Adsorption capacity of phenanthrene and pyrene to engineered carbon-based adsorbents produced from sewage sludge or sewage sludge-biomass mixture in various gaseous conditions

Adsorption of phenanthrene (PHE) and pyrene (PYR) by engineered carbon-based adsorbents produced from sewage sludge in an atmosphere of nitrogen (N-2) or carbon dioxide (CO2) at temperatures of 500, 600, and 700 degrees C was investigated. The addition of willow to the SSL decreased the biochar adsorption capacity. However, there was an increase in the adsorption capacity after changing N-2 to CO2. The addition of willow to SSL and the type of carrier gas affected the mechanism of adsorption. The adsorption of PHE and PYR on the SSL-derived adsorbents produced in N-2 occurred through pore filling. The adsorption on the SSL-derived adsorbents with willow followed the mechanism of pi-pi electron-donor-acceptor (EDA) interactions and hydrophobic interactions. A similar mechanism was observed with regard to the biochars produced from SSL in atmosphere of CO2. For the SSL-derived adsorbents with willow in CO2, the adsorption mechanism was observed to vary between PHE and PYR.