Photocatalytic degradation of real textile and tannery effluent using biosynthesized magnesium oxide nanoparticles (MgO-NPs), heavy metal adsorption, phytotoxicity, and antimicrobial activity

Abstract Industrial wastewater treatment is one of the greatest challenges of humanity that require an increased awareness to address water scarcity worldwide. Herein, an eco-friendly and cost-effective approach was established to cope with real textile and tannery effluents via the biosynthesis of highly adsorbent magnesium oxide nanoparticles (MgO-NPs). Physicochemical characterization of as-formed MgO-NPs confirms the successful fabrication of MgO nano-rods (30 – 85 nm) and nano-rectangular (18.6 – 27.6 nm) by harnessing metabolites secreted by Aspergillus niger strain F1. Moreover, the energy dispersive spectroscopy (EDX) confirms that Mg and O are the main components in the sample with weight percentages of 41.1% and 33.6%, respectively. X-ray photoelectron spectroscopy (XPS) confirms the successful formation of MgO at different bending energies. The catalytic degradation and decolorization analyses were conducted under sunlight and dark conditions. These analyses demonstrated that the highest decolorization of real textile and tannery effluents (92.8% ± 0.06% and 97.5% ± 0.7%, respectively) was accomplished after 180 min by treatment with 1.0 mg mL-1 of MgO-NPs in the presence of sunlight. At optimum experimental conditions, the quality of treated effluents was monitored by the reduction of total suspended solid (TSS), total dissolved solid (TDS), and chemical oxygen demand (COD) levels at the percentages of 86.9% ± 0.8%, 77.0% ± 0.8%, and 89.3% ± 0.9%, respectively, for textile effluent and the percentages of 94.3% ± 1.6%, 80.7% ± 1.6%, and 97.4% ± 0.9% respectively, for tannery effluent. The reusability of MgO-NPs showed its activity for textile effluents treatment for four cycles. Biosynthesized MgO-NPs showed a high adsorption capacity for predominant tannery heavy metals, namely, Cr, Co, Pb, Cd, and Ni having removal percentages of 94.2% ± 1.2%, 63.4% ± 1.7%, 72.7% ± 1.3%, 74.1% ± 1.8%, and 70.8% ±1.5%, respectively. The toxicity of treated effluents was assessed by the germination of corn and broad bean seeds, which exhibited a decreased toxicity as compared with untreated effluents. Interestingly, the biosynthesized MgO-NPs exhibit antimicrobial activity against different pathogenic microbes and their activities were dose-dependent.