Engineered Pyrogenic Materials as Tools to Affect Arsenic Mobility in Old Mine Site Soil of Mediterranean Region

The application of pyrogenic materials in immobilization processes of metalloids represents a burning issue in environmental and waste applications and management. The main objective of this study was to characterize the effect of biomass pretreatment by Cu, Fe and Mg blending and pyrolysis temperature on As sorption efficiency as a model of anionic metalloids from model solutions and As immobilization in old mine soil by pyrogenic materials. The physico-chemical characterization of engineered materials produced in slow pyrolysis process at 400 and 700°C from metal-blended hard wood chips (30% w/w) showed increasing of surface areas (1.4-1.8-fold), changes in pH, and more than 50% decrease in total C content. The batch sorption processes of As ions by Cu-modified pyrogenic materials (CuPM), Fe-modified pyrogenic materials (FePM), and Mg-modified pyrogenic materials (MgPM) showed increasing uptake in order CuPM700 (Q_max 2.56 mg g^-1) < CuPM400 (Q_max 3.88 mg g^-1) < FePM700 (Q_max 5.90 mg g^-1) < MgPM700 (Q_max 7.42 mg g^-1) < MgPM400 (Q_max 9.59 mg g^-1) < FePM400 (Q_max 10.55 mg g^-1). Engineered pyrogenic materials produced at 400°C showed higher immobilization effect on soluble As in soil pore water of old mine site soil from Mediterranean area. FePM400 reduced mobility of arsenic > 3.2 times and MgPM400 > 5 times compared to control. Promising pyrogenic material MgPM400 showed immobilization effect also on additional heavy metals (Cd, Cu, Fe, Mn, Pb, Sr, Zn) present in studied soil.