Preparation Of Microbial Foaming Multifunctional Hydrogel And Its Treatment Of Wastewater

At present,although the treatment effect of dye and ammonia nitrogen in industrial wastewater can reach the standard,there are still problems of high treatment costs or no degradation of pollutants or secondary pollution to the environment.Multifunctional hydrogels are a new type of hydrogels with two or more functions,which are made of single function hydrogels through modification or graft copolymerization.Among multifunctional hydrogels,the solidified microbial hydrogel that combines the biological treatment of microorganisms and the physical and chemical treatment of hydrogel has been widely used in wastewater treatment.However,most studies tended to study the adsorption capacity of immobilized microorganism hydrogel and the influence of various factors on its adsorption capacity.There were few materials which were prepared based on different wastewaters and could effectively deal with pollutants.Moreover,most immobilized hydrogels were difficult to degrade after being discarded.Based on the above background,this project designed two multi-functional hydrogels with a single structure and a core-shell structure respectively based on the characteristics of dye wastewater and ammonia nitrogen wastewater.The prepared hydrogels could provide a safe living environment for microorganisms.They could efficiently adsorb and degrade pollutants,and could also degrade the materials after the materials were discarded.These would improve a new idea for the advanced treatment of wastewater.The main research contents and conclusions are as follows:(1)PVA/CMC/YE double degradation hydrogel was prepared by yeast foaming.The chemical structure of the PVA/CMC/YE double degradation hydrogel was characterized by FTIR.Combined with Zeta potential analysis and XRD analysis,the synthesis mechanism of PVA/CMC/YE double degradation hydrogels was proved.The mechanism included the hydrogen bonding between PVA and CMC,the crystallization of PVA and CMC,and the electrostatic interaction between yeast and PVA/CMC.The SEM,BET and TG showed that the introduction of yeast was benefit to the construction of PVA/CMC/YE hydrogel three dimensional network.With the increase of yeast quantity,the three dimensional network structure of hydrogels was more obvious,the specific surface area was bigger,the average pore size was smaller and smaller,and the thermal stability and swelling degree also increased.(2)The removal of MB by PVA/CMC/YE double degradation hydrogel and the biodegradability of hydrogel were studied.The results showed that the introduction of yeast not only improved the adsorption efficiency of MB by PVA/CMC/YE hydrogel,but also improved the hydrogel have double degradability that could degrade MB to colorless and self-degrade the material.The adsorption mechanism was dominated by chemical adsorption and was accompanied by biodegradable and electrostatic adsorption.The kinetic data were fitted to the pseudo-second-order kinetic model.The adsorption isotherm model accords with Langmuir model.The enzymes produced by yeast promoted the degradation of PVA in the materials and enhanced the degradation rate of CMC in hydrogels.(3)PVA-CS/SA-Ca2+core shell hydrogel was prepared by using PVA and CS as raw materials,SA and Ca2+as shell materials.The formation mechanism of the core-shell hydrogel was proved by FTIR and XPS characterization tests,which mainly include:hydrogen bonding cross-linking between PVA/CS,chelation between SA/Ca2+,and hydrogen bond cross-linking between SA un-crosslinked hydroxyl group and CS un-crosslinked amino group in the core-shell structure.The morphology of core shell hydrogel was studied by SEM.The results showed that the shell structure of the hydrogel was dense and the core structure was relatively loose.Meanwhile the larger the PVA/CS mass ratio,the more obvious the core network structure;the larger the SA concentration and the longer the SA/Ca2+cross-linking time,the thicker the shell wall.Through single factor screening and surface response analysis,the best experimental conditions for swelling degree of hydrogels were SA concentration 5%,SA/Ca2+cross-linking time 90 min,PVA/CS mass ratio 1:0.7,swelling degree 50 g/g.(4)A double loaded PVA-CS/SA-Ca2+core-shell hydrogel was prepared by coating denitrifying bacteria in core structure of hydrogel and soaking loaded denitrifying bacteria in shell structure of hydrogel.The microstructure of double loaded core shell hydrogel was observed by SEM.The results showed that the three dimensional network structure of the hydrogel structure was more regular by the coating of nitrifying bacteria,and the pore structure of the shell structure was slightly increased by the denitrifying bacteria.The removal of ammonia nitrogen wastewater by double loaded core-shell hydrogel and lipase production by hydrogel were studied.The result showed that the core-shell hydrogel had the performance of simultaneous nitrification and denitrification.The core and shell structure avoided the effects of changes in pH and temperature on the activity of nitrifying bacteria and denitrifying bacteria in the water environment.At 3 0℃～35℃,it had good simultaneous nitrification and denitrification denitrification effect on ammonia nitrogen wastewater with low alkaline(pH=8.5)and low C/N(C/N=4).Moreover,the lipase produced by the nitrification bacteria in the shell enhanced the removal efficiency of the material for low C/N ammonia nitrogen wastewater,and improved the biodegradability of hydrogels.