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 qTH 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.

A promising composite adsorbent of activated carbon and natural alginate for Cu(II) ion removal from aqueous solutions
    Abstract
    1 Introduction
    2 Materials and methods
        2.1 Materials
        2.2 Preparation of adsorbents
            2.2.1 Preparation of CAB
            2.2.2 Preparation of PCAB
        2.3 Characterization of adsorbents
        2.4 Batch adsorption experiments
        2.5 Regeneration and reuse of PCAB
        2.6 Fixed-bed adsorption experiments
    3 Results and discussion
        3.1 Characterization of adsorbents
        3.2 Adsorption study
            3.2.1 Adsorption ability comparison
            3.2.2 Effect of pH and adsorbent dosage
            3.2.3 Effect of contact time and kinetic study
            3.2.4 Effect of initial concentration and isotherm fiting
            3.2.5 Regeneration and reuse of PCAB
        3.3 Column adsorption
    4 Conclusions
    Acknowledgements 
    References

• Xuan Minh Vu(Institute for Tropical Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi 100000, Vietnam)
• Thi My Hanh Le(Institute for Tropical Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi 100000, Vietnam)
• Van Cuong Bui(Institute for Tropical Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi 100000, Vietnam)
• Tuan Dung Nguyen(Institute for Tropical Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi 100000, Vietnam)
• D. D. Hrynshpan(Research Institute for Physical Chemical Problems, Belarusian State University, Prasp. Niezaliežnasci 4, 220000 Minsk, Belarus)
• Van Thuan Le(Center for Advanced Chemistry, Institute of Research and Development, Duy Tan University, 03 Quang Trung, Da Nang 550000, Vietnam, Faculty of Natural Sciences, Duy Tan University, 03 Quang Trung, Da Nang City 550000, Vietnam)
• Dai Lam Tran(Institute for Tropical Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi 100000, Vietnam)
• Thi Phuong Lan Nguyen(University of Economics and Technology for Industries (UNETI), 456, Minh Khai, Vinh Tuy, Hai Ba Trung District, Hanoi 100000, Vietnam)
• Thi Lan Pham(Institute for Tropical Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay, Hanoi 100000, Vietnam)