Removal of Ni(II) by magnetic nanoparticles

Superparamagnetic Fe3O4 nanoparticles were synthesized by co-precipitation method and characterized for TEM, XRD, FTIR, TGA/DTG, BET surface area, VSM, SQUID, and through the determination of pH(zpc). The Fe3O4 magnetic nanopartides were used for the removal of Ni(II) from aqueous solutions. The removal of Ni(II) is strongly dependent on pH of the medium with enhanced adsorption as the pH turns from acidic to alkaline side. The process was very fast initially and the maximum adsorption was observed within 35 min of contact time. The kinetics of the removal, tested with pseudo-first-order, pseudo-second-order and intra-particles diffusion model, showed better agreement with pseudo-second-order rate kinetics (k(2) = 6.740 x 10(-7) to 8.023 x 10(-9) g mg(-1) min(-1)). The adsorption data was modeled with Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin isotherms and yielded good fit with the Freundlich isotherm model. The nanoscale Fe3O4 particles have considerable Langmuir adsorption capacity to Ni(II) removal in the range of 209.205 to 362.318 mg g(-1). The adsorption process was endothermic with a positive value of Delta H (101.209 kJ mol(-1)) and spontaneous in nature (Delta G: -13.338 to -17.266 kJ mol(-1)). The results have established good potentiality of the Fe3O4 nanoparticles to remove Ni(II) from aqueous solutions. (C) 2015 Elsevier B.V. All rights reserved.