UTILIZATION OF CRAB SHELLS (Portunus pelagicus Linn) AS A BASE MATERIAL FOR SELECTIVE ADSORBENT OF Ni(II) AND Zn(II) IONS IN SEAWATER MEDIUM

This study systematically investigates the utilization of crab shell waste (Portunus pelagicus Linn) as a basic material for selective adsorbents of Ni(II) and Zn(II) metals in a seawater medium. The process began with the isolation of chitin and chitosan through the stages of deproteinization, demineralization, and deacetylation, followed by the optimization of reaction conditions by varying the concentrations of HCl and NaOH, temperature, and reflux time. The optimized chitosan product was converted into chitosan beads and several chitosan derivatives, which were then tested as heavy metal adsorbents using batch and solid-phase extraction (SPE) systems. The results showed that increasing the concentration of NaOH, temperature, and reflux time affected the degree of deacetylation of chitosan. The optimum adsorption process occurred at pH 5–6, with a mechanism dominated by chemisorption based on desorption efficiency and the stability of the adsorbent against variations in pH and salinity. Chitosan and its derivatives demonstrated high selectivity and could concentrate Ni(II) and Zn(II) metals from μg/L levels to mg/L in the SPE system. Additionally, the flow rate and HCl concentration as the eluent had an impact on the adsorptiondesorption efficiency. Overall, this study showed that crab shell chitosan derivatives had great potential as stable and selective adsorbents for applications involving the separation of heavy metals in marine environments.