Ionic adsorption and characterization of biochar from discarded potatoes

Studies aimed at mitigating environmental impacts have received attention in recent years. The use of biochar obtained from the pyrolysis is an alternative for the recovery of organic materials that usually are directly discarded in the environment. Biochar has the potential to recover nutrients from wastewater, and in the latter case, the reuse or recycling of biochar as a controlled-release fertilizer could be an option. However, the adsorption characteristics of the ions into different biochars have not been known. The aim of this study was to evaluate the ions adsorption in biochar derived from discarded potatoes, as well as to make physical and chemical characterization of the produced materials. The biochar derived from discarded potatoes was produced by pyrolysis at 450 degrees C under an N2 atmosphere. In order to define its ionic profile, the adsorption of HnPO4(3-n)-, Ca2+, Mg2+, and Al3+ was tested in pure biochar, as well as adsorption of HnPO4(3-n)- in biochar after it was doped with Al3+. The desorption of these ions was tested by washing with deionized water, and the KCl (1.0 mol.L-1)and Mehlich-1 extractors. In absolute values, the adsorption order of the ions was Al3+ (in acid pH value) = Ca2+ > Al3+ > HnPO4(3-n)- (biochar doped with Al3+) > Mg2+ > HnPO4(3-n)- (biochar without doping). The adsorption of HnPO4(3-n)- was positively influenced by the doping of biochar with Al3+. The biochar has preferential characteristics for cations adsorption, and the doping process can aid in adsorption of anions.