Removal of tetracycline and crystal violet from aqueous solutions by magnetic chitosan-lipid free Chlorella vulgaris biocomposite

The overuse and improper disposal of organic dyes and antibiotics, such as Crystal Violet (CV) and Tetracycline (TC), endanger aquatic ecosystems and water quality. In this work, a novel magnetic biocomposite was prepared by incorporating magnetite, chitosan, and residual biomass of Chlorella vulgaris after lipid extraction and applied for the adsorptive removal of TC and CV from water-based solutions. The highest removal of TC and CV occurred at pH 8, with the adsorption efficiency being influenced by the biocomposite dosage, the starting level of pollutants, and the time allowed for interaction. The adsorption behavior of TC aligned well with the Langmuir and Temkin adsorption isotherms, while the Langmuir model best described the CV one, indicating that this process follows monolayer-type adsorption, with the highest adsorption capacities of 864.382 mg/g for TC and 305.097 mg/g for CV. Kinetic studies showed that a pseudo-second-order model described the adsorption process, suggesting chemisorption as the primary mechanism. The thermodynamic evaluation indicated that the process was spontaneous and endothermic. This study highlights the effectiveness of the proposed biocomposite in removing antibiotics and dyes from water as an operative and sustainable adsorbent.