Activated carbons with high nitrogen content by a combination of hydrothermal carbonization with activation

This paper reports the production of carbons materials with a nitrogen content around 8%(w/w) and a well-developed porous structure, with BET surface area and pore volume up to 2130 m2 g−1 and 1.12 cm3 g−1, respectively, produced by a combination of hydrothermal carbonization, an environmental friendly method in the production of sustainable tunable carbon materials, with traditional activation methods. The porosity was developed through an activation process according to different routes, namely activation with CO2 and chemical activation using CaCO3 and K2CO3. The successful production of activated carbons using chitosan as a nitrogen source revealed to be a good alternative to post-synthesis methods.

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.

Production of activated carbons from single and mixtures of synthetic polymers

The production of activated carbons (ACs) involves two main steps: the carbonization of the carbonaceous of raw materials at temperatures below 1073 K in the absence of oxygen and the activation had realized at the temperature up to 1173 but the most useful temperature at 1073 K. In our study we used the most common industrial and consumer solid waste, namely PET, alone or blended with other synthetic polymer PAN. By mixing the two polymers in different ratios, an improvement of the yield of the AC production was found and some textural properties were enhanced by comparison with the AC prepared using each polymer separately. When all the samples were exposed through the carbonization process with a pyrolysis the mixture of PAN-PET (1:1w/w) yield around 31.9%, between that obtained with PET (16.9%) or PAN (42.6%) separately. The combine activation, with CO2 at 1073 K, allow ACs with a lower burn-off degree isothermally, when compared with those attained with PET or PAN alone, but with similarly chemicals or textural properties. The resultant ACs are microporous in their nature, as the activation time increase, the PET-PAN mixture AC are characterized by a better developed porous structure, when associated with the AC prepared from PAN. The AC prepared from PET-PAN mixture are characterized by basic surface characteristics, with a pHpzc around 10.5, which is an important characteristic for future applications on acidic pollutants removals from liquid or gaseous phase. In this study we had used the FTIR methods to determine the main functional groups in the surface of the activated carbons. The adsorbents prepared from PAN fibres presents an IR spectrum with similar characteristics to those obtained with PET wastes, but with fewer peaks and bands with less intensity, in particular for the PAN-8240 sample. This can be reflected by the stretching and deformation modes of NH bond in the range 3100 – 3300 cm-1 and 1520 – 1650 cm-1, respectively. Also, stretching mode associated to C–N, C=N, can contributed to the profile of IR spectrum around 1170 cm-1, 1585 – 1770 cm-1. And the TGA methods was used to study the loses of the precursors mass according to the excessive of the temperature. The results showed that, there were different decreasing of the mass of each precursors. PAN degradation started at almost 573 K and at 1073 K, PAN preserve more than 40% of the initial mass. PET degradation started at 650 K, but at 1073 K, it has lost 80% of the initial mass. However, the mixture of PET-PAN (1:1w/w) showed a thermogravimetric profile between the two polymers tested individually, with a final mass slightly less than 30%. From a chemical point of view, the carbonisation of PET mainly occurs in one step between 650 and 775 K.