Landfill gases--Purification

Amine-grafted silica (i.e., aminosilicas) was investigated for single-stage landfill gas purification via simultaneous removal of CO2, H2S, and water vapor. Aminosilica materials were synthesized by covalent triamine grafting onto mesoporous silica with custom amounts of water and amine. Screening adsorption experiments were completed in dry 30 vol.% CO2 in N2 at 40 °C and assessed using thermogravimetric analysis. Materials with equilibrium CO2 uptakes greater than 1.5 mmol/g were chosen for CO2 adsorption kinetics assessments. The highest-performing aminosilica achieved fast CO2 adsorption by reaching 80% of its equilibrium uptake in one minute. This material also maintained 100% of its initial CO2 uptake when subjected to rigorous 100-cycle testing. It underwent column-breakthrough tests in the presence of different dry and humid gas streams containing CO2, H2S, and water vapor, and achieved concurrent and complete (100%) removal of all target impurities. The results suggest that aminosilicas can purify landfill gas in a single stage.

The potential of paper waste-derived activated carbon was investigated for the removal of carbon dioxide and hydrogen sulfide from landfill gas. Activated carbon materials were prepared by carbonizing paper waste followed by acid treatment to remove ash, mixing with aqueous phase potassium hydroxide, and activation via microwave heating. Activated samples were tested using thermogravimetric analysis to determine their equilibrium uptake of carbon dioxide. The adsorbent materials were modified with both tetraethylenepentamine and diethanolamine to potentially increase the carbon dioxide uptake, however, all the modified samples had a performance significantly worse than their unmodified counterparts. Adsorbent screening was conducted in conditions mimicking that of landfill gas, namely temperature of 40 °C and 40% carbon dioxide in nitrogen. Performant samples were identified as those achieving uptakes greater than 3 wt.%. The best performing sample achieved an uptake of 5.03 wt.% and maintained 97% of its uptake during 100 successive adsorption-desorption cycles. Column-breakthrough experiments demonstrated that the final candidate achieved complete removal of both carbon dioxide and hydrogen sulfide, suggesting viability for larger scale landfill gas purification.

The potential of amine-grafted silica materials (i.e., aminosilicas) was investigated for single-stage biogas and landfill gas purification via simultaneous removal of CO2, H2S, and water vapor. Custom aminosilicas were synthesized by covalent tethering of primary amines onto commercially available mesoporous silica. Screening adsorption experiments were completed at 40°C in the presence of dry 30 vol.% CO2 in N2, and performance was measured using thermogravimetric analysis. Selected materials with equilibrium CO2 uptakes greater than 6 wt.% were chosen for additional assessments in terms of CO2 adsorption kinetics. The highest-performing aminosilica achieved fast CO2 uptake by reaching 82% of its equilibrium CO2 uptake in one minute. This material was subjected to rigorous 100-cycle testing and retained stable performance as evidenced by maintaining 99% of its initial CO2 uptake throughout cycling. The final candidate also underwent multicomponent column-breakthrough tests and achieved complete (100%) removal of all target impurities. The results suggest promising potential of aminosilicas as a viable method of biogas and landfill gas purification.