Research On Extraction And Modification Of Polysaccharide Of Algae In Salt Pond For Produce Bio-coagulant Aid

In extraction process of polysaccharide of algae in salt pond,the relation of extracting rate to extracting time,extracting temperature,the ratio of solid to liquid and pH was researched.Then by the orthogonal experiment,optimizing parameters,the extraction process was identified.Based on single modification,such as acid-alkali modification, oxidizing modification,grafting modification,exploring the effect of using the different modified reagent,the experimental index was the removal rate of turbidity to determine the optimal modification process of polysaccharide through composite modification.Finally, through the combination of polyaluminium chloride(PAC) and an original polysaccharide bio-coagulant aid(ABCA),which was made from algae in salt pond as coagulant aid,and by the means of jar test,the optimal dosage of them were studied.Comparing with the different coagulant aid(PAM,HCA),the performance of ABCA was analyzed in the water treatment.The results showed that diluted acid was a suitable extractant.The optimum extraction process was that the ratio of solid to liquid is 1:70,adding HCL to the mixture until PH=4, extracting at 95℃for 75 min.The best modification process of polysaccharide is as follows:followed by adding H₂O₂1.6‰,CH₃COONH₄36‰,composite acid,up to the PH of solution to 4,modified at 95℃for 90 min.The optimal dosage of PAC and ABCA were 16 mg·L^-1and 0.30 mg·L^-1 separately.And ABCA has better performances with the removal rate of turbidity more than 98%,the suitable floc and the quick sedimentation as well.In this thesis,it is first to produce bio-coagulant aid by modifying polysaccharide extracted from natural algae in salt pond.Comparing with the traditional chemical coagulant aid,it has some excellent advantages,such as stable effect,biodegradable,no secondary pollution,security,no toxicity,etc.It not only reduces the dosage of chemical reagent obviously and protects the security of the drinking water,but also makes good use of algae in salt pond.It has a good prospect of application.This achievement will be a good foundation for developing the resource of the algal in salt pond and new products of bio-coagulant aid.