Enhancement of phosphate adsorption by chemically modified biochars derived from Mimosa pigra invasive plant

Negatively charged biochar restricts adsorbing orthophosphate anions - a main cause of eutrophication, thus modified biochar is suggested to enhance phosphate (PO43-) adsorption from aqueous solution. This work tested the hypothesis that modified biochar results in the enhancement of PO43- adsorption compared to pristine biochar derived from Mimosa pigra. Aluminium-modified biochars with different concentrations of AlCl3 (i.e., 0.5, 1, 2, and 3 M) and the pristine biochar were performed for absorbing PO43- in batch experiments. Among the modified biochars, 2 M Al-modified biochar achieved the highest PO43- adsorption capacity (70.6 mgPO43-/g) which was 14 times greater than pristine biochar (5.1 mgPO43-/g). Chemical adsorption and electrostatic attraction may control significantly to the adsorption of PO43- on biochars. The 2 M Al-modified biochar presents the potential adsorbent for removing phosphorus from water. [Display omitted] •Al-modified biochars increased surface area, functional groups and reduced pHpzc.•2 M modified biochar obtained 70.6 mg/g in PO43- adsorption while biochar 5.1 mg/g.•Chemical and electrostatic mechanism may control to adsorption of PO43- on biochar.