High pressure CO2 adsorption onto Malaysian Mukah-Balingian coals: Adsorption isotherms, thermodynamic and kinetic investigations

CO₂ sequestration into coalbed seams is one of the practical routes for mitigating CO₂ emissions. The adsorption mechanisms of CO₂ onto Malaysian coals, however, are not yet investigated. In this research CO₂ adsorption isotherms were first performed on dry and wet Mukah-Balingian coal samples at temperatures ranging from 300 to 348 K and pressures up to 6 MPa using volumetric technique. The dry S1 coal showed the highest CO₂ adsorption capacity of 1.3 mmol g^-1, at 300 K and 6 MPa among the other coal samples. The experimental results of CO₂ adsorption were investigated using adsorption isotherms, thermodynamics, and kinetic models. Nonlinear analysis has been employed to investigate the data of CO₂ adsorption onto coal samples via three parameter isotherm equilibrium models, namely Redlich Peterson, Koble Corrigan, Toth, Sips, and Hill, and four parameter equilibrium model, namely Jensen Seaton. The results of adsorption isotherm suggested that the Jensen Seaton model described the experimental data well. Gibb's free energy change values are negative, suggesting that CO₂ adsorption onto the coal occurred randomly. Enthalpy change values in the negative range established that CO₂ adsorption onto coal is an exothermic mechanism. Webber's pore-diffusion model, in particular, demonstrated that pore-diffusion was the main controlling stage in CO₂ adsorption onto coal matrix. The activation energy of the coals was calculated to be below -13 kJ mol^-1, indicating that adsorption of CO₂ onto coals occurred through physisorption. The results demonstrate that CO₂ adsorption onto coal matrix is favorable, spontaneous, and the adsorbed CO₂ molecules accumulate more onto coal matrix. The observations of this investigation have significant implications for a more accurate measurement of CO₂ injection into Malaysian coalbed seams.

Metal–Organic Frameworks (MOFs) Containing Adsorbents for Carbon Capture

In this study, new composite materials of montmorillonite, biochar, or aerosil, containing metal–organic frameworks (MOF) were synthesized in situ. Overall, three different MOFs—CuBTC, UTSA-16, and UiO-66-BTEC—were used. Obtained adsorbents were characterized using powder X-ray diffraction, thermogravimetric analysis, nitrogen adsorption porosimetry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Fourier transform infrared spectrophotometry. Additionally, the content of metallic and nonmetallic elements was determined to investigate the crystalline structure, surface morphology, thermal stability of the obtained MOF-composites, etc. Cyclic CO2 adsorption analysis was performed using the thermogravimetric approach, modeling adsorption from flue gasses. In our study, the addition of aerosil to CuBTC (CuBTC-A-15) enhanced the sorbed CO2 amount by 90.2% and the addition of biochar (CuBTC-BC-5) increased adsorbed the CO2 amount by 75.5% in comparison to pristine CuBTC obtained in this study. Moreover, the addition of montmorillonite (CuBTC-Mt-15) increased the adsorbed amount of CO2 by 27%. CuBTC-A-15 and CuBTC-BC-5 are considered to be the most perspective adsorbents, capturing 3.7 mmol/g CO2 and showing good stability after 20 adsorption-desorption cycles.

MOFs-carbon hybrid nanocomposites in environmental protection applications

The demand for green engineering environmentally friendly nanomaterials had made carbon nanotube a suitable material to keep metal-organic frameworks (MOFs) in the application of wastewater treatment and air pollution monitoring systems. This review summarizes many of the recent research accomplishments in the synthesis of MOFs and MOFs-carbon hybrid nanocomposites for various applications such as wastewater treatment and removal of hazardous gases (CO, SO2, H2S and NH3) with emphasis on MOF/CNTs composites. This review focuses on the efficient removal of pollutants from the environment using adsorption techniques. Another important application of MOFs composite discussed in this review is sensor materials for environmental pollution.