Rates of Decomposition of N-Chloramine Disinfectant Compounds in Aqueous Solutions

Abdul-Rahim A. Samarkandy, Shaeel A. Al-Thabaiti and Abdel-Hameed A. El-BelliHi

Chemistry Department-Faculty of Science, King Abdulaziz University-Jeddah, (Kingdom of Saudi Arabia).

ABSTRACT:

In this project, the effect of temperature, pH, and salt effects on the kinetics of hydrolysis and the rate of decomposition N-chloramine disinfectant compounds (chloramine-B, chloramine-T, N-cholorsuccinimide (NCS) and 1,3-dichloro-5,5-dimethyl hydantoin (DCDMH or Halane)) in aqueous solutions were studied. The results showed that the hydrolysis stability of CB and CT is greater than that of NCS and halane. Using CT, which is practical for long contact times, reduced an initial contrectation of 100ppm after 6 months period. The study also showed that the rate of hydrolysis of NCS is almost independent on the H+ ions concentration, whereas the rates of hydrolysis CB and CT depend very much on the hydrogenous (H+) concentration from zero-order to a first-order reaction in hydrogen ion (H+) concentration. A mechanism of two independent pathways was used to explain this behavior. On the other hand in the case of NCS, the results indicate the reaction mechanism involves one-step direct attack of the water molecule on the substrate molecule. The results of salt effects on the hydrolytic decomposition of N-chloramines showed that the rate of hydrolysis depend on the ionic strength and were explained on the basis of secondary salt effects. The energies and enthalpies values of activation are the same and indicate that the N-Cl bond breakage is the rate-determining step in the N-chloramine hydrolytic decomposition. The entropies of activation have large negative values due to the increase in electrostriciton and a loss of freedom of the solvent water molecules associated with the separation of ions in the transition state. A linear compensation between DH+ and DS+ suggest that in the pure aqueous solution, the reaction mechanism is about the same for the chloramine compounds under investigation.

KEYWORDS: N-chloramine; disinfectants; kinetics of hydrolysis

Copy the following to cite this article: Samarkandy A. A, Al-Thabaiti S. A, El-BelliHi A. A. Rates of Decomposition of N-Chloramine Disinfectant Compounds in Aqueous Solutions. Mat.Sci.Res.India;5(2)

Copy the following to cite this URL: Samarkandy A. A, Al-Thabaiti S. A, El-BelliHi A. A. Rates of Decomposition of N-Chloramine Disinfectant Compounds in Aqueous Solutions. Mat.Sci.Res.India;5(2). Available from: http://www.materialsciencejournal.org/?p=1995

---

This work is licensed under a Creative Commons Attribution 4.0 International License.