Combined Application Of CTA Membrane And NIPAM/SA Hydrogel In Forward Osmosis With Concentrating Esterification Wastewater

The esterification wastewater produced by many industries with high concentration of complex pollution are stable chemical properties which is harmful for enviroment.An effective treatment would be needed.In this paper,a high recovery forward osmosis(FO)technology is used to concentrate the esterification wastewater combined with hydrogels.In this project,cellulose triacetate(CTA)was used as the film-forming material,and the CTA membrane was prepared by phase inversion method.The influence mechanism of the film-forming material was investigated and the performance of the film was optimized through performance tests such as water flux.And poly N-isopropylacrylamide-sodium acrylate hydrogel(NIPAM/SA)hydrogel agent were polymerized by N-isopropyl acrylamide(NIPAM)and sodium acrylate(SA)via physical copolymerization method.The effects of several parameters(monomer ratios,different concentrations of cross-linking agent,initiator and pore-forming agents)on the swelling kinetics,p H sensitivity,swelling and de-swelling properties of the prepared hydrogel were investigated.And optimized membrane and agent were applied for different concentration esterification wastewater.The impacts of system operating conditions(COD concentration,salt rejection ratios of draw agents,cross-flow velocity,the p H of wastewater and regeneration of agent)on water flux were investigated.Through the analysis of the film performance,the optimal film casting solution ratios was determined as: 14.5 wt.% CTA + 68.0 wt.% 1,4-dioxane + 7.5 wt.% Acetone + 10.0 wt.% Maleic acid.Among them,the mechanism of film formation is as follows: CTA concentration mainly affects the molecular chain density;maleic acid controls the number of hydrophilic groups and the film formation rate;different solvent ratios delay molecular chain polymerization by using the volatility of acetone.Through the analysis of the hydrogel performance test,the optimal ratios of the hydrogel preparation agent was determined to be: 46.5 wt.% NIPAM + 46.5 wt.% SA + 3 wt.% MBA + 2 wt.% APS + 2 wt.% PEG4000.Through Fourier transform infrared test,scanning electron microscope analysis and hydrogel performance test,it can be seen that the monomer ratio affects the hydrophobic balance of the hydrogel by controlling the SA concentration;the crosslinking agent affects the integrity of the internal network by affecting the crosslink density of the molecular chain;The initiator adjusts the molecular chain length during the chain reaction stage and thus affects the network pore size.The following conclusion can be obtained from the FO test.The optimal membrane surface velocity is 1.46 cm·s-1.The hydrogel can completely overcome the drawback of the reverse osmosis of the draw solution.The hydrogel agents are not affected by the alkalinity acidity change of wastewater and display a good reproducibility.What’s more,the concentration test of esterification wastewater shows that both NIPAM/SA/4000 and NIPAM/SA hydrogels can treat a certain concentration of wastewater with through FO technology,which means hydrogel has a certain application value.It can be seen from the FO test that the water flux and wastewater concentration effect generated by NIPAM/SA/PEG4000 is higher than that of NIPAM/SA,that is,the COD concentration of wastewater is concentrated respectively by 1.124 times and 1.09 times,The pore-forming agent can improve the forward osmosis efficiency by improving the swelling property,so adding the pore-forming agent can be an effective method to enhance the forward osmosis technology.