Biochar from carrot residues chemically modified with magnesium for removing phosphorus from aqueous solution

The continuous increase in the world population requires more agricultural production; therefore, phosphorus compounds (P) are essentials. Considering that P reserves are finite, studying its recycling and reusing is essential. Biochar made from agricultural residues is an interesting material to be studied for P recovery and reuse in agriculture. This study shows the preparation and characterization of a biochar obtained from the pyrolysis of carrot residue for P adsorption studies in aqueous solution. Carrot was pyrolyzed at different temperatures values, with and without pretreatment with MgCl2. Biochar impregnated with Mg and pyrolyzed at 400 °C showed higher efficiency in P removal in aqueous solution (138 mg g−1). The characterization techniques indicated that after P adsorption by biochar, a chemical reaction occurred between Mg and P species with formation of Mg(H2PO4)2. The biochar from carrot residue obtained in this work is a promising adsorbent for P recycling and has potential to be used as soil fertilizer.