Preparation Of Imprinting Polypyrrole Composite Membrane Material And Its H_xPO₄^3-x Electrochemically Switched Ion Exchange Properties

At present,the shortage of freshwater resources and water pollution pose great challenges to human survival.In particular,water eutrophication caused by excessive phosphate results in turbidity,anoxia and blooms,making many freshwater resources unusable and even destroying the ecological environment.Therefore,phosphorus treatment is imminent.At present,there are many phosphorus treatment technologies,but these technologies have many limitations.As a new technology,electronically switched ion exchange technology combines the traditional ion exchange technology with electrochemical method.By adjusting the potential change of material electrode,it can selectively controll the target ion embedding or removing,which has the advantages of high regeneration,high separation efficiency,and avoids chemical reagents and energy conservation.However,electronically switched ion exchange technology has the problem about low anion exchange capacity of conductive materials during using.This paper mainly studies the H_xPO₄³-x-x exchange performance of PPy and its composite materials.Firstly,PPy imprinting membrane material was prepared on gold plated quartz wafer by potentiostatic method.The morphology,structure and composition of membrane material were characterized by SEM,FT-IR and XPS.The results showed that the surface micromorphology of material was cauliflower and membrane contained H₂PO₄^-,which had the characteristics of H₂PO₄^-imprinting.Cyclic voltammetry and potentiostatic method were used to test the performance of PPy materials.The results showed that:?1?H_xPO₄³-x-x could be reversibly embedding or removing from PPy film material by adjusting membrane electrode potential.?2?Preparation conditions such as pH,concentration of NaH₂PO₄,concentration of pyrrole monomer,and polymerization time have a great influence on ion exchange capacity,power consumption and current efficiency.When prepared in pH with 0.28,0.5 M NaH₂PO₄,0.1 M pyrrole monomer and polymerization time with 3 min,the PPy membrane material had a higher ion exchange capacity.?3?Different electrolyte environments also have great influence on the ion exchange properties of PPy membrane materials.With the increasing of pH,the ion exchange capacity firstly decreases and then increases,showing a"V"shape.As the concentration of NaH₂PO₄ increasing,the ion exchange capacity monotonously increases.Even in 1 mmol·L^-11 NaH₂PO₄ electrolyte,PPy material can still control the ion exchange process.In different types of electrolytes,relative capacities of PPy materials were 62 mg·g^-11 and 40 mg·g^-11 during embedding and removing H₂PO₄^-.Secondly,PPy/CoNi LDH composite was prepared by potentiostatic method with PPy imprinting material as a working electrode on the gold plated quartz wafer.The composite surface morphology and crystal structure were analyzed by SEM and XRD.The composite ion exchange performance was investigated by cyclic voltammetry?CV?and potentiostatic method?CA?.The results showed that CoNi LDH has been successfully synthesized on surface of PPy and presented a thin layer of nanosheet structure.After electrochemical testing,PPy/CoNi LDH composites prepared by different molar ratios of Co²⁺/Ni²⁺have significant differences in ion exchange properties of H_xPO₄^3-x.When the ratio of Co²⁺/Ni²⁺is 1:5,the ion embedding capacity is the highest,up to 350 mg·g^-1,the removing capacity is up to 285 mg·g^-1.