Ricerc@Sapienza

Soil contamination by mixture of compounds represents a challenging environmental problem to face,
especially for the risk connected to the human health, due to the possible diffusion of the pollution in
the groundwater. One of the most used remediation technology is adsorbtion on carbonaceus material
and Activated Carbon (AC) is the most used one, even if it is usually connected to high costs. Biochar (BC)
is proposed as an alternative low-cost material for the removal of wide range of contaminants in the
environment (Alhashimi et al., 2017). BC is a carbon-rich product obtained by thermal decomposition of
organic raw material, under different conditions of process (e.g. feedstock, gasification and pyrolysis). Its
efficiency to reduce the bioavailability of heavy metals and to immobilize organic pollutants has been
reported. Moreover, it is possible to combine retention of contaminants with biological degradation
(bioremediation strategies), increasing the value of this by-product (Zhu et al., 2017).
In this study two different BCs, Pine Wood Biochar (PWB) and Rice Husk Biochar (RHB), have been used
for the adsorbtion of trichloroethylene (TCE), and lead (as Pb(II)), representing target contaminants for
chlorinated solvents and heavy metals. PWB is obtained by pine wood gasification (800°C and limited
supply of oxygen), while RHB is produced from rice husk pyrolysis (350°C, absence of oxygen). Both
materials were characterised in terms of physical-chemical properties: Scanning Electron Microscope
(SEM) analysis, Cation exchanged capacity (CEC), Fourier tranform infrared spectroscpy (FT-IR)). Kinetic
and equilibrium batch tests (with mono-component contaminated solution) have been carried out to
assess the BCs' adsorption capacities, changing solid/liquid ratio (from 1 to 5 mg mL-1). Furthermore,
PWB-column and RHB-column were performed to better simulate the groundwater conditions. The fixed
bed columns were filled with inert sand mixed with adsorbent material (4%w/w) and feeded with a bicomponent
contaminated solution (5 ppm of TCE and 20 ppm of Pb(II)). The breaktrough curves for both
contaminants has been assessed in order to get informations of the operational capacity of the
materials. Results suggest PWB has higher affinity for TCE and confirm its good efficiency in immobilizing
hydrophobic organic contaminants (HOCs)(Silvani et al.,2017), possibly due to the higher temperature
achieved during gasification which leads to a graphite-like structure. On the other hand, RHB shows
major Pb(II) removal. The low temperature of the RHB pyrolysis possibly allows to maintain a higher
content of functional groups involved in cations exchanging and binding. The RHB-column study confirm
the lower adsorption capacity for TCE considering that the saturation of the material has happened first,
while the breaktrough point for Pb(II) has been observed later, compared to PWB.
These results are very promsing, encouraging to consider BC as cost-effective alternative to AC in
groundwater contamination scenarios.