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UGent campus Kortrijk, Department of green chemistry and technology, Laboratory of Industrial Water- and Ecotechnology

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Abstract Bachelor Project 2019-2020: Deodorizing the plastics polyethylene and polypropylene to optimize their recycling process

By 2030 there must be an increase in plastic recycling of post-consumer waste to 55 %. This must be the beginning towards the circular economy. But after all, there are some various impurities that complicate the recycling of the plastic waste such as inks/dyes, adhesive residues and odour. With the latter, the subject of the thesis begins; deodorize of the plastics polyethene and polypropylene to optimize their recycling. These plastics will be washed on lab-scale with solvents as sodium hydroxide, the surfactant CTAB, water, ethyl acetate and a combination of the surfactant and sodium hydroxide. The aim of the thesis is to find the washing-step with the highest removal efficiency.

But firstly there must be known which odours qualify these plastics. With headspace-solid phase microextraction the odours will be characterized. These scents will be checked at repeatability with the technique solvent desorption. When there’s a repeatability underneath relative standard deviations of 30 %, the compounds will be adopted in a (Selective Ion Mode-)method and analyzed with the GC-MS. In this way there’s a Selective Ion Mode method formed with 19 identified odours. The post-consumer waste of polyethene and polypropylene can now be washed. The remaining odours will be detected with the same technique solvent desorption based on the adsorbent capacity of carbon.

This research showed in the first place that the removal efficiency increases over the time that the plastics spend in the solvent with an exception of sodium hydroxide, where reabsorption took place. The odour removal with the aqueous liquids shows overall the lowest removal efficiency. Therefore there might be an outcome that these aqueous liquids only remove the superficial odours present on the water repellent plastics. But when CTAB is used, it showed the highest removal efficiency among the aqueous solutions, in combination of NaOH the removal efficiency increased. This can be explained by the arise of micelles that reduce the surface tension of water. This results in more moisturized water repellent and a better wettability of the plastics. Also the micelles help with the removal of non-polar odorous compounds. In contrast with the aqueous solvents, the organic solvent, ethyl acetate has the highest removal efficiency of 91 %. The washing procedure of these plastics can be seen as an solid-liquid extraction process, using solubility to transfer components from the solid phase to the liquid phase.

Besides the time and solvents also the influence of the temperature was tested. When the plastics were washed at a lower temperature, the removal efficiency was also lower. This can be explained by the solubility in the solid-liquid extraction process that increases with increasing temperature.

In the future the washed plastics could be transformed into granules and checked again on the formed or remaining odours. Eventually the regranules of polyethene and polypropylene can be used in high end recycling routes.

 

Abstract Bachelor Project 2017-2018: Leaching of heavy metals and polycyclic aromatic carbohydrates from building materials using pilot roofs

Due to the urbanization, more and more houses are being built. Many of these houses have flat roofs because of the energy saving capabilities in contrary to the houses with triangular roofs. When it rains the water on the flat roofs stays on it for a longer period of time than on triangular roofs. While the rainwater touches the roofing materials the phenomenon “leaching” occurs. Some bound components from the roofing materials get leached into the rainwater. The rainwater runoff contaminates the soil and the groundwater. This groundwater finally goes to rivers. The issue is that if there are high concentrations of heavy metals and polycyclic aromatic hydrocarbons (PAHs) in the rainwater runoff due to the leaching from the roofing materials, this could be a problem for all aquatic environment in the first place. On the long term this would also affect humans. The purpose of this research is to observe the quantitative leaching of heavy metals and PAHs from certain roofing materials. The end goal is to determine which of the researched roofing materials are most polluting for the environment and if the pollution is severe or not.

The metals that are being researched are aluminium, chrome, iron, manganese, nickel, strontium, zinc, copper and lead. The PAHs that are being researched are naphthalene, acenaphthylene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, chrysene, benzo(b)fluorantheen, benzo(k)fluoranthene, benzo(a)pyrene, indeno(1,2,3-cd)pyrene, dibenzo(a,h)anthracene, benzo(g,h,i)perlene.

The roofing materials that are researched in this experiment are bitumen green, ethylene-propylene-diene monomer (EPDM), bitumen grey, polyurethane (PU) and polyvinylchloride. At this moment not much is known about the leaching behaviour of these roofing materials. Nonetheless, these materials are used very often as roofing materials. That is why this research is so valuable to the community.

To collect rainwater runoff, there have been made several pilot roofs. Each pilot roof contains one square meter of a roofing material. There are also two blank’s. One blank is to research the total atmospheric deposition. The other blank is to research only the atmospheric deposition that comes with rainfall. At the bottom of each pilot roof there is a set up to collect the rainwater runoff. The first litre of rainwater runoff is collected in a separate 1 l bottle, this is called the first flush. The rest of the rainwater runoff gets collected in a 20 l bottle, this is called the bulk. During the sampling, there is both a first flush (FF) and bulk (B) sampling. Samples were measured for heavy metals with inductive coupled plasma – optical emission spectrometry (ICP-OES). For the research of PAHs, 300 ml of the sample is concentrated with solid phase extraction (SPE). The extract is then redissolved in 4 ml dichloromethane. The concentrated PAHs were analysed with gas chromatography/mass spectrometry (GC/MS).

For the metals, only bitumen grey and the EPDM roofing materials release higher concentrations over the whole period of the experiment. The following metals were measured for bitumen grey: aluminium (0 - 82 µg/l), iron (0 – 112 µg/l), manganese (87 – 338 µg/l), nickel (4 – 23 µg/l), strontium (8 – 34 µg/l) and copper (3 – 16 µg/l). EPDM only releases zinc, in concentrations of 161 – 2815 µg/l in each batch. Bitumen green, PU and PVC only release moderate to high concentrations of metals in the first rainwater runoff sample(s). After the first samples the bitumen green, PU and PVC materials only release very low concentrations of some metals and for some metals nothing.

For the PAHs, only phenanthrene, fluoranthene and pyrene have been detected. All phenanthrene and fluoranthene concentrations are attributed solely to the atmospheric deposition. Pyrene was only released from the EPDM roofing material in concentrations of 8 – 33 ng/l in each batch. For all the other roofing materials also pyrene came solely from atmospheric deposition.

When the results from the metal and PAHs leaching tests are taken together, there can be concluded that the bitumen green, PU and PVC roofing materials are harmless for the environment. Bitumen grey is more harmful for the environment because the copper concentration (3 – 16 µg/l) surpasses the maximum reference value of 7 µg/l in batch 1, 2, 5, 6, 7, 8 and 9. This is not coming from the bitumen but from the crushed stones in the surface finish. EPDM roofing shows more harmful leaching because the zinc concentration (161 – 2815 µg/l) surpasses the maximum reference value of 20 µg/l 8 to 140 times. The leaching of PAHs is in no way harmful to the environment.

Abstract bachelorproef 2016-2017: Arsenic contamination in water: phytoremediation and fish research

This research focusses on arsenic contamination in water of the industrial gold mine of Youga in Burkina Faso. Gold mining zones are often enriched in arsenic and other potentially toxic metals. A project was initiated at Ghent University Campus Kortrijk to study phytoremediation to reduce soil and water pollution by metals to rehabilate the mine after closing.

Leucaena leucocephala was the plant tested for phytoremediation. A germination test was performed, 100% of the seeds germinated in pure water and in 0,2 ppm arsenic, while only 94% germinated in 1 ppm and 2 ppm and only 72% in 10 ppm arsenic.

Plants were grown in a mixture of 50% soil of the mine site and 50% compost and received water containing arsenic: 0 ppm, 50 ppm, 100 ppm and 200 ppm. A microwave digestion procedure was optimized and an ICP-OES was used to analyze the samples. The plants all contained arsenic (till 1177 ppm for the plants who got 200 ppm) which means they can be used for phytoremediation of arsenic. When the different parts of the plant (roots, leaves and stem) are analyzed, the roots contain the most arsenic (1923 ppm), while the leaves contain the lowest amount of arsenic (11 ppm).

Fish samples were collected in pits and a river at the mine site. A microwave digestion procedure was optimized and the metals were determined by ICP-OES. From the four different fish types, one of them (Clarias anguillaris) clearly contains less heavy metals than the others, with a mean concentration of 1 ppm. The arsenic content in the fish from the river is lower than in the fish from the pits.

From these results can be concluded that Clarias anguillaris fish from the Nakambé River contains the least heavy metals. Leucaena leucocephala can be used to perform phytoremediation of arsenic.

Address

Graaf Karel de Goedelaan 5
8500 Kortrijk
Belgium

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Traineeship supervisor
Ann Dumoulin
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