Abstract
Dye-containing industrial effluents create major concern nowadays. To address the problem, magnetic nickel oxide nanoparticles (NONPs) were synthesized using the autopropagator combustion technique assisted by sucrose as fuel and used for the removal of toxic malachite green (MG) from water. The material was characterized by scanning electron microscopy (SEM-EDS), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), vibrating sample magnetism (VSM), point of zero charge (pH(ZPC)), and Brunauer-Emmet-Teller surface area analysis. SEM images show flowerlike texture with the presence of multiple pores. VSM reveals a well-defined hysteresis at room temperature, confirming a permanent magnetic nature of the material. pH(ZPC) was found to be 6.63, which enables dye separation in the drinking water pH range. MG removal from water was carried out in the batch mode with optimized physicochemical parameters such as contact time, pH, temperature, and dose. Langmuir adsorption capacity was estimated to be 87.72 mg/g. Pseudo-second order kinetics (R (2) = 0.999) and Langmuir isotherm model (R (2) = 0.997) were found to best fit. The magnetic nature facilitates fast and quantitative separation of NONPs from solution using a hand-held magnet. Dye-loaded NONPs can be easily regenerated up to 89% and reused up to five cycles without significant loss of activity. The mechanism of adsorption is proposed to be a combination of electrostatic attraction and weak hydrogen bonding. Strategically designed straightforward synthetic protocol, low cost, high uptake capacity, and sustainable use render NONPs an ideal alternative for future dye treatment.