Study On Mg/Al Layered Double Hydroxides Regeneration Of Anion Exchange Resin By Field Intensification

Regeneration of ion exchange resin is one of the crucial operations during the ion exchange equipment operation,to purposely and effectively regenerate the exhausted anion exchange resin determines the economic cost of the operation.Therefore,to develop an effective regenerant of anion exchange resin and regenerative method has an important significance to the water treatment industry.In this thesis,firstly based on polluting property of the exhausted resins,the pneumatic stirring method with Mg/Al double metal hydroxides as regenerant was adopted to regenerate the resins,and then by using Mg/AlLDHs“roasting memory”function could realize the recycle of regenerant and several effective regeneration of resins.These results of conductivity“breakthrough experiment”showed the anion exchange resins could be well regenerated under anion resins of 50mL,Mg/Al molar ratio of 3,Mg/Al hydroxides of 0.045and 0.015mol respectively and regenerative time of 3h;when the volume ratio of anion resins and cation resins was 2:1,the maximum volume of effluent water could be obtained.In addition,in each cycle the regenerant could effectively regenerate exhausted anion exchange resins.By the SEM,XRD,EDX,FT-IR and TG-DTA characterizations of the regenerant after reaction,these results confirmed that there was CO₃^2-in the regenerant,which showed the regenerant had transformed into Mg/Al layered double hydroxides and had remarkable feature of Mg/Al layered double hydroxides.In addition,the homemade electrochemical device was used;the exhausted anion resins were regenerated by common action of the direct electric field and the Mg/Al double metal hydroxide.The results showed that both joint regenerated method was superior to single electrochemical regeneration and single Mg/Al double metal hydroxide regeneration.Voltage of 20V,regenerative time of 4h,Mg/Al hydroxides of 0.09 and 0.03mol respectively for100mL anion resins were the best regenerative conditions.Finally,by means of experiments and characterization analysis,the regeneration mechanism of resins and the synthesis mechanism of Mg/AlLDHs were explored.During the regeneration,Mg/Al double metal hydroxides gel after mixing recombined into Mg₄Al₂?OH?₁₂·?OH?₂,and the dissociated OH^-continually replaced with CO₃^2-or HCO₃^-on the resins,which could renew exchange capacity of resins,and the CO₃^2-in the solution reacted with[Mg₄Al₂?OH?₁₂]²⁺to generate Mg/AlLDHs.Under the electric field,the ionized OH^-from Mg/Al hydroxides and H₂O,and the dissociated OH^-from mixed hydroxide gel reacted together with the exhausted resins for the continuous ion exchange reaction to restore the ion exchange capacity of the resins,that is,the electric field could further enhance the regeneration of the resins.