Study On Coagulation And Adsorption Performance Of CS/CMC For Organic Matte In Water

In recent years,with the rapid development of industry,the problem of organic pollution in water bodies has become increasingly prominent,and the water environment has become more complex.Coagulation is an important part of the water treatment process,in which the coagulant determines the final effluent quality and operating cost.Natural organic polymer flocculant has become a research hotspot because of its high efficiency,safety and non-toxicity.Its removal effect and mechanism of pollutants in water bodies,especially organic matter,are worthy of in-depth study.Therefore,in this paper,natural organic polymer chitosan（CS）and sodium carboxymethyl cellulose（CMC）were used as raw materials,and the in-situ complex coagulation technology was applied to water treatment to explore the coagulation effect and removal mechanism of CS/CMC complex coagulation colloid on suspended turbidity and organic matter in water.The main research results are as follows:（1）The optimal complex condensation conditions of CS and CMC are as follows:p H is 4,mass ratio of complex condensation is 1.According to the infrared spectrum analysis,CS/CMC complex gel is generated through the electrostatic interaction between the amino group（-NH₃⁺）of CS and the carboxyl group（-COO^-）of CMC.（2）The coagulation results of CS/CMC on kaolin suspension,humic acid（HA）and kaolin-tetracycline hydrochloride（TC-HCl）mixture showed that CS/CMC had good coagulation effect on the three kinds of pollutants.Under the optimal coagulation conditions,the turbidity removal rate of high turbidity water（250～1000 NTU）is more than99%,the removal rate of HA can reach 97.6%,and the removal rate of TC-HCl and turbidity in kaolin tetracycline hydrochloride（TC-HCl）mixture are 38.67%and 99.98%,respectively.According to Zeta potential,particle size and infrared analysis,the mechanism of CS/CMC coagulant kaolin is electric neutralization and adsorption bridging.The mechanism of CS/CMC HA coagulation is a combination of compression double electric layer,electric neutralization and adsorption bridging.CS/CMC removes TC-HCl mainly through the adsorption and co-precipitation mechanism of TC-HCl and kaolin.（3）Using CS/CMC coagulated kaolin sediment（CCK）as the adsorbent,the adsorption process of TC-HCl in the kaolin-TC-HCl mixture treated by CS/CMC coagulation was studied through adsorption experiments.When the dosage of CCK was1.75 g/L,the initial concentration of TC-HCl was 5 mg/L,the p H was 4.9,and the adsorption time was 480 min,the removal rate of TC-HCl by CCK was as high as 98.46%.The adsorption process of CCK to TC-HCl conforms to the quasi-second-order kinetic model,and the adsorption process is mainly chemical adsorption.The fitting results of Freundlich isotherm model,Elovich and intra-particle diffusion model are consistent,and CCK is heterogeneous adsorption of TC-HCl in multi-molecular layers.The thermodynamic results show that the thermodynamic parameters are:ΔH⁰=19.42 k J/mol,ΔS⁰=76.71 J/（mol·K）,ΔG⁰=-3.05 k J/mol（293.15 K）,the adsorption process is endothermic and spontaneous.（4）Coagulation experiments were carried out on Yellow River,Yellow River-HA and Yellow River-TC-HCl with CS/CMC and polyaluminum chloride（PAC）,respectively.The results show that CS/CMC and PAC have certain treatment effects on the three.Under the optimal conditions,the turbidity removal rate of CS/CMC for the three is above 99.7%,the removal rate of HA is 95.15%,and the removal rate of TC-HCl is 56.72%.The removal rate of PAC for the three turbidity ranges from 99.52 to 99.75%,the removal rate of HA is 91.27%,and the removal rate of TC-HCl is 17.30%.The removal effect of CS/CMC on dissolved organic matter is significantly better than that of PAC,and its removal rate of TC-HCl can be 39.42%higher.Compared with PAC,CS/CMC has less dosing amount,good treatment effect,fast settling speed,and no secondary pollution.