I am doing the adsorption of copper on polystyrene microplastics and studying the temperature affecting the adsorption behavior (with temperature variations of 25, 30, 35-degree celsius) at a fixed concentration (0.1 mg/l) and pH at 6, as well as a fixed MPs amount used for the adsorption at 24 hours.
After the adsorption experiments, the results showed that the copper adsorption capacity on PS MPs decreased when the temperature increased. Gibbs free energy was spontaneous; enthalpy was negative, implying that the adsorption was exothermic. Entropy was also negative, which showed the orderness of MP/Cu ion during the adsorption process. However, when increasing the temperature, the qe of MPs was enhanced.
As a result, this study is reversed from previous studies that I have found in the literature review, in which the adsorption of copper on MPs was an endothermic reaction. To confirm the accuracy of my work, I would like to have all of your recommendations to verify whether this study can be trustful and which factors I should put into consideration.
I look forward to hearing from you.
Best regards,
Bunlong Ou
You correctly described the thermodynamics of adsorption and it is clear that you did it correctly. From the description, it's just not clear whether pure polystyrene was used or whether you used microplastic after it had been in the form of contamination. Compare your polystyrene and the polystyrene of the above article. To do this, you can make an IR spectrum.
How did you measure the law of massaction constant, which you use to determine ∆H, ∆G & ∆S? In the literature are often used wrong methodes, e.g. distribution coefficients to measure the values.
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