural waste, as an adsorbent in the removal of dyes and metal ions from aqueous solution. Bioresour. Technol.. 2001;80:233-235.
[Google Scholar]

[37] Ravikumar K., Deebika B., Balu K., . Decolourization of aqueous dye solutions by a novel adsorbent: application of statistical designs and surface plots for the optimization and regression analysis. J. Hazard. Mater.. 2005;B122:75-83.
[Google Scholar]

[38] Saban Tanyildizi M., . Modeling of adsorption isotherms and kinetics of reactive dye from aqueous solution by peanut hull. Chem. Eng. J.. 2011;168:1234-1240.
[Google Scholar]

[39] Tan I.A.W., Hameed B.H., Ahmad A.L., . Equilibrium and kinetic studies on basic dye adsorption by oil palm fibre activated carbon. Chem. Eng. J.. 2007;127:111-119.
[Google Scholar]

[40] Tan I.A.W., Hameed B.H., Ahmad A.L., . Optimization of preparation conditions for activated carbons from coconut husk using response surface methodology. Chem. Eng. J.. 2008;137:462-470.
[Google Scholar]

[41] Tseng R.L., Tseng S.K., . Pore structure and adsorption performance of the KOH-activated carbons prepared from corncob. J. Colloid Interface Sci.. 2005;287:428-437.
[Google Scholar]

[42] Tunay O., Kabdasli I., Eremektar G., Orhon D., . Colour removal from textile waste water. Water Sci. Technol.. 1996;34:9-16.
[Google Scholar]

[43] Wang S., Zhu Z.H., Coomes A., Haghseresht F., Lu G.Q., . The physical and surface chemical characteristics of activated carbons and the adsorption of methylene blue from wastewater. J. Colloid Interface Sci.. 2005;284:440-446.
[Google Scholar]

[44] Weber, W.J., Morris, J.C., 1962. Proceedings of the International Conference on Water Pollution Symposium, vol. 2, Pergamon, Oxford, pp. 231–266.

[45] Wenhong Li., Qinyan Yue., Peng Tu., Zuohao Ma., Baoyu Gao., Jinze Li., Xing Xu., . Adsorption characteristics of dyes in columns of activated carbon prepared from paper mill sewage sludge. Chem. Eng. J.. 2011;178:197-203.
[Google Scholar]

[46] Wu F.C., Tseng R.L., Juang R.S., . Comparisons of porous and adsorption properties of carbons activated by steam and KOH. J. Colloid Interface Sci.. 2005;283:49-56.
[Google Scholar]

Robust adsorption of Direct Navy Blue-106 from textile industrial effluents by bio-hydrogen fermented waste derived activated carbon: Equilibrium and kinetic studies

Abstract

Keywords

Bio-hydrogen fermented waste-activated carbon (BHFW-AC)

Direct Navy Blue-106 (DNB-106)

Adsorption

Activated carbon (AC)

Textile wastewater

1 Introduction

2 Experimental

2.1 Reagents

2.2 Bio-hydrogen fermented biomass

2.3 Preparation of BHFW-AC

2.4 Characterization of BHFW-AC

2.5 Adsorption capacity studies

2.6 Desorption studies

3 Result and discussion

3.1 Characterization of BHFW-AC

3.1.1 Porosity of BHFW-AC

3.1.2 SEM and FTIR of BHFW-AC

3.2 Optimization of adsorption parameters

3.2.1 Effect of pH

3.2.2 Effect of contact time and initial dye concentration

3.2.3 Effect of particle size

3.2.4 Effect of temperature

3.3 Equilibrium modeling

3.4 Kinetic modeling

3.5 Adsorption thermodynamics

3.6 Desorption studies of DNB-106 from the surface of BHFW-AC

3.7 Comparison study of BHFW-AC with previously reported adsorbents

4 Conclusion

Acknowledgments

References

Appendix A.

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