Adsorptive characteristics and performance of template-containing MCM-41 for removal of sodium dodecylbenzene sulfonate from aqueous solutions

The as-synthesized MCM-41 and its modified forms were studied as effective adsorbents for the removal of sodium dodecylbenzene sulfonate (SDBS) from contaminated aqueous solutions. The structure-directing template molecules of the as-synthesized MCM-41 was partially removed by treating the sample with an alcoholic ammonium nitrate solution through step by step procedure. The adsorbents were characterized using standard solid-state techniques such as X-ray diffraction, Fourier-transform infrared, Brunauer-Emmett-Teller, thermogravimetric analysis, and transmission electron microscopy. Optimization experiments were carried out as a function of pH, contact time, and the adsorbent dosage. The kinetics of the adsorption were well-described by the pseudo-second-order kinetic. The adsorption data were shown to be fitted with the Langmuir isotherm equation. The maximum adsorption capacities and pseudo-second-order rate constants were calculated. The efficiency of the adsorbents for removal of SDBS fluctuates with the amount of the template molecules retained in the mesoporous structures. Thermodynamic studies depicted that the adsorption of the surfactant is an endothermic process and it is controlled by entropy changes. The recycling of the adsorbent was studied, and the adsorption efficiency is significant even after three cycles of use. Ability of the adsorbent for removal of SDBS in real samples was also investigated.