Removal of 2,4-DCP from wastewater by CTAB/bentonite using one-step and two-step methods: A comparative study

Adsorption removal of 2,4-dichlorophenol (2,4-DCP) from aqueous solutions by bentonite/CTAB was studied using two ways: the first one using organophilic bentonite as adsorbent. This material was prepared by exchanging the organic cations as cetyltrimethylammonium bromide (CTAB) for sodium (Na+) on the layer surface of clay (two steps method). The second way was using bentonite as adsorbent, which is in contact with simultaneous 2,4-dichlorophenol and CTAB in solution (one-step method). This process of wastewater treatment is of interest for the stabilization of wastes in which simultaneous 2,4-DCP/surfactant contaminations occurs. This wastewater treatment was based on simultaneously synthesis of organophilic bentonite and removal of 2,4-dichlorophenol from water in one-step. Batch adsorption studies were conducted to evaluate the effect of various parameters such as the quaternary ammonium cation (CTAB) loading, contact time and initial 2,4-DCP concentration. Adsorption equilibrium reached earlier by one-step method than onto organophilic bentonite. The adsorption kinetics was tested for Elovich, intraparticle diffusion. pseudo-second-order, and pseudo-first-order reactions and rate constants of kinetic models were calculated. The equilibrium adsorption data were analysed by Freundlich, Langmuir, and Redlich-Peterson using non-linear regression technique. Freundlich isotherms best fitted the data for adsorption equilibrium for both methods. The experimental observations indicate that adsorption behaviour of 2,4-DCP is different in each case. Due to its organophilic nature, exchanged bentonite is able to adsorb 2,4-DCP at a very high extent (about 1.5 mmol/g) when the 2,4-DCP is the only solute. In the case of simultaneous presence of 2,4-dichlorophenol (2,4-DCP) and cetyltrimethylammonium bromide in solution, the adsorption capacity of 2,4-DCP strongly increases (about 2.5 mmol/g). The results indicated that the one-step process is an efficient, simple and low cost technology for removal of organic pollutants and cationic surfactants from water. (C) 2008 Elsevier B.V. All rights reserved.