Treatment of Cyanide Gold Extraction Wastewater by Adding Different Concentrations of Persulfate Oxidation AITranslate
Abstract AITranslate
Cyanide wastewater produced in cyanide gold extraction process is complicated in composition and difficult to treat. Direct discharge without treatment will cause great harm to the environment. The existing cyanide wastewater treatment methods generally have the problems of high energy consumption and immature development. Therefore，the search for an efficient，environmentally friend and energy-saving treatment method has aroused widespread concern of researchers. Persulfates have the advantages of high stability，easy operation and low price. Its activation can produce SO4·- with a long half-life （40 µs），a wide range of pH application，and strong oxidation，which has attracted extensive attention of researchers. In this paper，sodium persulfate was used as oxidant to treat cyanide wastewater，and the effect of sodium persulfate addition on the removal rate of cyanide and heavy metal ions and the catalytic oxidation reaction mechanism of the process were mainly studied. By means of flame atomic absorption spectrometer （AAS），X-ray diffraction （XRD） and quenching experiment，the changes of metal ions concentration，the types of main precipitation，the types of free radicals and their contributions during the oxidation process were systematically analyzed. In addition，the change of pH and the transformation of S2O82− with the increase of sodium persulfate addition were also discussed. The results showed that the initial pH value of the water sample was 12，the concentration of total cyanide （CNT） was 2862.2 mg·L−1，the free cyanide （CN−） was 1691.3 mg·L−1，Cu+ was 789.27 mg·L−1，Fe2+ was 42.197 mg·L−1，Zn2+ was 131.047 mg·L−1. With the increase of sodium persulfate addition，the removal of CNT and Cu+ firstly increased and then decreased，and the removal rate of CN− and Fe2+ soon reached the maximum and remained unchanged. This was because the strong alkalinity of cyanide wastewater and SO4·− produced by persulfate activated by Cu+ released from the breaking of metal cyanide complex ions strengthen the oxidation of the system and promote the degradation of cyanide. When the persulfate concentration was 0.084 mol·L−1，the maximum removal rates of CNT，CN−，Fe2+ and Cu+ were 89.2%，100%，97.4% and 92.7%，respectively. When the persulfate concentration increased to 0.105~0.125 mol·L−1，the concentration of sodium persulfate was so high that the excessive S2O82− in the system became the scrubber of SO4·−. At the same time，excessive free radicals also appeared self-quenching phenomenon，the oxidation capacity was weakened，and the removal rates of CNT and Cu+ began to decline. In the oxidation process，the metal cyanide complex ions in the system were removed in the form of precipitation. After the addition of sodium persulfate，the weak complex Cu（CN）32−and Zn（CN）42− occurred the detoxification reaction of Cu+ and Zn2+，CN− and the strong oxidizing S2O82− reaction was quickly consumed. Fe（CN）64− was removed from the solution by coprecipitation reaction with the dissociated Cu+ and Zn2+. At the persulfate concentration of 0.042 mol·L−1，CuCN and Zn2Fe（CN）6 were the main precipitates. With the increase of the persulfate concentration，CuCN dissolved gradually. Finally，the system formed Zn2Fe（CN）6，Cu2Fe（CN）6 and CuSCN precipitates，and cyanide ions were completely oxidized to CO2 and N2. As the reaction proceeded，the pH of the system gradually decreased，because S2O82− would hydrolyze and consume H2O or OH− in the system，resulting in the increase of H+ concentration in the solution. When the addition of persulfate was different，the concentration of S2O82− decreased gradually with the passage of reaction time. S2O82− was almost completely consumed in wastewater for about 5 min，this was because the persulfate oxidation process was very fast. Both direct oxidation and free radical oxidation consumed S2O82−，the added S2O82− was completely converted into SO42− and stored in the solution after the reaction. Methanol （MeOH） and tert-butanol （TBA） were added into the persulfate system as quenchers of active species to investigate the species of free radicals in the system. When tert-butanol was added into the system to quench the effect of ·OH，CNT removal rate decreased from 89.2% to 87%. When methanol was added，the removal rate of CNT decreased to 77.3% because it could simultaneously quench SO4·− and ·OH，which proved the existence of SO4·− and ·OH radicals in the system. The removal process of cyanide and metal ions in cyanidation wastewater was the result of the combined action of direct persulfate oxidation and free radical oxidation of SO4·− and ·OH produced by activation. The contribution of direct persulfate oxidation was 86.6%，while that of free radical oxidation was only 13.4%.
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Basic Information:
DOI：10.13373/j.cnki.cjrm.XY22060023
Chinese Library Classification Number:TF09
Citation Information:
Cyanide wastewater produced in cyanide gold extraction process is complicated in composition and difficult to treat. Direct discharge without treatment will cause great harm to the environment. The existing cyanide wastewater treatment methods generally have the problems of high energy consumption and immature development. Therefore，the search for an efficient，environmentally friend and energy-saving treatment method has aroused widespread concern of researchers. Persulfates have the advantages of high stability，easy operation and low price. Its activation can produce SO4·- with a long half-life （40 µs），a wide range of pH application，and strong oxidation，which has attracted extensive attention of researchers. In this paper，sodium persulfate was used as oxidant to treat cyanide wastewater，and the effect of sodium persulfate addition on the removal rate of cyanide and heavy metal ions and the catalytic oxidation reaction mechanism of the process were mainly studied. By means of flame atomic absorption spectrometer （AAS），X-ray diffraction （XRD） and quenching experiment，the changes of metal ions concentration，the types of main precipitation，the types of free radicals and their contributions during the oxidation process were systematically analyzed. In addition，the change of pH and the transformation of S2O82− with the increase of sodium persulfate addition were also discussed. The results showed that the initial pH value of the water sample was 12，the concentration of total cyanide （CNT） was 2862.2 mg·L−1，the free cyanide （CN−） was 1691.3 mg·L−1，Cu+ was 789.27 mg·L−1，Fe2+ was 42.197 mg·L−1，Zn2+ was 131.047 mg·L−1. With the increase of sodium persulfate addition，the removal of CNT and Cu+ firstly increased and then decreased，and the removal rate of CN− and Fe2+ soon reached the maximum and remained unchanged. This was because the strong alkalinity of cyanide wastewater and SO4·− produced by persulfate activated by Cu+ released from the breaking of metal cyanide complex ions strengthen the oxidation of the system and promote the degradation of cyanide. When the persulfate concentration was 0.084 mol·L−1，the maximum removal rates of CNT，CN−，Fe2+ and Cu+ were 89.2%，100%，97.4% and 92.7%，respectively. When the persulfate concentration increased to 0.105~0.125 mol·L−1，the concentration of sodium persulfate was so high that the excessive S2O82− in the system became the scrubber of SO4·−. At the same time，excessive free radicals also appeared self-quenching phenomenon，the oxidation capacity was weakened，and the removal rates of CNT and Cu+ began to decline. In the oxidation process，the metal cyanide complex ions in the system were removed in the form of precipitation. After the addition of sodium persulfate，the weak complex Cu（CN）32−and Zn（CN）42− occurred the detoxification reaction of Cu+ and Zn2+，CN− and the strong oxidizing S2O82− reaction was quickly consumed. Fe（CN）64− was removed from the solution by coprecipitation reaction with the dissociated Cu+ and Zn2+. At the persulfate concentration of 0.042 mol·L−1，CuCN and Zn2Fe（CN）6 were the main precipitates. With the increase of the persulfate concentration，CuCN dissolved gradually. Finally，the system formed Zn2Fe（CN）6，Cu2Fe（CN）6 and CuSCN precipitates，and cyanide ions were completely oxidized to CO2 and N2. As the reaction proceeded，the pH of the system gradually decreased，because S2O82− would hydrolyze and consume H2O or OH− in the system，resulting in the increase of H+ concentration in the solution. When the addition of persulfate was different，the concentration of S2O82− decreased gradually with the passage of reaction time. S2O82− was almost completely consumed in wastewater for about 5 min，this was because the persulfate oxidation process was very fast. Both direct oxidation and free radical oxidation consumed S2O82−，the added S2O82− was completely converted into SO42− and stored in the solution after the reaction. Methanol （MeOH） and tert-butanol （TBA） were added into the persulfate system as quenchers of active species to investigate the species of free radicals in the system. When tert-butanol was added into the system to quench the effect of ·OH，CNT removal rate decreased from 89.2% to 87%. When methanol was added，the removal rate of CNT decreased to 77.3% because it could simultaneously quench SO4·− and ·OH，which proved the existence of SO4·− and ·OH radicals in the system. The removal process of cyanide and metal ions in cyanidation wastewater was the result of the combined action of direct persulfate oxidation and free radical oxidation of SO4·− and ·OH produced by activation. The contribution of direct persulfate oxidation was 86.6%，while that of free radical oxidation was only 13.4%.
quote
| GB/T 7714-2015 | [1] Panpan Zhang, Yonghui Song, Long Liao, et al. Treatment of Cyanide Gold Extraction Wastewater by Adding Different Concentrations of Persulfate Oxidation[J]. Chinese Journal of Rare Metals, 2025, 49(2): 212-219. DOI:10.13373/j.cnki.cjrm.XY22060023. |
| MLA | [1] Panpan Zhang, et al., "Treatment of Cyanide Gold Extraction Wastewater by Adding Different Concentrations of Persulfate Oxidation." Chinese Journal of Rare Metals, vol. 49, no. 2, 2025, pp. 212-219, https://doi.org/10.13373/j.cnki.cjrm.XY22060023. |
| APA | [1] Panpan Zhang, Yonghui Song, Long Liao, Jiameng Zhou, & Yifan Wang. (2025). Treatment of Cyanide Gold Extraction Wastewater by Adding Different Concentrations of Persulfate Oxidation. Chinese Journal of Rare Metals, 49(2), 212-219. https://doi.org/10.13373/j.cnki.cjrm.XY22060023 |
| IEEE | [1] Panpan Zhang, Yonghui Song, Long Liao, Jiameng Zhou, and Yifan Wang, "Treatment of Cyanide Gold Extraction Wastewater by Adding Different Concentrations of Persulfate Oxidation," Chinese Journal of Rare Metals, vol. 49, no. 2, pp. 212-219, 2025, doi: 10.13373/j.cnki.cjrm.XY22060023. keywords: {cyanide wastewater;persulfate;oxidation;free radical} |