No abstract

In 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.

No abstract

No abstract

This paper examines the pyrolyzation of sewage sludge using a bench scale reactor and the characterization of its products. Non-isothermal degradation via thermogravimetry was used to estimate activation energy of regular and catalytic degradation under inert atmosphere. The pyrolysis reactor, a rotating cylinder coupled to a gas-washing column with a centrifuge at the top, was used to condensate pyrolysis vapors. The experimental procedure was divided into two parts: (I) pyrolysis of a sewage sludge guided by a 2 3 experimental design with center point, at temperatures of 520, 560, and 600 °C; inert flow rates of 3, 4.5, and 6 L h ; (II) determination of the activation energy of thermal degradation, with and without the USY zeolite catalyst, using an isoconversional analysis of integration. For the later, three heating rates were tested: 5, 10, and 20 °C min . The bio-oil consisted mostly of aliphatic and monoaromatic hydrocarbons, substituted aromatics, polyaromatic hydrocarbons, long amides, and amines. The components found in the gas phase were: H 2 , CO, CO 2 , CH 4 , C2, C3, C4, C5, and C6. The syngas maximum content was 59.2%. Results from the thermal analysis showed that the USY was effective in decreasing the thermal degradation activation energy. Near the temperature when the pyrolysis occurred, the activation energy dropped from 78.5 to 62.6 kJ mol -1 , and the conversion was 80%. The average values observed for the activation energy with and without catalyst, at conversions from 40 to 80%, were 103.9 and 155.0 kJ mol -1 , respectively, which indicates that the USY zeolite successfully enabled a new pathway for the sewage sludge's thermal degradation.