No abstract

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.

-In the present work, a synthetic effluent of phenol was treated by means of a total oxidation process-Catalyzed Wet Oxidation (CWO). A mixed oxide of Mn-Ce (7:3), the catalyst, was synthesized by co-precipitation from an aqueous solution of MnCl 2 and CeCl 3 in a basic medium. The mixed oxide, MnO 2 /CeO 2 , was characterized and used in the oxidation of phenol in a slurry reactor in the temperature range of 80-130ºC and pressure of 2.04-4.76 MPa. A phenol solution containing 2.4-dichlorophenol and 2.4-dichlorophenoxyacetic acid was also degraded with good results. A lumped kinetic model, with two parallel reaction steps, fits precisely with the integrated equation and the experimental data. The kinetic parameters obtained are in agreement with the Arrhenius equation. The activation energies were determined to be 38.4 for the total oxidation and 53.4 kJ/mol for the organic acids formed.

O objetivo deste trabalho é apresentar as principais formas de aproveitamento e destinação final de lodos de esgotos, destacando-se aqui, os processos de incineração e pirólise, a disposição no solo e a destinação final do lodo em aterros sanitários. As principais vantagens do uso agrícola de biossólido são, aumento da produtividade, melhoria da qualidade química do solo e economia com uso de fertilizantes químicos. Entretanto, as substâncias orgânicas, metais tóxicos e agentes patogênicos, contidos no resíduo, representam limitações ao uso. Os aterros sanitários são o destino mais comum para a disposição do biossólido produzido no Brasil. Apesar da sua simplicidade, a disposição em aterros pode causar vários problemas como, a poluição das águas subterrâneas e do solo com o chorume, poluição visual e emissão de metano para a atmosfera. A incineração não constitui um método de eliminação completa de lodo, uma vez que parte do resíduo permanece como cinzas. A pirólise é uma prática que pode ser empregada para o aproveitamento do lodo de esgoto como biomassa. Nesse processo térmico, são gerados produtos com valores agregados, tais como óleo, gases e carvão que podem ser utilizados como fonte de combustíveis ou em outros usos relacionados à indústria.

No abstract

No abstract

-A rotating cylinder reactor was designed for the synthesis of niobium carbide powders at 1173 K. Niobium carbide, NbC, was prepared by carbothermal reduction starting from commercial niobium pentoxide powders. The reactor was heated using a custom-made, two-part, hinged, electric furnace with programmable temperature control. The design and operational details of the reactor are presented. The longitudinal temperature gradient inside the reactor was determined. Total reaction time was monitored by a gas chromatograph equipped with an FID detector for determination of methane concentrations. The results show that time of reaction depended on rotation speed. NbC was also prepared in a static-bed alumina reactor using the same conditions as in the previous case. The niobium carbide powders were characterized by X-ray diffraction and compared with commercially available products. Morphological, particle size distribution and surface area analyses were obtained using SEM, LDPS and BET, respectively. Therefore, the present study offers a significant technological contribution to the synthesis of NbC powders in a rotating cylinder reactor.