Sustainable management of coffee cherry pulping wastewater using biogenically synthesized calcium oxide nanoparticles

Coffee processing wastewater poses serious environmental concerns due to its high organic load, acidity, and complex contaminant profile. This study developed an eco-friendly solution using green-synthesized calcium oxide nanoparticles derived from Ricinus communis L. and Calpurnia aurea seeds. Comprehensive characterization via UV-Vis spectroscopy, XRD, and FTIR confirmed the successful formation of crystalline nanoparticles with bioactive surface functional groups. Kaolin coagulation tests demonstrated effective turbidity removal. When applied to coffee effluent, Calpurnia aurea -derived nanoparticles showed optimal performance, removing 84–91 % of color, 59–70 % of TDS, and 63–77 % of COD, outperforming Ricinus communis L.-derived nanoparticles. FTIR analysis of post-treatment sludge identified key functional group interactions (-OH, -COOH, -NH₂) responsible for pollutant removal through combined electrostatic attraction, hydrogen bonding, and precipitation mechanisms. These findings demonstrate a sustainable, high-efficiency alternative for coffee wastewater treatment, offering dual environmental advantages through green synthesis and effective pollution mitigation.