| Polymer porous microspheres are widely used to remove metal ions in solution,due to the high specific surface area and can be functionalized.In this paper,the water-soluble polymer containing carboxyl group was synthesized by bulk polymerization method.The removal efficiency of metal ions(Ca2+,Mg2+,Zn2+)by polymer salt solution with different carboxyl content was investigated,and the condition of adsorption of metal ions was systematically studied.Due to the limitation of the removal effect of the metal salt solution on metal ion,porous polymer microspheres was proposed to be prepared.At first,the compatibility of various polymers in alkaline water and dichloromethane was evaluated,and a polymer which was insoluble in methylene chloride but soluble in alkaline water was selected;and then–the polymer was used to prepare porous polymer microspheres with carboxyl groups with high specific surface area in foam phase,which was developed in our research group..Secondly,the effects of the pore structure and particle size on the adsorption of metal ions was investigated;the effects of pH,metal ion concentration,adsorbent dosage,temperature and adsorption time on the adsorption of metal ions under static adsorption of polymer microspheres under optimal adsorption were studied.In addition,multi-stage adsorption of polymer microspheres was studied;the effect of metal ion removal rate was studied,and the adsorption process was simulated by Freundlich and Langmuir adsorption isotherm equations.Finally,the efficiency of desorption and reuse of polymer microspheres was preliminarily investigated.The main conclusions are as follows:1.The carboxylic acid-containing water-soluble polymer which was synthesized by bulk polymerization had limited removal efficiency of metal ions.The higher the carboxyl content,the higher the absorption of metal ions per unit mass concentration of polymer solution.However,with the polymer salt solution as the amount increaseed,the solubility of the precipitate of the polymer metal salt increasesed,resulting in a decrease in the removal rate of metal ions.On this basis,the amount of the initiator was lowered,the molecular weight of the polymer was increased,and the solubility of the polymer metal salt in the aqueous solution was lowered to increase the absorption efficiency of the metal ion by the polymer.However,the experimental results showed that even if the molecular weight was large to a certain extent,the adsorption efficiency of the polymer to metal ions was not significantly increased.2.According to the investigation of metal ion adsorption conditions,the experimental results showed that the adsorption efficiency of metal ions increased with the increase of metal ion solution concentration.By increasing the amount of polymer sodium salt with a lower carboxylic acid content,the maximum removal rates of the polymer salt solution for the concentration of 0.03 mol/L metal ions(Ca2+,Mg2+,Zn2+)were 75.01%,72.01%,and 85.92%,respectively.The pH value is an important factor affecting the ability of the polymer sodium salt to absorb metal ions and the ability of the salted polymer porous microspheres to adsorb metal ions.Since the adsorption process used hydrochloric acid and sodium hydroxide to adjust the pH value,hydrochloric acid increased the amount of H+in the solution to cause protonation of the functional group;while sodium hydroxide increased the sodium ion content in the solution,causing the sodium ion to compete with the metal ion for the polymer.Therefore,when the pH wasnot adjusted,the polymer sodium salt had the best effect on the metal ion absorption and the salted polymer porous microspheres to adsorb metal ions.3.In order to further increase the removal rate of metal ions by the polymer,a porous polymer microsphere containing carboxyl groups which is insoluble in methylene chloride in alkaline water was prepared by"foam method".It was found that the adsorption effect of the prepared polymer porous microspheres on metal ions was obtained at 300 rpm,polymer to methylene chloride ratio of 1:6.5,porogen and polymer ratio RHT/Polymer=3:5.the best.On this basis,the optimal conditions for the adsorption of metal ions by polymer porous microspheres were found by changing the adsorption conditions under static adsorption.When exploring the influence of temperature factors on the adsorption of polymer porous microspheres,it was found that the higher the temperature,the better the adsorption effect on metal ions;the appropriate temperature increased the adsorption amount of metal ions by the polymer porous microspheres.The adsorption amount of metal ions(Zn2+,Ca2+,Mg2+)by the polymer porous microspheres increased as the concentration of metal ions increases.From the efficiency point of view,when the pH value was not adjusted,the concentration of 0.03mol/L Zn2+,Ca2+,Mg2+solution was adsorbed at40°C,50°C,60°C for 30 min,respectively,to achieve adsorption equilibrium.Under the optimal adsorption conditions,the polymer porous microspheres can remove more than 99.8%of the metal ions(Zn2+,Ca2+,Mg2+)in the metal ion solution,at a concentration of about 0.03 mol/L through multistage adsorption.4.The adsorption process was simulated by Freundlich and Langmuir adsorption isotherm equations.The experimental data showed that the adsorption process of metal ions(Zn2+,Ca2+,Mg2+)by polymer porous microspheres was closer to the Langmuir isotherm adsorption equation.It further proved that the adsorption process belongs to the chemical adsorption of monolayers.The adsorbed polymer porous microspheres were desorbed with hydrochloric acid,and the adsorption efficiencies of the polymer porous microspheres for metal ions(Zn2+,Ca2+,Mg2+)were 72.3%,63.6%,60.3%of the first adsorption amount when the number of repeated reuses reached 5 times. |
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