Valorization of Modified Residual Durain Peel Biochar Loaded in Composite Beads for Enhancing Cu(II) Removal: Optimization and Performance Evaluation

Abstract Sustainable wastewater treatment requires the development of efficient adsorbents derived from agricultural residues. The durian peel biochar (B-DP) was proposed as a residual biomass adsorbent for such purposes. In this study, B-DP was activated its functional groups using potassium hydroxide (KOH) prior to immobilization within a pectin/cellulose as modified durian peel biochar (mB-DP) composite beads for the removal of Cu(II) from aqueous solutions. The surface functional groups and morphology were characterized using FTIR, BET, and SEM, respectively. The results confirmed an enhancement of oxygen-containing functional groups and the formation of a porous structure of mB-DP. The sufficient pH values for the removal and adsorption of Cu(II) were 5.4 and 4, respectively. The pH at the point of zero charge of mB-DP was estimated to be 3.7. Kinetic analysis revealed that Cu(II) adsorption followed the pseudo-first-order model, indicating that the adsorption process relied on an unoccupied site on the adsorbent. The effects of initial Cu(II) concentration (50–150 ppm), contact time (2–5 h), and adsorbent dosage (2–5 g/L) were optimized using central composite design coupled with response surface methodology. ANOVA results identified adsorbent dosage as the most significant factor for removal efficiency (p < 0.0001). Under the optimal conditions (150 ppm initial concentration, 3.42 g/L dosage, and 2.5 h contact time), the predicted removal efficiency and adsorption capacity were 43.98% and 86.19 mg/g, respectively, which were in good agreement with the experimental results. The quadratic model exhibited high reliability, with an R2 value of 0.98. XRD analysis supported the adsorption of Cu(II) onto the mB-DP composite beads. The mB-DP composite beads demonstrated an effective adsorbent for the remediation of heavy-metal-contaminated wastewater. The work embraced United Nations Sustainable Development Goals (UN-SDGs), i.e., #6, #12, and #14.