Hydrophobic-force-driven adsorption of bisphenol A from aqueous solution by polyethylene glycol diacrylate hydrogel microsphere

Polyethylene glycol diacrylate (PEGDA) hydrogel microsphere was synthesized by UV-assisted reverse emulsion polymerization as an efficient adsorbent for water purification. Optical microscopy and TEM proved its spherical and hollow structure, while XRD pattern proved that it was amorphous with limited crystallinity. Abundant oxygen-containing functional groups such as hydroxyl were detected by FTIR. The hydrogels exhibited low swelling capacities ranging from 0.19 to 0.77 g/g in water and would decrease in salty solutions. The effects of operation parameters on the bisphenol A (BPA) adsorption were studied, including the polymer composition between PEGDA and polyethylene glycol methacrylate (PEGMA), initial concentration of BPA, pH, and operation temperature. The resulting hydrogel, especially for PDM 2 (the ratio between PEGDA and PEGMA is 2), was able to effectively enrich BPA in water. The adsorption capacity was nearly stable below pH 8.0 and decreased when beyond 8.0. Thermodynamic parameters reflected that BPA adsorbed by hydrogel was a spontaneous ( ΔG 0  < 0) and exothermic ( ΔH 0  < 0) progress. The adsorption capacity increased with the increase of the concentration of NaCl, exhibiting salinity-enhanced adsorption capacity driven by hydrophobic force. Excellent results were also achieved by applying hydrogel for spiked real surface waters, which accounted for more than 91% compared to simulated solution. As-prepared hydrogel was expected to be good candidate for treatment of endocrine disruptors with lower solubility in water.