Preparação de materiais de carbono a partir de misturas poliméricas binárias para aplicação na remoção de pesticidas da fase líquda

Neste trabalho foram preparados carvões ativados, a partir de resíduos de polímeros sintéticos e naturais, num primeiro momento isoladamente e numa segunda fase, mais relevante, foi colocado um enfoque especial na formulação de combinações binárias, permitindo a valorização económica destes resíduos. Os precursores poliméricos utilizados foram o politereftalato de etileno (PET), o poliacrilonitrilo (PAN) e a madeira de teca. Os dois primeiros são polímeros sintéticos comummente utilizados e considerados desperdícios, enquanto que a teca surge também em quantidades consideráveis sem valor, em particular, como resultado da atividade madeireira e em países como Timor-Leste. Os adsorventes foram preparados por processos de ativação física com dióxido de carbono e ativação química com hidróxido de potássio e carbonato de potássio. As amostras foram caracterizadas estruturalmente e quimicamente, tendo-se obtido valores máximos de área superficial aparente na ordem de 2828 m2 g-1, volume poroso total de 1.38 cm3 g-1, volume microporoso de 0.61 cm3 g-1 e tamanhos médios de largura de poro na gama dos microporos. Numa fase posterior amostras selecionadas foram testadas na remoção de compostos poluentes, nomeadamente um conjunto de pesticidas em fase aquosa, tendo sido avaliados parâmetros como o tempo de equilíbrio, relação massa de adsorvente vs. volume e concentração de poluente, temperatura e pH do meio de adsorção, quantidade adsorvida. Os pesticidas testados foram o MCPA, o 2,4-D, o diuron e a atrazina, destacando-se entre as quantidades máximas adsorvidas o valor de 3.86 mmol g-1 para o MCPA. A transformação destes resíduos, que constituem um problema ambiental, em carvões ativados, mostra resultados muito promissores. Este produto de valor acrescentado, constitui uma âncora para a resolução de problemas identificados no Plano Estratégico de Desenvolvimento para Timor-Leste (2011-2030) onde estão incluídas as políticas relativas às infraestruturas, nomeadamente no que se refere à disponibilidade de água potável e ao saneamento básico; ABSTRACT: In this work, activated carbons were prepared from synthetic and natural polymer waste, initially separated and in a second more relevant phase, a special focus was placed on the formulation of binary combinations, allowing the economic recovery of this waste. The polymeric precursors used were polyethylene terephthalate (PET), polyacrylonitrile (PAN) and teak wood. The first two are synthetic polymers commonly used as and considered waste, while teak also appears in considerable quantities without value, particularly as a result of timber activity and in countries such as Timor-Leste. The adsorbents were prepared by physical activation processes with carbon dioxide and chemical activation with potassium hydroxide and potassium carbonate. The samples were characterized structurally and chemically, with maximum values of apparent surface area in the order of 2828 m2 g-1, total porous volume of 1.38 cm3 g-1, microporous volume of 0.61 cm3 g-1 and average pore width sizes in the range of micropores. After that, selected samples were tested on the removal of pollutant compounds, namely a set of pesticides on aqueous phase and parameters such as equilibrium time, adsorbent mass ratio vs. volume and concentration of pollutant, temperature and pH of the adsorption medium, adsorption amount were evaluated. The pesticides tested were MCPA, 2.4-D, diuron and atrazine, with a maximum adsorption value of 3.86 mmol g-1 for MCPA. The transformation of these residues, which constitute an environmental problem, into activated carbons, shows very promising results. This added-value product is an anchor for the resolution of problems identified in the Strategic Development Plan for Timor-Leste (2011-2030) where the strategic policies related to infrastructures are included, namely regarding the availability of drinking water and basic sanitation

Pesticides abatement using activated carbon produced from a mixture of synthetic polymers by chemical activation with KOH and K2CO3

Highly efficient low cost carbon adsorbents were prepared from synthetic polymers mixture, such as polyethyleneterephthalate (PET) and polyacrylonitrile (PAN), by chemical activation, with potassium hydroxide or potassium carbonate, at 1073 K. Mixtures polymers carbon activation is more effective with KOH than with K2CO3, since the apparent surface area and the micropore volume were always higher on those prepared with KOH. The activated carbons (ACs) obtained presented a high thermal stability, a basic character and a very high apparent surface area (between 1206 and 2828 m2 g−1), micropore volume (between 0.35 and 1.38 cm3 g−1), with mean pore sizes ranging the supermicropores region. These ACs were successfully tested on 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) removals from the liquid phase. The results achieved are very promising, as the adsorption capacity of these AC is higher than that obtained with commercial AC used for this end

Bétele (Piper Betle Linn): Análise de Metabolitos e acção sobre a Acetilcolinesterase

Mestrado em Controlo de QualidadeMSc in Quality ControlPiper betle L., conhecida como bétele, é uma espécie que se desenvolve largamente nos países do Sudeste Asiático, onde as suas folhas são económica e medicinalmente importantes. Para determinar o maior número possível de compostos voláteis e semivoláteis, as folhas foram sujeitas as diferentes processos de extracção, nomeadamente headspace - microextracção em fase sólida (HS-SPME), hidrodestilação e extracção por Soxhlet, e posteriormente analisadas por GC/MS, o que permitiu identificar 50 compostos, distribuídos por várias classes químicas, 23 dos quais foram descritos pela primeira vez. As diferentes técnicas permitiram a extracção de compostos distintos, sendo a HS-SPME aquela com que se obteve o perfil mais completo e com que se determinou maior teor de compostos. Dentro deste processo os melhores resultados foram obtidos utilizando a fibra revestida com divinilbenzeno/polidimetilsiloxano (DVB/PDMS). Considerando que a espécie é vulgarmente mascada, o seu extracto aquoso também foi analisado, tendo sido caracterizados apenas sete compostos, sendo o eugenol o composto principal. A composição em ácidos orgânicos deste extracto foi determinada por HPLC/UV e os ácidos oxálico, aconítico, cítrico, pirúvico, málico, chiquímico, acético e fumárico foram descritos pela primeira vez. O extracto aquoso também revelou capacidade para inibir a acetilcolinesterase de modo dependente da concentração.Piper betle L., popularly known as “Paan”, is a species widely growing in South East Asia, where its leaves are economically and medicinally important. In order to screen the highest possible number of volatile and semi-volatile components, the leaves were subjected to headspace solid-phase microextraction (HS-SPME), hydrodistillation and Soxhlet extraction, prior to their analysis by GC/MS, which allowed the identification of 50 compounds, distributed by several chemical classes, 23 of them described for the first time. The different techniques lead to distinct compounds' extraction, with HS-SPME extracting highest amounts and providing the most complete profile. Within this procedure, best results were obtaine using Divinylbenzene/Polydimethylsiloxane (DVB/PDMS) fibre. Considering the use of the species as masticator, an aqueous extract was also analysed, in which only seven compounds were characterize, being eugenol the main one. The organic acids composition of this extract was determine by HPLC/UV and oxalic, aconitic, citric, pyruvic, malic, shikimic, acetic and fumaric acids are reported for the first time in this species. The aqueous extract also displayed AChE inhibitory capacity, in a concentration-dependent way

Using Tectona Grandis Biomass to Produce Valuable Adsorbents for Pesticide Removal from Liquid Effluent

This work presents a first approach concerning the valorization of Tectona Grandis tree by-products, from East Timor through their transformation into high activated carbon (AC) by chemical activation with KOH and K2CO3. The better ACs, Teak-KOH-1-1-700 and Teak-K2CO3-1-2-700, presented a high ABET (995 and 1132 m2·g−1) and micropore volume (0.43 and 0.5 cm3·g−1), respectively. Both ACs were tested on the removal of four pesticides, from the liquid phase. Both ACs performed better than existing commercial types, presenting a maximum adsorption capacity of 1.88, 1.67, 1.10 and 0.89 mmol·g−1, for 4-chloro-2-methylphenoxyacetic acid, 2,4-dichlorophenoxyacetic acid, diuron and atrazine, respectively. Pesticide adsorption from diluted and concentrated solutions confirms that diffusion is the limiting factor. The possibility of implementing a production unit for ACs in East Timor is very promising for that country. It presents an opportunity for job creation, biomass waste reduction and a contribution to environmental sustainability, thereby following the principles of a circular economy