高分子重金属絮凝剂的性能及作用机理研究

以含Ni^2 废水作为处理对象，主要研究了几个影响高分子重金属絮凝剂去除废水中Ni^2 的因素，从而进一步了解高分子重金属絮凝剂的结构和性能．实验结果表明：(1)某些离子存在时，pH值对Ni^2 的最高去除率影响不大；(2)水中某些二价阳离子的存在不仅不会消耗高分子重金属絮凝剂的用量，而且会促进Ni^2 絮凝沉淀，Ni^2 的去除率均在95％以上；(3)水中Fe^3 会与Ni^2 竞争高分子重金属絮凝剂分子中二硫代羧基上的配位基，若高分子重金属絮凝剂投加量不足，Fe^3 的存在将影响螯合体MHMF-Ni^2 的生成；(4)Ni^2 和致浊物质会互相促进彼此的去除，浊度的去除率在97％以上．(5)高分子重金属絮凝剂对重金属离子具有选择性，可将部分重金属离子从其它离子中分离开、回收再利用．

Study on characteristics and action mechanisms of macromolecule heavy metal flocculant

Anovel approach for metal sequestration by the chelating and flocculating capabilities of water-soluble Macromolecule Heavy Metal Flocculant was introduced by using Ni²⁺ in wastewater as the target metal ion. The basic principle of removing heavy metal ion and turbidity with Macromolecule Heavy Metal Flocculant was mainly discussed, some factors which affected the removal rates in wastewater were also studied. The experimental results showed that: (1) Though the tendency of influence on the removal of Ni²⁺ and turbidity was opposite with pHvalue changed, an optimum pHexisted, and removal rates of Ni²⁺ and turbidity were both above 95% when the pHvalue was at 5.5. The pHvalue had little effect on the maximum removal rate of Ni²⁺ when some other ions (such as Ca²⁺ mg²⁺ ) also existed; (2) The existence of some bivalent ions (such as Ca²⁺ ) in wastewater not only consumed none of Macromolecule Heavy Metal Flocculant, but also promoted the flocculation and sedimentation of Ni²⁺ . The existence of Ca²⁺ made the double electricity layer thinner, speeded up the flocculation-sedimentation and broadened the range of the optimum input of Macromolecule Heavy Metal Flocculant. Therefore a better removal result was obtained, which could be advantagous to practical application. It was determined by two characteristics of Ca²⁺ : firstly, Ca²⁺ was not easy to react with Macromolecule Heavy Metal Flocculant. Secondl, Ca²⁺ had a higher positive charge; (3) Fe³⁺ and Ni²⁺ in wastewater competed for the ligand dithioic acid of Macromolecule Heavy Metal Flocculant, so the chelate production of MHMF-Ni²⁺ was affected by the existence of Fe³⁺ if the Macromolecule Heavy Metal Flocculant was not enough. On the contrary, the maximum removal rate of Ni²⁺ was higher than that when Fe³⁺ was absent;(4) Some factors such as charge neutralization as well as metal bridging contributed to the subsequent precipitation and separation of the chelate of MHMF-Ni²⁺ when Ni²⁺ was present. At the same time the existence of turbidity-causing substance accelerated the sedimentation chelate of MHMF-Ni²⁺ . Some dissolved Ni²⁺ would be absorbed onto the surface of floc and removed further. So Ni²⁺ and turbidity-causing substance promoted the removal of each other. Then the removal rate of turbidity was above 97%; (5) Macromolecule Heavy Metal Flocculant had the selectivity on the different heavy metal ions. When various heavy metal ions appeared in the wastewater, some of them could be separated and scaveged by the Macromolecule heavy metal flocculant based on the different chelation sequence of Macromolecule Heavy Metal Flocculant and different heavy metal ions(for example Hg²⁺ Cu²⁺ >Ni²⁺ ). The following conclusions were made in accordance with the experiments: (1) Arelatively insoluble chelate forms between Macromolecule Heavy Metal Flocculant and Ni²⁺ . It spent less time in forming the chelate,and the dimension of chelate were nearly same and it is easy to be separated from the original solution; (2) The solution containing heavy metal of industrial wastewater was generally acidic. And if it was treated with conventional chemical sediment action, the pHvalue must be higher, in order to adjust pHto neutral state which had to consume a large amount of alkal. (3) Treatment of wastewater containing heavy metal ions with Macromolecule Heavy Metal Flocculant had wild range of the pHvalue. In this process turbidity was reduced while removing heavy metal ions. Moreover, the additional equipments and structures are not needed;a better removal result of Ni²⁺ and turbidity could be attained by less input of Macromolecule Heavy Metal Flocculant. And it is easier to operate and more convenient to manage.