I'm interested in knowing / I want to know the mechanism behind the activation process either physical or chemical or physio-chemical activation of bio materials during preparation of activated carbon at high temperature.
What exactly happen with Bio-materials during activation, so that it gives high surface textural properties ( surface area, pore volume, etc..) after activation and thermal treatment.
I guess some internal chemical reaction makes them more active.
Regards
Anoop
during physical activation at higher temperatures some volatile matters get removed from the biomass due to which some cracks will get formed on the surface. while as the activating agents like superheated steam, nitrogen at higher pressure try to fill these cracks and thus these cracks get converted into pores. with increase in number of pores surface area will be increased.
The reactions involved depend on the route used.
Physical activation is basically a controlled gasification, through the mild oxidation of carbon (formerly obtained by a preliminary carbonisation step) into CO (if CO2 is used) or into CO + H2 (when using steam as the activating agent);
Chemical activation involves both oxidation and dehydation of the biomass, therefore many complex reactions occur at the same, leading to a material enriched in carbon whose porosity was developed by removal of volatile molecules.
Alain
The activation of bio-materials can be achieved with increases surface area by heating at higher temperatures 450-750 deg.centigrade e.g. chrcoal obtained by pyrolysis of bio-materials.
Dear Atul Maldhure,
The production of various biomaterials from bioresources and biowastes is a major industrial activity in bioeconomy. This includes pulp and paper, bioplastics from various biopolymers and microorganisms, as well as biochars and activated carbons with versatile applications such as energy storage, water and wastewater treatment, soil amendment and remediation, and CO2 sequestration.
***Mechanism
High pyrolysis in biochars, temperature promotes the production of biomaterials with a strongly developed specific surface area, high porosity, pH as well as content of ash and carbon, but with low values of CEC and content of volatile matter. This is most likely due to significant degree of organic matter decomposition. Biochars(charcoal produced from plant matter and stored in the soil as a means of removing carbon dioxide from the atmosphere, Biochar can improve soil fertility, which stimulates plant growth. Healthier plants are able to consume and convert more carbon dioxide (CO2), thus improving air quality. ) produced from animal litter and solid waste feedstocks exhibit lower surface areas, carbon content, volatile matter and high CEC(cation exchange capacity) compared to biochars produced from crop residue and wood biomass, even at higher pyrolysis temperatures.
What happens here?
The decrease in CEC is due to the removal of surface functional groups and the formation of aromatic carbon. The cation exchange capacity (CEC) of biochar decreases with increasing pyrolysis temperature. The detectable CEC suggested that when biochar was produced at temperatures up to 480 °C, some acidic oxygenated functional groups such as phenolic acid and carboxyl groups were retained.
Ashish
Dear Atul Maldhure,
The production of various biomaterials from bioresources and biowastes is a major industrial activity in bioeconomy. This includes pulp and paper, bioplastics from various biopolymers and microorganisms, as well as biochars and activated carbons with versatile applications such as energy storage, water and wastewater treatment, soil amendment and remediation, and CO2 sequestration.
***Mechanism
High pyrolysis in biochars, temperature promotes the production of biomaterials with a strongly developed specific surface area, high porosity, pH as well as content of ash and carbon, but with low values of CEC and content of volatile matter. This is most likely due to significant degree of organic matter decomposition. Biochars(charcoal produced from plant matter and stored in the soil as a means of removing carbon dioxide from the atmosphere, Biochar can improve soil fertility, which stimulates plant growth. Healthier plants are able to consume and convert more carbon dioxide (CO2), thus improving air quality. ) produced from animal litter and solid waste feedstocks exhibit lower surface areas, carbon content, volatile matter and high CEC(cation exchange capacity) compared to biochars produced from crop residue and wood biomass, even at higher pyrolysis temperatures.
What happens here?
The decrease in CEC is due to the removal of surface functional groups and the formation of aromatic carbon. The cation exchange capacity (CEC) of biochar decreases with increasing pyrolysis temperature. The detectable CEC suggested that when biochar was produced at temperatures up to 480 °C, some acidic oxygenated functional groups such as phenolic acid and carboxyl groups were retained.
Ashish
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