Removal of methylene blue and neutral red from aqueous solutions by surfactant-modified magnetic nanoparticles as highly efficient adsorbent

Sodium dodecyl sulfate-coated magnetic nanoparticles were utilized as the inexpensive and effective adsorbents to remove neutral red and methylene blue (two cationic dyes) from aqueous solutions. Factors affecting adsorption, including the amounts of adsorbent and surfactant, pH, and contact time, were investigated by an orthogonal central composite design. The kinetic processes of the dyes adsorption were described by applying the pseudo-first-order and the pseudo-second-order models. It was found that the pseudo-second-order kinetic equation described the data of dye adsorption with a good correlation (R-2>0.999) which indicated a chemisorptions mechanism. The extent of dye removal enhanced with increasing initial dye concentration. The adsorption of dyes at concentrations of 30-70 mg/L reached to equilibrium within 35 min. The adsorption data were represented by Langmuir isotherm model. In addition, the maximum monolayer capacities, (q(max)), of methylene blue and neutral red onto the modified nanoparticles were found to be as high as 294.12 and 416.67 (mg/g), respectively. These values are higher than the adsorption capacities of some other adsorbents that have recently been published in the literature. In addition, the required contact time to achieve equilibrium was reduced by the modified nanoparticles. (c) 2015 American Institute of Chemical Engineers Environ Prog, 34: 1683-1693, 2015