Synthesis and adsorption performance of lead ion-imprinted micro-beads with combination of two functional monomers

A novel ion-imprinted polymer, lead ion-imprinted micro-beads with combination of two functional monomers, was synthesized using the W/O/W polymerization method. Two functional monomers, 1,12-dodecanediol-O,O'-diphenyl-phosphonic acid (DDDPA) and 4-vinylpyridine, were used to form a suitable construction with micro-pores fitting the template and recognition sites. The effects of adsorbent dosage, solution pH and the competitive ions on the adsorption and separation efficiency of lead ions were investigated. The lead ion-imprinted micro-beads were efficient for lead ions removal from aqueous solution in a broad pH range (4-9), when the adsorbent dosage was above 0.1 g/L. The adsorption process obeyed the pseudo second-order kinetics model and it only took half an hour to reach the equilibrium. The adsorption isotherm of lead ion was described by the Langmuir model (R² >0.99) with a maximum adsorption capacity of 116.9 mg/g. In the presence of competitive ions Co²⁺ and Cd²⁺, the lead ion-imprinted micro-beads showed a high selectivity for lead ions. The selectivity coefficient of Pb²⁺/Cd²⁺ and Pb²⁺/Co²⁺are 99.3 and 114.7, respectively.