重金属絮凝剂DTMPAM去除Cr(Ⅵ)的性能与机理

Removal performance and mechanism of dithiocarboxyl hydroxymethy-polyacrylamide for Cr(Ⅵ) in aqueous solution

以二硫代羧基化羟甲基聚丙烯酰胺(DTMPAM)作为高分子絮凝剂,研究DTMPAM对水中Cr(Ⅵ)的去除性能,考察了DTMPAM投加量、pH值、Cr(Ⅵ)初始浓度以及共存浊度、无机物质、有机物质对DTMPAM处理含Cr(Ⅵ)废水性能的影响.结果表明,DTMPAM在酸性条件下对不同Cr(Ⅵ)初始浓度的含Cr(Ⅵ)水样均具有良好的去除效果,且Cr(Ⅵ)的去除率随着体系初始pH值的降低而升高;当pH值为3.0时,DTMPAM对Cr(Ⅵ)初始浓度为5,15,25和50mg/L水样中Cr(Ⅵ)的最高去除率分别达到94.78%,96.52%,96.53%和97.49%.共存浊度对DTMPAM去除Cr(Ⅵ)具有抑制作用.在低DTMPAM投加量下,共存无机阳离子K^(+)、Na^(+)、Ca^(2+)、Mg^(2+),共存无机阴离子SO_(4)^(2-)、NO_(3)^(-)、Cl^(-),以及共存有机物质柠檬酸钠、乙酸钠、三氯乙酸和氨基乙酸等对DTMPAM去除Cr(Ⅵ)均具有一定的抑制作用;而在高DTMPAM投加量下,这些物质的存在会对DTMPAM去除Cr(Ⅵ)表现出较小的促进作用.无机阳离子Fe^(3+)、Ni^(2+)、Ba^(2+)的存在对DTMPAM去除Cr(Ⅵ)具有较明显的抑制作用,其中Ba^(2+)的抑制作用最显著.红外光谱和能谱分析显示,DTMPAM高分子链上的二硫代羧基可将水样中Cr(Ⅵ)还原为Cr(Ⅲ),Cr(Ⅲ)进一步和DTMPAM分子链上的二硫代羧基、胺基发生螯合反应形成絮体.

The performance of dithiocarboxyl hydroxymethy-polyacrylamide(DTMPAM) in the treatment of Cr(Ⅵ)-containing wastewater was investigated with the influences of some parameters,such as DTMPAM dosage,pH value,initial concentration of Cr(Ⅵ),and coexisting turbidity,inorganic and organic substances.The results showed that DTMPAM had a good removal efficiency on Cr(Ⅵ) in water samples with different initial concentrations of Cr(Ⅵ) under acidic conditions,and the removal rate of Cr(Ⅵ)increased with the decrease of initial pH in the system.At pH value 3.0,the highest removal rates of Cr(Ⅵ) in water samples reached94.78%,96.52%,96.53% and 97.49% at the initial Cr(Ⅵ) concentrations of 5,15,25 and 50mg/L,respectively.The coexisting turbidity had an inhibitory effect on the removal of Cr(Ⅵ) by DTMPAM.At the low DTMPAM dosage,the coexisting inorganic cations(K^(+),Na^(+),Ca^(2+) and Mg^(2+)),the coexisting inorganic anions(SO_(4)^(2-),NO_(3)^(-) and Cl^(-) ),as well as the coexisting organic substances(sodium citrate,sodium acetate,trichloroacetic acid and aminoacetic acid) had a certain inhibitory effect on the removal of Cr(Ⅵ) by DTMPAM,while at the high DTMPAM dosage,the presence of these coexisting substances exhibited a little promotion for the removal of Cr(Ⅵ).The presence of inorganic cations,such as Fe^(3+),Ni^(2+) and Ba^(2+),had a significant inhibitory effect on the removal of Cr(Ⅵ) by DTMPAM,and Ba2+had the most significant inhibitory effect among these ions.Infrared spectroscopy and energy spectrum analysis showed that the dithiocarboxyl groups on the molecular chain of DTMPAM could reduce Cr(Ⅵ) to Cr(Ⅲ) in the water samples,and then Cr(Ⅲ) could further chelated with the dithiocarboxyl groups and amine groups on the molecular chain of DTMPAM to form flocs.