M.Sc. / In this study, natural and modified clinoptilolite (CLI) reinforced polypropylene (PP) composites possessing improved mechanical and adsorptive properties were prepared through melt-mixing. Determination of morphological, structural and thermal properties was achieved by means of different techniques (FTIR, TGA, DSC, electron microscopy and x-ray spectroscopy). Electron microscopy revealed that increasing filler loading beyond 20% leads to agglomeration of clinoptilolite particles reducing their dispersion within the matrix. Thermal studies showed that the reinforced composites had a lower thermal stability than the neat PP polymer, suggesting that the clinoptilolite interfered with polymer chain arrangement and bonding. It also showed that percentage crystallinity increased with increasing filler loading indicating that the filler particles acted as nucleating agents within the polymeric matrix during composite synthesis. Prior to the ion-exchange studies, water sorption behaviour of fabricated composites was evaluated because ion-exchange/adsorption studies were to be performed in aqueous media. It was therefore observed that the hydrophobic polymer, PP attained the property of water sorption mainly due to the porous structure of the composites created by mixing and extrusion and also by the addition of the hydrophilic filler material.

No description available.

Ph. D. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Driven by the need for sustainably sourced catalysts and the use of reaction systems that generate environmentally benign by-products, the present study aimed to deposit stable, dispersed palladium (Pd) nanoparticles on the modified surfaces of granular macadamia nutshell (MNS) biomass for catalytic reduction of hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)]. Through wet impregnation with Pd(II) ions and subsequent hydrazinemediated reduction to Pd(0), Pd nanoparticles were embedded in a scaffold of polyethyleneimine grafted on bleached MNS previously coated with a chemically bound layer of polyglycidyl methacrylate. Visualization and imagery from scanning electron microscopy showed the formation of different layers of the polymeric coating and dispersed palladium resulting from surface modification and palladium nanoparticle synthesis, respectively. X-ray diffraction, energy-dispersive X-ray spectroscopic, and X-ray photoelectron spectroscopic analysis confirmed the formation of Pd on the modified MNS surface. An estimate of 5.0 nm for crystallite size was calculated by application of the Scherrer equation. The composite material, denoted Pd@PEI-MNS, exhibited catalytic activity in formic acidmediated Cr(VI) reduction. Through a one-factor-at-a-time experimental design, the activity of the Pd@PEI-MNS was illustrated to be dependent on solution pH; initial Cr(VI) concentration, initial formic acid concentration, and presence of competing anions; Pd@PEI-MNS dose; and temperature. Subsequent modeling of the Cr(VI) removal process by response surface methodology revealed that the most influential factor was Pd@PEI-MNS dose followed by temperature and formic acid concentration. The influence of initial Cr(VI) concentration, was surpassed by the dose-temperature and dose-formic acid concentration interactive effects. Elucidation of the Cr(VI) removal mechanism by XPS and FTIR demonstrated the active participation of surface –CH2OH functional groups, the bulk of which originated from the reduction of esters of the grafted ligands. Replacement of formic acid with hydrochloric acid in the reaction medium limited the Cr(VI) removal process to adsorption with non-extensive redox reaction with –CH2OH groups. Where the redox reactions converted formic acid to carbon dioxide, the –CH2OH groups were converted to –COO– groups.

La double fonction absorption-photodégradation des composites CA-TiO2 vis-à-vis des polluants biorécalcitrants est une alternative prometteuse pour le traitement de l’eau par voie solaire. Dans ce travail, des composites CA-TiO2 sont élaborés suivants trois méthodes simples basées sur l’utilisation des biomasses trouvées dans la sous région ensoleillée de l’Afrique subsaharienne. Les charbons actifs (CA) obtenus après pyrolyse des biomasses développent une structure poreuse qui se modifie ensuite en fonction de la voie de fixation des nanoparticules TiO2 (NPs-TiO2) pour l’obtention des composites. Parmi les trois vois de fixation du TiO2, l’imprégnation du CA avec le sol de NPs-TiO2 préformées conduit à des matériaux (CAT.SX) avec du TiO2 déposé de façon homogène à la « surface externe » du CA. Cette microtexture permet un meilleur couplage des propriétés adsorption-photodégradation, favorables aux performances de dépollution évaluées à l’échelle de laboratoire sur des solutions de phénol à 100 mg.L-1. Le réseau pores/surface spécifique est moins développé sur les composites obtenus par fixation in situ des NPs-TiO2 sur du CA imprégné de gel de TiO2 (CAT.GX), ou par pyrolyse directe de biomasse pré-imprégnée de NPs-TiO2 (CAT.SBX) ; ce qui explique les performances de dépollution moins élevées enregistrées pour ces deux dernières familles de catalyseurs. Les cinétiques d’élimination du polluant obtenues après plusieurs cycles successifs d’utilisation des catalyseurs CAT.SX ont été correctement simulées avec un modèle dont le formalisme tient compte de la double fonctionnalité des catalyseurs. Ce modèle permet d’envisager le dimensionnement d’installations solaires en condition réelle d’utilisation de ces nouveaux catalyseurs en zones fortement ensoleillée / Adsorption/photodegradation dual property of AC-TiO2 composites materials towards biorefractory pollutants is a promising issue for solar water treatment. In this work, AC-TiO2 hybrid materials have been synthesized through 03 novel routes based on the conversion of typical biomasses, abundantly found in the subsaharian African sunny areas. Biomasses pyrolysis derived activated carbon (AC) developed a porous structure which is modified differently according to the method used to fix TiO2 nanoparticules (TiO2-NPs). AC impregnated with a sol containing TiO2-NPs suspension provides the derived composite material (CAT.SX) with TiO2-NPs regularly deposited at the “external surface”, leading to a good coupling of adsorption/photodegradation activities towards phenol elimination in 100 mg.L-1 polluted water, carried out on lab scale experiments. Pore/surface area network is less developed on composites obtained after in situ fixation of TiO2-NPs on TiO2 gel impregnated AC (CAT.GX), or obtained after direct pyrolysis of TiO2-NPs impregnated biomass (CAT.SBX) – which infers lesser decontamination performances for these two latter families of catalysts. Pollutant elimination kinetics curves depicted after recycling of CAT.SX over several running water treatment was simulated with a suitable mathematical model which takes into consideration the dual functionalities of the elaborated material. The established model is a promising attempt for future dimensioning of real solar water treatment plants, operating in sunny areas with the new composite catalysts.

The city of Falun has a rich history of mining with the open mine, Stora Stöten, centrally located in the city and nowadays a well-known world heritage tourist attraction. The mine is the main reason that Falun even exists. During its glory days, Falun was one of Sweden’s largest cities, at that time considered to be world-leading in mine engineering and Europe’s main supplier of copper.  A less flattering effect of the mining era was that the city became poisonous and almost unhabitable. Both waters from the mine and from piles of mining waste ended up in rivers and lakes around Falun. Over the years several successful actions have been taken to improve and restore the environment which has decreased the amount of heavy metals leaked into Faluån and lake Tisken. Though, the water is still polluted, and Tisken has in practice for a long period of time worked as a deposit with an increasing amount of poisonous sediments.  This has unfortunately made Falun central waterbodies disabled for human use and made humans no longer have a relationship to the water despite its central location, importance, and potential for the city.  This thesis project seeks to unlock the lost potential of water in Falun by reviving it as a living and interweaved spine in the city in a systematic and schematic approach. The project aims to address the polluted water and sediment challenges while promoting sustainable stormwater and flooding management. A connected green structure linked with a movement network for pedestrians and bicyclists promotes sustainable transport to the spine and existing nodes in the city. The different layers in the project enable new nodes with new potentials for Falun

The chemical contamination of natural waters is a global problem with a worldwide impact. Considering the relevance of this problem, this thesis is intended, on one hand, to develop different separation/preconcentration techniques based on membranes ability to permeate anions for the transport of toxic oxyanions of chromium(VI) and arsenic contained in aqueous matrices. In particular, we have investigated supported liquid membranes and polymer inclusion membranes, both of which contain the commercial quaternary ammonium salt Aliquat 336 as a carrier, as well as commercial anion exchange membranes. On the other hand, we have focused on the development of chemical sensors to facilitate the monitoring of several metals from different aqueous matrices. Thus, a selective optical sensor for Cr(VI) based on polymeric membranes containing Aliquat 336 as an ionophore has been designed. Additionally, mercury-based screen-printed electrodes have been evaluated for for cadmium, lead, copper and zinc detection. / La contaminació química de les aigües naturals és un problema global amb repercussió a nivell mundial. Donada la rellevància que té aquesta problemàtica, en la present tesi s’han desenvolupat d’una banda tècniques de separació/preconcentració basades en diferents sistemes de membrana en què el mecanisme de transport proposat és un bescanvi aniònic per als oxoanions tòxics de crom(VI) i arsènic presents en matrius aquoses. Concretament, s’ha treballat amb membranes líquides suportades que contenien el portador comercial Aliquat 336, membranes d’inclusió polimèriques amb el mateix portador i membranes de bescanvi aniònic comercials. D’altra banda, s’ha treballat en el desenvolupament de diferents sensors químics per monitoritzar diversos metalls presents en matrius aquoses. Així, s’ha dissenyat un sistema de sensor òptic selectiu a Cr(VI) basat en membranes polimèriques utilitzant també el portador Aliquat 336 i s’ha desenvolupat un sistema de monitorització per plom, coure, cadmi i zinc basat en microelèctrodes serigrafiats modificats amb mercuri.

PhD. (Department of Biotechnology, Faculty of Applied and Computer Sciences), Vaal University of Technology. / South Africa utilises more antiretroviral (ARV) compounds per capita than any other nation in the fight against Human Immune Deficiency Virus (HIV) or acquired immunodeficiency syndrome (AIDS). Considering the main entrance pathways of antiviral drugs into the urban water cycle, excretions via urine or faeces from treated individuals play a dominant role. Due to the limited efficiency of conventional biological treatment (activated sludge), ARVs were detected in South African wastewater treatment plant effluents and surface waters. This poses a threat to aquatic environments due to the toxicity of ARVs and can be a potential contributor to ARV resistance due to persistent low level ARV exposure in the general population. This study investigated the efficacy of a moving bed biofilm reactor (MBBR) for ctybtri8nthe elimination of five ARV compounds i.e., tenofovir, emtricitabine, nevirapine, ritonavir and efavirenz from synthetic wastewater. Furthermore, the study also looked at the shift in microbial community compositions of biofilms in the MBBR due to exposure to the ARV compounds. Lastly, the ecotoxicity of the MBBR’s influent and effluent along with the actual ARV compounds were examined. The capacity of ARV degradation by the MBBR was investigated by spiking synthetic wastewater influent with 10 μg/L of five ARV compounds. Actual removal during treatment was assessed by sampling the inlets and outlets of the reactor. A targeted solid phase extraction method with Ultra High Pressure Liquid Chromatography coupled to quadrupole time of flight mass spectrometry (LC-MS/MS) was used to quantify the five ARV compounds. Microbial diversity (alpha-diversity) of seeded sludge from a full-scale municipal WWTP and biofilm samples from a laboratory scale MBBR system during pre- and post-introduction of ARV compounds was investigated by Illumina sequencing of the 16S rRNA gene. Ecological toxicity of the MBBR’s influent and effluent along with the five ARV compounds was determined using the Vibrio fischeri, Daphnia magna and Selenastrum capricornutum toxicity test kits and measured as EC50. After MBBR treatment; Nevirapine, Tenofovir, Efavirenz, Ritonavir and Emtricitabine all showed marked reduction in concentration between the influent and effluent of the MBBR. On average, the percentage removed for Nevirapine, Tenofovir, Efavirenz, Ritonavir and Emtricitabine was 62.31%, 74.18%, 93.62%, 94.18% and 94.87% respectively. Microbial diversity results demonstrated that the introduction of antiretroviral drugs affects the bacterial community composition and diversity considerably. For instance, Nitrosomonas, Nitrospira and Alicycliphilus were found to be higher in post introduction of ARV compounds biofilm samples than in biofilm samples before the introduction of ARV compounds. The EC50 for Tenofovir, Emtricitabine, Nevirapine, Ritonavir and Efavirenz were 82.5, 41.7, 39.3, 60.3 and 0.21 mg/L respectively for S. capricornutum; 81.3, 50.7, 49, 87.1 and 0.43 mg/L respectively for D. magna; and 73.5, 55.1, 41.3, 83.6 and 0.55 mg/L respectively for V. fischeri. The EC50 of the influent and effluent were found to be above 100% concentration, therefore they could not be specifically determined. The ecotoxicity results show that ARV compounds are potentially toxic to the environment, with efavirenz being more toxic than the other four ARV compounds tested. Since there were no toxic effects observed from the effluent, it can be assumed that mineralisation has occurred, or the transformation products are of less or equal toxicity to the influent (because the influent did not show any toxic effects to the model organisms tested).

Ph. D. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Driven by the need of sustainably sourced catalysts and the use of reaction systems that generate environmentally benign by-products, the present study aimed to deposit stable, dispersed palladium (Pd) nanoparticles on the modified surfaces of granular macadamia nutshell (MNS) biomass for catalytic reduction of hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)]. Through wet impregnation with Pd(II) ions and subsequent hydrazine-mediated reduction to Pd(0), Pd nanoparticles were embedded in a scaffold of polyethyleneimine grafted on bleached MNS previously coated with a chemically bound layer of polyglycidyl methacrylate. Visualization and imagery from scanning electron microscopy showed the formation of different layers of the polymeric coating and dispersed palladium resulting from surface modification and palladium nanoparticle synthesis, respectively. X-ray diffraction, energy-dispersive X-ray spectroscopic analysis confirmed the formation of Pd on the modified MNS surface. An estimate of 5.0 nm for crystallite size was calculated by application of the Scherrer equation. The composite material, denoted Pd@PEI-MNS, exhibited catalytic activity in formic acid-mediated Cr(VI) reduction. Through a one-factor-at-a-time experimental design, the activity of the Pd@PEI-MNS was illustrated to be dependent on solution pH; initial Cr(VI) concentration, initial formic acid concentration, and presence of competing anions; Pd@PEI-MNS dose; and temperature. Subsequent modeling of the Cr(VI) removal process by response surface methodology revealed that the most influential factor was Pd@PEI-MNS dose followed by temperature and formic acid concentration. The influence of initial Cr(VI) concentration, was surpassed by the dose-temperature and dose-formic acid concentration interactive effects. Elucidation of the Cr(VI) removal mechanism by XPS and FTIR demonstrated the active participation of surface -CH2OH functional groups, the bulk of which originated from the reduction of esters of the grafted ligands. Replacement of formic acid to carbon dioxide, the -CH2OH groups were converted to -COO- groups.