Green Synthesis of Calcium Oxide Nanoparticles by Endophytic Fungi for Sustainable Textile and Leather Wastewater Remediation

Abstract

This study investigated the potential of endophytic fungi and calcium oxide nanoparticles (CaONPs) for bioremediation and industrial wastewater treatment. Five endophytic strains were isolated and evaluated for tolerance to heavy metals (Cu, Pb, Cd, Hg, and As) at concentrations of 25 – 100 ppm. Results indicated strain-specific tolerance patterns, with Curvularia lunata showing high Hg and Cd tolerance, Fusarium solani exhibiting exceptional Cd resistance, and Rhizopus oryzae tolerating moderate Hg and Pb levels, highlighting their potential for bioremediation of metal-contaminated environments. Morphological and microscopic characterization confirmed the identity of the isolates as Curvularia lunata, Aspergillus flavus, Alternaria alternata, Fusarium solani, and Rhizopus oryzae, supporting their selection for environmental applications. The CaONPs were synthesized and characterized, revealing high surface area and reactive morphology suitable for pollutant adsorption. The nanoparticles were applied to textile and leather wastewater, and treatment efficiency was evaluated under varying pH, temperature, concentration, and contact time. Optimal conditions for maximum removal were observed at neutral pH (7), moderate temperature (30 °C), intermediate concentration/dosage, and 60 minutes’ contact time. Treated wastewater showed significant improvement (p < 0.05) over controls, with textile effluents generally exhibiting slightly higher response values than leather wastewater. CaONPs demonstrated effective removal of contaminants through adsorption and coagulation mechanisms, with performance influenced by physicochemical conditions. Thus, this study highlighted the complementary potential of heavy metal-tolerant endophytic fungi and CaONPs for sustainable remediation strategies. The findings provide a foundation for developing integrated biological and nanomaterial-based approaches to manage industrial effluents and mitigate environmental contamination.