Valorization and optimization of Pistachio Shell Biochar for Sustainable Reduction of Hexavalent Chromium [Cr(Ⅵ)]

In the leather tanning industry, wastewater often contains hazardous hexavalent chromium [Cr(Ⅵ)]. Adsorption is recognized as an effective method for treating this type of wastewater. However, commercial adsorbents can be costly. This study explores the conversion of pistachio shells into biochar as a cost-effective and reusable adsorbent for chromium removal. The results showed that pistachio shell biochar (PSB) effectively removed up to 400 mg L⁻¹ of Cr(Ⅵ) at a pH of 4, with a contact time of 50 hours and a biochar concentration of 1.2 g L⁻¹. Batch studies indicated that adsorption efficiency depends on pH, biochar dosage, chromium concentration, and contact time. FT-IR analysis identified key adsorption sites for chromium, while SEM images displayed multiple attachment locations. These findings confirm the potential of PSB as an efficient, sustainable, cost-effective, and environmentally friendly approach for chromium remediation.