| Today,with the development of industrial manufacturing,heavy metal pollution is becoming more and more serious,which has posed a threat to the safety of natural water bodies.Heavy metals in water bodies can cause harm to fisheries,animal husbandry,agriculture,and even humans.The adsorption method for the treatment of heavy metal wastewater has been widely used in recent years due to its simple operation and good treatment effect.Cellulose is widely distributed in nature,and its surface has many functional groups that can be used for grafting,which can be used to prepare high-performance heavy metal ion adsorbents.In this experiment,carboxymethyl cellulose(CMC)was prepared by reacting microcrystalline cellulose as the matrix material with monochloroacetic acid,and acrylamide(AM)as a monomer,potassium persulfate and sodium bisulfite as the catalyst,N,N,-methylenebisacrylamide(MBA)as the crosslinker,and carboxymethyl cellulose-acrylamide P(CMC-AM)was prepared for adsorption of Zn(Ⅱ.)and Cr(Ⅵ.)in wastewater,in order to provide a reliable material for the treatment of heavy metal pollution wastewater.The main conclusions are as follows:After carboxylation of microcrystalline cellulose,the catalyst mole ratio of ammonium persulfate and sodium bisulfite is 1:2.Under the action of N,N-methylene diacrylamide,the carboxylcellulose-acrylamide P(CMC-AM)has better adsorption effect on Zn(Ⅱ)and Cr(Ⅵ)ions.Characterization and analysis of P(CMC-AM)adsorbents showed that microcrystalline cellulose before and after modification by infrared spectroscopy(FTIR)showed that carboxyl groups and amide groups were added to the modified microcrystalline cellulose,the same as the target product.Specific surface area and pore size analysis(nitrogen adsorption)show that the surface area,pore size and pore volume of the modified cellulose have increased significantly.Scanning electron microscopy analysis(SEM)showed that the smooth rod-like structure of the surface of microcrystalline cellulose,after modification,became a bumpy rough surface,which increased the surface area and provided good conditions for adsorption of Zn(Ⅱ.)ions and Cr(Ⅵ.)ions.Tiny particles appear on the surface of the modified cellulose after adsorbing Zn(Ⅱ)and Cr(Ⅵ.)ions,which may be adsorbed metal ions.Spectroscopic analysis(EDS)showed that the modified microcrystalline cellulose element composition contained Zn and Cr elements after the completion of the adsorption test,indicating that the modified cellulose was able to adsorb Zn(Ⅱ.)and Cr(Ⅵ.).The initial concentrations of p H,adsorption time,adsorption temperature,Zn(Ⅱ.)and Cr(Ⅵ.)were determined by influencing factors test research to have an impact on the test results.When the p H=6,the adsorption time is 90min,the adsorption temperature is 25℃,and the initial concentration of Zn(Ⅱ.)and Cr(Ⅵ.)is 2mg/L,the adsorption effect is the best,and the removal rates of P(CMC-AM)to Zn(Ⅱ.)and Cr(Ⅵ.)ions are 90.75%and 84%,respectively,and the adsorption capacity of Zn(Ⅱ.)and Cr(Ⅵ.)is 7.26mg/g and 6.72mg/g,respectively.In the adsorption kinetics test,the adsorption process of P(CMC-AM)to Zn(Ⅱ.)and Cr(Ⅵ.)was more fitted to the quasi-secondary kinetic model(R2=0.982,0.987;χ2=0.019,0.005),indicating that the adsorption process of chemical adsorption played a leading role;in the isothermal adsorption model experiment,it was found that the Process of P(CMC-AM)adsorption Zn(Ⅱ.)and Cr(Ⅵ.)was fitted with the Langmuir isothermal adsorption model(R~2=0.987).0.986;χ2=0.00018,0.00016,indicating that this adsorption is the adsorption of a single-molecular layer;through adsorption thermodynamic studies,it is found that the thermodynamic parameters of P(CMC-AM)adsorption Zn(Ⅱ.)and Cr(Ⅵ.)adsorption processes?H~θvalues are in the range of 20～400J/mol,and ?G~θ<0 indicates that this adsorption process can be spontaneously thermochemical adsorption reaction.In the experiment of optimizing adsorption conditions on the response surface,the experimental data of Zn(Ⅱ.)and Cr(Ⅵ.)adsorption by P(CMC-AM)were more significant by quadratic polynomial test F(F=79.75,12.52),P(<0.0001,0.0015),and predicted R2pre value(R2pre=0.8743,0.2161).The model calculates that the adsorbent adsorption Zn(Ⅱ.)reaches the maximum adsorption capacity condition:the amount of adsorbent is 0.25g/L,the adsorption temperature is 26.33℃,the initial concentration of Zn(Ⅱ.)is 2.07mg/L,and the solution p H is 6.13,and the maximum adsorption capacity is 7.3751mg/g.The model calculated that the adsorbent adsorption Cr(Ⅵ.)reached the maximum adsorption capacity condition:the amount of adsorbent was 0.25g/L,the adsorption temperature was 27.72℃,the initial concentration of Cr(Ⅵ.)was 2.20mg/L,and the solution p H was 6.31,and the maximum adsorption capacity was 6.8527mg/g.Microcrystalline cellulose modified to obtain carboxymethyl cellulose-acrylamide P(CMC-AM)has a strong adsorption capacity for Zn(Ⅱ.)and Cr(Ⅵ.),providing a new material for the treatment of Zn(Ⅱ.)and Cr(Ⅵ.)contaminated wastewater. |
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