Preparation Of Polyvinyl Alcohol Microspheres Modified By Methacrylic Acid And Study On Their Adsorption Properties

The composition of industrial wastewater is relatively complex,and most of them are toxic and harmful substances,which have a great influence on the stability of water body.The most representative pollutants are dyes,heavy metals,etc.,and various pollutants in wastewater have a very serious impact on people’s life.Therefore,the effective separation and removal of pollutants in industrial wastewater is of great significance to ecological balance and sustainable economic development.In line with the concept of economic environmental protection and green chemistry as the starting point,this study prepared a functional material based on biodegradable polyvinyl alcohol and methacrylic acid as the functional monomer,which was used for adsorption and removal of methylene blue and Cu²⁺in water.（1）Firstly,biodegradable cross-linked microspheres CPVA were successfully prepared by reverse suspension polymerization.After that,cerium-hydroxyl redox initiator was used to graft MAA onto the surface of CPVA,and the grafted microspheres CPVA-g-PMAA was successfully prepared.Fourier transform infrared spectroscopy（FT-IR）and scanning electron microscopy（SEM）were used to characterize the chemical structure and micromorphology of CPVA and CPVA-g-PMAA.The influence of main influencing factors on graft polymerization was investigated,and the optimum reaction conditions were obtained as follows:the MAA concentration of 5.1 mol/L,reaction temperature 55℃,concentration of ammonium cerium sulfate 7.0 mmol/L,concentration of concentrated sulfuric acid 0.45 mol/L,and reaction time 8 h.The degree of grafting was 21.2 g/100 g.（2）The adsorption of methylene blue（MB）by grafted microspheres CPVA-g-PMAA was studied.It can be concluded that:when the temperature is 25℃and the p H is 7,the adsorption of MB by CPVA-g-PMAA reached equilibrium at 160 min.The pseudo-first-order and pseudo-second-order adsorption kinetics models were used to fit the adsorption kinetics data of CPVA-g-PMAA towards MB.It was found that the adsorption kinetics data of CPVA-g-PMAA were in accordance with the pseudo-second-order adsorption kinetics model.With the increase of temperature,the adsorption capacity of the grafted microspheres CPVA-g-PMAA for MB also increases.Langmuir and Freundlich adsorption isotherm models were used to fit the adsorption isotherm at different temperatures.It was found that the isothermal adsorption data of CPVA-g-PMAA for MB at different temperatures accords with the Langmuir isotherm model.With the increase of p H,the adsorption capacity of CPVA-g-PMAA for MB also increases.In addition,the grafted microspheres have good reuse performance.（3）The adsorption of Cu²⁺by grafted microspheres CPVA-g-PMAA was studied.It can be concluded that:sat 25℃and p H 5.5,the adsorption of Cu²⁺by CPVA-g-PMAA reaches equilibrium after 180 min,and the pseudo-first-order and pseudo-second-order adsorption kinetics models are used to fit the adsorption kinetics data.It was found that the adsorption kinetics of Cu²⁺onto CPVA-g-PMAA was in accordance with the pseudo-first-order kinetics model.Langmuir and Freundlich adsorption isotherm models were used to fit the adsorption isotherm at 25℃.It was found that the adsorption isotherm data of Cu²⁺on CPVA-g-PMAA grafted microspheres at 25℃accorded with Langmuir isotherm model.With the increase of p H,the adsorption capacity of CPVA-g-PMAA toward Cu²⁺also increases.With the increase of temperature,the adsorption capacity of CPVA-g-PMAA for Cu²⁺also increases.With the increase of salinity,the adsorption capacity of the grafted microspheres CPVA-g-PMAA for Cu²⁺decreased.And the grafted microspheres CPVA-g-PMAA had good reuse performance.