Biochar from woody biomass for removing metal contaminants and carbon sequestration

• Pinewood waste biochar CEC was more than double that of the reference soil.
• Low O/C indicated long half-lives and a good carbon sequestration agent.
• Biochar contained high proportion of CaO.
• Biochar efficiently adsorbed Mg, Ca, Cr, and Pb ions in aqueous solution.

Biochar generated from pinewood via slow pyrolysis was studied for its viability as a soil amendment as well as for its absorptive capacity for Mg, Ca, Cr, and Pb in solution. Cation exchange capacity (CEC) measurements showed that the biochar sample has a CEC of roughly double that of the reference soil sample. A high CEC value indicates that not only can the biochar sample be used as a carbon sequestration agent, but also as a valuable soil amendment for increasing a soil's natural CEC. Biochar was characterized using elemental analysis, SEM, BET surface area, FTIR, and XRF. These results showed that biochar produced via slow pyrolysis possesses several highly beneficial attributes. The metal adsorption characteristics of biochar were studied in presence of various controlling parameters such as pH, contact time, adsorbent dosage, and interfering species. The results confirmed excellent adsorption capacity values of the biochar for Mg(II), Ca(II), Cr(VI), and Pb(II) by producing 440 (pH 7.0), 120 (pH 7.0), 680 (pH 1.0), and 520 (pH 6.0) μmol g−1, respectively. The potential applications of the biochar for removal of these four metal ions from real water samples were also studied and evaluated.