Removal of hexavalent chromium using durian in the form of rind, cellulose, and activated carbon: Comparison on adsorption performance and economic evaluation

Durian rind (DR) is one of the lignocellulose-containing agro-industrial wastes abundant in many South Asian counties. Contributing toward a sustainable and zero waste future, DR was utilized as raw material for cellulose and activated carbon production. A chemical delignification method was adopted to valorize DR into cellulose, while carbonization and subsequent KOH activation steps were used to convert the DR into activated carbon. The resulting materials exhibited high adsorption capacity toward Cr⁶⁺ (154.2 and 223.3 mg/g for cellulose and activated carbon, respectively). The activated carbon derived from DR exhibited a faster adsorption rate of Cr⁶⁺ compared to cellulose and raw DR. The adsorption of Cr⁶⁺ by DR-derived adsorbents exhibited a monolayer tendency, with isotherm and kinetics data following the Khan and pseudo-second-order models. The total production cost of converting DR into cellulose and activated carbon was evaluated using life-cycle cost analysis (LCCA). Compared to the cellulose production, DR to activated carbon conversion requires up to 6-fold higher cost for energy. Based on the economic analysis, ∼US$ 2.9 and US$ 4.2 were needed to convert 1 kg DR into cellulose and activated carbon, respectively.