Synthesis of carboxylic acid functionalized diatomite with a micro-villous surface via UV-induced graft polymerization and its adsorption properties for Lanthanum(III) ions

To develop a high efficiency absorbent for separating and recovering valuable rare earth ions from wastewater, a new carboxylic acid functionalized diatomite (denoted as DGA) was prepared by grafting the polyacrylic acid (PAA) chains on the surface of diatomite via surface-initiated polymerization under UV irradiation. On a micro level, it can be observed a uniform micro-villous layer obviously on DGA surface due to that a mild grafting was achieved, so the composite can maintain the morphology and strength of the substrate to the greatest extent. The introduction of abundant carboxylic acid on the surface of diatomite can contribute to an enhanced adsorption performance for rare earth ions. In order to investigate the adsorption performance of DGA, Lai(3+) was chosen as the model adsorbate, factors influencing Lai(3+) adsorption efficiency of DGA were systemically investigated, such as pH, ionic strength, contact time, and the initial concentration of Lai(3+). Under optimized condition, the saturated adsorption amount could reach to 139.5 mg/g. Moreover, Lai(3+) adsorption shows a rapid process, especially, at an initial Lai' concentration of 20 mg/L, the time to reach equilibrium was as short as 20 min. Adsorption kinetic as well as equilibrium isotherm was also evaluated. Results of regeneration experiments show that DGA can keep above 90% adsorption capacity and desorption rate in the eight consecutive cycles. The study suggests that the DGA is a promising adsorbent for removal of REE ions from aqueous solution. (C) 2016 Elsevier B.V. All rights reserved.