Novel <i>Lawsonia inermis</i> -mediated nickel oxide nanostructures: a sustainable approach for simultaneous textile effluent treatment and iodide recovery

ABSTRACT Water pollution is a threat to the survival of life on Mother Earth but due to industrialization, clean reservoirs of water deteriorate day by day, which demands eco-friendly, cheap, and highly efficient methods to counter this issue. Due to this pressing need, nickel oxide nanoparticles (NiO-NPs) are synthesized with a particle size of 42 nm using Lawsonia inermis as a reducing and capping agent. Green-synthesized NiO-NPs are analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and energy dispersive X-ray (EDX) spectroscopy. In this study, synthesized NiO-NPs are used to remove methyl red (MR) dye and radioactive iodine from polluted water. Maximum adsorption efficiency of MR is 96.8% at a contact time of 120 minutes, pH 5.0, temperature 22 °C, and an adsorbent dose of 0.1 g. NiO-NPs achieved gravimetric iodine uptake of 225 wt%, evaluated via gravimetric analysis after 24 h vapor-phase exposure (n = 3, RSD = 1.5%). The adsorption capacity was calculated to be 116.28 mg g−1 for MR under optimum conditions. Adsorption isotherms are studied, and the experimental data suggest that Langmuir isotherms are best fit with R2 = 0.9962. According to kinetic analysis, the pseudo-second-order kinetic model best fits the adsorption mechanism, having R2 = 0.9934.