Produção de carvões ativados a partir de carbonizados obtidos por HTC.

Os carvões ativados (CA) têm sido exaustivamente estudados durante o último século. A razão deste interesse deve-se à alargada gama de aplicabilidade destes materiais, desde a indústria ou tratamento de águas até à biomédica. Atualmente tem-se assistido a uma maior diversificação de técnicas de produção com a finalidade de especialização de cada material. Uma desses técnicas é a utilização da carbonização hidrotérmica (HTC) no passo prévio à ativação dos materiais, utilizando como precursores materiais puros e derivados lenhocelulósicos. Este processo mimetiza o processo natural de produção de carvão, fazendo uso de condições específicas de pressão e temperatura. Como resultado estes carvões apresentam morfologias regulares e química superficial rica, prevalecendo a presença de grupos ácido, hidroxilo e grupos aromáticos. No presente trabalho foram preparados carvões ativados a partir de quitosano utilizando HTC no passo de carbonização seguido de ativação por CO2. Verificou-se que o processo de HTC, dependendo da temperatura de carbonização, promoveu o aumento do teor em carbono e de nitrogénio até um máximo de 40 e 10%, respectivamente. Este elevado teor de nitrogénio, sem que se tivesse realizado qualquer pré ou pós-tratamento, é umas das vantagens do método usado neste trabalho. Como se verifica na figura 1(b), os carvões ativados perderam quase a totalidade das estruturas esféricas criadas durante o processo de HTC alterando significativamente a morfologia dos CA produzidos. Estes apresentam uma morfologia filamentosa resultante do processo de formação da estrutura porosa no processo de ativação. Nas condições testadas, os CA produzidos apresentam características microporosas com áreas superficiais aparentes entre 400m2g-1 e 2130m2g-1 e volumes microporosos entre 0.17 e 0.92cm3g-1

Adsorção de metformina em carvões activados preparados por carbonização hidrotermica seguida de activação

O processo de carbonização hidrotérmica pode ser considerado um processo amigo do ambiente para preparar materiais de carbono com propriedades especificas, tais como estrutura regular e química superficial rica, desenvolvidas para determinadas aplicações. Este processo é simples de executar e pelo facto de usar temperaturas moderadas e não usar solventes nem gases tem um saldo ambiental positivo quando comparado com o processo usual de pirólise [1]. A diabetes é considerada uma das epidemias do Sec. XXI encontrando-se em crescimento acentuado sendo a metformina um dos medicamentos mais usados para tratar a diabetes tipo 2. Este fármaco é um disruptor endócrino que merece toda a atenção por dois motivos: 1)pelo seu potencial impacto no meio ambiente motivado pelo facto de quase não ser metabolizada pelo corpo humano, sendo excretada directamente na urina, e pela colocação no lixo doméstico de excedentes deste fármaco; 2) pelo perigo de overdose medicamentosa com todos os efeitos secundários que daí advêm, em particular a acidose láctica, que em casos severos pode ser letal. Neste trabalho estudamos a adsorção in vitro desta droga em carvões activados usando fluidos simulados gástrico e intestinal

Production and characterization of activated carbons made from sunflower stems

Activated carbons (ACs) are artificial materials, prepared from natural or synthetic precursors that are worldwide extensively used. The ACs main characteristics are the noticeable adsorption capabilities provided by the highly developed porous structure and the rich surface chemistry. Because of their versatility and properties the final material can be tailored to have specific properties suitable for a wide range of applications such as medical uses, gas storage, removal of pollutants and odours, gas separation and purification as well as in catalysis. With the increase of activated carbon demand, one of the main challenges lies in the attempt to find new precursors, which are cheap and accessible with good valorisation potential, like industrial and agricultural residues. In the present work we report the production of ACs from sunflower stems, an agricultural by-product, through a physical activation process by CO2 and H2O, using a single step carbonisation at 400ºC, which as far as it came to our knowledge was never made for this precursor

Supporting proactive management in the context of climate change: Prioritizaing range-shifting invasive plants based on impact

Non-native, invasive plants are projected to shift their ranges with climate change, creating hotspots of risk where a multitude of novel species may soon establish and spread. The Northeast U.S. is one such hotspot. However, because monitoring for novel species is costly, these range-shifting invasive plants need to be prioritized. Preventing negative impacts is a key goal of management, thus, comparing the potential impacts of range-shifting invasive species could inform this prioritization. Here, we adapted the Environmental Impacts Classification for Alien Taxa (EICAT) protocol to evaluate potential impacts of 100 invasive plants that could establish either currently or by 2050 in the states of New York, Massachusetts, Connecticut, or Rhode Island. We searched Web of Science for each species and identified papers reporting ecological, economic, human health, or agricultural impacts. We scored ecological impacts from 1 (‘minimal concern’) to 4 (‘major’) and socio-ecological impacts as present or absent. We evaluated 865 impact studies and categorized 20 species as high-impact, 36 as medium-impact, and 26 as low-impact. We further refined high-impact invasive species based on whether major impacts affect ecosystems found in Northeast U.S. and identified five high-priority species: Anthriscus caucalis, Arundo donax, Avena barbata, Ludwigia grandiflora, and Rubus ulmifolius. Additional research is needed for 18 data-deficient species, which had no studies reporting impacts. Identifying and prioritizing range-shifting invasive plants provides a unique opportunity for early detection and rapid response that targets future problem species before they can establish and spread. This research illustrates the feasibility of using impacts assessments on range-shifting invasive species in order to inform proactive policy and management

Incorporating climate change into invasive species management: insights from managers

Invasive alien species are likely to interact with climate change, thus necessitating management that proactively addresses both global changes. However, invasive species managers’ concerns about the effects of climate change, the degree to which they incorporate climate change into their management, and what stops them from doing so remain unknown. Therefore, we surveyed natural resource managers addressing invasive species across the U.S. about their priorities, concerns, and management strategies in a changing climate. Of the 211 managers we surveyed, most were very concerned about the influence of climate change on invasive species management, but their organizations were significantly less so. Managers reported that lack of funding and personnel limited their ability to effectively manage invasive species, while lack of information limited their consideration of climate change in decision-making. Additionally, managers prioritized research that identifies range-shifting invasive species and native communities resilient to invasions and climate change. Managers also reported that this information would be most effectively communicated through conversations, research summaries, and meetings/symposia. Despite the need for more information, 65% of managers incorporate climate change into their invasive species management through strategic planning, preventative management, changing treatment and control, and increasing education and outreach. These results show the potential for incorporating climate change into management, but also highlight a clear and pressing need for more targeted research, accessible science communication, and two-way dialogue between researchers and managers focused on invasive species and climate change.https://link.springer.com/content/pdf/10.1007/s10530-019-02087-6.pdfPublished versio

Removal of amitriptyline from simulated gastric and intestinal fluids using activated carbons

In this work, the adsorption behavior of a tricyclic antidepressant, amitriptyline hydrochloride, onto several activated carbons (ACs) is reported. The adsorption was done using in vitro simulated gastric and intestinal fluid at 37◦C to test the performance of the carbons as treatment in overdose cases. The tested materials were one commercial AC (carbomix) and two ACs produced in our laboratory. The highest adsorption capacity was achieved by carbomix, followed by the laboratory-made carbons that still have a very good performance with adsorption capacity up to 120 and 100 mg/g for the gastric and intestinal fluids, respectively

Characterization of the surface of activated carbons produced from tire residues

The surface characterisation of new activated carbons produced from tire residues by activation with carbon dioxide was studied. The activated carbons produced were mainly basic with point of zero charge values above 8.8. The main surface functional groups identified by FTIR were ether, quinones, lactones, ketones, hydroxyls (free and phenol) and pyrones. The XRD analysis shows that the materials produced have a microstructural organisation with microcrystallite height around 1.5nm and width from 3 to 5.3nm. This analysis indicates also the possible presence of oxides (single or mixture) of the following heteroatoms: Fe, Al, Ca, Mg, Ti, Si, K, Pb, Cd, Ba, Zn and Sn. The results have shown the significant potential of this type of residues for activated carbon production. Furthermore, the environment friendly use of an industrial residue is also noteworthy

Systems involving hydrogenated and fluorinated chains: Volumetric properties of Perfluoroalkanes and Perfluoroalkylalkane Surfactants

As part of a combined experimental and theoretical study of the thermodynamic properties of perfluoroalkylalkanes (PFAAs), the liquid density of perfluorobutylpentane (F4H5), perfluorobutylhexane (F4H6), and perfluorobutyloctane (F4H8) was measured as a function of temperature from 278.15 to 353.15 K and from atmospheric pressure to 70 MPa. The liquid densities of n-perfluoropentane, n-perfluorohexane, n-perfluorooctane, and n-perfluorononane were also measured at room pressure over the same temperature range. The PVT behavior of the PFAAs was also studied using the SAFT-VR equation of state. The PFAA molecules were modeled as heterosegmented diblock chains, using different parameters for the alkyl and perfluoroalkyl segments, that were developed in earlier work. Through this simple approach, we are able to predict the thermodynamic behavior of the perfluoroalkylalkanes, without fitting to any experimental data for the systems being studied. Molecular dynamics simulations have also been performed and used to calculate the densities of the perfluoroalkylalkanes studied

Viscosity of Liquid Perfluoroalkanes and Perfluoroalkylalkane Surfactants

As part of a systematic study of the thermophysical properties of two important classes of fluorinated organic compounds (perfluoroalkanes and perfluoroalkylalkanes), viscosity measurements of four n-perfluoroalkanes and five perfluoroalkylalkanes have been carried out at atmospheric pressure and over a wide range of temperatures (278–353 K). From the experimental results the contribution to the viscosity from the CF2 and CF3 groups as a function of temperature have been estimated. Similarly, the contributions for CH2 and CH3 groups in n-alkanes have been determined using literature data. For perfluoroalkylalkanes, the viscosity results were interpreted in terms of the contributions of the constituent CF2, CF3, CH2, and CH3 groups, the deviations from ideality on mixing hydrogenated and fluorinated chains, and the contribution due to the formation of the CF2–CH2 bond. A standard empirical group contribution method (Sastri–Rao method) has also been used to estimate the viscosities of the perfluoroalkylalkanes. Finally, to obtain molecular level insight into the behavior of these molecules, all-atom molecular dynamics simulations have been performed and used to calculate the densities and viscosities of the perfluoroalkylalkanes studied. Although both quantities are underestimated compared to the experimental data, with the viscosities showing the largest deviations, the trends observed in the experimental viscosities are captured

Metformin adsorption onto activated carbons prepared by hydrothermal carbonization and activation

The hydrothermal carbonization can be considered an environmental friendly process for the production of carbon materials with tailored properties, such as regular porous structure and specific surface chemistry. This process is easy to perform and uses mild temperatures without the use of solvents or gases, which results in a positive environmental balance when compared with the usual pyrolysis process [1]. Diabetes affects more than 152 million people in Europe and is on the rise all over the World. Metformin is one of the most used drugs to treat type 2 diabetes. This drug is an endocrine disruptor with a potential negative impact in the environment due to the fact that metformin is almost not metabolized in the human body and the incorrect disposal into the domestic garbage. Another relevant aspect is the danger of overdose intake of the drug that can lead to lactic acidosis, which in extreme cases can be lethal. The work now reported study the in vitro adsorption of metformin onto activated carbons using simulated gastric and intestinal fluids