具有重金属捕集功能的高分子絮凝剂MAC去除Cd^(2+)的性能研究

Removal of Cd^(2+) by the macromolecular flocculant mercaptoacetyl chitosan via trapping heavy metal ions

以壳聚糖、巯基乙酸为原料,通过酰胺化反应合成了一种具有重金属捕集功能的新型高分子絮凝剂——巯基乙酰壳聚糖(MAC),研究了其对含Cd2+废水水样的处理性能,并对影响处理性能的因素(pH、有机络合剂及浊度等)进行了探讨.结果表明,该絮凝剂对Cd2+有很好的捕集功能,采用不同相对分子质量、不同脱乙酰度的壳聚糖合成的MAC,其对Cd2+的去除效果也不同,其中,采用相对分子质量20万～40万、脱乙酰度大于90%的壳聚糖合成的MAC对Cd2+的去除效果较好,处理Cd2+浓度为10mg·L-1的废水水样,在原水浊度为80NTU的条件下,最高去除率可达到93.10%.废水中Cd2+浓度与其最佳投药量存在一定的化学计量关系.pH值会影响Cd2+的去除,在pH为5.5～8.5的范围内,pH值升高,Cd2+的去除率也随之升高.腐殖酸对Cd2+的去除有促进作用,EDTA对Cd2+的去除有一定的抑制作用.Cd2+和致浊物质可以起到相互促进去除的作用,出水浊度可达3NTU以下.

A novel water-soluble macromolecular flocculant,mercaptoacetyl chitosan （MAC） which traps heavy metals,was synthesized by reacting chitosan with mercaptoacetic acid.The flocculation performance of MAC was evaluated using cadmium-containing water samples as the target.Some factors which affect the removal of Cd2＋ were also studied.The experimental results showed that：①MAC had strong binding capabilities for Cd2＋.The removal efficiency of Cd2＋ depended on the molecular weight and degree of deacetylation of chitosan.When MAC was prepared with chitosan with a molecular weight of 200000～400000 and degree of deacetylation over 90%,the highest removal rate of Cd2＋ （93.10%） was reached in the water sample containing 10 mg·L-1 Cd2＋ and 80 NTU turbidity.② Water samples with different concentrations of Cd2＋ had different optimum dosages of MAC,and there was a stoichiometric relationship between the optimum dosage of MAC and concentration of Cd2＋.③ The pH had some effect on the removal rate of Cd2＋.When pH value was changed from 5.5 to 8.5,the removal rate of Cd2＋ increased.④When humic acids were present in the cadmium-containing water sample,the removal rate of Cd2＋ increased,but,the presence of EDTA in the water sample impeded the removal of Cd2＋ to some extent.⑤ Cd2＋ and turbidity-causing substances were removed synergistically,and the water turbidity of the effluent was below 3 NTU.