基于硫化钠的垃圾焚烧飞灰EDTA提取液中重金属回收试验研究OA

To achieve the recovery of heavy metals from EDTA extraction solution of fly ash from waste incinera-tion,sodium sulfide solution was used as the precipitant to investigate the effect of its dosage on the recovery rate of heavy metals,and the impact of heavy metals on the environment after recovery was evaluated.Theoretical calculation results indicate that in the system with pH=9～12,S2-can form CdS,CuS,PbS,and ZnS metal sulfide precipitates with heavy metal ions in the extraction solution.The results of the recovery test showed that the suitable dosage of 5％Na2S was 40 mL per 1 L of extracted solution treated,and the dosage of Na2S had little effect on the overall reco-very rate of each element.Before the treatment of the extracted solution,the mass concentrations of Cd,Cu,Zn,and Cr were relatively low,and the mass concentrations of Cd and Pb exceeded the standard limit,especially Pb exceeding 20 times the standard limit.After recycling,the mass concentrations of Cd,Cr,Cu,Pb,and Zn in the extraction solution all comply with the provisions of GB 8978-1996.The recovery effect of Pb with higher concentration was most significant,with the recovery rate of 95.31％.The recovery rates of Cd,Cu,Zn,and Cr with lower concentra-tion were 63.16％,62.71％,66.37％,and 54.88％,respectively.Although Cr3+ does not react with S2-,it is co precipitated by other heavy metal sulfides into the heavy metal recovery slag through encapsulation,adsorption,and other methods,thereby achieving separation and recovery.The lead content in heavy metal recovery slag was as high as 4.24％,which is more than four times of the minimum production grade of primary lead ore,and can be used as a lead refining resource.This process is simple and practical,providing a new approach for the comprehensive utilization of fly ash from waste incineration.