Using 1:6 biomass to acid ratio resulted in a liquefied slurry that wasn't able to dry, and after carbonization it turned into a sticky chunks of carbon. When compared to samples using 1:2 ratios, samples with 1:4 ratios have higher yields of carbonized char.
I've read somewhere that the acid is to allow for the degradation of cellulose but how does this affect the carbonization process and resulting char yields?
Best regards,
Kok W. X.
Acid hydrolysis decomposes the polymers (e.g. cellulose) into smaller molecules, finally sugars, hydrolyzes esters or ethers, thus these smaller fragments becomes more reactive and tends to decompose with formation of smaller molecules (oil or gas) than carbon.
In general., I would expect more gaseous and liquid pyrolysis products and less solid, with higher char content, but it depends on the nature of biomass, nature of acid, concentration, temperature, etc. If we tajke into consideration, that metal content of biomass will turn into ionic due to acids, the effect of metal ions on the decomposition process can play role as well.
IN case of styrene-divinylbenzene copolymers, the crosslinking dramatically affected on formation of solid carbon, the higher crosslinking the more carbon and more hard were formed. At low crossllinking gases, liquids and char were formed.
Please clarify which biomass and which acid. Laszlo is right, as the result depends on several factors. With phosphoric acid, for example, the yield increases with the amount of acid, see Fig. 7(a) of the attached file.
Alain
I observed that and it has been reported in previous literature, the increase in acid concentration (e.g. H3PO4) yields high carbon yield due to the formation of organophosphates on the surface of carbon yield (Puziy et al, 2002 ).
Thanks all, I appreciate the help.
Additionally, yes I impregnated fine leaf powder with H3PO4 under a temperature range of 300oC to 500oC. It was observed 300oC had the better yield with 1:4 acid to biomass ratio.
However, will the formation of organophosphates/sugars/etc. affect the biosorptive capabilities of the carbon towards heavy metals, despite washing with distilled water after carbonization?
Even after thorough washing, the activated carbon will remain acidic, and EDAX scanning will show you that phosphorous is abundantly dispersed inside. What is really important is the corresponding surface area (and pore size distribution) if you plan to adsorb neutral species. The surface charge (related to pH) is important for adsorbing charged species, like heavy metals. Having a very acidic surface will help having a point of zero charge at pH < 7, which is favourable for your application (if metals are in the form of cations, of course, the opposite if they are anions).
Alain
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