Wood sawdust and sewage sludge pyrolysis chars for CO2 adsorption using a magnetic suspension balance

Abstract

AbstractIn view of global warming caused by the uncontrolled emissions of CO2 to the environment, there is a great need to develop methods able to eliminate this pollutant. Apart from establishing new techniques, the exploration of new materials with high separation performance and low cost are of importance. This work aims to treat carbon‐metals‐rich chars originated from the fast pyrolysis of sewage sludge and wood sawdust to be used as CO2 adsorbents. The samples were washed with ethanol and dichloromethane before their physical and chemical activation to remove impregnated bio‐oil. For the chemical activation, potassium hydroxide and hydrochloric acid were used as agents. The samples were analyzed via BET, TGA, XRD, and XRF. The results were used to investigate the role played by ethanol or dichloromethane and the effect of the activation on the properties of the materials such as specific surface area, total specific pore volume, and average pore size. CO2 isotherms were obtained experimentally at 25 °C using a magnetic suspension balance and the data was used to estimate Langmuir and Freundlich isotherm parameters. After chemical treatment, the sewage sludge char specific surface area increased 11 times and had an adsorptive capacity of 1.32 × 10−3 mol/g. The wood sawdust char specific surface area increased 90 times and had an adsorptive capacity of 3.73 × 10−3 mol/g. Desorption was carried out from 5 × 105 to 1 × 105 Pa at 37 °C and the efficiencies were 89.0 and 84.4 % for the sewage sludge and wood sawdust, respectively.