Phosphorus Removal from Aqueous Solutions Using Biochar Derived from Cyanobacterial Biomass

High phosphorus (P) content and eutrophication are chemically and biologically related processes. Reducing phosphorus levels in water is essential for controlling eutrophication. In this study, biochar was produced from cyanobacteria biomass and evaluated as an adsorbent for phosphorus removal from water. The cyanobacterial biomass was collected from a local swamp in the “Departamento del Atlántico”, Colombia, and heated at 350 °C for 2 h to induce partial carbonization. The resulting biochar was characterized using vibrational spectroscopy and scanning electron microscopy (SEM/EDS). The adsorption capacity of cyanobacteria-derived biochar was assessed through kinetic and isothermal adsorption studies. The kinetic analysis revealed a maximum adsorption capacity of 5.51 mg/g and a rate constant of 0.084 g mg−1 min−1, with the pseudo-second-order model providing the best fit. The isotherm analysis showed that the Langmuir model accurately described the adsorption process, with an adsorption constant (KL) of 0.360 L mg−1, suggesting monolayer adsorption on the biochar surface. These results confirm that biochar obtained from cyanobacterial blooms is an effective and sustainable material for phosphorus removal from aqueous solutions, offering a promising strategy for nutrient pollution control and environmental remediation.