Effects of cotton straw-derived biochar under different pyrolysis conditions on Pb (II) adsorption properties in aqueous solutions

Biochar has attracted great attention for the removal of heavy metals in aqueous solutions. In this paper, cotton straw was used as raw material to produce biochar via slow pyrolysis technology. The effects of different pyrolysis temperatures, retention time, and particle size on the adsorption properties and mechanism of biochar in Pb (II) removal were explored. Cotton straw-derived biochar at an optimal condition (600℃, pH 5.5) achieved the maximum Pb (II) adsorption capacity of 124.7 mg g−1. The adsorption effects of the biochar prepared under various operating conditions on Pb (II) are different, with pyrolysis temperature having the utmost influence. The isothermal adsorption curve of Pb (II) by biochar was in line with the Langmuir model. In addition, the adsorption kinetics was consistent with the pseudo-second order model, which can be deduced that chemical adsorption or a combination of physical and chemical adsorption was dominant.