No abstract

Solid amine adsorbents are among the most promising CO 2 adsorption technologies for biogas upgrading due to their high selectivity toward CO 2 , low energy consumption, and easy regeneration. However, in most cases, these adsorbents undergo severe chemical inactivation due to urea formation when regenerated under a realistic CO 2 atmosphere. Herein, we demonstrated a facile and efficient synthesis route, involving the synthesis of nano-Al 2 O 3 support derived from coal fly ash with a CO 2 flow as the precipitant and the preparation of polyethylenimine (PEI)-impregnated Al 2 O 3 -supported adsorbent. The optimal 55%PEI@2%Al 2 O 3 adsorbent showed a high CO 2 uptake of 139 mg•g −1 owing to the superior pore structure of synthesized nano-Al 2 O 3 support and exhibited stable cyclic stability with a mere 0.29% decay per cycle even under the realistic regenerated CO 2 atmosphere. The stabilizing mechanism of PEI@nano-Al 2 O 3 adsorbent was systematically demonstrated, namely, the cross-linking reaction between the amidogen of a PEI molecule and nano-Al 2 O 3 support, owing to the abundant Lewis acid sites of nano-Al 2 O 3 . This cross-linking process promoted the conversion of primary amines into secondary amines in the PEI molecule and thus significantly enhanced the cyclic stability of PEI@nano-Al 2 O 3 adsorbents by markedly inhibiting the formation of urea compounds. Therefore, this facile and efficient strategy for PEI@nano-Al 2 O 3 adsorbents with anti-urea properties, which can avoid active amine content dilution from PEI chemical modification, is promising for practical biogas upgrading and various CO 2 separation processes.

No abstract

No abstract

Current disposal methods of sewage sludge (SS) and its incinerated ash (ISSA) do not allow for the recycling of the phosphorus (P) present. The aim of this study was to fabricate a P compound fertilizer by using an optimal SS-derived biochar (SSB) with enhanced inherent Ca–P content to load P from the P extract of ISSA. For this purpose, SS was impregnated with four agents (MgCl2, CaCl2, MgO, and CaO) at mass ratios of 20 or 10% and pyrolyzed at 700 or 300 °C. Characterization of the produced SSBs indicated that those with 20% MgCl2, CaO, and MgO added and pyrolyzed at 700 °C exhibited high surface areas, abundant mesopores, and abundant plant-valuable P. When in contact with the P extract, these three SSBs showed the highest P adsorption efficiencies among the obtained SSBs but CaO/MgO-impregnated SSBs have more metal coprecipitation. The postsorption SSBs were P-enhanced and alkalinity decreased, which are favorable for fertilizer application. Furthermore, a pot experiment verified that these three postsorption SSBs had a comparable P fertilizer effect to that of the commercial P fertilizer. Therefore, the MgCl2-impregnated SSB with P loading from the ISSA extract has potential as a P fertilizer alternative that can support global P sustainability by reclaiming P from SS and ISSA.

As an alternative renewable energy, upgraded biogas by separating CH4 and CO2 can be used to replace natural gas in automobiles and power grids.

No abstract

No abstract