Polypyrrole Films Ion Exchange Property And Electrochemical Water Purification

Polypyrrole(PPy),a typical conductive polymer,has many advantages such as easy polymerization,harmlessness and good environmental stability.One of its promising behaviors is that it could be doped or dedoped by reversible ions exchanges controlled by electrochemical signals.Therefore,PPy composites could be used as a new kind of ion exchange resin potentially switched on and off electrochemically.Functional polypyrrole(PPy)films doped with dodecylbenzenesulfonate(DBS^-)as doping anion were prepared from aqueous solution.The electrochemically switched ion exchange ability and mechanism of the PPy/DBS film were investigated in various solutions using cyclic voltammetry(CV).It was found that the process of ion transport in PPy/DBS film exhibits quasi-reversible behavior and follows the semi-infinite diffusion rule.The ability of electrochemically switched ion exchange depends largely on the concentration of ion,the ion type and scan rates.For various cations,the order of exchange ability is K⁺＞Na⁺＞Ca²⁺＞Mg²⁺.Polypyrrole(PPy)composite films doped with dodecylbenzenesulphonate(DBS-)were electrochemically prepared on active carbon fiber felt(ACF)substrate electrode from aqueous solution.The ion exchange characteristics,current efficiencies and stability of APD_0.5and APD₁ two different thickness PPy composite films were studied(respective electrochemical polymerization time 0.5 and 1.0 h).The morphology of membrane was characterized using scanning electron microscope(SEM).The thickness of DBS/PPy composite films increased obviously with the electropolymerization time,resulting in the linear increase in the capacity of ion exchange.But the thickness of composite membrane did not influence the current efficiency remarkably.For the cation doping,ion doping capacity and current efficiency increased with the decrease of the cathodic polarization potential.Ion de-doping capacity was not influenced by the anodic polarization potential,but the current efficiency decreased obviously with the increase of the anodic polarization potential.After 50 times cyclic voltammetric scanning,the exchange capacity ofNa⁺ and Ca²⁺decreased to 92.35%and 88.1 %,98.8%and 94.1%of its starting value for APD0.s and APD₁ composite membranes, respectively.The ion exchange capacity of the PPy/DBS film on ACF was theoretically calculated to be 1.92 mmol/g and 0.96 mmol/g for Na⁺ and Ca²⁺exchange,respectively.The ion exchange capacity of the PPy/DBS film on ACF was actually calculated to be 1.064mmol/g and 0.379 mmol/g for Na⁺ and Ca²⁺exchange,respectively.Besides,an electrochemically induced precipitation method was studied for removing scale forming ions from cooling water using PtO/IrO₂/Ti electrode.This offers a new way in improving cooling water quality.