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ABSTRACT
Gamma-radiation-induced degradation of ciprofloxacin (CIP) in aqueous solution and the factors affecting the degradation process have been investigated. The results showed that CIP (4.6 mg/L) was almost completely degraded at an absorbed dose of 870 Gy. The kinetic studies of aqueous solutions containing 4.6, 10, 15 and 17.9 mg/L indicated that the decomposition of CIP by gamma irradiation followed pseudo-first-order kinetics and the decay constant (k) decreased from 5.9 × 10−3 to 1.6 × 10−3 Gy−1 with an increase in CIP initial concentration from 4.6 to 17.9 mg/L. The effect of saturation of CIP solution with N2, N2O or air on radiation-induced degradation of CIP was also investigated. The effects of radical scavengers, such as t-BuOH and i-PrOH, showed the role of reactive radicals towards degradation of CIP in the order of . The apparent second-order rate constant of
with CIP was calculated to be 2.64 × 109 M−1 s−1. The effects of solution pH as well as natural water contaminants, such as
,
,
and
, on CIP degradation by gamma-irradiation were also investigated. Major degradation products, including organic acids, were identified using UPLC-MS/MS and IC, and degradation pathways have been proposed.
Acknowledgements
Authors are thankful to the Nuclear Institute for Food and Agriculture (NIFA), Peshawar for their kind permission to use their gamma-irradiator facility. MS is also thankful to Prof. Pengyi Zhang for his help in carrying out UPLC-MS/MS experiments at the School of Environment, Tsinghua University, Beijing, China.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
HMK is grateful to the Higher Education Commission of Pakistan (HEC) for research project (HEC 20-376) and MS acknowleges HEC for award of fellowship under International Research Support Initiative Programme (IRSIP).
ORCID
Murtaza Sayed http://orcid.org/0000-0002-2194-8058
Hasan M. Khan http://orcid.org/0000-0002-2207-6992
Supplemental data
Supplemental data for this article can be accessed at doi:10.1080/09593330.2015.1075597
