Enhanced removal efficiency of clinoptilolite nano-particles toward Co(II) from aqueous solution by modification with glutamic acid

Natural clinoptilolite tuff was pretreated and converted to micro (MCP) and nano (NCP) particles by mechanical method. The raw materials and their co-exchanged forms were modified by glutamic acid(GLU) and characterized by XRD, IR, SEM, BET, TG and energy dispersive X-ray analysis (EDX). Removal of Co(II) by the modified and unmodified samples was investigated in batch procedure. The higher removal efficiency was obtained by NCP-GLU under the following optimal conditions: pH: 6, C-Co(II): 600 mg L-1, contact time: 360 min and GLU dosage: 5 mmol L-1. The modified zeolite showed good selectivity for cobalt in the presence of different multivalent cations. Adsorption isotherms of Co(II) ions were fitted to Langmuir equation, that indicates the monolayer sorption of Co(II). The adsorption kinetic obeyed the pseudo-second-order rate equation that indicates that a chemical reaction is responsible for the rate limiting step. The negative Delta H and Delta G indicate an exothermic and spontaneous process while negative Delta S confirms that the adsorption of Co(II) cations from solution occurs with lower amount ion replacement. (C) 2015 Elsevier B.V. All rights reserved.