Hi, I am working on activated carbon now for heavy metal removal. Based on the papers that I have read all the result showed that the modified-activated carbon has better adsorption removal and higher capacity, but it did not work with the material that I already synthesized. Could you please give some reason behind this? Thank you.
you can use sulfurized activated carbon (SAC) adsorbents made up from a mixture of solid sulfur and AC (1:3). SAC has an increased surface area as well as micropore volume when compared with the AC absorbent.
Octa Octa
There are physical and chemical adsorption process on activated carbon. Adsorption on activated carbon is determined by the specific surface area. The larger the specific surface, the greater the adsorption. The oxidized activated carbon may contain carboxyl groups. Ion exchange will be added to physical adsorption. This can lead to selective adsorption and change in physical and chemical adsorption.
So, actually, I oxidized the activated carbon prior to modification, using HNO3 as a oxidating agent, but though it has carbonyl groups, as shown new peak in FTIR spectra, the result of adsorption is lower than the AC. Further I tried to increase the sulfur functional groups, the EDS showed that the sulfur FGs are exist around 10%, but then the %removal even lower. I did the adsorption at pH 5.5 since this one is the best condition for all the materials.
The pH 5,5 it is not necessary the best condition for your adsorption.
This might depend on the heavy metal adsorbed (for instant, Cd is better adsorbed at higher pH values - must search in the literature for speciation of Cd in aqueous solution).
On the other hand, as already mentioned (Yuri Mirgorod), if ion exchange occurs, than competition between heavy metal ions and H(+) has to be considered.
Peace, I do not think that adjusting activated carbon to oxidized carbon will reduce its removal process, because from experience it removes it wonderfully and works without changing the PH
Suggest to follow the hint of Yuri and compare the BET surface of starting and modified carbon.
This is interesting, i think adsorption is highly depends on solution pH, specific surface area of adsorbent, particle size of adsorbent & reaction time, porosity, active sites indeed. You should measure firstly your adsorbent surface character based on BET, SEM, AFM, XRD, FTIR analysis and then compare the two types of adsorbents which you already have applied for this study. Thus you can identify your problem deeply i,e. Who is actually responsible for this unwanted happening. Is it due to those factor or the experimental setup indeed.
Hope this will help you a lot
Activated carbon has selective retention/absorption capacity and bond strengths will allow the AC to release a lower bond strength compound for one that has stronger ties. When you oxidize, you have already given the AC a bonding to the oxidizer. So only compounds with stronger bond strengths will bind with the AC that has been oxidized.
Think of this as "relative affinity" and a fickle connection.
Please read my paper on this problem
Article Insights into the mechanism of cationic dye adsorption on ac...
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