IMMOBILIZED TITANIUM DIOXIDE (TIO₂) IN DIFFERENT SUPPORT MATERIALS TO USE IN HETEROGENEOUS PHOTOCATALYSIS

Abstract

is the retention and reuse of the catalyst, which brings opportunities for studying techniques for its immobilization on solid supports. The main objective of this paper was to test different methods to effectively immobilize TiO 2 on granular activated carbon (GAC), crushed ceramic material (CCM) and zeolite (ZEO) in order to use the catalyst for sulfamethoxazole (SMX) removal from aqueous solutions. For this, three TiO 2 immobilization methods (1-immersion of the support in TiO 2 slurry; 2-covering by sol-gel synthesis using titanium isopropoxide; 3-impregnating the support with white wall paint doped with TiO 2 ) were tested and the resulting catalyst were characterized and evaluated for SMX removal. The results showed that GAC was the best support and that its immersion in a 50% (w/v) TiO 2 suspension was the best immobilization method. Photodegradation assays with such catalyst carried out with 10 mg.L -1 of the antibiotic sulfamethoxazole (SMX) led to 90% of removal of this pharmaceutical after 3.5 hours, which was ~38% higher than the UV photolysis at the same contact time.Keywords: pharmaceuticals, catalyst immobilization, titanium dioxide, heterogeneous photocatalysis, granular activated carbon. INTRODUÇÃONas últimas décadas houve um aumento significativo, em todo o mundo, no consumo de medicamentos de diversas classes como antipiréticos, analgésicos, reguladores lipídicos, antibióticos, drogas contraceptivas e outras e, consequentemente, a preocupação da comunidade científica com a presença de fármacos no meio ambiente tem se tornado cada vez maior.1,2 Isso porque os efeitos à saúde humana provocada pela ingestão de água contendo fármacos, ainda que não estejam completamente elucidados, podem incluir desenvolvimento de resistência em bactérias patogênicas, genotoxicidade e distúrbios endócrinos. 3A presença de fármacos em águas superficiais é um risco real uma vez que o processo de clarificação -coagulação, floculação, sedimentação e filtração -utilizada na maioria das estações de tratamento de água (ETA) não é eficaz na sua remoção de águas contaminadas.4 Além disso, sabe-se que o uso de cloro na etapa de desinfecção pode levar à formação de compostos organoclorados, cuja toxicidade pode ser maior do que os seus precursores.5 Assim novas alternativas para tratamento destes compostos precisam ser investigadas.Uma opção para complementar o sistema convencional de tratamento de água seria a utilização de processos oxidativos avançados (POA), que envolvem a geração e consumo de uma espécie altamente oxidante e não seletiva como os radicais hidroxila (*OH). Tais radicais tem a capacidade de oxidar substâncias dissolvidas ou dispersas, reduzindo assim a concentração de diversos contaminantes em fase aquosa. Uma maneira de gerar radicais hidroxila é por meios fotoquímicos com radiação ultravioleta (UV) em combinação com um semicondutor sendo o mais utilizado dióxido de titânio (TiO 2 ), no processo conhecido como fotocatálise heterogênea.A maioria dos estudos utilizando TiO 2 como fotocalisador são realizado...

ZnO semiconductors obtained by slip casting: Application and reuse in photocatalysis

“…However, after its use, it is necessary to apply complex procedures to separate the semiconductors, which generates additional costs to the catalytic process and an increase in wastewater treatment time. 29 The preparation and use, in photocatalysis, of immobilized semiconductors, [30][31][32][33][34][35][36][37][38] that is, in the form of thin films [39][40][41][42] or ceramic pieces, is advantageous, since the removal of the catalyst from the reaction medium is facilitated, in addition to the possibility of its reuse in other reaction cycles, thus ensuring greater financial viability in an industrial aspect.…”

“…The preparation and use, in photocatalysis, of immobilized semiconductors, 30–38 that is, in the form of thin films 39–42 or ceramic pieces, is advantageous, since the removal of the catalyst from the reaction medium is facilitated, in addition to the possibility of its reuse in other reaction cycles, thus ensuring greater financial viability in an industrial aspect.…”

Photodegradation of Rhodamine B catalyzed by ZnO pellets

“…The use of photocatalysts in the form of powder, although common due to the high surface area, presents several difficulties that affect its applicability in large scale. One is the withdrawal complexity, which is usually a costly process due to the size of the particles, generally smaller than 1 μm [15,16]. The suspended particles also tend to aggregate, which decreases their efficiency, especially in cases where the concentration of suspended particles is high.…”

“…The suspended particles also tend to aggregate, which decreases their efficiency, especially in cases where the concentration of suspended particles is high. In addition, the use of suspensions is hampered in continuous flow systems and often the photocatalyst is lost [15][16][17][18]. One of the alternatives is the use of these materials in the immobilized form, since they can be removed in a much simpler way, besides the possibility of reuse, being an industrially desired technique [16,17].…”

“…One of the alternatives is the use of these materials in the immobilized form, since they can be removed in a much simpler way, besides the possibility of reuse, being an industrially desired technique [16,17]. Therefore, the immobilized pellets must have high porosity in addition to high adsorption capacity, aiming a greater surface area and a greater interaction with the organic pollutant [15]. For this purpose, this paper aimed to obtain pellets as the immobilization form using ZnO by slip casting.…”