Does CC go out in pool by sunlight?

[victorinfomail]

Hi,

Combined chrorine are depleted by sunlight. Is that true? In my observations, in season, mainly with FC/CYA in range indicated.

Ive searching for Internet and have found a few evidences.

Has Somebody a cientific view or can indicate if is really correct?

 

[mknauss]

CC - Further Reading

www.troublefreepool.com

 

[JamesW]

UV in sunlight or from a UV system will oxidize chloramines.

Monchloramine 245 nanometers
Dichloramine 297 nanometers
Trichloramine 260 and 340 nanometers

ANSI/APSP/ICC-11 2019 American National Standard for Water Quality in Public Pools and Spas

The ANSI/APSP/ICC-11 2019 American National Standard for Water Quality in Public Pools and Spas provides recommended minimum guidelines for the specifications for recreational water quality parameters in public pools and spas. An Appendix A includes explanatory sections about the values for the...

issuu.com

https://www.phta.org/pub/?id=53c77806-1866-daac-99fb-e555a02ec432

https://www.in.gov/health/eph/files/How-To-Shock-The-Pool-2022.pdf

 

[JamesW]

When chlorine bonds to ammonia, it tries to oxidize the nitrogen by removing electrons, but the nitrogen holds on to the electrons and it is a slow process.

UV light is absorbed by the electrons and gives them enough energy to move from the nitrogen to the chlorine causing the nitrogen to convert into nitrogen gas and the chlorine to become chloride.

4NH₃ + 3HOCl + 3OCl^- --> 2NClH₂+ 2NCl₂H + 3H₂O + 3OH^- --> 2N2 + 6H₂O + 3H⁺ + 6Cl^-

 

[JamesW]

 

[JamesW]

The ultraviolet (UV) photolysis of monochloramine (NH2Cl), dichloramine (NHCl2), and trichloramine (NCl3) in aqueous solution was investigated at wavelengths of 222, 254, and 282 nm. All three chloramines can be degraded by UV irradiation, and the quantum yields for these processes are wavelength-dependent. Stable photoproducts include nitrite, nitrate, nitrous oxide, and ammonium.

UV photodegradation of inorganic chloramines - PubMed

The ultraviolet (UV) photolysis of monochloramine (NH2Cl), dichloramine (NHCl2), and trichloramine (NCl3) in aqueous solution was investigated at wavelengths of 222, 254, and 282 nm. All three chloramines can be degraded by UV irradiation, and the quantum yields for these processes are...

pubmed.ncbi.nlm.nih.gov

UV Photolysis of Mono- and Dichloramine Using UV-LEDs as Radiation Sources: Photodecay Rates and Radical Concentrations - PubMed

UV-LEDs with four characteristic wavelengths (255, 265, 285, and 300 nm) were used to investigate the wavelength-dependence of the photolysis of two inorganic chloramines (NH₂Cl and NHCl₂) and their subsequent radical formation. The fluence-based photodecay rates of...

pubmed.ncbi.nlm.nih.gov

 

[JamesW]

When an electron absorbs energy, it transitions to a higher energy level, and when it returns to its original energy level, it re-emits the energy as light.

The electron in the higher energy level is in an "excited" state, which is unstable.

Basically, you have the photoelectric effect knocking electrons into a higher orbit and this allows the chlorine atom to take the electrons.

 

[JamesW]

The loss of chlorine by sunlight is the same phenomenon where the chlorine oxidizes the oxygen into oxygen gas.

2OCl^- + UV --> O₂ + 2Cl^-

 

[JamesW]

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[JamesW]

The nitrogen atom in ammonia has three extra electrons and this makes it -3 in charge.

Chlorine in hypochlorous acid has 6 electrons in the outer shell and this makes +1 in charge.

Chlorine wants 8 electrons, so it tries to take 2 electrons from other atoms and become -1 charge (chloride).

Nitrogen can lose 3 electrons to become nitrogen gas N₂ by covalently bonding with another nitrogen atom and both atoms will have a charge of 0.