Both citrate and hypophosphite in aqueous solution were degraded by advanced oxidation processes （Fe^2＋/H2O2, UV/Fe^2＋/H2O2, and electrolysis/Fe^2＋/H2O2） in this study. Comparison of these techniques in oxidation...Both citrate and hypophosphite in aqueous solution were degraded by advanced oxidation processes （Fe^2＋/H2O2, UV/Fe^2＋/H2O2, and electrolysis/Fe^2＋/H2O2） in this study. Comparison of these techniques in oxidation efficiency was undertaken. It was found that Fenton process could not completely degrade citrate in the presence of hypophosphite since it caused a series inhibition. Therefore, UV light （photo-Fenton） or electron current （electro-Fenton） was applied to improve the degradation efficiency of the Fenton process. Results showed that both photo-Fenton and electro-Fenton processes could overcome the inhibition of hypophosphite, especially the electro-Fenton.展开更多
Citrate (Ct) was chosen as a typical chelator used in the Fe^(2+)-peroxydisulfate (PDS) process to improve sludge dewaterability.The PDS-Fe^(2+)-Ct process exhibited better performance in sludge dewatering than PDS-Fe...Citrate (Ct) was chosen as a typical chelator used in the Fe^(2+)-peroxydisulfate (PDS) process to improve sludge dewaterability.The PDS-Fe^(2+)-Ct process exhibited better performance in sludge dewatering than PDS-Fe^(2+).Specifically,with a PDS dosage of 1.2 mmol/g VS,the molar ratio of PDS/Fe^(2+)and Ct/Fe^(2+)were 4:5 and 1:4,respectively,the capillary suction time decreased from 155.8 to 24.8sec,and the sludge cake water content decreased from 82.62%to 64.11%(-0.06MPa).The oxidation led to a reduced negative charge and a decrease in particle size.The enhanced sludge dewaterability and changes of sludge properties were attributed to the decomposition of extracellular polymeric substances,and it was explored by protein,polysaccharide,3D-EEMs,and FT-IR.Additionally,the quenching experiments of radical species demonstrated that SO_(4)-·played a more important role than·OH,and its productivity was improved with the addition of Ct.Moreover,the reasons for the improved productivity of radicals with the addition of Ct were discussed.The results of this study could serve as a basis for improving sludge dewatering using the PDS-Fe^(2+)-Ct process and suggest that the addition of Ct may improve the productivity of SO_(4)-·in the activation o PDS via Fe^(2+).展开更多
Wastewater produced from the soil washing process contains heavy metals, which limits its reuse for washing. So it is necessary to develop an efficient and economical way to recycle it, and this study presented a bios...Wastewater produced from the soil washing process contains heavy metals, which limits its reuse for washing. So it is necessary to develop an efficient and economical way to recycle it, and this study presented a biosorption method to realize this goal. A typical soil sample contaminated by lead was taken from the real field near a lead smelting factory, used for the toxic metals extraction with dilute citric acid. A leach liquor was obtained with lead ions at the level of 12.35 mg/L, Cd 1.2 mg/L, Cu 1.5 mg/L, Zn 2.6 mg/L, as well as the coexisting anions, such as sulphate, silicate, chloride at the concentration of several hundred miligram per liter. The garlic peel was modified by a simple chemical saponification process and used as the biosorbent for toxic metal removal. Firstly, the adsorp- tion behavior of lead ions on the saponified garlic peel was systematically investigated using the synthetic solutions, and then the adsorption mechanisms were explored by detailed experhnents combining with the thermodynamic calculation reuslts of the aqueous system of Pb（II）-citrate-H2O. It was found that in artificial solution containing 0.01 mol/L citrate, the maximum adsorption capacity of 261.0 mg/g was reached at pH near 3.0, and also at this very pH value the Pb^2＋ and Pb（H2Cit）＋ were the dominant lead species, which are favorable for adsorption due to its easier approaching to the --COO^- ligands in the saponified garlic peel partilces via charge attraction, and the appearance of Pb（HCit）; and Pb（Cit）- at pH above 3.0 inhibits the adsorption. Secondly, the real leach liquor was used for adsorption tests, and twice adsorption under the optimal conditons would decrease the residual concentrations of Pb, Cd, Cu and Zn to zero. After elution by using 0.1 mol/L nitric acid, the adsorbed metals can be recovered and garlic peel can be reused for at least 10 cycles effectively. This study presents a prospective biosorption method for economical and efficient removal of the lead ions from soil washing wastewater with citric acid as the leaching reagent.展开更多
基金The authors thank the "National" Science Council, Taiwan, China for financially supporting (No. NSC95- 2211-E-006-032).
文摘Both citrate and hypophosphite in aqueous solution were degraded by advanced oxidation processes （Fe^2＋/H2O2, UV/Fe^2＋/H2O2, and electrolysis/Fe^2＋/H2O2） in this study. Comparison of these techniques in oxidation efficiency was undertaken. It was found that Fenton process could not completely degrade citrate in the presence of hypophosphite since it caused a series inhibition. Therefore, UV light （photo-Fenton） or electron current （electro-Fenton） was applied to improve the degradation efficiency of the Fenton process. Results showed that both photo-Fenton and electro-Fenton processes could overcome the inhibition of hypophosphite, especially the electro-Fenton.
基金supported by the National Water Pollution Control and Management Technology Major Project (No. 2018ZX07110005)the National Natural Science Foundation of China (No. 52170097)the Fundamental Research Funds for Beijing University of Civil Engineering and Architecture (Nos. X18288, X18289 and X20137)。
文摘Citrate (Ct) was chosen as a typical chelator used in the Fe^(2+)-peroxydisulfate (PDS) process to improve sludge dewaterability.The PDS-Fe^(2+)-Ct process exhibited better performance in sludge dewatering than PDS-Fe^(2+).Specifically,with a PDS dosage of 1.2 mmol/g VS,the molar ratio of PDS/Fe^(2+)and Ct/Fe^(2+)were 4:5 and 1:4,respectively,the capillary suction time decreased from 155.8 to 24.8sec,and the sludge cake water content decreased from 82.62%to 64.11%(-0.06MPa).The oxidation led to a reduced negative charge and a decrease in particle size.The enhanced sludge dewaterability and changes of sludge properties were attributed to the decomposition of extracellular polymeric substances,and it was explored by protein,polysaccharide,3D-EEMs,and FT-IR.Additionally,the quenching experiments of radical species demonstrated that SO_(4)-·played a more important role than·OH,and its productivity was improved with the addition of Ct.Moreover,the reasons for the improved productivity of radicals with the addition of Ct were discussed.The results of this study could serve as a basis for improving sludge dewatering using the PDS-Fe^(2+)-Ct process and suggest that the addition of Ct may improve the productivity of SO_(4)-·in the activation o PDS via Fe^(2+).
文摘Wastewater produced from the soil washing process contains heavy metals, which limits its reuse for washing. So it is necessary to develop an efficient and economical way to recycle it, and this study presented a biosorption method to realize this goal. A typical soil sample contaminated by lead was taken from the real field near a lead smelting factory, used for the toxic metals extraction with dilute citric acid. A leach liquor was obtained with lead ions at the level of 12.35 mg/L, Cd 1.2 mg/L, Cu 1.5 mg/L, Zn 2.6 mg/L, as well as the coexisting anions, such as sulphate, silicate, chloride at the concentration of several hundred miligram per liter. The garlic peel was modified by a simple chemical saponification process and used as the biosorbent for toxic metal removal. Firstly, the adsorp- tion behavior of lead ions on the saponified garlic peel was systematically investigated using the synthetic solutions, and then the adsorption mechanisms were explored by detailed experhnents combining with the thermodynamic calculation reuslts of the aqueous system of Pb（II）-citrate-H2O. It was found that in artificial solution containing 0.01 mol/L citrate, the maximum adsorption capacity of 261.0 mg/g was reached at pH near 3.0, and also at this very pH value the Pb^2＋ and Pb（H2Cit）＋ were the dominant lead species, which are favorable for adsorption due to its easier approaching to the --COO^- ligands in the saponified garlic peel partilces via charge attraction, and the appearance of Pb（HCit）; and Pb（Cit）- at pH above 3.0 inhibits the adsorption. Secondly, the real leach liquor was used for adsorption tests, and twice adsorption under the optimal conditons would decrease the residual concentrations of Pb, Cd, Cu and Zn to zero. After elution by using 0.1 mol/L nitric acid, the adsorbed metals can be recovered and garlic peel can be reused for at least 10 cycles effectively. This study presents a prospective biosorption method for economical and efficient removal of the lead ions from soil washing wastewater with citric acid as the leaching reagent.
