Effects of Moisture on NH3 Capture Using Activated Carbon and Acidic Porous Polymer Modified by Impregnation with H3PO4: Sorbent Material Characterized by Synchrotron XRPD and FT-IR

Abstract

The performances of reactive adsorbents, H3PO4/C (activated carbon) and H3PO4/A (Amberlyst 35), in removing NH3 from a waste-gas stream were investigated using a breakthrough column. Accelerated aging tests investigated the effects of the water content on the performance of the adsorbents. Results of breakthrough tests show that the adsorption capacity greatly decreased with the drying time of H3PO4/C preparation. Synchrotron XRPD indicated increased amorphous phosphorus species formation with drying time. Nitrogen adsorption-desorption isotherms results further suggested that the evaporation of water accommodated in macropores decreases adsorption capacity besides the formation of the amorphous species. Introducing water moisture to the NH3 stream increases the adsorption capacity concomitant with the conversion of some NH4H2PO4 to (NH4)2HPO4. Due to the larger pore of cylindrical type and more hydrophilic for acidic porous polymer support, as opposed to slit-type for the activated carbon, the adsorption capacity of H3PO4/A is about 3.4 times that of H3PO4/C. XRPD results suggested that NH3 reacts with aqueous H3PO4 to form NH4H2PO4, and no significant macropore-water evaporation was observed when acidic porous polymer support was used, as evidenced by N2 isotherms characterizing used H3PO4/A.

Advanced Materials for NH3 Capture: Interaction Sites and Transport Pathways

“…Among various polymers, BPP-5 with a multiply interpenetrated structure dominated by pores smaller than 6 Å pores exhibits an NH 3 uptake of 17.7 mmol g −1 at 1 bar, and BPP-7 with larger pore size shows improved NH 3 absorption kinetics at low pressure (3.15 mmol g −1 at 480 ppm), but the recyclability of these POPs is not clear. Since then, various POPs modified by acid groups have been developed for NH 3 adsorption, such as COOH-copolymer PDAB-AA [ 95 ], PIM-1-COOH [ 96 ], H 3 PO 4 modified POPs [ 97 ], H 2 SO 4 -modified ethylene glycol dimethacrylate (EGDMA) polymers [ 98 , 99 ] and sulfonated POPs [ 100 ], and the regeneration abilities of most materials have also been investigated systematically. Table 3 presents the NH 3 adsorption performance and regeneration properties of representative POPs.…”