Cost-effective biochar from spent coffee grounds as a sampling device of gaseous polycyclic aromatic hydrocarbons

Biochar derived from spent coffee grounds was used for the first time as an adsorbent for monitoring and application in a sampling device of gaseous polycyclic aromatic hydrocarbons (PAHs), rather than for the removal of PAHs from the environment, as had been attempted in previous research. The device consists of three parts: an air filtration component, an air sampling component (glass tube filled with lab-made biochar), and a flow controller component. The findings demonstrated that the developed sampling device has a high potential for the collection of gaseous PAHs in ambient air, including naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, and pyrene, under conditions involving low air flow rates (≤ 4 L/min) and low temperatures (≤ 10 °C). Moreover, two connected glass sampling tubes packed with lab-made biochar performed better than a single tube and required less than three hours to prevent significant loss of gaseous PAHs. By using the spiking method on biochar prior to sampling, accuracy levels greater than 80% were achieved for all compounds. Additionally, the efficiency of the biochar was compared with that of a commercial adsorbent (XAD-2), and no significant differences were found. These results suggest that biochar has strong potential for practical applications in the sampling of gaseous PAHs. When comparing production costs, the average price of biochar produced from biomass was estimated to be around 0.18% of the cost of the commercial adsorbent (XAD-2) per sampling.