I have used activated carbon for chlorophenol adsorption (2-CP, 4-CP) and got the UV absorption spectra from Perkin Elmer spectrophotometer (Lambda 25). For example, the absorption spectra before and after adsorption were 0.0705 and 0.0302. The initial concentration was 20 ppm and the contact time was held uptil 2 hours. I understand that adsorption took place very well. But how do I know the concentration for the latter spectrum?
I shall appreciate your time and effort to help me with the answers.
The wavelengths for 2-CP and 4-CP were 274 and 280 nm, respectively. Could you please demonstrate me how to get the coefficient value considering 2 hours of contact time? Thank you.
You have to prepare a calibration curve to accommodate the values of the final concentration or absorbance. Then, determine your regression equation from the plot.
Using this equation you should be able to find the concentration of the final spectrum using the absorbance for it.
Good luck
I request you to refer this link:
http://web.iitd.ac.in/~arunku/files/CEL311_Y13/Adsorption%20Theory%20to%20practice_Dabrowski.pdf
Hello there,
You have to prepare a calibration graph for concentration of chlorophenol from 1, 3, 5, 10, 20 and 40 ppm. Then read your sample, preferably in duplicate and calculate the concentrationof chlorophenol using the calibration graph of your standards.
However how did you know that equilbrium was reached in 2 hours? You must do the experiment at different times to evaluate the time required for equilibrium to be achieved. This is called kinetics. By plotting concentration adsorbed versus time you can calculate equilibrium time, rate of adsorption and equilibrium loading of chlorophenol on the adsorbent.
Check out my papers:
1. Zaynab Aly, Adrien Graulet, Nicholas Scales, Tracey Hanley, “Removal of aluminium from aqueous solutions using PAN-based adsorbents: characterisation, kinetics, equilibrium and thermodynamic studies, Journal of Environmental Science and Pollution Research (2014) 21: 3972-3986. DOI 10.1007/s11356-013-2305-6.
2. Z. Aly and V. Luca, “Uranium extraction from aqueous solution using dried and pyrolyzed tea and coffee wastes”, J. Radioanaly. Nucl. Chem., Volume 295, issue 2, (2013) pages 889-900. DOI: 10.1007/s10967-012-1851-6.
I appreciate your detailed answer to my question, Z.Aly. I have prepared these activated carbons from Residual Oil Fly Ash. For phenol uptake experiments, the AC I used had a surface area of 272 m2/g. But after 1.30 hrs., there was not any benefit to adsorb more pollutant from aqueous solution and thus considered 2 hrs.
If these are model experiments with a defined composition of only chlorophenol you will be o.k. when doing appropriate calibration. For less defined solutions, i.e. real waste water you should work with derivative spectroscopy (4th derivative) this will give you a finger print of your contamination only marginally effected by other compounds and turbidity.
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