Chitosan Crosslinking from Clam Shells (Cerithidea obtusa) with Tripolyphosphate for Cadmium (II) Adsorption

Abstract

The study investigates chitosan crosslinking from clam shells ( Cerithidea obtusa) with tripolyphosphate for cadmium (II) adsorption. Chitosan was prepared by deacetylating chitin using 60% NaOH and heating at 140°C for 60 minutes. Chitin was isolated from Cerithidea obtusa shells, an abundant waste in East Kalimantan. Crosslinking of chitosan with tripolyphosphate was synthesized via gelation methods, dissolving 5 g of chitosan in acetic acid and adding 0.1% tripolyphosphate as a crosslinker. The chitosan-tripolyphosphate characterization was conducted using FTIR, XRD, and SEM. FTIR spectra revealed an N-H vibration at 1635 cm −1, NH 3 + deformation at 1534 cm −1, C-O stretching at 1072 cm −1, and P-O vibration at 1026.91 cm −1, indicating the presence of tripolyphosphate in chitosan. The XRD pattern showed broad peaks at 19.85° and 23.50°, characteristic of amorphous chitosan-tripolyphosphate. SEM images depicted a flat sheet without pores and a tight surface. Cadmium (II) adsorption on chitosan-tripolyphosphate at an optimum pH of 4 followed a pseudo-second-order kinetic model. It adhered to the Langmuir isotherm model, with a maximum adsorption capacity of 27.8 mg/g. The results demonstrate that chitosan crosslinked with tripolyphosphate effectively for cadmium (II) adsorption.