Influence of pyrolysis time on removal of heavy metals using biochar derived from macroalgal biomass (Oedogonium sp.).

[Display omitted] • Pyrolysis is applied at different times to convert Oedogonium biomass into biochar. • Pyrolysis time affected on biochar properties and removal of heavy metals. • Biochar obtained from a 40 min pyrolysis time exhibits higher removal efficiency. • The Langmuir isotherm and PSO model are fitted to explain the adsorption mechanism. In this study, pyrolysis was performed at different times to convert Oedogonium biomass into biochar. The physicochemical properties show that the pyrolysis time significantly impacts structural and morphological changes in biochar samples. The influence of pyrolysis time on the removal of multiple heavy metals was investigated. Owing to the presence of abundant functional groups, inorganic minerals and porous nature, biochar obtained from a 40 min pyrolysis time showed higher removal efficiency of heavy metals compared to biochars pyrolyzed at 20 mins and 60 mins even with higher concentrations of metal ions. The maximum adsorption capacity was observed 9.33, 10.74, 322.58, 13.70 and 9.11 mg/g with the biochar prepared at the pyrolysis time of 40 mins for Co, Ni, Cu, Zn and Cd, respectively. The adsorption isotherm is well fitted with the Langmuir adsorption model for heavy metals adsorption, and the kinetic study is well-defined by a pseudo second-order model. [ABSTRACT FROM AUTHOR]