The investigation of copper-based impregnated activated carbons prepared from water-soluble materials for broad spectrum respirator applications.

The preparation of impregnated activated carbons (IACs) from aqueous, copper-containing solutions for broad spectrum gas filtration applications is studied here. Several samples were studied to determine the effect that impregnant loading, impregnant distribution and impregnant recipe had on the overall performance. Dynamic flow testing was used to determine the gas filtration capacity of the IAC samples versus a variety of challenge gases. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) were used to characterize the impregnant distribution on the carbon as a function of impregnant loading. Oven tests were performed to determine the thermal stability of the IAC samples exposed to elevated temperatures. The role impregnant distribution plays in gas filtration capacity and the overall performance of the IAC samples is discussed. The IAC samples prepared in this work were found to have gas filtration capacities as good as or better than broad spectrum respirator carbon samples prepared from the patent literature. IACs impregnated with an aqueous 2.4 M Cu(NO(3))(2)/0.04 M H(3)PO(4).12MoO(3)/4M HNO(3) solution that were heated to 200 degrees C under argon were found to have the best overall performance of the samples studied in this work.

Investigation of copper oxide impregnants prepared from various precursors for respirator carbons.

Copper oxide impregnated activated carbon was prepared by three methods and studied as a respirator carbon. Using techniques such as dynamic flow testing, X-ray diffraction (XRD), thermal analysis, scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX), copper oxide impregnants, derived from different sources such as basic copper carbonate (Cu(2)CO(3)(OH)(2)), copper nitrate (Cu(NO(3))(2)) and copper chloride (CuCl(2)) reacted with sodium hydroxide (NaOH), have been studied. Dynamic flow tests performed using sulfur dioxide (SO(2)), ammonia (NH(3)) and hydrogen cyanide (HCN) challenge gases allow the determination of the stoichiometric ratio of reaction (SRR) between challenge gas and impregnant. Thermal gravimetric analysis experiments showed that an inert heating environment was required when thermally decomposing the Cu(NO(3))(2) impregnant to CuO to avoid damaging the activated carbon substrate. SEM has been used to investigate dispersal and particle size of the impregnant on the activated carbon. XRD permits the identification of crystalline and amorphous phases as well as the grain size of the impregnant. XRD analysis of samples before and after exposure to SO(2) has allowed the active impregnant in SO(2) adsorption to be identified. The relationship between SRR, impregnant loading and grain size is discussed. Methods to improve impregnant distribution are presented and their impact discussed.

Understanding the role of each ingredient in a basic copper carbonate based impregnation recipe for respirator carbons.

Basic copper carbonate (Cu(2)CO(3)(OH)(2)) is often used as an impregnant in activated carbons for respiratory filters. The mechanisms that allow adsorption of toxic gases by an activated carbon loaded with a Cu(2)CO(3)(OH)(2)-based impregnation recipe are studied here. Several samples were studied to determine the effect of ingredients added during impregnation, impregnant loading and drying temperature on performance. The filtering capacity of the samples is quantified by the stoichiometric ratio of reaction (SRR) between the impregnant and the challenge gas. X-ray diffraction (XRD), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) were used to characterize the impregnant both on and off the carbon as a function of loading and heat-treatment temperature. The influence of the phase and dispersion of the impregnant on the SRR is the focus of this report.

Ammonia, cyclohexane, nitrogen and water adsorption capacities of an activated carbon impregnated with increasing amounts of ZnCl(2), and designed to chemisorb gaseous NH(3) from an air stream.

The adsorption capacity of ZnCl(2)-impregnated activated carbon (AC) for NH(3) is reported in terms of stoichiometric ratio of reaction (NH(3) per ZnCl(2)). This ratio depends on the testing conditions used. Compared to the ratio obtained under dry conditions, the ratio is higher under humid conditions or increased NH(3) concentrations. The linear increase of the NH(3) capacity with increasing loading of ZnCl(2) breaks down at about 3.5 mmol ZnCl(2)/g AC. This behavior is explained in terms of preferential adsorption of a monolayer of salt followed by aggregation of the impregnant once a monolayer is completed. The effect of increasing the loading of ZnCl(2) on the capacity for gases for which the impregnants are not intended, namely cyclohexane, nitrogen, and water vapor, is also discussed. A break in the linear relationship between water capacity and impregnant loading at about 3.5 mmol ZnCl(2) seems to correspond to a full monolayer coverage of ZnCl(2) on AC. The monolayer of ZnCl(2) is shown to reduce the uptake of water into AC, while the ZnCl(2) aggregates are shown to be hydrophilic.