The Use of an Organo-Kaolinite Sorbent in a Permeable Reactive Barrier for Remediating Groundwater Contaminated with Methylene Blue Dye: Experimental and Theoretical Investigation

Abstract

The removal of aqueous methylene blue (MB) dye using organically modified natural Na-kaolinite was optimized. Organo-kaolinite was synthesized by replacing exchangeable Na+ ions in Na-kaolinite with cetyltrimethylammonium bromide (CTAB), and the adsorption behaviour was systematically explored as an efficient adsorbent for the removal of dyes. Furthermore, the properties of the obtained samples were characterized by FTIR spectrophotometric analysis, which confirmed that CTAB cations had modified the kaolinite to possess a new functional group. Batch mode experiments were conducted to test the performance of the modified kaolinite in removing MB dye to optimize the following experimental conditions: adsorbent quantity, initial concentration, mixing speed, contact time and initial pH. The findings indicated that the MB adsorbent efficiency could reach up to 100% when the above conditions were set at 0.3 g/100 mL, 50 mg/L, 200 rpm, 60 min and pH = 12, respectively. The adsorption isotherms and kinetics of the organic-modified kaolinite for MB concurred with Freundlich adsorption equation and the pseudo-second-order kinetics, respectively. In accordance with the principles of environmental preservation and reuse of waste, granulated glass waste was used to optimize the adsorption efficiency of kaolinite. Furthermore, two tested reactive systems were used in two-dimensional (2D) domain experiments by mixing a 1:1 ratio of modified kaolinite:granulated glass waste. The COMSOL Multiphysics 3.5a software was utilized to determine the spread of MB within the permeable reactive barrier (PRB) for the 2D domain at equilibrium conditions. • Kaolinite was modified by cetyltrimethylammonium bromide to remove methylene blue. • Organo-kaolinite was used in a two-dimensional permeable reactive barrier. • The COMSOL Multiphysics model was used to simulate the permeable reactive barrier.