Saturday, November 12, 2011

Gas Adsorption Properties of the Ternary ZnO/CuO/CuCl2 Impregnated Activated Carbon System for Multigas Respirator Applications Assessed through Combi

A ternary library of 64 ZnO/CuO/CuCl2 impregnated activated carbon samples was synthesized and screened automatically using a combinatorial (combi) method. The ability of the samples to adsorb toxic gases was screened gravimetrically. The stoichiometric ratio of reaction (SRR) between the moles of toxicant and the total moles of impregnant was obtained from the calculated mass increase of the samples after chemisorption, with a high SRR indicating high efficiency of toxicant removal. The combi samples that exhibited good dry SO2 and NH3adsorption were prepared in bulk using the incipient wetness method and were evaluated for multigas respirator function by dynamic adsorption studies of SO2, NH3, HCN, and C6H12gases in either dry or humid conditions at ambient temperature. The bulk samples showed equivalent gas adsorption capacities when exposed to the different challenge gases indicating the value of the combi method for initial screening. Cu2Cl(OH)3 was identified to be a potential multigas adsorbent.
A library containing a ternary ZnO, CuO, and CuCl2-impregnated activated carbons was prepared and screened using the combinatorial method. The compositions of the library were selected so that all samples contained ZnO or CuO, which have been shown to adsorb SO2.(9) CuCl2 was added sequentially across the library to study its impact. CuCl2 has been shown to perform well as an NH3 adsorber.(16) Ideally, the SO2 adsorption properties of the metal oxides will be maintained with the addition of CuCl2 while the NH3 adsorption is improved.
After exposure to the toxic gas, the increase in the mass of each of the samples indicated the effective chemisorption of these gases onto the impregnated carbon. This mass increase (the recorded mass increase of the sample – average mass increase of unimpregnated control samples) after exposure was translated into gas adsorption capacity denoted as mmol of gas adsorbed per gram of AC.
A fast and reliable method of screening for the gas adsorption properties of impregnated activated carbon materials has been established. The method was shown to be useful in assessing the adsorption capacity of the components of the ternary ZnO/CuO/CuCl2 system of impregnants for SO2 and NH3. This allowed potentially useful multigas formulations to be identified at a faster rate. The formation of the Cu2Cl(OH)3 phase was identified together with CuO and ZnO in samples initially impregnated with large amounts of CuCl2 and the metal nitrates. The presence of large crystals of Cu2Cl(OH)3 did not compromise the SO2, NH3, and HCN gas adsorption.

Reference
ACS Comb. Sci., Article ASAP
DOI: 10.1021/co200121c

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