Research On The EDTA Complexation Nanofiltration Removel Of Copper, Cadmium And Lead From Soil Acidic Leachate

With the rapid development of urbanization and industrialization, the main heavy metal copper, cadmium and lead pollution in soil was serious, Copper cadmium and lead pollution because of its difficult degradation and persistence in soil for biological,chemical and physical law difficult to remove. Therefore, the removal of copper, lead and cadmium in soil has become the focus and difficulty of the study. Soil washing was considered to be an efficient and thorough treatment of soil heavy metal pollution.But the heavy metal ions in the soil acidic leaching solution still could not be removed.In recent years, because of the nanofiltration technology for heavy metal ions removal rate was high, the advantages of simple operation and no transformation was widely used. But the nanofiltration technology processing low concentration wastewater removal rate was relatively low. In order to simultaneously improved the mixed metal ion removal rate, through nearly ten years of research showed that in the nanofiltration added complexing agent could improved the nanofiltration low concentration of metal ion removal efficiency and membrane flux, referred to as complexation-nanofiltration process. It could effectively removed heavy metals from wastewater, and has important significance for the treatment of heavy metal pollution in soil.Ethylenediaminetetraacetic acid?EDTA? was chosen as the complexing agent to study the enhanced effects of nanofiltration for the removal of copper, lead and cadmium ions from synthetic soil acidic leachate. The effects of pH, EDTA and metal ion concentration ratio and applied pressure on ions rejection were examined in complexation-nanofiltration. And the corresponding optimization conditions were obtained by orthogonal experiment. The specific contents as followed:?1? For low concentration of single heavy metal ion Cu²⁺?3mmol·L-1?,Pb2+?0.45mmol·L-1? and Cd²⁺?0.97mmol·L-1?from simulation soil acidic leachate, in a certain temperature, pH, pressure conditions, as long as the addition of a small amount of EDTA could increased the Cu²⁺?Pb2+and Cd²⁺retention and membrane flux.The addition of EDTA has a significant effect on the retention and membrane flux of single lead ions, copper ions and cadmium ions. And the corresponding optimization conditions were obtained by orthogonal experiment.?2? For low concentration of equimolar ratio admixture heavy metal ion Cu²⁺,Pb2+and Cd²⁺?all were 0.8 mmol·L-1?from simulation soil acidic leachate, in a certain temperature, pH, pressure conditions, as long as the addition of a small amount of EDTA could also achieved the improvement of the Cu²⁺? Pb2+and Cd²⁺retention, but also to maintain a high membrane flux of double effect. And the corresponding optimization conditions are obtained by orthogonal experiment.?3?The hydration number of metal ions and EDTA in different pH under theexisting body distribution, and theoretically calculated for the first time when the conditions used the complex of EDTA and metal ions, explained the mixed Cu²⁺, Pb2+and Cd²⁺system pH, EDTA and metal ions concentration ratio and the operating pressure of complexation nanofiltration effect and mechanism.In general, whether it is a single lead, copper, cadmium ions system or all kinds of copper, cadmium, lead mixed ions system, as long as a small amount of EDTA,and pH with the material was similar, it could achieved the same time to improve the copper, cadmium, lead ion removal rate, and could maintained a high membrane flux of double effect. Therefore, the use of EDTA complexation nanofiltration approached to economic and efficient removal of acid leaching solution of soil of copper,cadmium, lead, and the removal of copper in soil, cadmium and lead pollution.