Comparative Removal Properties of Sodium Magadiite and Its Protonic Form on Basic-Blue 41 from Contaminated Aqueous Solution

Abstract

Sodium magadiite (Na-Mgd) was hydrothermally prepared and converted to its protonic (H-Mgd) form by reaction with hydrochloric (HCl) solution. The obtained products were studied as adsorbents for basic blue 41 (BB-41) removal from polluted aqueous solution. Na-Mgd and H-Mgd were characterized by different techniques. Powder X-ray (PXRD) diffraction data confirmed a pure Na-Mag phase and its conversion to acidic form (H-Mgd) with shift in d001 value from 1.54 nm to 1.12 nm. X-ray fluorescence (XRF) data supported the exchange of Na cations by protons for H-Mag. 29Si magic angle spinning nuclear magnetic resonance (MAS-NMR) indicated a change in the local environment of silicon nucleus when Na-Mgd was treated with HCl solution. The BB-41 removal dyes were investigated throughout the batch process. Effects of selected parameters, for example, the adsorbent dosage, pH of the BB-41 solution, pH of the H-Mag solid, and starting concentration, were explored. The equilibrium data were fitted to the Langmuir and Freundlich isotherm models. The maxima removal capacities of Na-Mgd and H-Mgd were 219 mg/g and 114 mg/g, respectively. The regeneration and reusability tests were performed using initial concentrations of 50 mg/L and 200 mg/L for seven cycles. The efficiency was maintained for 5 to 6 cycles with a decline of 10% using low initial concentration; however, a decline of efficiency to 30 to 50% was achieved when a higher initial concentration was employed after 3 to 4 regeneration tests for Na-Mgd and H-Mgd samples. Adsorber batch design using the Langmuir and Freundlich isotherm parameters was used to predict its performance for commercial usage. The predicted masses of H-Mgd were higher than those of Na-Mgd to treat different effluent volumes contaminated with 200 mg/L of BB-41 dyes at desired removal percentages