Use of spent coffee ground biochar as ambient PAHs sorbent and novel extraction method for GC-MS analysis

In recent years, biochar has received a significant amount of attention for its potential beneficial applications in various fields due to its bio-physico-chemical properties. The spent coffee ground biochar was prepared by slow pyrolysis for adsorption of 16-polycyclic aromatic hydrocarbons (PAHs) in ambient air. New materials and extraction methods were developed for PAHs analysis, particularly for low molecular weight (2-4 rings) PAHs, which are likely to evaporate at room temperature. Production and characterization of biochar and its extraction parameters after PAHs adsorption were investigated and optimized. The biochar production at 500 °C provided adequate quality for PAHs adsorption with a 35% yield. An effective clean-up method for biochar was proposed. A new method of PAHs extraction from biochar was developed using 25 mL of a mixture of dichloromethane and 2-propanol (4:1) for 30 min at low temperatures (5-10 °C). A test on the efficiency of the extraction method was carried out and recoveries of 85-104% of PAHs were obtained. The lab-made biochar was also tested for its potential in ambient PAHs sampling and compared with a commercial sorbent (XAD-2). The results revealed that almost the same concentrations of ambient PAHs (ng/m³) were absorbed by both sorbent types, particularly with regard to the 4 ring-PAHs.