PHOTOCHEMICAL SELF-PURIFICATION OF AQUATIC SYSTEMS IN THE PRESENCE OF VITAMIN B₆

Viorica GLADCHI; Vladislav BLONSCHI; Gheorghe DUCA; Angela LIS; Radu SILAGHI-DUMITRESCU

doi:10.24193/subbchem.2026.2.07

PHOTOCHEMICAL SELF-PURIFICATION OF AQUATIC SYSTEMS IN THE PRESENCE OF VITAMIN B₆

Authors

Viorica GLADCHI Moldova State University, Faculty of Chemistry and Chemical Technology, 60 Mateevici str., MD-2009, Chisinau, Republic of Moldova https://orcid.org/0000-0002-5847-4466
Vladislav BLONSCHI Moldova State University, Faculty of Chemistry and Chemical Technology, 60 Mateevici str., MD-2009, Chisinau, Republic of Moldova https://orcid.org/0000-0001-8628-6756
Gheorghe DUCA Moldova State University, Institute of Chemistry, 3 Academiei str., MD-2028, Chisinau, Republic of Moldova https://orcid.org/0000-0001-7265-6293
Angela LIS Moldova State University, Faculty of Chemistry and Chemical Technology, 60 Mateevici str., MD-2009, Chisinau, Republic of Moldova. *Corresponding author: angela.lis@usm.md https://orcid.org/0000-0003-1111-7485
Radu SILAGHI-DUMITRESCU Department of Chemistry and Chemical Engineering, Babes-Bolyai University, 11 A. Janos Street, RO-400028, Cluj-Napoca, Romania https://orcid.org/0000-0003-3038-7747

DOI:

https://doi.org/10.24193/subbchem.2026.2.07

Keywords:

Vitamin B₆, pyridoxine, photolysis, H₂O₂, Cu(II), water self-purification, reaction kinetics

Abstract

Vitamin B₆ (pyridoxine, PN) released from anthropogenic and biogenic activities can influence the chemical self-purification of surface waters through its photochemical transformations. The present study aimed to investigate the kinetics and mechanisms of pyridoxine photodegradation under conditions that partially simulate the natural environment (pH ~7, aerated medium) using simulated solar irradiation. Three model systems were investigated: (1) PN–hν; (2) PN–H₂O₂–hν; (3) PN–H₂O₂–Cu(II)–hν, using direct spectrophotometry (λ = 328 nm). The kinetic parameters determined included partial reaction orders (using the van’t Hoff method), effective rate constants, and half-lives (τ₁/₂). Direct photolysis of PN follows a partial reaction order of 0.2 with respect to [PN], with k = (5.38±0.26)·10^-4 s^-1and τ₁/₂ = 21±0.5 min. However, the low quantum yields (7.31–10.70)·10^-3 indicate that direct photolysis of vitamin B₆ is negligible under natural aquatic conditions. In the presence of H₂O₂, the partial reaction orders are 0.3 (PN) and 0.7 (H₂O₂), with W = k·[PN]^0.3·[H₂O₂]^0.7, k = (3.69±0.11)·10^-4 s^-1 and τ₁/₂ = 31.1±0.30 min. For PN–H₂O₂–Cu(II), the partial reaction orders are 0.2 (PN), 0.4 (H₂O₂), and 0.3 (Cu²⁺) with k = (3.91±0.17)·10^-4 s^-1, and τ₁/₂ = 29.2±0.53 min. In conclusion, PN undergoes measurable photodegradation under simulated natural conditions.

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STUDIA UBB CHEMIA, Volume 71 (LXXI), No. 2, June 2026

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Published

2026-06-23

How to Cite

GLADCHI, V., BLONSCHI, V., DUCA, G., LIS, A., & SILAGHI-DUMITRESCU, R. (2026). PHOTOCHEMICAL SELF-PURIFICATION OF AQUATIC SYSTEMS IN THE PRESENCE OF VITAMIN B₆. Studia Universitatis Babeș-Bolyai Chemia, 71(2), 125–145. https://doi.org/10.24193/subbchem.2026.2.07