Publications by authors named "Ardhendu Sekhar Giri"

3 Publications

  • Page 1 of 1

Kinetics, degradation mechanisms and antibiotic activity reduction of chloramphenicol in aqueous solution by UV/HO process.

Water Sci Technol 2021 Aug;84(3):524-537

Department of Chemical Engineering, Indian Institute of Science Education and Research Bhopal, Bhopal 462066, India.

In this study, the aim was to explore the effectiveness of the UV/HO photolysis (UVP) process in terms of antimicrobial activity reduction and increasing the mean oxidation number of carbon (MONC) under the degradation of chloramphenicol (CHPL) drug. CHPL degradation kinetics and the effects of foreign anions on CHPL degradation were explored in this study. The order of the inhibition effect was found as Cl > NO > HCO due to their different in HO radical scavenging capacity. A pseudo-first-order model for CHPL degradation was well established, and the rate constant (k) was 2.93 × 10 min (R = 0.98) in UVP. Thirteen intermediate products were detected in MS-chromatogram and were identified through different proposed degradation pathways. The cleavage of the amide side chain in CHPL was more effective in CHPL degradation due to an electrophilic attacks by HO radicals on it. The inactivation rates of E. coli were decreased due to the reduction of -NO group into -NH functional group in CHPL that leads to the production of low toxic compounds on CHPL degradation.
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http://dx.doi.org/10.2166/wst.2021.254DOI Listing
August 2021

Ciprofloxacin degradation in photo-Fenton and photo-catalytic processes: Degradation mechanisms and iron chelation.

J Environ Sci (China) 2019 Jun 27;80:82-92. Epub 2018 Sep 27.

Department of Chemical Engineering, Indian Institute of Technology Guwahati, Assam, 781039, India. Electronic address:

Ciprofloxacin (CIP) is a broad spectrum synthetic antibiotic drug of fluoroquinolones class. CIP can act as a bidentate ligand forming iron complexes during its degradation in the photo-Fenton process (PFP). This work investigates on PFP for the degradation of CIP to understand the formation mechanism and stability of iron complexes under ultraviolet (UV)-light illumination. A comparison was made with the UV-photocatalysis (UV/TiO) process where CIP doesn't form a complex. In PFP, the optimal dose of Fe and HO were found to be 1.25 and 10 mmol/L with pH of 3.5. An optimal TiO dose of 1.25 g/L was determined in the UV/TiO process. Maximum CIP removal and mineralization efficiency of 93.1% and 47.3% were obtained in PFP against 69.7% and 27.6% in the UV/TiO process. The mass spectra could identify seventeen intermediate products including iron-CIP complexes in PFP, and only seven intermediate products were found in the UV/TiO process with a majority of common products in both the processes. The proposed mechanism supported by the mass spectra bridged the routes of CIP cleavage in the PFP and UV/TiO process, and the decomposition pathway of Fe-CIP chelate complexes in PFP was also elucidated. Both in PFP and UV/TiO processes, the target site of HO radical attack was the secondary-N atom present in the piperazine ring of the CIP molecule. The death of Escherichia coli bacteria was 55.7% and 66.8% in comparison to the control media after 45 min of treatment in PFP and UV/TiO process, respectively.
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http://dx.doi.org/10.1016/j.jes.2018.09.016DOI Listing
June 2019

Decomposition of drug mixture in Fenton and photo-Fenton processes: comparison to singly treatment, evolution of inorganic ions and toxicity assay.

Chemosphere 2015 May 6;127:254-61. Epub 2015 Mar 6.

Department of Chemical Engineering, Indian Institute of Technology Guwahati, Assam 781 039, India. Electronic address:

The degradation of three pharmaceutical compounds i.e. chloramphenicol (CHPL), ciprofloxacin (CIP) and dipyrone (DIPY) singly and from equimolar (CCD) mixture has been investigated in Fenton and photo-Fenton processes. Drug mineralization was slightly less when present singly than their mixture. The degradation efficiency was likely hindered due to formation of common ions like Cl(-), F(-), NH4(+) and NO3(-). Addition of the same ions i.e. Cl(-) and F(-) in drug solution released upon cleavage of CHPL and CIP in CCD mixture suppressed the decomposition efficiency remarkably in both the oxidation processes. The major intermediates appeared in the mass spectra in combination of ion chromatograph were used to validate the routes of CCD decomposition and evolution inorganic ions. Furthermore, the bacterial toxicity assay was investigated using Escherichia coli (E. coli). The average reduction in cell death was about 38% in CCD system compared to 52%, 42% and 47% for CHPL, CIP and DIPY, respectively.
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http://dx.doi.org/10.1016/j.chemosphere.2015.02.010DOI Listing
May 2015
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