Morgan Adams

Novel photocatalytic reactor development for removal of hydrocarbons from water

Hydrocarbons contamination of the marine environment generated by the offshore oil and gas industry is generated from a number of sources including oil contaminated drill cuttings and produced waters. The removal of hydrocarbons from both these sources is one of the most significant challenges facing this sector as it moves towards zero emissions. The application of a number of techniques which have been used to successfully destroy hydrocarbons in produced water and waste water effluents has previously been reported. This paper reports the application of semiconductor photocatalysis as a final polishing step for the removal of hydrocarbons from two waste effluent sources. Two reactor concepts were considered: a simple flat plate immobilised film unit, and a new rotating drum photocatalytic reactor. Both units proved to be effective in removing residual hydrocarbons from the effluent with the drum reactor reducing the hydrocarbon content by 90% under 10 minutes.

A new generation of biocides for control of crustacea in fish farms

Farming of salmon has become a significant industry in many countries over the past two decades. A major challenge facing this sector is infestation of the salmon by sea lice. The main way of treating salmon for such infestations is the use of medicines such as organophosphates, pyrethrins, hydrogen peroxide or benzoylphenyl ureas. The use of these medicines in fish farms is, however, highly regulated due to concerns about contamination of the wider marine environment. In this paper we report the use of photochemically active biocides for the treatment of a marine copepod, which is a model of parasitic sea lice. Photochemical activation and subsequent photodegradation of PDAs may represent a controllable and environmentally benign option for control of these parasites or other pest organisms in aquaculture.

Photocatalytic Splitting of Water

The use of photocatalysis for the photosplitting of water to generate hydrogen and oxygen has gained interest as a method for the conversion and storage of solar energy. The application of photocatalysis through catalyst engineering, mechanistic studies and photoreactor development has highlighted the potential of this technology, with the number of publications significantly increasing in the past few decades. In 1972 Fujishima and Honda described a photoelectrochemical system capable of generating H2 and O2 using thin-film TiO2. Since this publication, a diverse range of catalysts and platforms have been deployed, along with a varying range of photoreactors coupled with photoelectrochemical and photovoltaic technology. This chapter aims to provide a comprehensive overview of photocatalytic technology applied to overall H2O splitting. An insight into the electronic and geometric structure of catalysts is given based upon the one- and two-step photocatalyst systems. One-step photocatalysts are discussed based upon their d0 and d10 electron configuration and core metal ion including transition metal oxides, typical metal oxides and metal nitrides. The two-step approach, referred to as the Z-scheme, is discussed as an alternative approach to the traditional one-step mechanism, and the potential of the system to utilise visible and solar irradiation. In addition to this the mechanistic procedure of H2O splitting is reviewed to provide the reader with a detailed understanding of the process. Finally, the development of photoreactors and reactor properties are discussed with a view towards the photoelectrochemical splitting of H2O.

From ideal reactor concepts to reality: the novel drum reactor for photocatalytic wastewater treatment.

Abstract This article reports the development of a novel drum photocatalytic reactor for treating dye effluent streams. The parameters for operation including drum rotation speed, light source distance, catalyst loading and H2O2 doping have been investigated using methylene blue as a model pollutant. Effluent can be generated by a number of domestic and industrial sources, including pharmaceutical, oil and gas, agricultural, food and chemical sectors. The work reported here proposes the application of semiconductor photocatalysis as a final polishing step for the removal of hydrocarbons from effluents sources, initial studies have proved effective in removing residual hydrocarbons from the effluent.

A study of annulus lubrication for oil well completion using scale model tests

When an oil reservoir reaches the end of its production life the well which has been drilled to extract the oil must undergo completion or ldquowell abandonmentrdquo. Abandonment is the process whereby all the productive zones within the well are isolated with cement, removing some or all of the production tubing and setting a surface plug in the well with the top of the plug between 30 and 50 m below the mudline. The process of abandonment can be hampered if it is not possible to remove pipes from within the well casing. It is proposed that by lubricating the annulus, the space between the casing and pipe, it may be possible to extract problematic pipe work by reaching pressure equilibrium between the reservoir and annulus. Experiments have been carried out to investigate the mixing time of a heavy brine with water. This mixing is known as lubrication. Lubrication can be used to increase the pressure (or fluid weight) at the bottom of a well. When heavy brine is added at the top of a column of water the fluids will mix and the resulting fluid has a greater density than that of water which increases the pressure at the bottom of the well. The experiments were carried out in test rigs comprising of a clear plastic tube sealed at the lower end and connected to a Perspex tank by a ball valve at the top of the tube. The dimensions of the test rigs were chosen to be a scale representation of a typical oil well. The well geometry was simplified with the upper part of the tube vertical and the lower part of the tube inclined at an angle to the vertical with the joint occurring at roughly 60 % of the vertical distance from the top. The diameter of the tubing could not be scaled using the same length scale and so instead a number of tube diameters were tested. The ratio of fluid volumes above and below the circulation point was conserved with the brine volume being equal to 75 % of the water volume; i.e. a 3:4 ratio. The pressure at the lower end of the tube was measured using a piezoelectric sensor inserted through the centre of the plug sealing the end of the tube. Tests were carried out for 10 mm, 20 mm, 40 mm, 60 mm and 100 mm diameter tubes. The aim of these tests was to demonstrate the relationship between tube diameter and time taken to reach equilibrium. For all of these tests the total vertical distance from the top of the tube to the pressure sensor was 3.0 m. Additional experiments were carried out to establish if the relationship between tube length and time taken to reach equilibrium is linear. Straight lengths of 1.0 m, 1.5 m, 2.0 m, 2.5 m, and 3.0 m of 40 mm diameter tube were tested. Initially the mixing of the brine and the water is rapid but as the time from valve opening increases the rate of change of pressure with time reduces approaching the final value asymptotically. This makes it unlikely that the lubrication process will be carried out in order to reach the final pressure and so results are presented in terms of the time taken to reach 75 % of the final pressure. Increasing the tube diameter was shown to reduce the time required to reach 75 % of the final pressure. It was also established that there is not a linear relationship between tube length and time taken to reach equilibrium. This demonstrates that whilst lubrication can be used to increase the pressure at the bottom of an oil well the time scale needed to produce a significant increase in pressure is very large.

Sensitive Novel Fluorescent Tracers for Environmental Monitoring

This paper discusses the development and use of novel glass and polymer tracers, based on narrow band atomic fluorescence, which have been developed for deployment as environmental tracers. The use of discrete fluorescent species in an environmentally stable host has been developed to replace existing toxic, broad band molecular dye tracers. The narrow band emission signals offer the potential for the tracing of a large numbers of signals in the same environment. This will give significant competitive advantage and increased data accuracy and also allow multiple source environmental monitoring of environmental parameters. These novel environmental tracers exhibiting highly discrete fluorescent emissions can also be formed into many shapes, forms and densities to mimic naturally occurring media.

Waveguide-based machine readable fluorescence security feature for border control and security applications

Border security challenges and immigration issues are increasing considerably in recent years. Counterfeiting and fraudulent use of identity and other travel documents are posing serious threats and safety concerns worldwide, ever since the advancement of computers, photocopiers, printers and scanners. Considering the current scenario of illegal migration and terrorism across the world, advanced technologies and improved security features are essential to enhance border security and to enable smooth transits. In this paper, we present a novel dual waveguide based invisible fluorescence security feature and a simple validation system to elevate and strengthen the security at border controls. The validation system consists of an LED (light emitting diode) as excitation source and an array photodetector which helps in the simultaneous detection of multiple features from the fluorescence waveguides. The fluorescence waveguides can be embedded into the identity document as micro-threads or tags which are invisible to the naked eye and are only machine readable. In order to improve the sensitivity, rare earth fluorescence materials are used which absorb only specific ultraviolet (UV) or visible (VIS) wavelengths to create corresponding fluorescent emission lines in the visible or infrared wavelengths. Herein, we present the preliminary results based on the fluorescence spectroscopic studies carried out on the fabricated rare earth doped waveguides. The effect of different rare earth concentrations and excitation wavelengths on the fluorescence intensity were investigated.

Novel Tracers for Environmental Applications

Novel glass tracers, based on narrow band atomic fluorescence, have been developed for deployment as environmental tracers. The use of discrete fluorescent species in an environmentally stable host has been developed to replace existing toxic, broad band molecular dye tracers. The narrow band emission signals offer the potential for the tracing of a large numbers of signals in the same environment. This will give significant competitive advantage and increased data accuracy and also allow multiple source environmental monitoring of environmental parameters. The work presented here aims to outline potential parameters for using lanthanide doped borosilicate glass as environmental tracers.