Light induced growth of polyelectrolyte brushes on kaolinite surface with superior performance for capturing valuable rare-earth Ce 3+ from wastewater

Abstract In order to obtain a low-cost and effective adsorbent for separating valuable rare-earth ions from wastewater, a surface rich carboxyl decorated kaolinite composite (PAA-KLN) was fabricated through poly(acrylic acid) grafting via an integrated UV-initiated grafting approach, involving surface hydrophobic modification under ordinary temperature and the coating of liquid photosensitizer (benzophenone) film to meet the specific initiator/substrate combination. The successful grafting was characterized by XRD, SEM/TEM, FTIR and TG/DTG/DSC. Due to the good hydrophilic property of poly(acrylic acid) brushes, their free-end would extend into the solution to form a surface villus layer, bringing lots of highly accessible adsorption sites. The resultant PAA-KLN exhibited outstanding adsorption capacity for Ce 3+ of 189.63 mg/g and rapid adsorption rate (reaching equilibrium within 40 min). Furthermore, PAA-KLN displayed an excellent reusability with high desorption ratio even at low concentration stripping liquid (0.2 M HCl), demonstrating its excellent application potential in recycling valuable metal from wastewater.