Efficiency of dye adsorption of modified biochar: A comparison between chemical modification and ball milling assisted treatment

Ball milling technology was employed to increase the adsorption capacity of biochar with respect to methylene blue as a model pollutant. Comparative studies on the adsorption ability were conducted on ball-milled biochar and biochar chemically modified by oxidation and alkaline treatment, showing that ball milling produces higher performances since increases available active sites. The particle size reduction, with the consequence of an increase in the surface area was hypothesized to be responsible for the high removal efficiency. The adsorption kinetics follows a pseudo-second-order model, implying that the process is affected by chemisorption. Moreover, the Langmuir model proved that the maximum monolayer adsorption capacity increased to 185.18 mg/g. Design of experiments allowed for evaluating the pH and initial concentration values, which maximized the removal efficiency. The milled biochar was also regenerated and reused over six times, resulting in a drop of only 1 %.