Preparation Of Carbon-based Electroactive Ion Exchange Materials And Its ESIX Performance

Electrochemically switched ion exchange（ESIX）method is an environmentally benign ion separation and recovery technique,which provides a selective and reversible process for the separation of target ions.In conventional ion exchange,the regeneration of the ion exchanger generally produces secondary wastes based on acid/base elution.However,in the ESIX process,the ion uptake and elution can be controlled directly by modulating the electrochemical potential of electroactive materials deposited on the conductive substrate.Since electricity is the main driving force for ion transport,secondary pollution from the chemical regenerant and associated rinse water of conventional ion exchange technology can be avoided.For the application of ESIX,the key lies in the preparation and selection of materials.In this study,an intercalated PANI/MMT hybrid material was synthesized by electrochemical method and applied in the separation of Pb²⁺ions.The structure,morphology,and composition of PANI/MMT hybrid film were investigated by X-ray diffraction（XRD）,Fourier transform infrared spectroscopy（FT-IR）,scanning electron microscopy（SEM）,transmission electron microscopy（TEM）and energy dispersive spectroscopy（EDS）.Cyclic voltammetry coupled with electrochemical quartz crystal microbalance（EQCM）was used to detect the ESIX performance of PANI/MMT hybrid film.It is found that PANI deposited on the MMT sheet tightly,the hybrid film exhibits rapid ion and electron transfer ability due to the electrostatic attraction between the MMT sheet and PANI.This hybrid film not only has good electrical activity but also possesses excellent ion exchange performance based on the synergistic effect of organic and inorganic components in the hybrid film.PANI/MMT hybrid film shows fast uptake/release ability for the removal of Pb²⁺ions from aqueous solution and the equilibrium of adsorption-desorption can be achieved within 80s,the adsorption capacity for Pb²⁺by ESIX is about 4 times higher than those of traditional ion exchange.In addition,the synthesized PANI/MMT hybrid film not only has a high selectivity for Pb²⁺ions,but also possesses sensing effect on low concentration Pb²⁺ions（ppb level）.For the application of electronically switched ion exchange,the choice of matrix is also particularly important.In this paper,three-dimensional porous tubular coal-based carbon membranes with good electrical conductivity,high mechanical strength,and good chemical stability were used as substrates.NiHCF with good stability and excellent ion exchange performance was loaded into its porous structure by chemical precipitation method to prepare NiHCF/CTCM.And the coated tubular coal-based carbon membrane was used as a membrane electrode material combined with a self-designed tube-type electronically controlled vacuum filtration device to investigate the effect of its electronically controlled separation for radioactive Cs⁺ions.The results show that NiHCF/CTCM can effectively remove low concentration Cs⁺ions driven by the electrode potential due to the unique affinity of NiHCF for Cs⁺ions.The removal efficiency is above 98%,and it can directly reach the emission standard without secondary treatment.Moreover,the adsorption effect is not affected by other interference ions,and it has high selectivity for Cs⁺ions.In addition,It is obvious that the NiHCF/CTCM had good desorption efficiency with around90%in each cycle which guarantee the requirements of multiple cycles of regeneration and repeated reuse in practical applications.