Magnetic Polyacrylic Anion Exchange Resin: Preparation, Characterization and Adsorption Behavior of Humic Acid

Magnetic polyacrylic resin (R0) was prepared by suspension polymerization in the presence of gamma-Fe2O3 and gamma-methacryloxypropyltrimethoxysilane (gamma-MPS). The obtained magnetic resin (R0) was modified sequentially by ammonolysis and alkylation to produce a magnetic weakly basic anion exchange resin (R1) and a magnetic strongly basic anion exchange resin (R2). Infrared (IR) spectra, elemental analysis, scanning electron microscopy (SEM), magnetization, Brunauer-Emmett-Teller (BET) surface area and chemical analysis were all determined to characterize these resins. The investigation of humic acid (HA) adsorption on R0, R1, and R2 showed that chemical interactions between the functional groups of the resin and HA were responsible for HA adsorption. The adsorption capacity of HA on R1 was similar to 20%-60% less than that of R2, but the R1 resin was easier to regenerate with NaOH aqueous solution. A mixture of 1% NaCl and 1% NaOH was found to be highly efficient for the regeneration of both R1 and R2 resins, with desorption efficiencies measuring >90%. Pseudo-second-order model and Freundlich equation fit better for HA adsorption onto R1 and R2 than other typical kinetic and thermodynamic models, respectively. The effects of pH, coexisting salts (i.e., NaCl and Na2SO4), and recyclability were also assessed.