Nano-Adsorptive Remediation of Hexavalent Chromium [Cr(VI)] Using CamelliaSinensis–Derived Biochar–Melamine Nanocomposites

Abstract

Hexavalent chromium [Cr(VI)] is a highly toxic and carcinogenic contaminant commonly found in industrial wastewater. The development of sustainable, low-cost biosorbents for its removal is critical for effective environmental remediation. Conventional chromium removal technologies are often expensive and generate secondary pollutants. Therefore, the synthesis of efficient, biomass-derived adsorbents represents a promising alternative for wastewater treatment applications. A nitrogen-enriched carbonaceous biosorbent was synthesized via pyrolytic carbonization of a 1:1 (w/w) mixture of spent tea leaf powder and melamine at 500 °C for 2 h. Batch adsorption experiments were conducted by varying adsorbent dosage (0.25–1.5 g), initial Cr(VI) concentration (10–100 mg L⁻¹), and contact time (24–48 h). Residual Cr(VI) concentrations were determined using UV–Visible spectrophotometry at 400 nm. Adsorption efficiency increased with higher adsorbent dosage and longer contact time, while decreasing with increasing initial chromium concentration. The maximum removal efficiency of 92.5% was achieved at 1.5 g dosage and 10 mg L⁻¹ Cr(VI) after 48 h. The enhanced performance is attributed to nitrogen functionalization and the porous carbon matrix formed during carbonization. The tea leaf–melamine-derived composite demonstrates high efficiency for Cr(VI) removal and offers a cost-effective, sustainable solution for chromium-contaminated wastewater treatment.