A promising composite adsorbent of activated carbon and natural alginate for Cu(II) ion removal from aqueous solutions

Abstract

Activated carbon (AC) is a versatile and extensively employed adsorbent in environmental remediation. It possesses distinct properties that can be enhanced to selectively target specific pollutants through modifications, including chemical impregnation or incorporation into composite materials. In this study, porous calcium alginate beads (PCAB) were synthesized by incorporating AC and natural alginate through ion gelation in a Ca(II) ion-containing solution, with the addition of sodium lauryl sulfate as a surfactant. The prepared PCAB was tested for Cu(II) removal. PCAB exhibited a spherical shape with higher porosity and surface area (160.19 m².g⁻¹) compared to calcium alginate beads (CAB) (0.04 m².g⁻¹). The adsorption kinetics followed the pseudo-first-order model for PCAB and the pseudo-second-order model for CAB. The Langmuir isotherm model provided the best fit for adsorption on PCAB, while the Freundlich model was suitable for CAB. Notably, PCAB demonstrated a maximum adsorption capacity of 75.54 mg.g⁻¹, significantly higher than CAB's capacity of 9.16 mg.g⁻¹. Desorption studies demonstrated that 0.1 M CaCl₂ exhibited the highest efficiency (90%) in desorbing Cu(II) ions from PCAB, followed by 0.1 M HCl and 0.1 M NaCl. PCAB showed efficient reusability for up to four consecutive adsorption–desorption cycles. The fixed-bed column experiment confirmed the match with the Thomas model to the breakthrough curves with q_TH of 120.12 mg.g⁻¹ and 68.03 mg.g⁻¹ at a flow rate of 1 mL.min⁻¹ and 2 mL.min⁻¹, respectively. This study indicated that PCAB could be an effective adsorbent for Cu(II) removal, offering insights for further application and design considerations.