Valorization of Modified Residual Durain Peel Biochar Loaded in Composite Beads for Enhancing Cu(II) Removal:...

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 R ² 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.