Investigating the performance of biomass-derived biochars for the removal of gaseous ozone, adsorbed nitrate and aqueous bisphenol A

Abstract

In this study, we evaluated for the first time the capacity of six biochars to remove gaseous ozone, adsorbed nitrate and aqueous bisphenol A (BPA). An experimental setup was developed to study the heterogeneous chemistry of ozone and nitrate on the surface of biochars. Biochars showed excellent performance in removing ozone (55 ppbv) for periods up to 24 h, and no volatile byproducts were observed during the reaction process. Challenging biochars with adsorbed nitrate led to the formation of reduced nitrogen oxides (NO and NO2) under UV irradiation. The photoreduction of nitrate was induced by the reduced carbon present in the biochars which led to the formation of nitrite followed by photoreduction to NO in the gas phase and on the surface. Adsorption capacities of biochars for removing BPA from water were also estimated. After long-term aging by ozone, BPA adsorption capacities of all biochars did not change while they were found to decrease slightly after nitrate aging. This could be attributed to partial oxidation of biochar surface as evidenced by infrared analysis and the formation of surface-hydroxyl and -carbonyl groups. This study will allow a better evaluation of biochars as promising materials for removal of air and aqueous pollutants.