5.2
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
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:

Original Article
2025
:18;
2882024
doi:
10.25259/AJC_288_2024

Selective extraction of germanium from lead slag washing wastewater by tannic acid coordination and precipitation method

, , , , , ,
aState Key Laboratory of Complex Nonferrous Metal Resources Clean Utilization, Kunming University of Science and Technology, Kunming, Yunnan 650093, China
bKey Laboratory of Unconventional Metallurgy, Ministry of Education, Kunming, Yunnan 650093, China
cFaculty of Metallurgical and Energy Engineering, Kunming University of Science and Technology, Kunming, Yunnan 650093, China

Corresponding authors: E-mail addresses: truepsyche@sina.com (K. Yang), zhanglibopaper@126.com (L. Zhang)

Received: , Accepted: ,
© 2025 Arabian Journal of Chemistry - Published by Scientific Scholar
Licence
This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-Share Alike 4.0 License, which allows others to remix, transform, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.

Abstract

With rapid development of the global digital economy and aerospace industry, the recovery of germanium from the “three wastes” (Waste gas, wastewater, and waste residue) is an important way to alleviate resource shortages. This paper proposes a selective extraction method for germanium from lead slag washing wastewater by tannic acid (TA) coordination. The selective mechanism was investigated by analyses using Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) spectra of the precipitate, and the UV spectra of TA-Zn, TA-Fe(II), and TA-Ge. The results indicate that TA exhibits much higher selectivity for Ge compared to Zn and Fe(Ⅱ), with the hydroxyl group of TA phenol reacting with Ge and not with Zn and Fe(Ⅱ). At pH 3∼6, there was no shift in the TA-Zn and TA-Fe(II) titration curve, while the TA-Ge titration curve exhibited a redshift from 275 to 299 nm (the TA characteristic UV absorption peaks), and it was evident that TA selectively coordinates with Ge at a molar ratio of Ge:TA=4:1. The appropriate time for selective extraction of germanium from lead slag washing wastewater is 2 mins, with 96.63% Ge precipitation, and just 1.25% Zn, and 5.08% Fe(Ⅱ) precipitation. Zn mainly precipitates as ZnHSO4, and the main compound of Fe(Ⅱ) is Fe(OH)2. After roasting to remove organic matter from the precipitation, the non-oxide (germanate) was converted to oxide (GeO2) with a Ge content of 32.5%. In addition, the treated wastewater can be reused in the production process.

Keywords

Germanium
Lead slag washing wastewater
Selective coordination
Tannic acid

1. Introduction

Germanium is a typically rare and dispersed element. It is a trace component in the Earth’s crust and natural waters and is the most important semiconductor material besides silicon [1]. Ge minerals are not present in economically mineable aggregates, but they are scattered in their surroundings. Therefore, Ge is obtained as an accompanying element during the processing of other raw materials [2]. Germanium-based products possess unique properties such as strong radiation resistance, high detection efficiency, and high infrared refractive index. They play an irreplaceable role in the defense, military, and civilian fields such as infrared optics, fiber optic communications, and solar cells [3-7]. With rapid development of the global digital economy and aerospace industry, the supply-demand gap for germanium is increasingly prominent, and the recovery of germanium from the “three wastes” is an important way to alleviate resource shortages.

In China, germanium production mainly relies on the by-product of lead-zinc smelting, zinc oxide fumes as raw material [8]. During leaching, the fumes generate lead slag washing wastewater containing trace amounts of germanium. Enterprises typically discharge and dispose of this wastewater externally, leading to significant waste of germanium resources. Current reports on germanium recovery from wastewater mainly include three methods. Liu et al. achieved efficient recovery (90%) of germanium from wastewater using chloride distillation [9], while it is not suited for wastewater with a high content of other metal elements. Xi et al. accomplished germanium recovery by coprecipitating it with iron through neutralization and precipitation, The Ge precipitation yield was greater than 98% [10], while it was also not suitable for wastewater with a high content of other metal elements. Wang utilized resin adsorption followed by acid desorption to recover germanium, The average recovery rate of Ge reached 95% [11] but the process was very costly.

Tannic acid (TA) is a heterogeneous mixture of gallic acid, low molecular weight gallic acid derivatives, and gallotannins [12,13]. TA can adsorb metal ions in wastewater, achieving the purpose of water purification [14]. Tannins (hydrolysable tannins) containing several o-dihydroxy and trihydroxy aromatic rings (polyhydroxy polyphenols) are capable of forming chelates with metal ions [15]. Our research team previously utilized TA for extraction from wastewater [16] and achieved selective recovery of Ge. The precipitation yield of Ge was 97.19%. We employed the TA coordination and precipitation method to extract germanium from lead slag washing wastewater. By examining and comparing the reactivity and mechanism of different elements in wastewater with TA, we analyzed the feasibility of the process and conducted research on the productization of the extracted Ge.

2. Materials and Methods

2.1. Materials

The wastewater from lead-zinc smelting used in the experiment was sourced from a lead-zinc smelting enterprise in Yunnan, China. Its specific composition has been shown in Table 1, with the main elements being Zn and Fe(Ⅱ), at concentrations of 56.11 g/L and 2.745 g/L, respectively, while the Ge content is 35.5 mg/L. The Zn and Fe(Ⅱ) concentrations are 1580.56 and 77.32 times higher than that of Ge, making them the elements most likely to affect germanium enrichment. Therefore, this study primarily investigates the reaction capability and mechanism of Zn, Fe(Ⅱ), and Ge with TA.

Table 1. Main elemental components of lead slag washing wastewater (g/L).
Zn Fe(Ⅱ) Fe(Ⅲ) Ca SiO2 As Ge*
56.11 2.745 0.058 0.028 0.057 1.03 35.5
* mg/L

All chemical reagents used in the experiment were analytically pure, as shown in Table 2. The solution was prepared with deionized water.

Table 2. List of reagents used in the experiment.
Reagent Purity Molecular formula Manufacturer
Tannic acid AR C76H52O46 Tianjin Zhiyuan Reagent Co., Ltd
Germanium dioxide AR GeO2 Shanghai Macklin Biochemical Technology Co., Ltd
Zinc Sulfate AR ZnSO4 Tianjin Zhiyuan Reagent Co., Ltd
Ferrous sulfate AR FeSO4 Tianjin Zhiyuan Reagent Co., Ltd
Sulfuric acid 95%-98% H2SO4 Xilong Scientific Co., Ltd
Sodium hydroxide AR NaOH Tianjin Zhiyuan Reagent Co., Ltd

2.2. Analysis

The IRIS Intrepid II XSP inductively coupled plasma optical emission spectrometer (ICP-OES) was used to analyze the elemental content of the solution, precipitate, and roasted solid. All UV-visible spectrophotometric measurements were conducted using a Shimadzu UV-2600 spectrophotometer. The pH values were measured using a PH8008 intelligent sensor pH meter. X-ray photoelectron spectroscopy (XPS) spectra were acquired using a Thermo Scientific K-Alpha instrument. Time of flight- secondary ion mass spectrometry (TOF-SIMS) analysis was performed using a PHI NanoTOFII instrument from Germany. Infrared spectra were measured with an iS50 FTIR spectrometer.

2.3. Experiment

Extraction was performed using TA on both the simulated solution and the lead slag washing wastewater. The excellent flocculation ability of TA can precipitate metal ions from the solution. Three sets of simulated solutions with equal mass concentrations of Zn, Fe(Ⅱ), and Ge were prepared by the authors, with metal ion concentrations selected at 50 mg/L, 75 mg/L, and 100 mg/L. TA, twenty times the mass concentration of metal ions, was added to the simulated solutions. The reactions were conducted at 60°C for 60 mins, with pH maintained at 3. After completion of the reactions, liquid-solid separation was performed. The precipitation yield, which is the ratio of the element content in the solid phase after solid-liquid separation to the element content in the original solution, of Zn, Fe(Ⅱ), and Ge was determined. The element content can be measured by ICP. TA, twenty-five times the mass concentration of metal ions, was added to the lead slag washing wastewater. The reactions were conducted at 60°C for 30 mins, with pH maintained at 3. After solid-liquid separation, the precipitation yield was determined and the solid precipitates were roasted.

UV-visible spectrophotometry was employed to investigate the reaction mechanisms of Zn, Fe(Ⅱ), and Ge with TA. The procedure involved adding 2980 μL of pH 3, 4, 5, and 6 acetic acid-sodium acetate buffer solution to a colorimetric dish, followed by the addition of 20 μL of 1 mmol/L TA solution. After thorough mixing, 1 mmol/L Zn/Fe(Ⅱ)/Ge solutions were incrementally added to the mixed solution using a microsyringe, with each addition being 4 μL for a total of 20 μL. Subsequently, Zn/Fe(Ⅱ)/Ge metal ion solutions were added incrementally, with each addition being 20 μL for a total of 180 μL, followed by incremental additions of Zn/Fe(Ⅱ)/Ge solutions, with each addition being 100 μL for a total of 300 μL. The solution was thoroughly mixed after each addition, followed by a 2-min incubation for complete reaction. The absorbance values of the mixed solutions were recorded at 200∼400 nm using a UV-visible spectrophotometer. The titration experiments were repeated thrice. All solutions were ambient and freshly prepared on the day of use.

3. Results and Discussion

3.1. Study of the ability of Zn, Fe(Ⅱ), and Ge to interact with TA

The residual concentrations of Zn, Fe(Ⅱ), and Ge in the reaction solution were measured to assess their respective interactions with TA, as depicted in Figures 1(a-c). It was observed that under all three mass concentrations, Ge exhibited a stronger interaction capability with TA compared to Zn and Fe(Ⅱ). The reaction between Ge and TA was rapid, reaching equilibrium in approximately 2 mins, with precipitation rates of Ge being 86.02%, 95.04%, and 97.08%, respectively. In contrast, the reactions of Zn and Fe(Ⅱ) with TA proceeded relatively slowly, requiring 40 mins to reach equilibrium, with precipitation rates of Zn and Fe(Ⅱ) being less than 30%. Therefore, it is feasible to selectively separate Ge from Zn and Fe(Ⅱ) using TA, and efficient separation of Zn, Fe(Ⅱ), and Ge can be achieved by adjusting the reaction time with TA.

The ability of Zn, Fe(Ⅱ), and Ge to interact with TA at (a) 50 mg/L, (b) 75 mg/L, (c) 100 mg/L.
Figure 1.
The ability of Zn, Fe(Ⅱ), and Ge to interact with TA at (a) 50 mg/L, (b) 75 mg/L, (c) 100 mg/L.

XPS O1s fine spectrum analysis was conducted on TA, TA-Zn, TA-Fe(Ⅱ), and TA-Ge, as seen in Figure 2. In the TA O1s XPS spectrum, two peaks appeared at 533.28 eV and 531.98 eV, with a peak area ratio of approximately 2.81:1. The O1s XPS spectra of TA-Zn and TA-Fe(Ⅱ) were consistent with that of TA, whereas in the TA-Ge O1s XPS spectrum, the positions of the two peaks remained unchanged while the area decreased to approximately 1.98:1. This shift indicates a lowering of the binding energy of the TA-Ge O1s spectrum towards the low-energy end, suggesting an ion exchange between the hydrogen ions on the -OH of TA and the metal ions to form O-M complexes. This results in an increase in electron cloud density around the oxygen atom and a decrease in the binding energy of the -OH bond [17]. Based on the XPS analysis, it is inferred that TA only coordinates with Ge, while TA-Zn and TA-Fe(Ⅱ) may be attributed to the physical adsorption of Zn and Fe(Ⅱ) by TA.

XPS fine spectral analysis of (a) TA O1s, (b) TA-Zn O1s, (c) TA-Fe(II) O1s, (d) TA-Ge O1s.
Figure 2.
XPS fine spectral analysis of (a) TA O1s, (b) TA-Zn O1s, (c) TA-Fe(II) O1s, (d) TA-Ge O1s.

Fourier transform infrared (FT-IR) analysis was performed on TA, TA-Zn, TA-Fe(Ⅱ), and TA-G; results have been depicted in Figure 3. The stretching vibration peak of O-H was observed at 3362 cm-1 [18], and the vibration peak of C=O was observed at 1716 cm-1 [19]. Three absorption peaks at 1612 cm-1, 1534 cm-1, and 1448 cm-1 correspond to the benzene ring [20,21]. The vibration peak of O-H was detected at 1320 cm-1, and the stretching vibrations of C-O at 1088 cm-1 and 1026 cm-1 are characteristic infrared absorption spectra of polysaccharides [22,23]. The height of the O-H vibrational peak at 1320 cm-1 in the TA-Ge FT-IR spectra was found to be reduced in the comparison, demonstrating that the hydroxyl group of TA phenol reacted with Ge and did not coordinate with Zn and Fe(Ⅱ).

FT-IR spectra of TA, TA-Zn, TA-Fe(Ⅱ), and TA-Ge.
Figure 3.
FT-IR spectra of TA, TA-Zn, TA-Fe(Ⅱ), and TA-Ge.

3.2. Reaction mechanisms of Zn, Fe(Ⅱ) and Ge with TA

Under pH conditions ranging from 3 to 6, the UV spectra of the TA-Zn titration curve are shown in Figure 4. It can be observed that the UV spectrum of the TA-Zn titration curve primarily exhibits two absorption peaks at 213 nm and 275 nm, both of which are characteristic peaks of TA [24]. With the addition of Zn, there is no shift in the position of the TA characteristic absorption peaks, indicating that no coordination reaction occurs between TA and Zn. This validates the results obtained from XPS and FT-IR analyses. The decrease in peak intensity is attributed to the dilution of the TA solution by the addition of the Zn solution.

UV spectra of TA-Zn titration curves at (a) pH 3, (b) pH 4, (c) pH 5, (d) pH 6.
Figure 4.
UV spectra of TA-Zn titration curves at (a) pH 3, (b) pH 4, (c) pH 5, (d) pH 6.

Under pH conditions ranging from 3 to 6, the UV spectra of the TA-Fe(Ⅱ) titration curve have been depicted in Figure 5. It can be observed that from pH 3 to 5, the UV spectra of the TA-Fe(Ⅱ) titration curve also exhibit two main absorption peaks at 213 nm and 275 nm, both belonging to the characteristic peaks of TA. With the addition of Fe(Ⅱ), there is no change in the position of the TA characteristic absorption peaks, indicating that no coordination reaction occurs between TA and Fe(Ⅱ). This confirms the results obtained from XPS and FT-IR analyses. At pH 6, a slight redshift is observed in the UV spectrum of the TA-Fe(Ⅱ) titration curve, indicating that coordination between TA and Fe(Ⅱ) begins after pH > 6. At pH 3, the physical adsorption of TA to Fe(Ⅱ) is stronger than that to Zn, resulting in a higher precipitation rate of Fe(Ⅱ) compared to Zn at the same concentration.

UV spectra of TA-Fe(Ⅱ) titration curves at (a) pH 3, (b) pH 4, (c) pH 5, (d) pH 6.
Figure 5.
UV spectra of TA-Fe(Ⅱ) titration curves at (a) pH 3, (b) pH 4, (c) pH 5, (d) pH 6.

Under pH conditions ranging from 3 to 6, the UV spectra of the TA-Ge titration curve have been shown in Figure 6. It can be observed that at pH 3, the UV spectrum of the TA-Ge titration curve exhibits a red shift to 299 nm with the addition of Ge, indicating coordination between TA and Ge. The coordination of the -OH in the TA structure with metal ions, induces changes in the distribution of electrons on the aromatic ring, leading to a redshift in the characteristic absorption wavelength of TA spectra [25]. Furthermore, it can be observed from the figure that as the pH increases, the coordination effect becomes more significant. This is attributed to the increased pH facilitating deprotonation of the -OH, forming O2- for coordination [26]. Figure 7 illustrates the changes in absorbance of the TA-Ge complex at 299 nm, which gradually levels off at a molar ratio of Ge to TA of 4:1.

UV spectra of TA-Ge titration curves at (a) pH 3, (b) pH 4, (c) pH 5, (d) pH 6.
Figure 6.
UV spectra of TA-Ge titration curves at (a) pH 3, (b) pH 4, (c) pH 5, (d) pH 6.
(a-b) Absorbance change of TA-Ge complex at 299 nm.
Figure 7.
(a-b) Absorbance change of TA-Ge complex at 299 nm.

3.3. Extraction of germanium from lead slag washing wastewater

The extraction of Ge, Fe, and Zn from lead slag washing wastewater using TA at different times has been depicted in Figure 8, with a Ge extraction temperature of 60°C and a pH of 3. The concentration of TA added was 25 times the mass concentration of Ge ions. It can be observed that with increasing time, the content of Ge, Zn, and Fe in the lead slag washing wastewater gradually decreases. Ge precipitation is nearly completed in about 2 mins, with residual Ge content at 1.2 mg/L and a precipitation rate reaching 96.63%. Zn precipitation reaches equilibrium after approximately 20 mins, with residual Zn content at 49.95 g/L and a precipitation rate of 10.98%. Fe(Ⅱ) precipitation completes after around 20 mins, with residual (Ⅱ) content at 2.35 g/L and a precipitation rate of 14.24%. To effectively separate Ge, a precipitation time of 2 mins is selected, during which the precipitation rates of Zn and Fe(Ⅱ) are only 1.25% and 5.08%, respectively.

(a) Content of Ge, Fe, and Zn in the solution after extraction, (b) precipitation yield of Ge, Fe, and Zn after extraction.
Figure 8.
(a) Content of Ge, Fe, and Zn in the solution after extraction, (b) precipitation yield of Ge, Fe, and Zn after extraction.

The figures of lead slag washing wastewater, TA-Ge, and post-precipitation liquid have been illustrated in Figure 9. It can be observed that after TA extraction of Ge, the post-precipitation liquid becomes clear and bright, allowing it to be returned and reused in the production process.

 Figures of (a) wash wastewater, (b) TA-Ge, (c) post-germanium precipitation solution.
Figure 9.
 Figures of (a) wash wastewater, (b) TA-Ge, (c) post-germanium precipitation solution.

TOF-SIMS analysis of TA-Ge is conducted, and the results of cation and anion fragments are shown in Figure 10. Ge-containing fragments include Ge, GeO, Ge2O2H, and C2H3GeO2, indicating coordination between Ge and TA. Zn fragments include Zn and ZnHSO4, suggesting that Zn is physically adsorbed in the form of ZnHSO4, while Fe(Ⅱ) fragments include FeO2 and FeO3, representing Fe(OH)2 formed during air drying, indicating Fe(Ⅱ) adsorption in the form of Fe(OH)2.

(a) TOF-SIMS positive spectra of TA-Ge, (b) TOF-SIMS negative spectra of TA-Ge.
Figure 10.
(a) TOF-SIMS positive spectra of TA-Ge, (b) TOF-SIMS negative spectra of TA-Ge.

The TOF-SIMS anode surface scan of TA-Ge has been presented in Figure 11, showing localized enrichment of Zn and Fe(Ⅱ), attributed to physical adsorption, while the distribution of Ge is relatively uniform, confirming the coordination precipitation of TA with Ge.

TOF-SIMS anodic surface sweep of TA-Ge.
Figure 11.
TOF-SIMS anodic surface sweep of TA-Ge.

High-temperature roasting of TA-Ge converts non-oxides (germanates) into oxides (GeO2) and removes organic matter, which is shown in Figure 12, with a Ge grade reaching 32.5%, and a total Ge recovery rate of 96.65% from the wastewater. Almost all Ge in the treated lead slag washing wastewater is extracted, while the presence of a certain amount of Zn allows for its reuse in the process.

The GeO2 after roasting at 500°C.
Figure 12.
The GeO2 after roasting at 500°C.

4. Conclusions

In this paper, we propose a method to extract Ge from lead slag scrubber wastewater using selective coordination of TA and determine the coordination between TA and Ge using XPS, FTIR spectroscopy, and UV characterization. The results indicate that compared to Zn and Fe(Ⅱ), TA exhibits higher selectivity towards Ge extraction. The -OH of TA reacts with Ge without coordinating with Zn and Fe(Ⅱ). UV-visible spectrophotometry confirms that the coordination ratio between TA and Ge was Ge:TA=4:1, with the UV absorption peak of the TA-Ge complex at 299 nm. The optimal time for selective extraction of Ge from lead slag washing wastewater using TA was 2 mins, resulting in a Ge precipitation rate of 96.63%, while the precipitation rates for Zn and Fe(Ⅱ) were only 1.25% and 5.08%, respectively. From TOF-SIMS results, it was observed that Zn primarily physically adsorbed and precipitated as ZnHSO4, while Fe(Ⅱ) mainly precipitated in the form of Fe(OH)2. Finally, the precipitate is calcined to produce GeO2, with a grade of 32.5%. The treated wastewater can be recycled back into the process. This study provides a recycling solution for wastewater generated during lead-zinc smelting, elucidates the coordination mechanisms between TA and Ge, Zn, and Fe(Ⅱ)for the first time, and addresses both environmental pollution and the scarcity of germanium resources by extracting Ge from wastewater using TA.

Acknowledgment

This work was supported by Joint Special Project of Basic and Applied Basic Research in Yunnan Province [No.202401BN070001-006], Yunnan Fundamental Research Projects [grant NO.202301BE070001-020], Yunnan Fundamental Research Projects [202301AT070480], Major Science and Technology Project of Yunnan Province [grant number 202202AB080005], and The Introduction of Talent Research and Start-up Fund for Kunming University of Science and Technology [KKKP201852032].

CRediT authorship contribution statement

Kehan Liu: Writing - original draft, Methodology, Investigation, Formal analysis, Conceptualization. Yan Hong: Formal analysis, Visualization. Jie Dai: Formal analysis, Visualization. Haokai Di: Conceptualization, Visualization. Ming Liang: Conceptualization, Supervision. Kun Yang: Conceptualization, Methodology, Resources, Supervision, Project administration, Funding acquisition. Libo Zhang: Conceptualization, Methodology, Resources, Supervision, Project administration, Funding acquisition.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Declaration of Generative AI and AI-assisted technologies in the writing process

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

References

  1. , , , , . Mechanism of extracting germanium from Ge-containing solution with Tannins. Metals. 2023;13:774. https://doi.org/10.3390/met13040774
    [Google Scholar]
  2. , , , , , , . Precipitation of germanium from sulphate solutions containing tin and indium using tannic acid. Applied Sciences. 2019;9:966. https://doi.org/10.3390/app9050966
    [Google Scholar]
  3. , , , , . Study on the current situation of germanium mining resources in China and countermeasures for their sustainable development. Mineral Conservation and Utilization. 2017;2:6-12. https://doi.org/10.13779/j.cnki.issn1001-0076.2017.02.002
    [Google Scholar]
  4. , . Application of metallic germanium in high-tech fields. Coal & Chemicals. 2018;41:32-34+37. https://doi.org/10.19286/j.cnki.cci.2018.02.010
    [Google Scholar]
  5. , , . Global substance flow analysis of gallium, germanium, and indium: quantification of extraction, uses, and dissipative losses within their anthropogenic cycles. Journal of Industrial Ecology. 2015;19:890-903. https://doi.org/10.1111/jiec.12287
    [Google Scholar]
  6. , . Germanium: A review of its US demand, uses, resources, chemistry, and separation technologies. Separation and Purification Technology. 2021;275:118981. https://doi.org/10.1016/j.seppur.2021.118981
    [Google Scholar]
  7. , , , , , . Recent advances in the recovery of germanium during the zinc refining process. Chemical Engineering Journal. 2022;446:137445. https://doi.org/10.1016/j.cej.2022.137445
    [Google Scholar]
  8. , , , , , , . Low environmental impact process for germanium recovery from an industrial residue. Minerals Engineering. 2018;128:106-114. https://doi.org/10.1016/j.mineng.2018.07.022
    [Google Scholar]
  9. , , , , , , , , . The process of Ti recovery in a kind of germanic waste liquid from low concentration. CN106756126A.
  10. , , , , , , , , , . Method for recovering germanium from germanium-containing waste liquid. CN113652558A.
  11. . A method of germanium in the germanic waste liquid of recycling. CN106086481B.
  12. , , , , . Binding and precipitation of germanium(IV) by four hydrolyzable tannins. BioResources. 2020;15:1205-1232. https://doi.org/10.15376/biores.15.1.1205-1232
    [Google Scholar]
  13. , , , , . Binding and precipitation of germanium(IV) by penta-O-galloyl-β-d-glucose. Journal of Agricultural and Food Chemistry. 2018;66:11000-11007. https://doi.org/10.1021/acs.jafc.8b03653
    [Google Scholar]
  14. , . Tannins for wastewater treatment. SN Applied Sciences. 2020;2:1-21. https://doi.org/10.1007/s42452-020-2879-9
    [Google Scholar]
  15. , , , , . Behavior of tannins in germanium recovery by tannin process. Hydrometallurgy. 2008;93:140-142. https://doi.org/10.1016/j.hydromet.2008.03.006
    [Google Scholar]
  16. , , , , , , , . Removal kinetics and reaction mechanism of germanium from waste solutions with tannic acid enhanced by ultrasonic. Chemical Engineering and Processing - Process Intensification. 2023;192:109491. https://doi.org/10.1016/j.cep.2023.109491
    [Google Scholar]
  17. . Study on ultrasonic intensification technology for germanium extraction by tannin precipitation from germanium-containing leach solution 2021 https://doi.org/10.27200/d.cnki.gkmlu.2021.001175
  18. , , , , , . Efficient stepwise-purification and mechanism of germanium-containing materials with ammonium. Arabian Journal of Chemistry. 2023;16:105119. https://doi.org/10.1016/j.arabjc.2023.105119
    [Google Scholar]
  19. , , . Development of methodology for identification the nature of the polyphenolic extracts by FTIR associated with multivariate analysis. Spectrochimica acta. Part A, Molecular and Biomolecular Spectroscopy. 2016;153:94-101. https://doi.org/10.1016/j.saa.2015.08.020
    [Google Scholar]
  20. . G. Sokrates: Infrared and Raman characteristic group frequencies: Tables and charts. Colloid and Polymer Science. 2004;283:235. https://doi.org/10.1007/s00396-004-1164-6
    [Google Scholar]
  21. , , , . A specific case in the classification of woods by FTIR and chemometric: Discrimination of Fagales from Malpighiales. Cellulose. 2014;21:261-273. https://doi.org/10.1007/s10570-013-0093-2
    [Google Scholar]
  22. , , . Classification of red wines analysed by middle infrared spectroscopy of dry extract according to their geographical origin. OENO One. 2016;35:165. https://doi.org/10.20870/oeno-one.2001.35.3.1703
    [Google Scholar]
  23. , , , , . Simultaneous determination of sulfur, nitrogen and ash for vegetable tannins using ATR-FTIR spectroscopy and multivariate regression. Microchemical Journal. 2019;149:103994. https://doi.org/10.1016/j.microc.2019.103994
    [Google Scholar]
  24. , , , . Analysis of iron complexes of tannic acid and other related polyphenols as revealed by spectroscopic techniques: implications in the identification and characterization of iron gall inks in historical manuscripts. ACS Omega. 2022;7:27937-27949. https://doi.org/10.1021/acsomega.2c01679
    [Google Scholar]
  25. , , , , . Spectrophotometric determination of tannic acid-Fe3+ reaction binding constants and their stoichiometric ratios. Journal of Forest Engineering. 2018;3:47-52.
    [Google Scholar]
  26. , , , , . Metal ion interactions with methyl gallate characterized by UV spectroscopic and computational methods. Food Chemistry. 2019;293:66-73. https://doi.org/10.1016/j.foodchem.2019.04.083
    [Google Scholar]

Fulltext Views
1,772

PDF downloads
779
View/Download PDF
Download Citations
BibTeX
RIS
Show Sections

Suggested read for related articles: