The adsorption of direct brown 1 dye using kaolinite and surfactant modified kaolinite

Abstract

This paper elucidates the removal of Direct Brown 1 (DB 1 1) dye from wastewater by using the natural kaolinite (NK) compared to Hexadecyltrimethylammonium bromide (HDTMA) modified kaolinite (HMK) as adsorbent materials at bench scale. The materials were characterized by X-Ray Diffraction (XRD) and FT-IR spectroscopy. The surface areas were determined using Sears’ method. The test effects efficiency of natural and surfactant modified kaolinite in adsorption of DB 1 1 dye has been applied as a function of initial concentrations, pH, contact times and temperatures using the batch technique. Removal of dye from aqueous solution by HMK for the test effects showed a general increase of two to five times amount of DB 1 1 adsorbed compared to NK. The DB 1 1 adsorption was influenced by temperature with an increase of sorption (15 mg/g) for HMK compared to NK. The adsorption increased with temperature suggesting that the adsorption process was endothermic. The adsorption percentages of DB 1 for pH and contact time test effects showed 93 % and 82.7 % respectively for HMK compared to 6 % for NK. Adsorption percentages of DB 1 on equilibrium concentration effect resulted with 57.5 % for HMK compared to 6 % for NK. Intraparticle diffusion and mass driving force were found to be the reasons of increase rate of DB 1 adsorption onto HMK and NK. The temperature increase influenced the total energy of the adsorbate molecules to obtain a higher rate of adsorption. Pseudo-second-order of kinetics identifies rate limiting step as the chemical adsorption involving valent forces through sharing or interparticular diffusion between NK and HMK on DB 1. The adsorption patterns data correlated well with Langmuir (R2=0.93) and Freundlich (R2=0.90) isotherm models. From the comparison showed by increase in adsorption percentages, HMK was a better choice to be used as effective adsorbents for Direct Brown 1 (DB 1 1) dye compared to NK.