Abstract：The coordination agent EDTA is usually found in industrial wastewater containing copper, and the stable soluble compound Cu-EDTA can be formed between EDTA and Cu(II), which makes it difficult to remove Cu(II) from the wastewater. In order to improve effectively the removal of Cu(II) from Cu-EDTA wastewater, dithiocarboxyl aminomethy-polyacrylamide (DTAPAM) was employed as heavy metal flocculant. The effects of hydraulic conditions, DTAPAM dosage, pH value, EDTA concentration, and initial Cu(II) concentration on the removal performance of Cu-EDTA with DTAPAM were investigated, and the optimal removal conditions for Cu-EDTA in water sample were determined. The removal mechanism of Cu-EDTA with DTAPAM was also explored by using some characterization methods, such as UV, IR, SEM and EDS. The results show that the optimal hydraulic conditions were as follows: the fast stirring time was 2min, the fast stirring speed was 160r/min, the slow stirring time was 20min, and the slow stirring speed was 50r/min. The removal performance of Cu-EDTA by DTAPAM was favorable for the initial Cu(Ⅱ) concentration of 25mg/L at pH 5.0~7.0, and the highest removal rate of Cu(II) reached 99.07% at pH 7.0. When the coordination ratio between EDTA and Cu(II) was 1:1, it had the ideal removal efficiency for Cu-EDTA with DTAPAM at different initial Cu(II) concentrations. The characterization results show that the chelation reaction should occur between Cu(II) and dithiocarboxylic groups (—CSS-) on the molecular chain of DTAPAM. At pH 2.0~9.0, the logarithm values of the chelation stability constant for DTAPAM-Cu were in the range of 13.09~13.71. For the removal mechanism of Cu-EDTA by DTAPAM, Cu(II) was replaced from Cu-EDTA by DTAPAM due to coordination competition, and the flocs were formed though chelation reaction between Cu(II) and DTAPAM. In addition, the adsorption bridging and net sweeping among flocs played a major role in the flocculation, which promoted the settlement of the flocs and improved the removal rate of Cu(II).
张航, 王刚, 周雅琦, 马玉. 重金属絮凝剂DTAPAM去除水中Cu-EDTA的条件优化和机理[J]. 中国环境科学, 2023, 43(2): 532-543.
ZHANG Hang, WANG Gang, ZHOU Ya-qi, MA Yu. Condition optimization and mechanism of heavy metal flocculant DTAPAM in the removal of Cu-EDTA from water. CHINA ENVIRONMENTAL SCIENCECE, 2023, 43(2): 532-543.
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