10.8
CiteScore
 
5.3
Impact Factor
Generic selectors
Exact matches only
Search in title
Search in content
Post Type Selectors
Search in posts
Search in pages
Filter by Categories
Corrigendum
Current Issue
Editorial
Erratum
Full Length Article
Full lenth article
Letter to Editor
Original Article
Research article
Retraction notice
Review
Review Article
SPECIAL ISSUE: ENVIRONMENTAL CHEMISTRY
10.8
CiteScore
5.3
Impact Factor
Generic selectors
Exact matches only
Search in title
Search in content
Post Type Selectors
Search in posts
Search in pages
Filter by Categories
Corrigendum
Current Issue
Editorial
Erratum
Full Length Article
Full lenth article
Letter to Editor
Original Article
Research article
Retraction notice
Review
Review Article
SPECIAL ISSUE: ENVIRONMENTAL CHEMISTRY
View/Download PDF

Translate this page into:

Review
9 (
2_suppl
); S1208-S1213
doi:
10.1016/j.arabjc.2012.01.001

Progress of catalytic wet air oxidation technology

, ,
 College of Chemistry and Chemical Engineering, Northeast Petroleum University, Daqing 163318, PR China

⁎Corresponding author. Address: College of Chemistry and Chemical Engineering, Northeast Petroleum University, No. 199 Development Road of Daqing, PR China. Tel./fax: +86 459 650 3502. jingguolin@yahoo.cn (Guolin Jing)

Received: , Accepted: ,
© The Author(s) 2012
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

Catalytic wet air oxidation (CWAO) is one of the most economical and environmental-friendly advanced oxidation process for high strength, toxic, hazardous and non-biodegradable contaminants under milder conditions, which is developed on the basic of wet air oxidation. Various heterogeneous catalysts including noble metals and metal oxides have been extensively studied to enhance the efficiency of CWAO. The advances in the research on wastewater treatment by CWAO process are summarized in aspects of reaction mechanism investigation, reaction kinetics study and catalyst development. It is pointed out that the preparation of active and stable catalysts, the investigation on reaction mechanisms and the study on reaction kinetics models are very important for the promotion of CWAO application.

Keywords

Catalytic wet air oxidation
Catalyst
Reaction mechanism
Reaction kinetics
1

1 Introduction

Rapid development of industry promoted rapid growth of economy, but environmental pollution has become a constraining factor of economic development, and high concentrations, toxicity, harmfulness, difficult in biological treatment of wastewater and sludge are still major factors of environmental pollution. Wet air oxidation (WAO) has been proven as one of the efficient technologies to eliminate highly concentrated, toxic and hazardous organic compounds as CO2, H2O and other innocuous end products under high temperature and high pressure using oxygen as the oxidant, and without the emissions of NOx, SO2, HCl, dioxins, furans, and fly ash (Luck, 1999). The WAO is very attractive for treating wastewaters that are too toxic for biological technology to be treated and too dilute for incineration to be eliminated. However, the severe operating conditions and high costs limit its application in wastewater treatment. Catalytic wet air oxidation (CWAO) has gained some attention. The addition of catalysts decreases the operating conditions, enhances the reaction rate, and shortens the reaction time (Luck, 1996; Levec and Pintar, 2007). In recent years, CWAO technology has made many achievements, and the advances in the research on wastewater treatment by CWAO process are summarized in aspects of reaction mechanism investigation, reaction kinetics study and catalyst development. Fig. 1 is schematic diagram of the experimental setup.

Schematic diagram of the experimental setup.
Figure 1
Schematic diagram of the experimental setup.

2

2 Reaction mechanisms and reaction kinetics of CWAO

CWAO adds catalyst into the system of traditional WAO, thus it reduces the harsh reaction conditions, increases the oxidation capacity of oxidants and shortens reaction time and thereby it reduces the investment in operating costs. Usually CWAO can be divided into heterogeneous and heterogeneous CWAO according to different forms of catalysts.

Reaction mechanism of CWAO and WAO has no essential difference, and the addition of the catalyst enhances the production of free radicals. Reaction mechanism of WAO is very complicated, and WAO reaction is generally regarded as free radical reactions. The present study is also at a relatively shallow stage, which mainly contains the detection of intermediate and free radicals. Free radical reaction is generally regarded as a chain reaction that is divided into three phases namely chain initiation, chain transfer and chain termination. Li et al. (1991) proposed the mechanism of radical reaction for WAO that has been widely recognized. They believe that there are several free radicals in the reaction system, such as the O•, HO2• and HO•, and HO2•, HO• are the primary radicals among them. Robert et al. (2002) applied WAO to treat cellulose and the study showed that HO• and H2O2 play the role of intermediates in the initial phase of the oxidation reactions. HO• was detected by the electron spin resonance spectroscopy coupled to the spin trapping technique using the 5,5-dimethyl 1-pyrroline N-oxide (DMPO) as a spin trap agent. The spin adduct (DMPO/HO•), resulting from the trapping of HO• with DMPO, showed a characteristic electron spin resonance signal which was inhibited when catalase was added, indicating that HO• was provided from H2O2. These transient species were only observed at the beginning of the reaction and were not oxygen dependent. Delgado et al. (2006) studied CWAO of phenol in some detail and high mineralization performances were observed by operating at moderate temperatures and oxygen partial pressures. The mechanism proposed for the mineralization process includes the initial polymerization of phenol with the rapid formation of a carbonaceous deposit on the catalytic surface, which is later oxidized to CO2 and H2O. At milder conditions, no mineralization was observed and only the first process operates producing the irreversible polymer deposition until the total activity loss of the catalyst for phenol elimination. Devlin and Harris (1984) had a very systematic study on the intermediate products of phenol degradation, and they found hydroquinone, catechol, benzoquinone, o-benzoquinone, maleic acid, fumaric acid, propionic acid, butyric acid, acrylic acid, oxalic acid, malonic acid, acetic acid and formic acid are the main intermediates. So they proposed the reaction paths for WAO of phenol on the basis of these intermediate products.

According to the literature (Yang et al., 1998b, 2002), wet oxidation reaction, organic molecules and unstable intermediate compounds (they are collectively referred to as A) are oxidized to form a stable intermediate product (B), then oxidized to the final product (C). This process can be expressed and shown in Fig. 2.

Sketch map of reaction process.
Figure 2
Sketch map of reaction process.

Many researchers reported different empirical formula for wastewater (Gallezota et al., 1997; Bin et al., 2000; Barbier et al., 1998), most are expressed in the following equation: - dc / dt = K 0 e - E a / RT [ C ] m [ O ] n

With K0 being the pre-exponential factor, Ea the activation energy (kJ/mol), T the temperature (K), C the organic matter concentration (mol/L), O the oxidant concentration (mol/L), t the reaction time (s), m, n the reaction order, R the gas constant [8.314 J/(mol K)].

3

3 Homogeneous CWAO

Early studies on CWAO are mainly focused on the homogeneous catalyst, and homogeneous CWAO has been studied more in Europe (Luck, 1999). Homogeneous catalyst represented by Cu, Fe, Ni, Co and Mn is better. According to the literature (Wang et al., 1993; Lin and Ho, 1996; Bi, 1999; Liu and Zhou, 1998), usually ammonia is added as a stabilizer when Cu2+ is used as a homogeneous catalyst, then alkali is added and ammonia is evaporated out after CWAO treatment, So this can precipitate out of copper and residual copper is made a resin treatment for recovery. Although homogeneous catalyst has high activity, strong selectivity and is easy to obtain, the homogeneous catalyst is difficult to recovery and easy to drain, which will cause secondary pollution easily.

4

4 Heterogeneous catalytic wet air oxidation

Heterogeneous catalyst has the advantages of high activity, easy separation and has no secondary pollution, so studies on heterogeneous catalysts have been widely concerned since late 70s in the 20th century. Heterogeneous catalyst can be divided into two categories namely non-noble metal catalysts and noble metal catalysts. In recent years, carbon materials catalysts have also been reported.

4.1

4.1 Non-noble metal catalyst

Non-noble metal catalysts are mainly one or several of Cu, Mn, Co, Ni, Bi and other metals. The advantage of non-noble metal catalysts is inexpensiveness, but catalytic activity is relatively low, the active component of non-noble metal catalyst is largely leaching , therefore, non-noble metal catalysts mainly are focused on improving their stability. Fortuny et al. (1999) had a lengthy study on the activity and stability of Cu catalysts, and the oxidation was carried out in a packed bed reactor operating in trickle flow regime at 140 °C, 0.9 MPa oxygen partial pressure, the highest residual phenol conversion was obtained for the ZnO–CuO, but deactivation of the catalyst was detected due to the dissolution of Cu. Xu et al. (2006) studied The activity and stability of the Cu0.5-xFexZn0.5A12O4 in the CWAO of phenol. All catalysts showed high catalytic activity and leach-proof ability, Fe and Cu in the leaching was down to 8 × 10−6 mg/L. When the phenol initial concentration is 1500 mg/L, reaction temperature is 150 °C, partial pressure of oxygen is 1.0 MPa, COD removal reaches more than 90% after 120 min. Leitenburg et al. (1996) utilized a series of ceria-containing mixed oxides as catalysts in the oxidation of acetic acid in water. The incorporation of even relatively small amounts of ZrO2 and MnOx or CuO into the fluorite lattice of CeO2 strongly enhances the redox properties of the material with a consequent promotion of the oxidation activity. The best results are obtained with the ternary mixed-oxides CeO2–ZrO2–CuO and CeO2–ZrO2–MnOx which benefit from a synergetic interaction between CeO2 (whose properties are already modified by the presence of Zr) and CuO or MnOx. Analysis of metal ion concentration in the effluents after reaction indicates also a high stability of the mixed-oxide catalysts under the conditions employed. Béziat et al. (1999) investigated WAO aqueous solutions of carboxylic acids in the presence of Ru/TiO2 catalyst, and the result showed that the absence of metal ions (Ru, Ti) in the effluents after reaction and the absence of particle sintering indicate also a high stability of the catalyst under the conditions employed. The catalyst can be recycled without loss of activity after the second run. The activity becomes stable after the attainment of steady-state coverage of the Ru particles by oxygen. The study of the effect of reduction–oxidation treatments of the catalyst showed that the activity depends on the oxidation state of the surface. Lin et al. (2002) made CeO2 catalyst by different heating treatment and carried out CWAO of phenol. At phenol concentrations between 400 and 2500 mg/L, oxygen pressure in the range of 0.5–1.0 MPa, and temperatures above 160 °C phenol conversion stood at more than 90% after 4 h. Under the reaction conditions, CO2 selectivity was about 80% or more after 4 h reaction. The reduced catalytic ability of regenerated CeO2 was caused either by stabilization of CeO2 during the process of regeneration or by the deposition of some reaction residues. Wang (2007) had carried out the research on CeO2–TiO2 and CeO2–ZrO2 catalysts, and the results showed that when the optimal atomic ratio of Ce and Zr was 9, activity is best. When it is used to treat acetic acid by CWAO, initial concentration of acetic acid is 5000 mg/L, reaction temperature is 230 °C, reaction pressure is 5 MPa, COD removal is 76% after 120 min and dissolution of Ce is less than 2 × 10−7 mg/L. Yang et al. (2006) developed and examined CeO2–TiO2 catalysts for CWAO. The results showed that the average crystal size of CeO2 decreased and the surface areas increased. In CWAO of acetic acid, the optimal atomic ratio of Ce and Ti was 1, and the highest COD removal was over 64% at 230 °C, 5 MPa and 180 min reaction time over Ce/Ti 1/1 catalyst. The excellent activity and stability of CeO2–TiO2 catalysts was observed in this study.

4.2

4.2 Noble metal catalyst

Noble metal catalyst is typically made for one or more of Ru, Rh, Pt, Ir, Au, Ag and other precious metal loaded on the carrier. Although noble metal is high cost, the catalytic activity is better. Components of noble metals are more stable in the CWAO process, so the stability of noble metal catalyst primarily depends on the stability of the carrier. Al2O3 is the most common carrier. Lee (2000) used Pt/Al2O3 and the sulfonated poly resin as catalysts. The result showed that oxalic acid and formic acid were readily oxidized into carbon dioxide and water at 80 °C and atmospheric pressure. The pathways of maleic acid oxidation were proposed, and the conversion of maleic acid into oxalic acid was the rate-determining step. When the sulfonated resin catalyst was present together with the Pt/Al2O3 catalyst, maleic acid could be oxidized at 80 °C and atmospheric pressure. The sulfonated resin catalyst was suggested to hydrolyze maleic acid into readily oxidizable compounds. Zhang and Karl (1998) added Ce on alumina support promotes the catalytic activity for WAO of black liquor. Pt–Pd–Ce/alumina catalyst shows a promising activity for wet catalytic oxidation of black liquor. The oxidation reaction over a Pt–Pd–Ce catalyst is characterized by an initial fast reaction step followed by a slow reaction step. Activated carbon and graphite are also good carriers. Gallezot et al. (1996) made a systematic study on carbon-supported platinum catalysts in CWAO) of aqueous solutions of carboxylic acids. CWAO reactions were performed at 0.1 or 1.5 MPa pressure in stirred, batch reactors. Total conversion of formic and oxalic acids into carbon dioxide was obtained under very mild conditions. The Pt/C catalyst was almost inactive for the oxidation of acetic acid but maleic acid was oxidized under moderate conditions which indicates that the degradation of this acid does not occur via acetic acid. Hung (2009) used CWAO of ammonia and the results of the study demonstrate that the CWO of ammonia over a nanoscale platinum–palladium–rhodium composite catalyst removed more ammonia, particularly at low temperatures. The overall by-product selectivity of the produced nitrates and nitrites varied from 22.6% to 99.9% ammonia conversion when a nanoscale platinum–palladium–rhodium composite catalyst was used. CWO thus has potential for treating highly concentrated ammonia solutions, and can help industrial plants to meet discharge standards. Pintar et al. (2001b) developed TiO2, ZrO2 or Ru supported on these oxides to treat two acidic and alkaline Kraft bleaching plant effluents by WAO. At 190 °C and 5.5 MPa total air pressure, a drastic extent of TOC removal up to 88% and 79% with addition of the oxides. The rate of TOC removal was further enhanced by deposition of metallic ruthenium on the oxides. No leaching of Ru, Ti or Zr was detected. The quality of water obtained may allow its recycling in the process. Besson et al. (2003) investigated CWAO of a representative organic compound over Au/TiO2 and compared to experiments performed over a Ru/TiO2 catalyst. These preliminary results demonstrate that gold catalysts are efficient for the degradation of this organic acid. The catalytic activity is strongly dependent on the gold particle size characterized by transmission electron microscopy (TEM) with smaller particles producing higher turnover frequencies. Modification of metal dispersion occurs during reaction, leading to minor activity. Benoit et al. (2006) carried out CWAO of oleic acid in a batch reactor on Pt/CeO2 catalyst. The Pt/CeO2 catalyst is active in the conversion of oleic acid and selective to carbon dioxide. In alkaline medium, oleic acid is initially saponified which increases the solubility of the reactant before it to be oxidized. The catalyst characterizations show no significant difference before and after the reaction. Qin et al. (2001) investigated heterogeneous catalytic wet oxidation of aqueous p-chlorophenol (p-CP) solution and compared the performance of noble metal catalysts with that of traditional manganese catalysts. The result showed that activated carbon supported catalysts showed significant higher activities for total organic carbon (TOC) reduction than those supported on alumina or cerium oxide. Pt was found to be the most active metal for p-chlorophenol oxidation. The activities of noble metal catalysts were found to correlate with heat of formation of metal oxides. CO2 is the predominant oxidation product with the formation of minor p-benzoquinone and acetic acid as intermediate compounds.

4.3

4.3 Carbon catalyst

Carbon nanotubes (CNTs) are one-dimensional carbon materials, and have gained more attention because of their unique chemical and thermal stabilities. Gomes et al. (2004) tested multi-walled nanotubes (MWNT), carbon xerogels (CX) and activated carbon (AC) supported on platinum catalysts in the treatment of aqueous aniline solutions by CWAO. All catalysts presented a very high activity for the removal of aniline and total organic carbon (TOC). Catalyst activity and selectivity toward CO2 formation were found to depend on the nature of the support and concentration of oxygen containing functional groups on the surface of the materials. Garcia et al. (2004 and 2006) made a further research on the basis of Gomes and prepared Pt/CNTs catalyst by using three different Pt precursors for CWAO of aniline. The result showed that when the initial aniline concentration is 2000 mg/L, reaction temperature is 200 °C, oxygen partial pressure is 0.69 MPa, aniline removal is more than 98% after 2 h. A direct relationship between metal load and catalyst stability was found and attributed to the strength of metal-support interactions. Rodríguez et al. (2008) tested the catalytic performance of 3 wt.% copper supported on carbon nanofibers (CNFs) in liquid phase oxidation using a batch stirred tank microreactor in order to determine the decolorization and total organic carbon (TOC) removal efficiency in washing textile wastewater (WTW). TOC removal and toxicity reduction were as high as 74.1% and 43%, respectively at 140 °C and 8.7 bar, after 180 min reaction. Application of CWAO to the treatment of a textile effluent at 160 °C and 0.87 MPa of oxygen partial pressure showed that the use of a Cu/CNF catalyst significantly improves the TOC and color removal efficiencies. CWAO catalyst carrier carbon nanotubes have a large specific surface area, pore structure, appropriate and good stability, etc and are promising catalyst supports, but because carbon nanotubes have not been industrialized, making such catalysts practical applicable has been under a lot of constraints.

5

5 Application of CWAO to wastewater treatment

As mentioned above, heterogeneous catalysts have been extensively studied for the CWAO of various model compounds. However, few works have focused on the feasibility of solid catalysts for the treatment of real wastewater. Some of studies on the CWAO of industrial wastewaters are summarized in Table 1.

Table 1 Wastewater treatment by CWAO.
The treated material References Catalyst Treatment effect
Emulsification wastewater Zeng et al. (2006) CuO/γ–Al2O3 CODCr removal is 88.4%
Carbohydrate-containing waste streams Patrick and Abraham (2000) Pt/Al2O3 Conversion rate of glucose is 70%
Perfume wastewater Yang et al. (1998a,b) ABO3 rare earth COD, TOC and colorindex removal could reach 69.1%,74.8% and 79.5% respectively
Nitrogen-containing wastewater Huang et al. (2001) SDB/Pt Conversion rate of NH3 is from 80% to 100%
Phenol-containing wastewater Cao et al. (2003) Pt/AC, Ru/AC Cu/AC, /AC, Mn/AC, Ru/Al2O3 Conversion rate of phenol is about 100%
Paper and pulp industrial waste liquor Akolekar et al., (2002) Cu, Mn, Pd, Cu/Mn, Mn/Pd, Cu/Pd The highest TOC removal is more than 84%
Alcohol-distillery liquors Belkacemi et al. (2000) Pt/Al2O3, Mn/Ce, Cu(II)-exchanged NaY zeolite The highest TOC removal is achieved with Mn/Ce and Cu(II)/NaY catalysts
Wastewater in pesticide plant Zhao et al. (2008) Cu/Mn COD removal is 93.2% and the concentration of leached Mn and Cu is lower
Acrylic acid wastewater Li et al. (2007) MnO2–CuO–CeO2–Fe2O3 COD reduces from 80,000 mg/L to nearly 2000 mg/L and COD removal is 68%
Kraft bleaching plant effluents Pintar et al. (2001a) TiO2, ZrO2, Ru/TiO2, and Ru/ZrO2 99% of TOC removal was achieved within 8 h of reaction at 190 °C and 5.5 MPa of air
Kraft bleaching plant effluents Pintar et al. (2001b) TiO2 and Ru/TiO2 The ultimate destruction of parent organics and their mineralization are CO2
Kraft bleaching plant effluents Pintar et al. (2004) TiO2 and Ru/TiO2 The reaction was characterized by a fast initial step with rapid fragmentation of large molecules to short organic acids, followed by a slow reaction step as these acids, especially acetic acid, tend to be resistant to further oxidation

Pulp and paper industry uses very large amounts of water during processing. Especially, the bleaching process produces refractory organic compounds including lignin and polysaccharide fragments, organic acids, aliphatic alcohols, etc., which are hardly degraded by biological treatment. Pintar et al. (2001a) investigated the CWAO of acidic and alkaline Kraft bleaching plant effluents (TOC = 665 and 1380 mg/L, respectively) in a batch slurry reactor. The results showed that TiO2 and ZrO2 were considerably active in the TOC removal of both acidic and alkaline effluents, and the rate of TOC removal increased with the specific surface area of metal oxides. Doping of Ru on these metal oxides enhanced the catalytic activity, and thus more than 99% of TOC removal was achieved within 8 h of reaction at 190 °C and 5.5 MPa of air. The CWAO of Kraft bleach plant effluents in a trickle-bed reactor packed with Ru/TiO2 demonstrated the ultimate destruction of parent organics and their mineralization to CO2, and proved the long-term activity and chemical stability of the Ru/TiO2 catalyst (Pintar et al., 2001b). The reaction was characterized by a fast initial step with rapid fragmentation of large molecules to short organic acids, followed by a slow reaction step as these acids, especially acetic acid, tend to be resistant to further oxidation (Pintar et al., 2004). Complete destruction of acetic acid is not necessary because acetic acid can be eliminated by biological treatment due to its low ecotoxicity. Therefore, the CWAO process can be adapted as a pretreatment process integrated with subsequent biological treatment of acetic acid to recycle the industrial effluents.

6

6 Conclusion

CWAO is an effective advanced oxidation technology used to treat high concentrations of toxic and hazardous wastewater, and further studies are necessary to develop more active and stable catalysts which can be effectively utilized on industrial scale. Base metal oxide catalysts are more desirable than noble metals in terms of cost and resistance to poisoning by halogen-containing substance, though their activities are still lower than noble metals. Among them, Cu, Mn, and Ce are the most prospective species to compete with noble metals. At present, reaction mechanism of CWAO is lack of study. Detection of free radicals is less reported , but a more dynamic model of the reaction is reported. In short, improving the catalytic activity and stability, studying reaction mechanism and dynamic model in depth play an important role in the promotion of CWAO technology, and these are very significant for the better treatment of high concentrations of toxic and hazardous substances.

References

  1. , , , , . Appl. Catal., A. 2002;236:255-262.
  2. , , , , , , . J. Catal.. 1998;177:378-385.
  3. , . Ind. Catal.. 1999;5:24-30.
  4. , , , , . J. Catal.. 1999;182:129-135.
  5. , , , , . Chinese J. Environ. Sci.. 2000;21:77-80.
  6. , , , , . Appl. Catal., A. 2000;199:199-209.
  7. , , , , , . Catal. Commun.. 2003;4:471-476.
  8. , , , , . React. Kinet. Catal. Lett.. 2006;87:269-279.
  9. , , , , . Catal. Today. 2003;88:37-47.
  10. , , . Ind. Eng. Chem. Fundam.. 1984;23:387-391.
  11. , , , , . Catal. Commun.. 2006;7:639-643.
  12. , , , , . J. Hazard. Mater.. 1999;64:18l-193.
  13. , , , . Appl. Catal., B. 1996;9:L11-L17.
  14. , , , , . J. Catal.. 1997;168:104-109.
  15. , , , , , , . Appl. Catal., B. 2004;54:175-182.
  16. , , , , , , . Catal. Today. 2004;102–l03:10l-109.
  17. , , , , , , . Carbon. 2006;44:2384-2391.
  18. , , , . Water Res.. 2001;35:2113-2120.
  19. , . J. Hazard. Mater.. 2009;163:180-186.
  20. , , , . AIChE J.. 1991;37:1687-1697.
  21. , , , , , . Appl. Catal., B. 1996;11:L29-L35.
  22. , . Catal. Today. 1996;1996(27):195-202.
  23. , , . Appl. Catal. B: Environ.. 1996;9:133-147.
  24. , , . Water Purif. Technol.. 1998;65:6-10.
  25. , . Catal. Today. 1999;53:8l-9l.
  26. , . Catal. Today. 2000;63:249-255.
  27. , , , , . Water Res.. 2002;36:3009-3014.
  28. , , , , , . J. Jilin Inst. Chem. Technol.. 2007;24:3-6.
  29. , , . Catal. Today. 2007;124:172-184.
  30. , , . Environ. Sci. Technol.. 2000;34:3480-3488.
  31. , , , . Appl. Catal. B: Environ.. 2001;30:123-139.
  32. , , , . Appl. Catal. B: Environ.. 2001;31:275-290.
  33. , , , , . Appl. Catal. B: Environ.. 2004;47:143-152.
  34. , , , . Appl. Catal., B. 2001;29:115-123.
  35. , , , , . Water Res.. 2002;36:482l-4829.
  36. , , , , , , . J. Supercrit. Fluids. 2008;46:163-172.
  37. , , , , . Environ. Chem.. 1993;12:408-413.
  38. Wang, J.B., 2007. Beijing, Tsinghua University.
  39. , , , , . Catal. Commun.. 2006;7:513-517.
  40. , , , , . China Environ. Sci.. 1998;18:170-172.
  41. , , , . Res. Environ. Sci.. 1998;11:62-64.
  42. , , , , . J. Harbin Instit. Technol.. 2002;34:540-543.
  43. , , , , , . Appl. Surf. Sci.. 2006;252:8499-8505.
  44. , , . Appl. Catal., B. 1998;17:321-332.
  45. , , , , . Chem. Ind. Eng. Prog.. 2006;25:213-217.
  46. , , , , , , . Chinese J. Environ. Eng.. 2008;2:340-343.

Fulltext Views
38

PDF downloads
3
View/Download PDF
Download Citations
BibTeX
RIS
Show Sections

Suggested read for related articles:

© Copyright 2025 – Arabian Journal of Chemistry.

Published by Scientific Scholar on behalf of King Saud University together with Saudi Chemical Society, Riyadh, Saudi Arabia.

ISSN (Print): 1878-5352
ISSN (Online): 1878-5379
Scientific Scholar CrossRef Creative Commons Open Acess Portico