NF/RO faujasite zeolite membrane-ammonia absorption solvent hybrid system for potential post-combustion CO₂ capture application

A novel concept regarding nanofiltration/reverse osmosis (NF/RO) membrane-ammonia absorption solvent hybrid process for potential application to post-combustion CO₂ capture was developed and proven experimentally, in which the synthesis of selective membranes was investigated in detail. For this purpose, FAU-type zeolite membranes prepared with and without TMAOH by secondary growth method were selected for NF/RO reclamation of ammonia water and water components from 2 carbon-rich electrolyte solutions (0.15 and 0.56M total carbon loadings) close in chemical composition to aqueous ammonia based post-combustion CO₂ scrubbing solution. It was found that the incorporation of TMAOH as an structure-directing agent (SDA) into the synthetic gel precursors leads to the formation of FAU membranes with superior separation performances to those prepared without SDA. Without SDA, the resulting membranes were severely contaminated with the byproduct Na-P1 zeolites. This study further demonstrates that neither ion exchange nor calcination step is necessary to remove the occluded SDA, without trading off the permeation fluxes of FAU zeolite membranes. In the presence of SDA, both morphology and crystallinity of the membranes are strongly dependent upon the basicity of the synthetic gel, and have an important effect on the NF/RO separation performances of the obtained membranes. The physicochemical properties of these zeolite membranes were characterized by a series of techniques including X-ray diffractometer (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray fluorescent spectroscopy (XRF).