Thesis (DTech (Chemistry))--Cape Peninsula University of Technology, 2016. / The use of ozone as an advanced oxidation process is gathering wide spread attention with the major limitation to its application being its cost of operation and design considerations. While the general approach of most researches is to buttress the already known fact of the efficacy of the process, little attention is given to studying the by-products of ozone reactions with organics. The aims of this study were to investigate the efficacy of the ozonation process for removing recalcitrant phenolics: phenol, 2-chlorophenol (2CP), 4-chlorophenol (4CP) and 2,4-dichloropheno (2,4DCP) from aqueous medium with a view of understanding various reaction pathways of the process and identifying possible intermediates and residual compounds using liquid chromatography-mass spectrometry (LC-MS). The choice of the selected chlorophenols would also elucidate the role of the positioning of the chlorine atoms in determining reaction rates, pathways and subsequent mechanisms and by-products. Sequel to this, oxy-hydroxy iron in β-phase (β-FeOOH, akaganite) and various β-FeOOH bonded composites on support metal oxides (Al2O3, NiO and TiO2) were prepared via hetero-junction joining, and explored as a possible promoter to improve the efficiency of the ozonation process. Apparent first order reaction rates constants of tested phenolics was in the order 2,4-DCP > 2-CP > Phenol > 4-CP, irrespective of the tested pH. The individual rates however increased with increasing pH. The position 4 chlorine atom was found to be least susceptible to hydroxylative dechlorination. Catechol intermediate and pathway was identified as the major degradation pathway for phenol and 2-CP, while 4-chlorocatechol pathways were more important for 4-CP and 2,4-DCP. The formation of polymeric dimers and trimers by all compounds was pronounced at alkaline pH. Heterogeneous catalytic ozonation using β-FeOOH reduced ozonation time for 4-CP by 32%. Mechanism for β-FeOOH/ozone catalysis showed that the catalyst suffered reductive dissolution in acidic pH and the kinetics of 4-CP removal using the catalyst was best described using a two stage kinetic model. The first stage was attributed to heterogeneous catalysis of ozone breakdown on β-FeOOH surface generating faster reacting radicals, while the second stage was due to homogeneous catalysis by reduced Fe2+ ions in solution. β-FeOOH stabilized on NiO at a 5% ratio exhibited superior catalytic property compared to the other tested composites. Characterization by high-resolution transmission electron microscopy (HRTEM) affirmed a β-FeOOH-NiO bonded interfaced composite which was stable as a iv catalyst over four (4) recycle runs. The mechanism of operation of the composite was via an increased ozone breakdown to radicals as monitored via photoluminescence experiments. The composite material produced satisfactory results when tested on real wastewater samples. Results from this study contribute to the current understanding on reaction mechanisms for ozone with phenols and chlorophenols, for the first time monitoring time captured intermediates via liquid chromatography-mass spectrometric method, which preserves the integrity of reaction intermediates. Also this study proposes heterogeneous catalysts; β-FeOOH and β-FeOOH bonded composites as possible improvements for simple ozone based water purification systems.

Co-disposal with refuse in a controlled landfill is the cheapest option for the disposal of hazardous waste and, if carefully controlled, can be an effective treatment option. In this present study a high-strength phenolic wastewater and activated sewage sludge were co-disposed with refuse. The effectiveness of phenol catabolism at two organic loading rates (500mgt1 and 1000mgtl) was assessed in the presence of various co-disposal strategies. Leachate recycle at the lower phenol organic loading rate was found to facilitate the greatest rate of phenol catabolism. Despite the effective removal of phenol, however, leachate recycle promoted the production of high concentrations of ammoniacal-N and hydrogen sulphide. At the higher phenol organic loading rate, recirculation was ineffective in reducing the residual phenol concentration due to inhibition of the phenol-catabolisers. Microcosms operated with single elution and batch co-disposal strategies at both phenol organic loading rates resulted in serious detrimental effects on the refuse fermentation and subsequent leachate quality. A high-strength leachate obtained from a closed co-disposal site was characterised to determine its chemical composition and was assessed for its susceptibility to biological treatment. If carefully controlled, co-disposal sites should produce leachates which differ little in quality to those produced by municipal waste sites. The exceptionally high specific conductivity of the leachate used in this present study was, however, uncharacteristic of a leachate from a municipal waste site. The leachate required dilution to 25 % (v/v) before responding to aerobic biological treatment due to the presence of bactericidal/bacteriostatic components. Anaerobic treatment was ineffective even at a final dilution of 10% (v/v) of the original due to the inhibition of methanogenesis caused indirectly by the high concentration of sulphate in the leachate. Following phosphate addition, aerobic biological treatment effected a significant reduction in the chemical oxygen demand (COD) but did not reduce the ammoniacal-N concentration. Scaling and precipitation occurred following addition of the phosphate, and although these did not affect the biological process they can cause operational problems in full-scale leachate treatment plants. Ion exchange, with soil, and lime treatment, were, therefore, considered for their ability to reduce the inorganic content of the leachate prior to biological treatment. However, these particular pretreatments were unsuitable due to their ineffectiveness to reduce calcium, the main inorganic element involved in scaling, to an acceptable concentration. / Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1996.

D. Tech. Chemical Engineering / Aims of this research project was to add value to largely wasted South African sawdust by development of low-cost AC of high efficiency for removal of toxic Cr (VI), phenol and glutaraldehyde from dilute aqueous media. The main objectives of the research project were: a) To develop low-cost AC based on South African P. patula sawdust using economical physical superheated steam activation.Characterization of carbon samples for selection of optimum preparation conditions for development of low-cost AC of effective microporosity mesoporosity and surface functionality for enhanced adsorption capacity of Cr (VI) and/or phenol and/or glutaraldehyde from dilute aqueous solution. Acid-amine surface groups modification of optimally developed AC for further enhancement of adsorption capacity for mixed polarized glutaraldehyde molecules from aqueous solution. b) To evaluate the aqueous phase batch adsorption properties of developed AC for Cr (VI) and phenol and, of acid-amine modified developed AC for glutaraldehyde. Determination of optimum pH for adsorption; accurate adsorption isotherm modelling for determination of maximum adsorption capacity, comparison of maximum adsorption capacities for Cr (VI) and phenol of developed AC with commercial AC and literature ACs, and attempt to establish average micropore size for enhanced capacity for Cr (VI) and phenol from dilute aqueous solution.Kinetics reaction and diffusion modelling for determination of adsorption rate constants and diffusion parameters; and determination of adsorption thermodynamic parameters.Evaluation of equilibrium selectivity of developed AC for Cr (VI) and/or phenol in binary aqueous solutions. c) To evaluate aqueous phase fixed-bed adsorption characteristics of developed AC for single Cr (VI) and mixed solution using Rapid Small Scale column Tests (RSSCTs). Generation of breakthrough curves at optimum adsorption conditions for evaluation of column performance indicators at different process conditions, bed regeneration-reusability potential, and dynamic adsorption selectivity of developed AC for Cr (VI) from solution of base metals. Determination of column diffusion parameters; accurate mass transfer and empirical modelling of breakthrough data; determination of applicable RSSCT scaling equation; and optimization of breakthrough data for accurate RSSCT scale-up.