Chemically Treated Pistachio Green Hull as an Effective and Economical Adsorbent for Cadmium Removal: Optimization and Mechanistic Insights

Nowadays, heavy metal contamination in water sources is a critical environmental concern directly related to human health, necessitating the development of sustainable and cost-effective remediation techniques. Traditional adsorbents are often expensive and less environmentally friendly, highlighting the need for alternative materials with high adsorption efficiency. This study proposes using pistachio green hull, an agricultural byproduct, in both untreated and chemically treated forms as an adsorbent for removing cadmium (Cd2+) from aqueous solutions. Batch adsorption experiments were conducted using untreated, HNO3-treated, NH3/H2O2-treated, and acetone/H2O2-treated pistachio green hulls at an initial Cd2+ ions concentration of 20 mg/L. The adsorption kinetics, equilibrium isotherms, and pH dependence were analyzed to determine the adsorption efficiency and mechanism. The removal efficiencies for untreated, HNO3-treated, NH3/H2O2-treated, and acetone/H2O2-treated samples in laboratory scale were 68%, 55%, 88%, and 95%, respectively. Maximum adsorption occurred within a broad pH range of 4-9. The kinetic analysis revealed that Cd2+ adsorption follows a pseudo-second-order model, with rapid adsorption (<4 min). The adsorption isotherm followed the Langmuir model, suggesting monolayer adsorption, and electrostatic interactions were identified as a key mechanism. The findings demonstrate that pistachio green hulls, particularly after chemical modifications, serve as an effective and eco-friendly adsorbent for Cd2+ removal. This study contributes to advancing sustainable and low-cost solutions for heavy metal remediation.