Effects of Moisture on NH(3 )Capture Using Activated Carbon and Acidic Porous Polymer Modified by Impregnation with H(3)PO(4): Sorbent Material Characterized by Synchrotron XRPD and FT-IR

The performances of reactive adsorbents, H(3)PO(4)/C (activated carbon) and H(3)PO(4)/A (Amberlyst 35), in removing NH(3) 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 H(3)PO(4)/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 NH(3) stream increases the adsorption capacity concomitant with the conversion of some NH(4)H(2)PO(4) to (NH(4))(2)HPO(4). 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 H(3)PO(4)/A is about 3.4 times that of H(3)PO(4)/C. XRPD results suggested that NH(3) reacts with aqueous H(3)PO(4) to form NH(4)H(2)PO(4,) and no significant macropore-water evaporation was observed when acidic porous polymer support was used, as evidenced by N(2) isotherms characterizing used H(3)PO(4)/A.