Carbon–Silica Composites from Sago Waste for the Removal of Chromium, Lead, and Copper from Aqueous Solution: Kinetic and Equilibrium Isotherm Studies

Utilizing agricultural wastes into value-added products of a low-cost adsorbent has become of interest in recent years. In this study, sago-silica composite with a ratio of 80:20 (w/w%) was prepared via chemical grafting of abundantly available sago waste and rice husk. The physicochemical properties of the composites were characterized, and their efficiencies as adsorbents on the removal of chromium (Cr), lead (Pb), and copper (Cu) in aqueous media were studied as a function of pH, adsorbent dosage, initial concentration, and contact time. Results showed that the sago-silica composite has a more extensive surface area of 227.7 m 2 /g compared to SAC (167.3 m 2 /g). The adsorption of Cr and Cu gave excellent monolayer and heterolayer adsorption on sago-silica composite represented by Langmuir and Freundlich’s isotherm based on coefficient regression, R 2 > 0.9. Pseudo-second-order kinetics model showed best fitted with excellent adsorption capacity q e of Cr, Pb, and Cu adsorption on sago-silica composites, which demonstrated the occurrence of chemisorption process between the composite and metal ions. The composite from carbon–silica is one of the cost-effective natural sorbents which demonstrate excellent removal of heavy metal from the aqueous environment.