Improved mechanical strength and adsorption capacity of anion exchange resin by poly (acrylic acid)/phenolic interpenetrating polymer networks

Polyacrylic anion exchange resin (AER) is effective in removing many contaminants in water, but their poor mechanical strength limits their industrial application. In this study, AER-1 with poly (acrylic acid) /phenolic interpenetrating polymer networks was prepared under acidic conditions, and the resin was characterized and evaluated for its adsorption performance. The sphericity after attrition of AER-1 was 97.5 %, while the AER was only 57.1 %. This improved mechanical strength could be partially attributed to hydrogen bonds. Moreover, the increased pore volume and average pore size results in the enhanced adsorption amount from 0.22 mmol/g to 0.26 mmol/g at equilibrium with 0.05 g resin in 100 mL of ibuprofen solution (0.15 mM). An increasing kinetic constant from 0.024 to 0.033 can be obtained from the pseudo-first order kinetic fitting (R2 > 0.99). Compared with AER-1, AER-2 synthesized under alkaline conditions shows a less improved performance in mechanical strength and pore structure. The Langmuir adsorption isotherm model (R2 > 0.98) is more consistent with the experimental data, indicating monolayer adsorption on a homogeneous surface. Small molecule acidic organics are more competitive due to the expansion of resin pore channels. Gallic acid (80 mg/L) lowers the adsorption capacity by 64.3 %, while humic acid only produces a 10 % reduction in adsorption capacity because of pore exclusion. Excellent reusability of AER-1 for ibuprofen adsorption has been demonstrated by adsorption-regeneration cycle experiments.