Dear researchers,
I am conducting an adsorption study of urea using biochar derived from rice husk. I varied the contact time to investigate the adsorption kinetics. After the adsorption process, I analyzed the remaining urea concentration in the solution using the PDMAB (p-dimethylaminobenzaldehyde) colorimetric method.
Surprisingly, the measured urea concentration increased significantly after the adsorption process, even compared to the initial concentration before contact with the adsorbent. This phenomenon occurred consistently across different contact times.
Has anyone experienced similar results, or could anyone suggest possible reasons for this anomaly? Could it be due to interference from biochar leachates with the PDMAB method, or is there a chance that some component from the biochar is affecting the reaction?
I would appreciate any insights or suggestions to help troubleshoot this issue. Thank you.
I don't know the cause but it appears to be a lack of method selectivity. The urea appears to be displacing something that reacts like urea with the reagents ....
Muhammad Erik Ferdian
You do not write how you obtained biochar. Rice husk contains not only cellulose, but some amount of protein may get there. If you carried out the process of obtaining biochar by heating in a closed space, i.e. without a vacuum, then during the decomposition of rice husk, ammonia could be obtained, which was adsorbed on the biochar. You need to check the ammonia content in the biochar before studying the adsorption of ammonia.
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