Synthesis and characterization of chitosan-silica hybrid adsorbent from the extraction of timor-east nusa tenggara island silica and its application to adsorption of copper(II) ion

Chitosan-silica hybrid adsorbent has been successfully synthesized by extracting the silica of Timor Island-East Nusa Tenggara (NTT) in order to study its application to Cu²⁺ adsorption in water samples. This work consists of several steps which include silica extraction from Takari sand of East Nusa Tenggara, preparation of chitosan-silica hybrid, FTIR and SEM characterization, and adsorption of Cu²⁺. The successful extraction of silica was indicated by the existence of–OH, siloxane (Si-O-Si), Si-O in silanol (Si-OH) peaks at 3433.29 cm^-1,468.70 cm^-1, and 958.62 cm^-1, respectively. The formation of chitosan-silica hybrid adsorbent was denoted by a peak shift of-OH in silica to3404.36 cm^-1, N-H stretching vibration at 1544.98 cm^-1due to an interaction between O-H in silica with N-H in chitosan, and amine (primary-NH) bending vibration at1639.49 cm^-1. The surface morphology of silica changed when it was modified with chitosan from homogeneous granule to a cluster (larger particle sizes). Optimum adsorption conditions toward Cu²⁺ were achieved at pH 8 and contact time of 50 min, resulting in excellence adsorption efficiency of 99.3%. Adsorption of Cu²⁺ fitted Langmuir isotherm with the adsorption capacity of 27 mg/g.