Preparation Of A Surface-imprinted Polymer And Its Adsorption Behavior For Cooper-citrate Complex

The wastewaters discharged from industries such as electroplating contain many heavy metal complexes(HMCs)due to the wide application of complexing agents in these industries.HMCs are highly toxic and can be enriched through the food chain,seriously harming the ecological environment and human health.Traditional treatment technologies for heavy metal wastewaters such as chemical precipitation have low removal efficiency for HMCs.Moreover,compared with free heavy metal ions,HMCs have much higher stability in water,and it is difficult to treat wastewaters containing HMCs to discharge standards by using traditional treatment technologies like chemical precipitation.In order to remove specific HMCs efficiently from wastewaters,it is of great practical significance to develop novel selective adsorbents.In this study,a novel surface imprinted polymer(SIP)was synthesized for selective removal of Cu-citrate(Cu-Cit)complexes from water.Polyethyleneimine(PEI)was initially grafted on the surface of chloromethylated crosslinked polystyrene(CMPS)microspheres and PEI resin was prepared.Then Cu-Cit complexes were imprinted on PEI resin with ethylene glycol diglycidyl ether(EGDE)as crosslinking agent.Finally,SIP was obtained by eluting the templates by hydrochloric acid.The physicochemical properties of SIP were investigated by total exchange capacity,BET specific surface area,FT-IR and XPS.Effects of various parameters such as initial p H,temperature,solution concentration and contact time were studied by batch tests.The optimal initial p H for CuCit complexes adsorption by SIP was 4.High temperature was favorable for the adsorption.The fitting of Langmuir isotherm model showed that the maximum adsorption capacity of SIP for Cu-Cit at 303 K was 1.376 mmol/g.The adsorption process followed the pseudo-second-order kinetics model.The exhausted SIP can be regenerated by HCl and the adsorption capacity did not decrease obviously after 6 times of repeated use.SIP had a good resistance to inorganic salts even adding concentrations up to 20 mmol/L.The selectivity of SIP to Cu-Cit was confirmed by competitive adsorption experiments in bicomponent systems.When Cu(II)-Cit coexisted with Fe(III)-Cit,Cd(II)-Cit,Ni(II)-Cit and Zn(II)-Cit,the selectivity coefficients of SIP for Cu-Cit were 15.32,20.81,1.52 and 2.73,respectively.Fixed-bed adsorption using real electroplating wastewater showed that SIP column can produce 114 bed volume(BV)clean water(< 0.5 mg Cu/L)with 171.45 mg Cu/L in the influent.Meanwhile,the COD concentration decreased significantly.The desorption rate of SIP column was higher than 99% using 1mol/L HCl as a desorption agent,which demonstrated that SIP had a good regenerability.The adsorption mechanisms involve electrostatic interaction,coordination and spatial matching of Cu-Cit complex anions and imprinting cavities.