Study On Synthesis And Performance Of Poly(Chloride Diallylammonium)-based Heavy Metal Chelating Flocculant

The heavy met al i ons, suc h as Pb²⁺, Cd²⁺, Hg²⁺, Cr6+, and As3+, canproduce kinds of signi fi cant toxic effects due to thei r toxici ti es andnonbiodegradabilities. Ther efore, the wastewater containing heavy metalions will do great harm to the environment and the health of human beings.Chelating fl occ ulat ion c an make heavy metal ions become into insolubl echelati ng preci pitat es separat e dir ectl y by usi ng c helati ng floccul ant i n t hetreat ment for t he heavy metal wastewater, which can reduce cost, simp lifyproce sse s, and e nha nce fl occ ulation e ffici ency, and parti cularl y suitablefor t reat ment for large heavy metal wast ewater tr eat ment. It is key t oper for ma nce of c helate d fl occ ulant. In thi s pa per, pol y（chloridediallylammoniu m）–based heavy met al chelati ng fl occulant （PDAHCF） wasdesi gne d and s ynthesiz ed, the properties of chel ati ng fl occ u lant a ndcoor dina ti on che mi s try wer e r esearc he d.First of all chloride diallylammonium （DAAC） were synthesized byusing dia llyla mine （DAA） and hydr ochl oric acid; the n pol y（c hlori dediallylammoniu m）（PDAAC）, poly（chl o ride diall yla mmoni u m-a cryl a mi de）（PDAAM） and pol y（chlori de diallyla mmonium-di met hyl diallylammoniumchloride）（PDADM） were synthesized by new type DAAC and withacrylamide （AM） or dimethyldiallylammonium chloride （DMDAAC）initiated by2,2′-azobi s（2-met hyl propiona mide）dihydr ochlori de （AI BA）.Then with PDAAC, PDAAM and PDADM as raw materials, Poly（chloridediallylammoniu m）-based dithiocarba ma te s odi um（PDACDTC）, poly（chlori de diallyl a mmoniu m-acryla mi de）-based dithi ocarbamate sodium（PDAM DTC） a nd poly（c hlori dedial lyla mmoni um-dimethyldiallylammonium chloride）–ba sed dithi ocar ba matesodi um（PDADM DTC） were s ynthesiz d by the reaction with carbon di sul fide（CS2） and sodium hydr oxi de （Na OH）. Th e structure of PDACDTC,PDAM DTC a nd PDADM DTC was characterized by elementar y analysis,ultravoilet spectros copy, FTI R and1H NMR spectra. The results show that,poly（chl o ride di all yla mmoni u m）–bas ed heavy metal chelating fl occul ant（PDAHCF） wa s synthe size d succ ess fully. Wit h commo n hea vy met al ion Cu2+,Ni2+,Zn2+,Pb2+,Cd2-,Hg2+simulated wastewater as treatment object, effect of PDAHCF and pH on removal rate of Cu2+,Ni2+,Zn2+,Pb2+,Cd2+Hg2+.The results show that,when the corresponding molar ratios of—CSS+to Cu2+,Ni2+,Zn2+,Pb2+,Cd2+all close to2:1,High removal efficiency,and the residual heavy metal concentrations are all below the limit set by the National Integrated Wastewater Discharge Standards of China（GB8978-1996） and Nation Electroplating Pollutants Emission Standards（GB21900-2008）.when the corresponding molar ratios of—CSS—to Hg2+are1:1,and the residual Hg2+concentrations are all below the limit set by the National Integrated Wastewater Discharge Standards of China （GB8978-1996）.Synthesis of3kinds of chelating polymer flocculant has a wide pH range.The absorption spectra of the Cu2+,Ni2+,Zn2+,Pb2+,Cd2+and Hg2+chelates of PDACDTC.PDAMDTC and PDADMDTC were measured via ultraviolet spectrophotometry.The composition of the chelates were discussed,and their stability constants were calculated.The results show that,the—CSS-group of PDACDTC,PDAMDTC and PDADMDTC reacted with Cu2+,Ni2+,Zn2+,Pb2+and Cd2+in a molar ratio of2:1to from the chelate s,with Hg2+in a molar ratio of1:1. Synthetic polymer chelated flocculant with Cu2+,Ni2+,Zn2+,Pb2+,Cd2+and Hg2+having a better stability. For the same kind of high polymer chelating agent steady sequence wasPDAHCF-Hg2+>PDAHCF-Cu2+>PDAHCF-Pb2+>PDAHCF-Cd2+>PDAHCF-Zn22+>PDAHCF-Ni2+;for the same ion,PDADMDTC-M> PDAMDTC-M>PDACDTC-M.The images and compositions of the flocs were investigated by using polarizing microscope.The results show that, the aqueous flocs of the chelating sediments were loose and retiform.The above results indicate that PDAHCF has both strong chelating ability and good flocculation performance.The heavy metal wastewater, which was took from the hydroxyethylidenediphosphonic acid（HEDP）copper plating wastewater, was treated effectively by PDACDTC,PDAMDTC and PDADMDTC. When using PDACDTC,PDAMDTC,PDADMDTC or CaCl2,all cannot effectively deal with HEDP copper plating wastewater.When PDACDTC, PDAMDTC or PDADMDTC is used together with CaCl2, can effectively deal with HEDP copper plating wastewater, and the residue concentrations of Cu2+and COD can meet the Effluent Standard of Pollutants for Electroplating （GB21900-2008）.In a word, PDACDTC, PDAMDTC and PDADMDTC has both strong chelating ability and good flocculation performance. PDAHCF can treat the heavy metal wastewater in an effective way under a certain condition and undoubtedly it had a favourable application prospect.