BIOSORBENT of brown algae (Lessonia nigrescen) for mercury ions (HG2+) removal from aqueous solution

Mercury contamination in water poses significant risks to both human health and ecosystems. This study developed a biosorbent using brown algae (Lessonia nigrescens) to remove Hg²⁺ ions from aqueous solutions. The biosorbent was prepared using biomass with particle sizes between 0.5 and 1.0 mm and treated with a 0.20 M CaCl₂ solution. Characterization of the materials was performed using Fourier Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM) techniques. Adsorption experiments were conducted in a batch system, examining the effects of pH and contact time on adsorption efficiency. Results indicated that the biosorbent contains surface functional groups that significantly enhance Hg²⁺ ion biosorption. Additionally, pH variations within the tested range of 3.5 to 7.5 showed minimal impact on biosorption efficiency. Kinetic analysis revealed that the pseudo-second-order model best described experimental data, suggesting that chemisorption is the primary mechanism governing the process. The maximum adsorption capacity (qₑₓₚ) was found to be 26.87 mg g⁻¹. Additionally, equilibrium data were better fitted by the Freundlich isotherm model, indicating heterogeneous and multilayer adsorption behavior.