Dye adsorption onto magnetic and superparamagnetic Fe3O4 nanoparticles: A detailed comparative study

Environmental pollution from textile industries has become a serious problem. So far, adsorption technology is one of the most effective methods for dye removal, due to its simplicity, high efficiency, and low cost. Superparamagnetic nanoparticles hold great promise for this application. In this work, superparamagnetic magnetite nanoparticles (NP-SYN) were synthesized by chemical co-precipitation, and their adsorption performance was compared to commercial magnetite nanoparticles (NP-COM). The nanoparticles (NPs) were characterized by XRD, TEM, magnetometry, FTIR, and porosimetry. The D-XRD for NP-COM and NP-SYN were around 63 and 27 nm, respectively. The magnetization curves show SM values of 82 and 72 emu g(-1) for NP-COM and NP-SYN, respectively. Coercive field for the NP-COM was 1.6 x 10(-2) Oe but could not be measured for NP-SYN, characterizing its superparamagnetic behavior. The surface areas for NP-COM and NP-SYN were around 50 and 127 m(2) g(-1), respectively. Meanwhile, indigo carmine (IC) dye adsorption performances on NPs were investigated. Parameters as pH 4.0, 150 min contact time and 20 mg L-1 dye concentration were chosen for further studies. Maximum NP-COM and NP-SYN adsorption capacity was 6.12 and 17.45 mg g(-1), respectively. Batch adsorption process obeys pseudo-second-order kinetics and Langmuir, Freundlich and Temkin isotherms onto NPs. The IC dye removal efficiency was 33 % to NP-COM and 87 % to NP-SYN. After IC dye desorption, NPs were recovered and reused 5 times without losing efficiency. Hence, superparamagnetic magnetite nanoparticles were proposed as potential adsorbent at the solid-liquid interfaces.