10 research outputs found
Treatment of persistent organic pollutants in wastewater with combined advanced oxidation
Philosophiae Doctor - PhDPersistent organic pollutants (POPs) are very tenacious wastewater contaminants with negative
impact on the ecosystem. The two major sources of POPs are wastewater from textile industries
and pharmaceutical industries. They are known for their recalcitrance and circumvention of
nearly all the known wastewater treatment procedures. However, the wastewater treatment
methods which applied advanced oxidation processes (AOPs) are documented for their
successful remediation of POPs. AOPs are a group of water treatment technologies which is
centered on the generation of OH radicals for the purpose of oxidizing recalcitrant organic
contaminants content of wastewater to their inert end products. Circumvention of the reported
demerits of AOPs such as low degradation efficiency, generation of toxic intermediates, massive
sludge production, high energy expenditure and operational cost can be done through the
application of the combined AOPs in the wastewater treatment procedure. The resultant
mineralisation of the POPs content of wastewater is due to the synergistic effect of the OH
radicals produced in the combined AOPs.
Hydrodynamic cavitation is the application of the pressure variation in a liquid flowing through
the venturi or orifice plates. This results in generation, growth, implosion and subsequent
production of OH radicals in the liquid matrix. The generated OH radical in the jet loop
hydrodynamic cavitation was applied as a form of advanced oxidation process in combination
with hydrogen peroxide, iron (II) oxides or the synthesized green nano zero valent iron (gnZVI)
for the treatment of simulated textile and pharmaceutical wastewater
Quantification of radicals generated in a sonicator
The hydroxyl radical (OH•) is a powerful oxidant produced as a consequence of cavitation in water. It can react nonspecifically in
breaking down persistent organic pollutants in water into their mineral form. It can also recombine to form hydrogen peroxide which is
very useful in water treatment. In this study, terephthalic acid (TA) and potassium iodide dosimetry were used to quantify and investigate
the behaviour of the generated OH radical in a laboratory scale sonicator. The 2-hydroxyl terephthalic acid (HTA) formed during
terephthalic acid dosimetry was determined by optical fibre spectrometer. The production rate of HTA served as a means of evaluating and
characterizing the OH• generated over given time in a sonicator. The influence of sonicator power intensity, solution pH and irradiation
time upon OH• generation were investigated. Approximately 2.2 x 10-9 M s-1 of OH radical was generated during the sonication process.
The rate of generation of the OH radicals was established to be independent of the concentration of the initial reactant. Thus, the rate of
generation of OH• can be predicted by zero order kinetics in a sonicator
Development of adsorptive materials for selective removal of toxic metals in wastewater: A review
Removal of toxic metals is essential to achieving sustainability in wastewater purification.
The achievement of efficient treatment at a low cost can be seriously challenging. Adsorption methods
have been successfully demonstrated for possession of capability in the achievement of the desirable
sustainable wastewater treatment. This review provides insights into important conventional and
unconventional materials for toxic metal removal from wastewater through the adsorption process.
The importance of the role due to the application of nanomaterials such as metal oxides nanoparticle,
carbon nanomaterials, and associated nanocomposite were presented. Besides, the principles of
adsorption, classes of the adsorbent materials, as well as the mechanisms involved in the adsorption
phenomena were discussed
Synthesis of oxygen deficient tio2 for improved photocatalytic efficiency in solar radiation
The photocatalytic activities of TiO2 have been limited mainly to absorbing in the ultraviolet
spectrum which accounts for only 5% of solar radiation. High energy band gap and electron
recombination in TiO2 nanoparticles are responsible for its limitations as a photocatalyst. An oxygen
deficient surface can be artificially created on the titanium oxide by zero valent nano iron through
the donation of its excess electrons. A visible light active TiO2 nanoparticle was synthesized in the
current investigation through simple chemical reduction using sodium boro-hydride. The physical
and textural properties of the synthesized oxygen deficient TiO2 photocatalyst was measured using
scanning/ transmission electron microscopy while FTIR, XRD and nitrogen sorption methods (BET)
were employed for its further characterizations. Photochemical decoloration of orange II sodium
dye solution in the presence of the synthesized TiO2 was measured using an UV spectrophotometer.
The resulting oxygen deficient TiO2 has a lower energy band-gap, smaller pore sizes, and enhanced
photo-catalytic properties
Theory as a driving force to understand reactions on nanoparticles: general discussion
International audienc
Treatment of persistent organic pollutants in wastewater using hydrodynamic cavitation in synergy with advanced oxidation process
Persistent organic pollutants (POPs) are very tenacious wastewater contaminants. The consequences of their existence have been acknowledged for negatively affecting the ecosystem with specific impact upon endocrine disruption and hormonal diseases in humans. Their recalcitrance and circumvention of nearly all the known wastewater treatment procedures are also well documented. The reported successes of POPs treatment using various advanced technologies are not without setbacks such as low degradation efficiency, generation of toxic intermediates, massive sludge production, and high energy expenditure and operational cost. However, advanced oxidation processes (AOPs) have recently recorded successes in the treatment of POPs in wastewater. AOPs are technologies which involve the generation of OH radicals for the purpose of oxidising recalcitrant organic contaminants to their inert end products. This review provides information on the existence of POPs and their effects on humans. Besides, the merits and demerits of various advanced treatment technologies as well as the synergistic efficiency of combined AOPs in the treatment of wastewater containing POPs was reported. A concise review of recently published studies on successful treatment of POPs in wastewater using hydrodynamic cavitation technology in combination with other advanced oxidation processes is presented with the highlight of direction for future research focus
Quantification of Radicals Generated in a Sonicator
The hydroxyl radical (OH•) is a powerful oxidant produced as a consequence of cavitation in water. It can react nonspecifically in breaking down persistent organic pollutants in water into their mineral form. It can also recombine to form hydrogen peroxide which is very useful in water treatment. In this study, terephthalic acid (TA) and potassium iodide dosimetry were used to quantify and investigate the behaviour of the generated OH radical in a laboratory scale sonicator. The 2-hydroxyl terephthalic acid (HTA) formed during terephthalic acid dosimetry was determined by optical fibre spectrometer. The production rate of HTA served as a means of evaluating and characterizing the OH• generated over given time in a sonicator. The influence of sonicator power intensity, solution pH and irradiation time upon OH• generation were investigated. Approximately 2.2 ´ 10-9 M s-1 of OH radical was generated during the sonication process. The rate of generation of the OH radicals was established to be independent of the concentration of the initial reactant. Thus, the rate of generation of OH• can be predicted by zero order kinetics in a sonicator