and 71.2% were noted against mineralization efficiency of 49.3, 58.2, 47 and 24.6% in FP, PFP, UVP and UVPC, respectively.
Most of the intermediates were formed by the degradation of side chain of CHPL molecule and aliphatic amide chain was cleaved by HO• attack at C2 centre. The faster initial rate of TOC reduction was resulted from hydrolysis of amide chain and the slow second stage was associated with the opening of substituted benzene ring.
Four primary daughter ions were originated upon cleavage of CIP and MONC increased from 1.27 to 2.1 at the optimal treatment condition. The proposed 2nd order kinetic model for the decomposition of both CIP and degradation products (DPs) exhibited excellent agreement to the experimental data. The rate constant of CIP and DPs oxidation was obtained between the range from 2.19×103 to 5.07×103 and 3.57×103 to 6.91×103 1/M.s, respectively. The model gave an initial hydroxyl radical concentration of 11.30 to 11.74 µM.
UVPC formed more hydroxylated intermediates of DIPY resulted from the attack of HO• at the catalyst surface. Total twenty nine intermediate products appeared in the mass spectra within the mass to charge ratio of 100 to 400 in four oxidation processes from the same parent molecule. The pyrazolinone ring was degraded preceded by cleavage of methyl moieties. The proposed mechanism implies that most of the intermediates were originated by the pyrazolinone ring degradation.
Slightly lower mineralization efficiency of CHPL, CIP and DIPY was noted in an equimolar CCD mixture compared to the individual drug degradation. Cl- and F- were originated upon degradation of CHPL and CIP and its addition inhibited the decomposition efficiency of CHPL and CIP by about 11.9 and 12.4%, respectively. NO3-
commonly formed didn't suppress decomposition of drugs both in singly and CCD mixture. Hetero-atoms were converted into their respective ions like Cl-, F-, NH4+ and NO3-
. PFP exhibited the ‘highest’ biodegradability and ‘lowest’ antimicrobial activity irrespective to the type of drug and treatment process both in singly and CCD mixture.
7.2 Limitations of the Work
o The present study acted on the fixed concentration of individual drug both in single and mixed drug system. The concentration used was much higher than a PhAC commonly present in industrial and municipal wastewater. This is one of the limitations of the work.
Even though the concentration of individual PhAC varies from ng/L to µg/L, however, the cumulative concentration is as high as few hundred mg/L (Table 6.1). This was the main reason of taking higher drug concentration so that it could give higher TOC value (Table 6.1). The mechanistic aspects, iron-chelation and kinetic approach elucidated even at high concentration would provide significant information on drug degradation that would be useful for real application and understanding the process.
o The number of compounds present in an industrial effluent is many and it varies from the sites to sites. Also the background ions could alter the treatment efficiency as well as the antimicrobial activity. The percentage death of E. coli in treated CHPL, CIP and DIPY solutions was 21.8, 3.8 and 21.2 % lower in PFP compared to CCD system. The mixture of three drugs in presence of common ions could suppress the decomposition efficiency by about 1.2 to 15.1, 0.7 to 16.2 and 1.9 to 35.8 % in FP, PFP and UVP compared to CCD mixture. The background ions added in CCD solution will help to uncover their influence on treatment efficiency that could be anticipated in an industrial effluent.
o It is generally accepted that the state-of-the art electron spins resonance spectroscopy gives a better estimation of HO• radicals over DMSO probe method. Nevertheless, DMSO is highly water soluble and does not form complexes with iron or other metals ions.
7.3 Recommendations for the Future Work
The present study can be extended for the degradation of ß-blockers, steroids, different classes of antibiotics and antipyretic compounds to understand the cleavage pathways and antimicrobial behavior.
The degradation mechanisms and, particularly, the kinetics in aqueous solution are quite different to those running in a complex pharmaceutical matrix. The present work can be carried forward for industrial effluent treatment in order to develop some kind of correlations between them.
The future study should focus on the electronic interactions between other 3d-trasition metals used as catalyst in AOPs and PhACs as a chelating agent.
The future work may include fabrication of photocatalyst for solar light assisted pharmaceutical wastewater detoxification.
The studies on AOPs followed by biological treatment of pharmaceutical effluent are also a prudent area of future research.
A.S. Giri and A.K. Golder, “Formation of Fe(II)-Chloramphenicol chelate and its decomposition in Fenton and Photo-Fenton: Identification and biodegradability assessment of primary by products”, Ind. Eng. Chem. Res. doi: 10.1021/ie501508d.
A.S. Giri and A.K. Golder, “Fenton, Photo-Fenton, H2O2-photolysis and TiO2 photo- catalysis for Dipyrone oxidation: Drug removal, mineralization, biodegradability and degradation mechanism”, Ind. Eng. Chem. Res. 2014, 53 (4), 1351-1358.
A.S. Giri and A. K. Golder, “Ciprofloxacin degradation from aqueous solution by Fenton oxidation: Reaction kinetics and degradation mechanisms”, RSC Adv. 2014, 4, 6738- 6745.
A.S. Giri and A. K. Golder, “Kinetics and mechanisms of Ciprofloxacin cleavage in light assisted Fenton reaction”, Int. J. Rec. Res. Sci. Technol. 2014, 6(1), 78-82.
A.S. Giri and A. K. Golder, “Drug mixture decomposition in photo-assisted Fenton process:
comparison to singly treatment, evolution of inorganic ions and toxicity assay”, Chemosphere (Under review).
Conference Publications
A.S. Giri and A.K. Golder, “Degradation of pharmaceutical from wastewater: Oxidative Fenton process”, Chemical Engineering Congress (CHEMCON-2011), 27-30th December, 2011, Bangalore, India.
A.S. Giri and A.K. Golder, “Fenton oxidation process for the removal of an antimicrobial drug from wastewater”, 2nd International Conference on Advanced Oxidation Processes (AOP 2012), 5-8th October, 2012, Kottayam, Kerala.
A.S. Giri and A.K. Golder, “Oxidative degradation of Dipyrone from wastewater using Fenton reagent”, Indian Chemical Engineering Congress (CHEMCON-2012), 27-30th December, 2012, Dr. B.R. Ambedkar National Institute of Technology, Jalandhar, Punjab, India.
A.S. Giri and A.K. Golder, “Dynamics of photo Fenton process for Dipyrone degradation and hydroxyl radical quantification”, International Exhibition and Conference on Water Technologies and Environmental Technology and Renewable Energy (OMICS group), 11-14th February, 2013, Mumbai, India.
A.S. Giri and A.K. Golder, “Mechanism and identification of reaction byproducts for the degradation of Chloramphenicol drug in heterogeneous photo-catalytic Process”, International Conference on Chemical and Bioprocess Engineering (ICCBPE-2013), 16-17th November, 2013, National Institute of Technology Warangal, Andhra Pradesh, India.
A.S. Giri and A.K. Golder , “Mechanism and identification of reaction byproducts for the degradation of an antibiotic drug in heterogeneous photo-catalysis using TiO2”, International Conference on Frontiers in Chemical Engineering (ICFCE-2013), 9-11th December, 2013, NIT Rourkela, India.
A.S. Giri and A.K. Golder, “Photolytic decomposition of aqueous Ciprofloxacin:
Transformation products and mechanisms”, Indian Chemical Engineering Congress (CHEMCON-2013), 27-30th December, 2013, Institute of Chemical Technology, Mumbai, India.
A.S. Giri and A.K. Golder, “Kinetics and mechanisms of Ciprofloxacin cleavage in light assisted Fenton reaction”, Emerging Challenges and Issues in Environmental Protection, 23-24th January, 2014, Raipur Institute of Technology, Raipur (C.G.), India.