Microfluidics: A Groundbreaking Technology for PET Tracer Production?

Application of microfluidics to Positron Emission Tomography ( PET) tracer synthesis has attracted increasing interest within the last decade. The technical advantages of microfluidics, in particular the high surface to volume ratio and resulting fast thermal heating and cooling rates of reagents can lead to reduced reaction times, increased synthesis yields and reduced by-products. In addition automated reaction optimization, reduced consumption of expensive reagents and a path towards a reduced system footprint have been successfully demonstrated. The processing of radioactivity levels required for routine production, use of microfluidic-produced PET tracer doses in preclinical and clinical imaging as well as feasibility studies on autoradiolytic decomposition have all given promising results. However, the number of microfluidic synthesizers utilized for commercial routine production of PET tracers is very limited. This study reviews the state of the art in microfluidic PET tracer synthesis, highlighting critical design aspects, strengths, weaknesses and presenting several characteristics of the diverse PET market space which are thought to have a significant impact on research, development and engineering of microfluidic devices in this field. Furthermore, the topics of batch- and single-dose production, cyclotron to quality control integration as well as centralized versus de-centralized market distribution models are addressed

Synthesis and evaluation of novel porous materials for environmental remediation

Porous materials have been widely used as adsorbents for water treatment due to their unique properties such as high surface area, excellent mechanical properties and good chemical stability. The work in this thesis aimed to develop novel porous materials for pollution remediation, with the focus being on materials that can be produced economically and environmentally friendly. The first part of this thesis covers two types of mesoporous carbon materials including mesoporous and magnetic mesoporous carbon materials which were fabricated through a soft templating method (Chapter 3). It has been shown that these porous carbon materials with monolithic form have high surface area, which is envisaged excellent adsorbent capacity. But there are some drawback which limit their use for water treatment as the preparation of these materials is time consuming, there are high operation cost and difficulties in regeneration and operation. Cellulose was considered as an attractive alternative material for preparation of porous materials for pollution remediation because it is naturally abundant, renewable, non-toxic and a lowcost biopolymer.In the second part of this work a cellulose-based hydrogel was successfully synthesized using hydroxypropyl cellulose (HPC) with divinyl sulfone (DVS) as a chemical crosslinker via a modified temperature induced phase separation (TIPS) method (Chapter 4). The HPC hydrogel obtained was characterised and the results showed that the properties of this hydrogel depended on the gelation temperature. The FTIR results confirmed the chemical cross-linking between HPC and DVS. HPC hydrogel demonstrated a flexible behaviour without breakage under compression tests. In addition, there were good shape recovery properties upon adsorption of water. The morphology of the cross-linked HPC hydrogel showed an interconnected macroporous network structure, which allowed application for water purification.Further work was then carried to develop a new and simple method to prepare a novel thermoresponsive HPC hydrogel with a graded pore size (Chapter 5). This method combined two approaches, varying the temperature between the upper and lower part of the hydrogel utilising the lower critical solution temperature (LCST) via the temperature induced phase separation (TIPS) method, which achieved a gradual change in pore geometry and pore size. The added inclusion of cryogenic treatment of the sample ensured a gradient porous HPC hydrogel was obtained with high permeability. Double network (DN) hydrogels have a structure that can effectively improve the adsorption capacity as the second network can introduce more functional groups into hydrogel structures, which is of great importance in the adsorption process due to improve the adsorption capacities. The DN hydrogels can also improve the mechanical strength of hydrogel materials, which makes it easier to regenerate. To this purpose, novel hybriddouble networks hydrogel was prepared in this work via mixing two types of crosslinked polymers, these were covalently crosslinked HPC with DVS and ionically crosslinked alginate with calcium ions (Chapter 6). Alginate was selected to be the second network polymer as alginate has carboxylate functional groups that can be used to remove cationic pollutant by electrostatic interactions, thus improving the adsorption capacity of the HPC single network (HPC SN) hydrogel. SEM images of the double network produced s confirmed that the hydrogel was composed of two independently cross-linked networks with a homogeneous interconnecting porous structure. The mechanical tests on the DN hydrogel showed that it was much stronger compared with HPC SN hydrogel. The adsorption and filtration of organic pollutants by HPC hydrogel were investigated through dye adsorption experiments (Chapter 7). The results were showed a great ability of HPC hydrogel for selective adsorption towards MB dye. In order to evaluate the possibility of reuse of HPC hydrogel, the recyclability of these materials was examined. The obtained results indicated that the reusability of the HPC hydrogel was at some cycles without any loss in its sorption behaviour. Therefore, the HPC hydrogel can be a good reusable and economical adsorbent to remove the cationic species. It is important to note that HPC hydrogel column was further used for the first time for selective separation of dye mixtures by simple gravity filtration and the hydrogel can be re-used multiple times. Despite being one of the most promising types of porous materials for environmental applications, their low adsorption capacity is a significant disadvantage for their use inthese applications. Adsorption of methylene blue dye (MB) on HPC/CA DN hydrogel was investigated through batch and column adsorption experiments and compared with HPC SN hydrogel (Chapter 7). The adsorption isotherms for both HPC SN and HPC/CA DN hydrogels fitted well with the Langmuir adsorption model and the maximum adsorption capacity of HPC/CA DN hydrogel was found to be 169.49 mg g-1, which is larger than for the HPC SN hydrogel (112.35 mg g-1). The results showed a significant pH-dependent equilibrium for the adsorption capacity of MB dye for both hydrogels in this study, which decreased dramatically with decreasing the pH of the MB dye solution. This meant that the MB-loaded HPC hydrogel could be easily regenerated under acidic conditions. The thermodynamic analysis of MB dye adsorption onto both HPC SN andHPC/CA DN hydrogels were also studied and the process was shown to be an exothermic and spontaneous process. An adsorption kinetic study was also carried out and the results obtained showed that the adsorption of MB dye adsorption on both hydrogels was well described by the pseudo-second-order kinetic model. In the column study, the adsorbent reuse was investigated and the selective separation of a dye mixture was also studied through ten cycles. Both hydrogels columns showed efficient selective adsorbent for cationic dyes, with the removal of MB dye being very efficient, whilst extremely low removal of FL dye. However, the HPC/CA DN hydrogels column exhibited a higher adsorption capacity than HPC SN hydrogel due to the dual functional groups (hydroxyl and carboxyl groups) in HPC/CA DN hydrogel. Based on the selective adsorptiontowards cationic methylene blue over anionic sodium fluorescein dye, HPC SN and HPC/CA DN hydrogels columns could easily separate two dyes from aqueous solutions of dye mixtures by simple gravity filtration. Both HPC SN and HPC/CA DN hydrogel column showed high separation efficiency of more than 99%. It was also found that separation efficiency of the HPC SN decreased to 86% by the 10th cycle for this column, while no significant losses in the separation efficiency were detected even after ten cycles for the HPC/CA DN hydrogel column. These results show that the HPC/CA double network polymer hydrogels have great potential for improving the adsorption capacity with good reusability and would be a promising eco-friendly adsorbent for the treatment of dye wastewaters

DEVELOPMENT OF MAGNETIC NANOCOMPOSITE MATERIALS AS REUSABLE ADSORBENTS FOR CHLORINATED ORGANICS IN CONTAMINATED WATER

The constant growth in population worldwide over the past decades continues to put forward the need to provide access to safe, clean water to meet human needs. There is a need for cost-effective technologies for water and wastewater treatment that can meet the global demands and the rigorous water quality standards and at the same maximizing pollutant efficiency removal. Current remediation technologies have failed in keeping up with these factors without becoming cost-prohibitive. Nanotechnology has recently been sought as a promising option to achieve these goals. The use of iron oxide magnetic nanoparticles as nanoadsorbents has led to a new class of magnetic separation strategies for water treatment. We have developed magnetic nanocomposite systems able to capture polychlorinated biphenyls (PCBs), as model organic pollutants, in aqueous solution, providing a cost-effective water remediation technique. Two distinct methods were employed to develop these polyphenolic nanocomposite materials. The polyphenolic moieties were incorporated to create high affinity binding sites for organic pollutants within the nanocomposites. The first method utilized a surface initiated polymerization of polyphenolic-based crosslinkers and co-monomers on the surface of iron oxide magnetic nanoparticles to create a core-shell nanocomposite. The second method utilized a bulk polymerization method to create macroscale films composed of iron oxide nanoparticles incorporated into a polyphenolic-based polymer matrix, which were then processed into microparticles. Both methods produce nanocomposite materials that can bind chlorinated organics, can rapidly separate bound organics from contaminated water sources using magnetic decantation, and can use thermal destabilization of the polymer matrix for contaminant release and material regeneration. The polyphenol functionalities used to bind organic pollutants were quercetin multiacrylate (QMA) and curcumin multiacrylate (CMA), which are acrylated forms of the nutrient polyphenols quercetin (found in berries) and curcumin (found in turmeric), both with expected affinity for chlorinated organics. The affinity of these novel materials for PCB 126 was evaluated at equilibrium conditions using a gas chromatography coupled to electron capture detection (GC-ECD) for quantification purposes, and the data was fitted to the nonlinear Langmuir model to determine binding affinity (KD) and maximum biding capacity (Bmax). The KD values obtained demonstrated that the presence of the polyphenolic-based moieties, CMA and QMA, as crosslinkers enhanced the binding affinity for PCB 126, expected to be a result of their aromatic rich nature which provides sites for π – π stacking interactions between the nanoparticle surface and the PCBs in solution. These values are lower that the reported affinity coefficients for activated carbon, which is the gold standard for capture/binding of organic contaminants in water and waste water treatment. Furthermore, upon exposure to an alternating magnetic field (AMF) for a period of 5 minutes, over 90% of the bound PCB on these materials was released, offering a low-cost regeneration method for the nanocomposites. Additionally, this novel regeneration strategy does not require the use of large volumes of harsh organic solvents that oftentimes become harmful byproducts. Overall, we have provided strong evidence that these novel nanocomposites have a promising application as nanoadsorbents for specific organic contaminants in contaminated water sources providing high binding affinities, a low-cost regeneration technique and are capable of withstanding use under environmental conditions offering a cost effective alternative to current remediation approaches

Air pollution and livestock production

The air in a livestock farming environment contains high concentrations of dust particles and gaseous pollutants. The total inhalable dust can enter the nose and mouth during normal breathing and the thoracic dust can reach into the lungs. However, it is the respirable dust particles that can penetrate further into the gas-exchange region, making it the most hazardous dust component. Prolonged exposure to high concentrations of dust particles can lead to respiratory health issues for both livestock and farming staff. Ammonia, an example of a gaseous pollutant, is derived from the decomposition of nitrous compounds. Increased exposure to ammonia may also have an effect on the health of humans and livestock. There are a number of technologies available to ensure exposure to these pollutants is minimised. Through proactive means, (the optimal design and management of livestock buildings) air quality can be improved to reduce the likelihood of risks associated with sub-optimal air quality. Once air problems have taken hold, other reduction methods need to be applied utilising a more reactive approach. A key requirement for the control of concentration and exposure of airborne pollutants to an acceptable level is to be able to conduct real-time measurements of these pollutants. This paper provides a review of airborne pollution including methods to both measure and control the concentration of pollutants in livestock buildings