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Filtros de espumas biocidas e fotocatalíticas para a remoção de poluentes em fluidos
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Abstract(s)
A contaminação da água por contaminantes biológicos e poluentes orgânicos emergentes é um problema global que acarreta graves consequências socioeconómicas, ambientais e de saúde pública. Nesta tese apresentam-se duas metodologias inovadoras de controlo da bioincrustação, um fenómeno indesejável que ocorre em superfícies em contacto com a água e promotor de biocontaminação, e uma metodologia de remediação de poluentes orgânicos aquáticos, passível de promover sinergias para com a bio-descontaminação.
Numa primeira metodologia antivegetativa não-lixiviante, revestimentos de diferentes bases poliméricas (polidimetilsiloxano e poliuretano) contendo o biocida Econea® enxertado, obtidos por um processo de imobilização previamente desenvolvido e patenteado, foram investigados para a proteção de superfícies metálicas e de filtros cerâmicos aplicados em diferentes sistemas em meio aquático.
Esta metodologia revelou resultados antivegetativos promissores sob condições hidrodinâmicas de formação de biofilmes e quasi-estáticas simuladas, bem como de campo (condições reais), em particular para os revestimentos de base polidimetilsiloxano. Nestes revestimentos também se obtiveram reduções consideráveis na lixiviação do biocida para o meio aquático, compreendidas entre 34% a 100% (lixiviação indetetável), dependendo da matriz.
Na segunda metodologia antivegetativa, desenvolveram-se espumas de poliuretano contendo Econea enxertado na sua estrutura celular com efeitos antivegetativos igualmente promissores, e similares aos obtidos pela metodologia de revestimentos não-lixiviantes, demonstrando a versatilidade da estratégia de imobilização de biocida, neste caso para estruturas poliméricas capazes de atuar como filtros bioativos por si só.
Para a remedição de poluentes orgânicos, fotocatalisadores de TiO₂ anatase co-dopadas com cobalto e nitrogénio sintetizados revelaram atividades promissoras, com uma remoção de triclosan superior a 99%, em apenas 20 min sob irradiação de luz LED ultravioleta (365 nm) e visível (450 nm).
A dopagem com cobalto revelou ainda poder potenciar efeitos antimicrobianos contra bactérias patogénicas, em particular para a Legionella pneumophila. Os fotocatalisadores demonstraram também compatibilidade para com revestimentos poliméricos inferindo a sua atividade fotocatalítica nos mesmos.
Water contamination by biological contaminants and emerging organic pollutants is a worldwide problem, with significant socioeconomic, environmental, and public health impacts. This thesis presents two innovative methodologies for biofouling prevention, a natural unwanted colonization phenomenon that occurs on surfaces in contact with water and promotor of biocontamination, as well as an emergent aquatic organic pollutants remediation methodology, with the ability to promote synergetic biodecontamination effects. In a first non-leaching antifouling methodology, coatings of different polymeric bases (polydimethylsiloxane and polyurethane) containing the grafted Econea® biocide, obtained by a previously developed and patented immobilization process, were investigated for the protection of metallic surfaces and ceramic filters applied in different systems in the aquatic environment. This methodology has revealed promising antifouling outcomes under simulated hydrodynamic conditions (biofilm formation) and simulated quasi-static as well as field conditions (real conditions), in particular for polydimethylsiloxane-based coatings. Considerable reductions in biocidal leaching into the aquatic environment were also achieved in these coatings, ranging from 34% to 100% (undetectable leaching), depending on the matrix. In the second antifouling methodology, polyurethane foams containing Econea grafted into its cell structure were developed, with equally promising antifouling effects and similar to those obtained with the non-leaching biocide coatings methodology, demonstrating the versatility of the functionalized biocide immobilization strategy with isocyanate function, in this case, for polymeric structures capable of acting as a bioactive filter on its own. For the remediation of organic pollutants, synthesized cobalt-nitrogen co-doped TiO₂ anatase photocatalysts showed promising activities, with triclosan removals higher than 99%, after only 20 min under ultraviolet (365 nm) and visible (450 nm) LED light irradiation. Cobalt doping also revealed ability to enhance antimicrobial effects against pathogenic bacteria, particularly Legionella pneumophila. The photocatalysts have also demonstrated compatibility with polymeric coatings, inferring their photocatalytic activity on them.
Water contamination by biological contaminants and emerging organic pollutants is a worldwide problem, with significant socioeconomic, environmental, and public health impacts. This thesis presents two innovative methodologies for biofouling prevention, a natural unwanted colonization phenomenon that occurs on surfaces in contact with water and promotor of biocontamination, as well as an emergent aquatic organic pollutants remediation methodology, with the ability to promote synergetic biodecontamination effects. In a first non-leaching antifouling methodology, coatings of different polymeric bases (polydimethylsiloxane and polyurethane) containing the grafted Econea® biocide, obtained by a previously developed and patented immobilization process, were investigated for the protection of metallic surfaces and ceramic filters applied in different systems in the aquatic environment. This methodology has revealed promising antifouling outcomes under simulated hydrodynamic conditions (biofilm formation) and simulated quasi-static as well as field conditions (real conditions), in particular for polydimethylsiloxane-based coatings. Considerable reductions in biocidal leaching into the aquatic environment were also achieved in these coatings, ranging from 34% to 100% (undetectable leaching), depending on the matrix. In the second antifouling methodology, polyurethane foams containing Econea grafted into its cell structure were developed, with equally promising antifouling effects and similar to those obtained with the non-leaching biocide coatings methodology, demonstrating the versatility of the functionalized biocide immobilization strategy with isocyanate function, in this case, for polymeric structures capable of acting as a bioactive filter on its own. For the remediation of organic pollutants, synthesized cobalt-nitrogen co-doped TiO₂ anatase photocatalysts showed promising activities, with triclosan removals higher than 99%, after only 20 min under ultraviolet (365 nm) and visible (450 nm) LED light irradiation. Cobalt doping also revealed ability to enhance antimicrobial effects against pathogenic bacteria, particularly Legionella pneumophila. The photocatalysts have also demonstrated compatibility with polymeric coatings, inferring their photocatalytic activity on them.
Description
Keywords
bioincrustação enxerto de biocidas superfícies anti-vegetativas TiO₂ co-dopado fotodegradação catalítica de poluentes biofouling biocides grafting antifouling surfaces co-doped TiO₂ photocatalytic degradation of pollutants