Pinewood sawdust biochar as an effective biosorbent for PAHs removal from wastewater

Biochar is known to be an efficient bio-sorbent for a multitude of pollutants from wastewater due to its eco-friendly and economically advantages. In this study, three different biochar adsorbents were synthesized from pinewood sawdust by no activation, chemical and physical activation followed by pyrolysis process at 500 °C for 3 h. The morphologies and compositions of the three adsorbents were systemically measured by Brunauer–Emmett–Teller, Fourier-transform infrared spectroscopy, scanning electron microscope, and elemental analysis. The batch experiments were established, and HPLC analyzed the adsorption uptake of naphthalene, phenanthrene, and anthracene compounds on the surface of the three pinewood sawdust biochars (PWSDB) at different predefined times intervals. The studies elucidated that the pseudo-second-order kinetic model best-represented naphthalene (NAP), phenanthrene (PHE), and anthracene (ANT) adsorption on the three adsorbents. The sorption equilibrium and kinetic studies show no competition between PAHs for the adsorption sites, demonstrating homogeneity in the adsorption process. The isotherm modeling was employed and fitted well by Langmuir and Freundlich’s models. The removal efficacy of polycyclic aromatic hydrocarbons (PAHs) reached approximately 90%, which is considered a promising and valuable outcome for separating PAHs from wastewater. The economic cost analysis for the sawdust biochar was estimated and compared with activated carbon. This study proves that the pinewood sawdust feedstock-based biochar has promising adsorption efficacy in removing NAP, PHE, and ANT from synthetic wastewater, besides the feasibility and economic benefits upon application.