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

Abstract

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.