摘要
An advanced cost-saving method of removal of high-As(Ⅲ)from SO_(4)(-Ⅱ)-rich metallurgical wastewater has been developed by diluting the SO_(4)(-Ⅱ)content with As(Ⅲ)-Cl(-Ⅰ)-rich metallurgical wastewater and then by the direct precipitation of As(Ⅲ)with Fe(Ⅲ)at pH 2.3.As(Ⅲ)removal at various SO_(4)(-Ⅱ)/Cl(-Ⅰ)molar ratios and temperatures was investigated.The results showed that 65.2–98.2%of As(Ⅲ)immobilization into solids occurred at the SO_(4)(-Ⅱ)/Cl(-I)molar ratios of 1:1–32 and 15–60℃in 3 days,which were far higher than those in aqueous sole SO4(-Ⅱ)or Cl(-Ⅰ)media at the equimolar SO_(4)(-Ⅱ)or Cl(-Ⅰ)and the same temperature.SO_(4)(-Ⅱ)/Cl(-Ⅰ)molar ratio of 1:4 and 25℃were optimal conditions to reach the As removal maximum.Mixed aqueous SO4(-Ⅱ)and Cl(-Ⅰ)played a synergetic role in the main tooeleite formation together with(Cl(-Ⅰ)-free)ferric arsenite hydroxychloride(FAHC)involving the substitution of AsO_(3)^(3−)for Cl(-Ⅰ)for enhanced As fixation.The competitive complexation among FeH_(2)AsO_(3)^(2+),FeSO_(4)^(+)and FeCl^(2+)complexes was the main mechanism for the maximum As(Ⅲ)precipitation at the SO4(-Ⅱ)/Cl(-I)molar ratio of 1:4.Low As(Ⅲ)immobilization at high temperature with increased Fe(Ⅲ)hydrolysis was due to the formation of As(Ⅲ)-bearing ferrihydrite with the relatively high Fe/As molar ratio at acidic pH.
基金
supported by the National Key Research and Development Program of China (No.2019YFC1804400)
the National Natural Science Foundation of China (Nos.41877393,41877379,42007364 and 42077309)
Youth Innovation Promotion Association CAS (No.2021196)
Liao Ning Revitalization Talents Program (Nos.XLYC1807185 and XLYC1807025)