Insights into the adsorption of CO2 generated from synthetic urban wastewater treatment on olive pomace biochar

Abstract

In this investigation, a sustainable and low-cost method to capture CO2 generated from the treatment of urban wastewater was evaluated. We studied the adsorption of CO2 on olive pomace biochar. The experiments of degradation of synthetic wastewater mimicking effluents of municipal wastewater treatment plant (WWTP) with an initial Total Organic Carbon (TOC) concentration of 10 mg L−1 were conducted by using the UV-C/H2O2 process in the absence or presence of biochar. The biochar was placed in a fixed bed column through which air from the UV reactor was circulated. First, the effects of different parameters such as H2O2 initial concentration and pH on wastewater mineralization efficiency were determined. Total Organic Carbon (TOC) removal was 87% in 2 h under optimal degradation conditions. The maximal concentration of CO2(gas) in air, in a closed system (air volume: 7.3 10−4 m3), after 11 h was 12,500 μmol mol−1 in the absence of biochar and only 150 μmol mol−1 when 10 g biochar were used. The results proved that by combining biochar with oxidative degradation of organic compounds, it is possible to mineralize organic compounds and reduce the requisite CO2 emissions by about 99%. The experimental equilibrium results were fit well with both Langmuir and Freundlich isotherms models concluding that CO2 adsorption on biochar followed both chemisorption and physisorption and both monolayer and multi-layer CO2 adsorption could occur. The total desorption of CO2 from biochar was reached in 120 min by simultaneously increasing the temperature to 150 °C and introducing a purge N2(gas).