| Palladium(Pd)as platinum group metals(PGMs),are naturally occurring chemical elements with spectacular physical and chemical properties.Furthermore,it is an indispensable key material in the field of high technology and automobile manufacturing,especially in navigation,aerospace,aviation,nuclear energy and weapons.Moreover,palladium is also an investment variety that can not be ignored in the international precious metal investment market.High market demands provoked enhanced commercial values for these metals.Therefore,it is of great significance to the recovery of palladium ions.Herein,we fabricated a novel surface ion-imprinted ceramic membrane by combining the membrane-based separation technique with ion-imprinting technology,to remove palladium ions from aqueous solutions selectively.In this paper,palladium ion imprinted alumina(IIP-PVI/AO)was synthesized by reversible addition fragmentation chain transfer(RAFT)polymerization,The optimum reaction conditions were determined as concentration:20 wt%,temperature:70℃,time:8 h.The adsorption behavior of IIP-PVI/AO for Pd(Ⅱ)was significantly affeected by pH value.The adsorption capacity of IIP-PVI/AO for Pd(Ⅱ)were 27.52 mg/g at pH 4.The adsorption could be well described by the Freundlich model and pseudo-second-order kinetic model.When the competitive Cu2+、Ni2+and Pt2+were present,the selection coefficients of Pd2+/Cu2+、Pb2+/Ni2+and Pb2+/Pt2+were 8.46,9.81 and 6.56,respectively,indicating that IIPs had strong recognition ability for Pd2+.IIP-PVI/AO also has good adsorption during dynamic adsorption;Also,the regeneration and reusability experiments indicated the preservation of approximately 93.6%of the initial efficiency after the performance of five consecutive cycles.In this paper,a new type of surface ion imprinted composites for selective adsorption of palladium ions in water was prepared by combining surface ion imprinting technique with Ceramic membrane separation technology.Based on mussel principle,CM was modified by self-polymerization of dopamine with CuSO4/H2O2 as catalyst.the hydrophilic ceramic membrane(CM-PDA)are synthesized by selfpolymerization of dopamine(DA)in aqueous solution.The hydroxyl and amino groups on dopamine were reacted with trithioester to obtain a modified CM-TTC.The modified CM-TTC was obtained by grafting the hydroxyl group and amino group into trithioester.Subsequently,PVI-CM.was obtained by grafting monomer 1-vinyl imidazole onto trithioester group by RAFT(reversible addition broken chain transfer).Cross-linked blotting to obtain imprinted ceramic membrane(IIP-PVI/CM)with palladium ion imprinted holes on the surface.The chemical combination and results of the materials were studied.It is found that when the pH value is 4.0,the IIP-PVI/CM reaches the maximum adsorption capacity,and the maximum adsorption value is 129.19 mg/100g.Through the study of static adsorption,it is found that the thermodynamic adsorption process of Pd(Ⅱ)by IIP-PVI/CM accords with the Freundlich model,and the kinetic adsorption process is more in accordance with the quasi-second-order kinetic process than the static adsorption process.The adsorption of Pd(Ⅱ)by IIP-PVI/CM reached the adsorption equilibrium within 2 h.In the study of selective adsorption,it is found that in the presence of interfering ions,such as:Cu(Ⅱ),Ni(Ⅱ),IIP-PVI/CM showed high adsorption selectivity for Pd(Ⅱ).After eight adsorption-desorption processes,the adsorption rate of Pd(Ⅱ)by IIP-PVI/CM was only reduced by 5%,and it had good reusable performance.These studies show that IIP-PVI/CM coincidence materials have a good application prospect.In this work,we used an aluminum ceramic membrane as a support material and deposited a polydopamine active layer through the mussel principle.Subsequently,modified by γ-methacryloxy propyl trimethoxyl silane(MPS).An novel ion-imprinted ceramic membrane(IIP-PVP/CM)has been prepared by incorporating Pd(Ⅱ)ion matching sites.The selective properties of IIP-PVP/CM for Pd(Ⅱ)ions were examined by static adsorption and dynamic separation experiments in the presence of Pd(Ⅱ)ions.Then,a series of adsorption experiments were carried out using IIP-PVP/CM and NIP-PVI/CM,and it was found that adsorption effect was best under the condition of pH=2,which was consistent with previous results.The maximum Pd(Ⅱ)ion capacities of the IIP-PVP/CM and the NIP-PVI/CM were determined by performing the isotherm studies under different Pd(Ⅱ)initial concentrations and treating the obtained experimental results using Langmuir and Freundlich models.The maximum capacity was around 167.19 mg/100g,which is considered a high competing value.When 10 mg/L single Pd(Ⅱ)solution was separated,IIP-PVP/CM did not penetrate until it was filtered for 35 min.Finally,recyclability study was carried out.It was found that the adsorption capacity of IIP-PVP/CM only decreased by 8.02%after 6 cycles compared with the result of first time. |
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