Preparation And Study Of A New Starch-Modified Heavy Metal Chelating Flocculant ISXA

A large amount of heavy metal wastewater is discharged with complex pollutants, which causes a serious damage to environment and health of human. There is an urgent need to study water treatment agents with high practicality and economic efficiency further. Heavy metal chelating flocculant is a kind of water treatment agents which has functions for both trapping heavy metal ions and flocculating. In this study, a starch-modified heavy metal chelating flocculant, ISXA was synthesized by starch, carbon disulfide and crylamide. Efficiency and main factors of the removal of free copper, cadmium, lead and complexing copper by ISXA were studied. And application prospect of ISXA was discussed.ISXA was prepared through water bath reaction in three phases. Optimum conditions of the preparation were concluded through single factor experiment and orthogonal experiment as follows: in starch-crosslinking phase, mass ratio between epichlorohydrin and starch is 1.2:10, reaction temperature is 40℃ and p H is 10; in xanthation phase, mass ratio between carbon disulfide and starch is 6.3:10, reaction temperature is 35℃ and p H is 11;in acrylamide-grafting phase, mass ratio between acrylamide and starch is 1.5:10. Analyses of product were conducted by infra-red spectrum and elementary analysis, confirming that ISXA molecule had xanthate and amide groups. And the sulfur content of ISXA was 12.78% under optimum conditions.Simulated wastewater of single heavy metal ions was treated by ISXA, respectively. The effects of species and dosage of heavy metal ions, dosage of ISXA, p H, on removal efficiency were investigated. The results showed that a positive correlation was between removal efficiency of heavy metal ions and p H. ISXA can effectively remove single heavy metal ions in weak acid condition. And the removal efficiency decreased With the reduction of p H. To treat simulated wastewater under conditions of p H 6.0 with single Cu2+、Cd2+、Pb2+、Cu-EDTA, the removal efficiency of an ion concentration of 5mg/L was up to 99% when ISXA dosage was 24mg/L、30mg/L、30mg/L、35mg/L respectively, the removal efficiency of an ion concentration of 20mg/L was up to 99% when ISXA dosage was 90mg/L、110mg/L、70mg/L、120mg/L respectively, and the removal efficiency of an ion concentration of 20mg/L was up to 99% when ISXA dosage was 200mg/L、220mg/L、140mg/L、220mg/L respectively.Simulated wastewater of mixed heavy metal ions was treated by ISXA. A obvious selectivity was showed in the removal of heavy metal ions. The trapping order is Cu2+>Pb2+>Cd2+>Cu-EDTA. Coordination reaction between ISXA and different heavy metal ions reacts in accordance with the trapping order.ISXA can effectively remove heavy metal ions from complex wastewater of electroplating enterprises. The chelating flocs of ISXA and heavy metal ions showed good stability and had a low possibility of secondary pollution..