Preparing Shrimp Shell-Derived Chitosan with Rice Husk-Derived Biochar for Efficient Safranin O Removal from Aqueous Solution

In this study, the shrimp shell-derived chitosan was coated onto rice husk-derived biochar to form chitosan/biochar bio-composite beads. The physicochemical properties of biochar (BC) and chitosan/biochar beads (CS@BC) were characterized by BET, SEM-EDX, FTIR, and pHpzc analyses, which were then tested for their capacity to remove Safranin O (SO) from water. In kinetics, the pseudo-second-order model was found to well represent experimental data, indicating the adsorption was mainly a chemical process. The intra-particle diffusion model was not the sole rate-limiting step, because the results did not pass through the origin. In isotherms, both the Langmuir and Freun-dlich models described well the equilibrium adsorption data. The CS@BC adsorbent showed adsorption capac-ity at 77.94 mg/g for SO, which is higher than BC adsorbent with 62.25 mg/g (experimental conditions: pH similar to 7.0, dosage = 0.2 g, contact time = 240 min, and temperature = 298 K). The findings revealed that the biochar-loaded chitosan can improve the adsorption capacity of SO. It is predicted that the enhancement in the functional groups (i.e.,-NH2 and-OH groups) of CS@BC could contribute to the electrostatic interactions and the complexation between SO and CS@BC, thereby enhancing the Safranin O adsorption from water.