Preparation of smart brush-type cation-exchange adsorbents grafted nanosurface via SI-ATRP for dye removal

Abstract

Application of brush-type cation-exchange adsorbents is attractive for efficient treatment of wastewater. But one of the great challenges in this field is the fabrication of adsorbents with high adsorption efficiency and stability under different pHs and temperatures as well as reusability. Here, promising organic-inorganic hybrid adsorbents were employed to remove organic dyes from water which are fast, reusable, and efficient. Poly(glycidyl methacrylate) p(GMA) was attached to the surface of TiO2 nanoparticles (NPs) via the SI-ATRP. Primarily, hydroxyl groups of the surface of TiO2 NPs were functionalized using aminopropyltriethoxysilane (APTES) followed by alpha- bromoisobutyryl bromide (BIBB) for covalent attachment of the ATRP initiator (0.3 mmol Br/g of nanoparticles) onto the surface. Decreasing the surface area after modification of TiO2 nanoparticles (NPs) with BIBB was observed from 59.25 m2/g for TiO2 to 51.46 m2/g for TiO2-Br macroinitiator. Then grafting of p(GMA) brushes on the surface of the macroinitiator was performed via the SI-ATRP method. The surface area was decreased to 5.06 m2/g and TiO2-p(GMA) polymer brushes with a grafting density of 1.12 chains/nm2 were formed. The cation-exchange adsorbent was formed through modification of epoxide groups of the grafted p(GMA) to sulfonate (SO3-) groups. The adsorption capacity of the prepared adsorbent for methylene blue (MB) was investigated under different pHs, adsorbent dosages, salt concentrations, and temperatures. Decreasing the dye removal efficiency to 57.4% was found after increasing the concentration of salt to 0.8 M. The maximum adsorption capacity for MB was 91.49 mg/g. Adsorption isotherm of Freundlich and pseudo-second-order kinetic model have exactly matched with experimental data of MB adsorption. The dye removal efficiency of the adsorbent did not decrease significantly after six cycles of adsorption.