No abstract

Small-angle neutron scattering (SANS) and N 2 -BET analysis were used to characterize the microstructure of a series of activated carbons produced from paper mill sludge using ZnCl 2 . N 2 -BET and SANS data indicate that the micro-and mesoporous surface areas of the carbons increase with the concentration of ZnCl 2 used in their preparation. Contrast variation SANS studies demonstrate the existence of two different phases, a zinc-rich particle phase and a bulk carbon phase with nanopores. Both phases are largely accessible to the solvent. The size and morphology of the pores and inclusions were determined from the SANS data. The pores are found to be roughly rodlike. The radii and volumes of the pores increase with increasing the amount of activating agent (ZnCl 2 ) used for the production of the carbons. On the basis of SANS results, we propose a conceptual model describing structural characteristics of the produced carbons.

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With growing concerns in CO 2 emissions, cost effective processes for CO 2 capture at massive scales are being developed. Membranes show great potential in this field due to their simple operation and durability. Carbon molecular sieve (CMS) membranes can separate gases in a unique mechanism which targets CO 2 . In our work, we prepared CMS films from proprietary Novolak and Resole phenolic resins on existing high gas selectivity silica membranes developed from multiple silica layers using dip coating and vacuum impregnation. CMS layers were coated with various resin dilutions followed by pyrolysis in N 2 . Precise control of the thickness and dilution was found to be critical to uniform, defect free films. Effective CMS membranes resulted in He/CO 2 permselectivity less than unity, as low as 0.5 indicating 'reverse selectivity'. In this mechanism, the more sorbing molecule (CO 2 ) diffuses faster than the smaller, but nonsorbing He. The same membranes also displayed the best selectivity of CO 2 to N 2 confirming the adsorption selective transport. This initial work showed Novolak resins lead to better CMS structures than Resole, with optimum dilutions and curing techniques. Combining dip coating with vacuum impregnation confirmed better selectivities can be achieved from CMS/silica films. Further development of the promising CMS on silica membrane technology is required to increase selectivity for cost effective CO 2 capture.