Application of a Novel Heterogeneous Fenton Catalyst in the Treatment of BTEX-Contaminated Waters

The performance of a novel nano-coated surface functionalised PAN-(Fe3+) system as a heterogeneous Fenton catalyst has been investigated in this work and the results show that the heterogeneous Fenton catalyst is a suitable technology for the effective oxidation of organic compounds. When the heterogeneous Fenton system was applied towards the oxidation of aqueous BTEX solutions in batch reactions, there was an 80% decrease in BTEX concentrations after 3 hours (reaction conditions: [BTEX]o: 100 mg/L, [H2O2]o: 50 mg/L, PAN-(Fe3+): 9 g, pH: 3, reaction volume: 160 mL). Similar results were observed when the catalyst was reused in six cycles reflecting its stability and reusability potential. The amount of iron which leached per cycle ranged between 2.1mg/L to 2.4mg/L. The iron leaching as a percentage of the catalyst iron content was 0.5% per cycle which means that just 3% of the total iron content of the catalyst had leached after the six cycles. Evidence of the oxidation of the aromatic compounds was provided by the results of HPLC-UV and GC-MS analysis of the reaction solution. The oxidation products which were detected include; phenol, p-benzoquinone, benzaldehyde, benzyl alcohol, o-cresol, p-cresol, 1-phenylethanol, 2-ethylphenol, 3-ethylphenol, acetophenone and 2-methylbenzyl alcohol. Optimisation studies were then conducted on the batch reaction system using response surface modelling. The rate of BTEX oxidation was found to increase with increasing initial H2O2 concentration, amount of catalyst and time. However, the effect of the initial H2O2 concentration and time on the rate of BTEX oxidation became marginal after a certain point (depending on the initial BTEX concentration). Of particular note was the interaction between the initial BTEX concentration and the initial H2O2 concentration. The consumption of the peroxide was found to be increasingly inhibited with increasing initial BTEX concentrations. Analysis of the results suggest this interaction may be governed by competition for hydroxyl radicals which are widely believed to be responsible for the oxidation of organic substrates in simple Fenton systems. Additionally, the performance of the PAN catalyst was investigated in a continuous flow reaction set-up. The heterogeneous Fenton system was applied towards the treatment of a laboratory simulated produced water. The PAN catalyst demonstrated good durability and prospects for long term use with consistent results throughout the 36 days of the continuous flow reaction. High rates of BTEX oxidation (roughly 82% removal when residence time was 10.42 hours and roughly 94% when residence time was 15.62 hours) were recorded and steadily maintained. And the total amount of iron which leached as a percentage of the total catalyst iron content was < 15%. Evidence for the oxidation of BTEX in the continuous flow reaction is provided by the results of ion chromatography analysis which indicated the presence of organic acids including succinic acid, acetic acid and formic acid.

Name dc:type.qualificationname

PhD

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

De Montfort University

Year dc:date.issued

2017

Author dc:creator

• Ekpruke, Aghogho O.

Licence

• https://dora.dmu.ac.uk/bitstreams/65a6fe4f-9dbc-4a00-af24-127114821892/download