Hello Researchers, I am looking for a tracer material that can reversibly adsorb onto Activated carbon in a packed bed reactor. To find the contacting efficiency, there are various methods reported - one of these reports the use of adsorbing and non-adsorbing tracer for the tracer experiments. The mean residence time obtained from the pulse tracer experiments will be compared for two phase gas-liquid flows and single phase liquid flows to evaluate the contacting efficiency. Attached is the useful reference, however, I am struggling to find the adsorbing tracer for activated carbon as I am using air-water system and NaCl as a non-adsorbing tracer.