Cross-linked carboxymethyl cellulose biosorbent for zinc removal: a sustainable remediation of heavy metal-polluted waters

This study focuses on the preparation and characterization of cross-linked carboxymethyl cellulose (CMC) biosorbent for efficient removal of Zn2⁺ ions from aqueous solutions. The microstructural features of the biosorbent were examined using scanning electron microscopy (SEM), while elemental analysis was conducted using an elemental analyzer to determine carbon (C), hydrogen (H), nitrogen (N), and sulfur (S) content. Fourier transform infrared (FTIR) spectroscopy was employed to identify functional groups within the biosorbent. Sorption experiments revealed that increasing the biosorbent dose led to higher Zn2⁺ removal rates until equilibrium was reached. The optimal pH for Zn2⁺ removal was determined to be ≥ 5, attributed to the conversion of acetate group to its ionic form. Rapid kinetics were observed, with 99% removal achieved within 5 min. The biosorbent exhibited a maximum sorption capacity of 10.809 mg/g and a removal rate of 99% at pH 5. Desorption studies demonstrated efficient Zn2⁺ recovery using 0.25 M HCl solution, with a total desorption rate exceeding 99%. The findings indicate the potential for cost-effective regeneration of the biosorbent using dilute acid solutions, enhancing its sustainability and practical applicability in water purification processes. Additionally, the biosorbent’s selectivity for Zn2⁺ ions over competing ions and its effectiveness in treating real water samples, including those containing Na⁺, K⁺, Ca2⁺, and Mg2⁺, highlight its suitability for practical water purification applications.