| SM ISO690:2012|
PETUHOV, Oleg; LUPASCU, Tudor. Application of thermal analysis in modeling processes of obtaining activated carbon. In: Ecological and environmental chemistry 2017The 6th International Conference. 2-3 martie 2017, Chișinău. Chisinau, Republic of Moldova: Academy of Sciences of Moldova, 2017, p. 71.
|Ecological and environmental chemistry 2017 2017|
Conferința "Ecological and environmental chemistry 2017" |
Chișinău, Moldova, 2-3 martie 2017
Thermal analysis and the methods derived from it provide a multifunctional tool to study the reactions in the solid phase. Besides the furnished qualitative and quantitative information mathematical processing of the data allows calculation of the thermodynamic and kinetic parameters of the studied processes. In virtue of the usefulness of the method, thermal analysis is also broadly applied in study of the processes of obtaining the activated carbons, starting from the analysis of raw materials, which include determination of moisture content, volatile substances, fixed carbon, ash content and ending with the detailed study of the mechanisms of the activation process. Knowledge of the temperature ranges, at which biomass activation occurs, allows efficient use of energy resources and obtaining the increased parameters for final products as well. Thermal analysis permits to determine the temperatures, at which interaction between activating agent and raw material begins, the reaction rate and mass loss at each stage. In the light of the results obtained by using thermal analysis, the following aspects of activation of nut shells with chemical agents can be highlighted: being a strong dehydrating agent, phosphoric acid leads to greater losses of weight at temperatures up to 200 °C. At the same time, the polyphosphate bonds formed at moderate temperatures, help to prevent volatilization and loss of the structural carbon atoms. Appropriate temperature regime for obtaining the activated carbons is 460-650 °C. Lower rate of reactions that occur in this region allows the facile control of the activation process and prevents the destruction of links between phosphorus-oxygen-carbon atoms that stabilize the structure of activated carbon. Potassium hydroxide does not exert the role of a dehydrating agent, the activation processes occur at temperatures higher than 850 °C, whatever the degree of carbonization of the raw material. Summary processes and temperatures, at which they occur, are presented in the table 1. Table1. Processes and temperatures of obtaining the activated carbon from walnut shells H3PO4 KOH walnut shells dehydration* → activation dehydration → carbonization→ activation 20-460 460-860 20-290 290-880 T>890 charcoal of walnut shells dehydration*→ activation dehydration → activation 20-360 480-910 20-360 360- 880 T>880 *- process enabled by activation agent