Palygorskite in sodium sulphide solution via hydrothermal process for enhanced methylene blue adsorption

Palygorskite (PAL) has been recognized as a potential adsorbent for the removal of various dyes from aqueous solution, and so how to enhance its adsorption capability by an efficient approach becomes the subject of great interests. Herein, natural PAL was modified via a simple one-pot hydrothermal process in the presence of sodium sulphide to enhance the adsorption capabilities. The resultant material was characterized by Fourier transform infrared spectroscopy, X-ray diffraction and field-emission scanning electron microscopy, and the adsorption properties were evaluated using methylene blue (MB) as the model dye to explore the synergetic effect of hydrothermal process and sodium sulphide on the structure, physico-chemical features and adsorption properties. It was found that the PAL rod crystal was partially evolved as new silicate with relatively higher adsorption activity. The adsorption capacity for MB evidently enhanced from 129.71 mg/g to 187.56 mg/g after hydrothermal modification, and the adsorption kinetics can be accurately fitted by a pseudo-second-order model. The chemical adsorption is the main driving force for the adsorption process, and the intensified electrostatic and hydrogen-bonding interaction between MB and PAL and the chemical association of-Si-O- groups with MB molecules plays a key role to enhance the adsorption properties. (C) 2015 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.