Synthesis of Dithizone Immobilized Chitosan-Silica as an Adsorbent of Cr Ions in Electroplating Liquid Waste

The increasing demand for metals has led to the growth of the metal industry in Indonesia. This has resulted in a rise in the amount of waste generated. Various methods can be used in the treatment of metal waste, such as flotation, flocculation-coagulation, and adsorption. One biopolymer that can be used for metal removal is chitosan. This study aims to synthesize chitosan from shrimp shell waste, which is then modified with silica to enhance its mechanical strength and stability in acidic conditions using the sol-gel method. The chitosan-silica composite is then immobilized using dithizone to increase the adsorption capacity through immersion variations of 4, 6, and 8 hours. The adsorbent, characterized using Fourier Transform Infrared, showed the presence of bonds in chitosan at wavenumbers 3454 cm -1 (N-H) and 1647 cm -1 (C=O), chitosan-silica at wavenumbers 966 cm -1 (Si-O in Si-OH), 798 cm -1 (Si-O in Si-O-Si), and 466 cm -1 (Si-O-Si), and chitosan immobilized with dithizone at wavenumbers 2343 cm -1 (S-H) and 1083 cm -1 (S=C). Adsorption was performed by mixing the adsorbent with the waste for 1 hour, then the waste was added with 0.25 ml of phosphoric acid and analyzed using a UV-Vis Spectrophotometer. Based on the results of the study, the highest adsorption efficiency was obtained with the adsorbent variation of 8 hours immersion at 59%, while the adsorption efficiency for immersion times of 4 and 6 hours was 0.3% and 6%, respectively.