Batch Equilibrium and Kinetic Studies of Anionic and Cationic Dyes Adsorption onto Al−Pillared Clay from a Local Cameroonian Clay Materials in Aqueous Medium

Abstract

The present work report removal of acid red 14 (AR14) and basic violet 3 (BV3) as anionic and cationic dyes, respectively, by adsorption process in batch mode from aqueous solution onto natural and modified forms of a local Cameroonian clay. The efficiency of these adsorbents materials (purified natural clay, P−Clay, sodium−clay, Na−Clay, and aluminium−pillared, Al−PILC) to remove dyes from aqueous medium was examined at different initial concentrations, pH, and ionic strengths. At the optimal contact time of 20 minutes, the maximum adsorbed dye amount on various adsorbents was obtained at pH 9 and pH 3 for AR14 and BV3 dyes, respectively. Adsorption process of both dyes on purified or modified clay was pH depend and the dyes molecules sorption over the clay surface occurs by electrostatic interactions. Ionic strength influenced significantly AR14 and BV3 dyes adsorption. Homo-ionization and pillaring clay increased its adsorption capacity. Kinetic studies showed that adsorption follows a pseudo−second−order model, and rate constants were evaluated. Non-linear fit of adsorption isotherm, q_e vs C_e, were S−class for adsorption of both dye onto AL−PILC, indicating the heterogeneity of the adsorbent surface which leaded to a multilayer adsorption with interactions between dye molecules. Langmuir and Freundlich models were the best fits to the experimental data with the maximum adsorption capacities of AL−PILC for AR14 and BV3 dyes of 1.4 mg g^-1 and 3.0 mg g^-1, respectively. Lower adsorption capacities calculated from Langmuir isotherm model than the experimental values indicated adsorption mechanism occurs by multilayer formation on the adsorbent surface.