Use of MCM-41 as an Efficient Adsorbent for Removal of Nonionic Surfactant from Aqueous Solutions

摘要

The as-synthesized MCM-41 and its modified forms are used as adsorbents for the removal of nonylphenol ethoxylate (NP-10) from aqueous solutions. The partial template containing MCM-41 is prepared by treating the as-synthesized sample with ethanolic ammonium nitrate solution. Complete removal of the template is performed using the calcination process. The prepared adsorbents are characterized by X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, transmission electron microscopy, and nitrogen physisorption techniques. The effect of adsorbent weight, pH, contact time, and initial concentration on the adsorption efficiency is studied. The equilibrium adsorption data are well defined, and they are fitted with Langmuir isotherm model. The maximum adsorption capacities (q(m)) and pseudo-second-order rate constants (k(2)) are calculated. The best adsorbent, in terms of removal efficiency, results to be the thermally treated MCM-41, characterized by the highest surface area, and thus with the largest porosity. Specifically, the removal efficiency for NP-10 is around 84% (558 mg g(-1)) with an initial concentration of 700 mg L-1, which is increased to 91% (455 mg g(-1)) for a 500 mg L-1 initial concentration. Thermodynamic studies depict that the adsorption of NP-10 onto MCM-41 is an endothermic process and the spontaneity is controlled by entropy.