How to Quantify the Adsorption of Cyanuric Acid on Activated Carbon Used from Swimming Pool Disinfection?

The physical and chemical characteristics of an adsorbentare keyfactors determining its efficiency in relation to a particular adsorbatemolecule. The adsorption of cyanuric acid (cya) on activated carbon(AC) has not been extensively explored in terms of its basic phenomenonand specific surface interactions. Cya is an important molecule inthe swimming pool industry, as it protects free chlorine from UV lightdegradation. A proper characterization of AC will be beneficial forswimming pool product suppliers to determine the criteria while purchasingit to remove excess cya accumulated in pools. A detailed investigationof the physicochemical properties of activated carbon was conductedto assess its potential to adsorb cya from water. The effect of theadsorption capacity under various pH conditions was studied and itwas found that acidic pH favors the adsorption process. With the helpof temperature-programmed desorption coupled with mass spectrometry(TPD-MS) and X-ray photoelectron spectroscopy (XPS), the surface chemistrywas well analyzed for a proper understanding of the adsorbent-adsorbateinteraction. While conventional pool test equipment gives inconsistentreadings of the cya concentration, a UV-vis spectroscopy-basedmethodology has been developed to accurately measure traces of cyain water. This method can be helpful to validate the accuracy of pool-testersfor research and development purposes. The batch adsorption experimentsrevealed that cya adsorption on activated carbon follows pseudo-second-orderkinetics, which confirms that the adsorption mechanism is chemisorption,which in fact, depends highly on the surface chemistry of the AC andthe reaction pH.