Simultaneous analysis and removal of various heavy metal ions has received increasing concerns because they are usually co-existent with different toxicological effects. Ion imprinted polymers (IIPs) can effectively identify water-soluble ions especially heavy metal ions, however, multi-ion imprinting is rarely performed owing to possible cross-reactivity and matrix interferences. In this work, a novel and generally applicable IIPs strategy was proposed for simultaneous preconcentration and removal of four heavy metal ions based on dithizone chelation. Multi-ion imprinted polymers (MIIPs) embedded in a sol–gel matrix were prepared by using Hg2+, Cd2+, Ni2+ and Cu2+ as templates and 3-aminopropyltriethoxysilane as a functional monomer, and the possible synergy mechanism was explored between dithizone coordination chemistry and multi-ion imprinting. The structures, morphologies and thermostability of MIIPs were well characterized by Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) and thermogravimetry analysis (TGA). The resultant MIIPs showed high binding capacity and fast dynamics, and the adsorption processes obeyed Langmuir isotherm and pseudo-second-order dynamic models. The MIIPs displayed excellent selectivity toward the four target ions particularly over Pb2+, Zn2+ and Co2+ with selective coefficients of 6.8–16.9, as well as high anti-interference ability when confronted with common co-present various ions. Moreover, a high preparation yield of 41% and good reusability over 90% desorption efficiency were obtained. Consequently, the MIIPs were used as solid-phase extraction sorbents for preconcentration of trace Hg2+, Cd2+, Ni2+ and Cu2+, presenting high detectability up to 6.0–22.5 ng L−1 and satisfactory recoveries ranging from 94.7–110.2% in seawater samples. The developed MIIPs-based method proved to be a practically feasible method in heavy metal removal and water pretreatment.

A novel kind of Pb2+ ion imprinted polymers (IIPs) was prepared based on ionic interactions via the synergy of dual functional monomers of methacrylic acid and vinyl pyridine for selective solid-phase extraction (SPE) of Pb2+ in water samples. Suspension polymerization was employed for the formation of template Pb2+/monomer complex by self-assembly in the presence of ethylene glycol dimethacrylate cross-linker. The resulted Pb2+ IIPs showed fast kinetics, high binding capacity, and the adsorption processes obeyed intraparticle diffusion kinetics and Langmuir isotherm models. The IIPs displayed excellent selectivity toward Pb2+ over other metal ions such as Cu2+, Cd2+, Zn2+, and Mn2+ with selective coefficients above 30, as well as high anti-interference ability for Pb2+ confronting with common coexisting various ions. Through 10 adsorption–desorption cycles, the reusable IIPs exhibited a good recoverability with the standard error within 5%. These features suggested the IIPs were ideal candidates for extraction and removal of Pb2+ ions. Consequently, the IIPs were utilized as SPE sorbents and related parameters were optimized. An excellent linearity was presented in the range of 0.2–50 μg L–1 (R2 = 0.9998), as well as the limits of detection and quantification were achieved of 0.06 and 0.19 μg L–1, respectively. A good repeatability was obtained with the relative standard deviation of 2.8%. Furthermore, real water samples were successfully analyzed and satisfactory recoveries varying from 95.5 to 104.6% were attained. The IIPs-SPE demonstrated potential application perspectives for rapid and high-effective cleanup and enrichment of trace Pb2+ ions in complicated matrices.Keywords: dual functional monomers; ion imprinted polymers; ionic interaction; Pb2+; suspension polymerization; synergy;

Core–shell molecularly imprinted polymers (CS-MIPs) have aroused increasing interest owing to their easy accessibility and favorable mass transfer. Herein, we explore the correlation between shell thickness and binding capacity by using Sudan I as template molecule to prepare different CS-MIPs at the surface of carboxyl polystyrene through emulsion polymerization with a two-step temperature-rising process. Extensive characterization was performed using techniques such as SEM/TEM, FT-IR, BET, and TGA. Main factors were systematically studied such as the amount of prepolymer solution, the amount of SDS, and the temperature step. Under the optimized conditions, CS-MIPs with a shell thickness of 2.60 μm presented the highest binding capacity of 30.1 μmol g−1 and the most rapid mass transfer rate. A uniform sphere model was constructed, and it was found that template molecules located in the spherical MIPs with a diameter of 5.20 μm will be completely eluted, thereby attaining the maximum binding capacity. The static adsorption isotherm followed the Langmuir–Freundlich adsorption model, and the fast kinetics obeyed the pseudo-second-order kinetics model. High recognition specificity for Sudan I with respect to its analogues was displayed, with an imprinting factor of 2.7. The establishment of a critical value of shell thickness provides new insights into the preparation methodology and molecular recognition mechanism of core–shell imprinted polymers.