Zeolite for removing ammonia

EnviNOx Two related processes for removing N20 and NOx from the tailgases from nitric acid manufacture by the Ostwald process. Both variants use two beds of two zeolite catalysts modified with iron. The first variant is for gases hotter than 425°C and involves injecting ammonia between the beds. The second variant, for gases cooler than 425°C, injects ammonia before the first bed and a volatile hydrocarbon between the beds. Developed by Uhde in association with Agrolinz Melamine International. The first variant was installed in Linz, Austria, in 2003. The second variant was installed in Egypt in 2007. The catalysts are supplied by Sud-Chemie. 

Zeolites have also proven applicable for removal of nitrogen oxides (NO ) from wet nitric acid plant tail gas (59) by the UOP PURASIV N process (54). The removal of NO from flue gases can also be accomplished by adsorption. The Unitaka process utilizes activated carbon with a catalyst for reaction of NO, with ammonia, and activated carbon has been used to convert NO to N02, which is removed by scrubbing (58). Mercury is another pollutant that can be removed and recovered by TSA. Activated carbon impregnated with elemental sulfur is effective for removing Hg vapor from air and other gas streams the Hg can be recovered by ex situ thermal oxidation in a retort (60). The UOP PURASIV Hg process recovers Hg from clilor-alkali plant vent streams using more conventional TSA regeneration (54). Mordenite and clinoptilolite zeolites are used to remove HQ from Q2, clilorinated hydrocarbons, and reformer catalyst gas streams (61). Activated aluminas are also used for such applications, and for the adsorption of fluorine and boron—fluorine compounds from alkylation (qv) processes (50). 

In addition to the removal of water, zeolites are industrially utilized for removal of trace constituents such as carbon dioxide,. sulfur compounds, ammonia etc. from different gas mixtures. 

In the alteration manipulations, the toxicant is changed from a toxic form to a less toxic form through the TIE chemical manipulation. In general, like the addition manipulation, the alteration manipulation is introduced into the sediment by mixing. The TIE manipulation results in the removal of the toxicant from the exposure and ultimately a decrease in toxicity. The manipulation described below for characterizing ammonia toxicity in which the mineral zeolite is added exemplifies this type of manipulation. The addition of zeolite to the sediment results in ammonium adsorbing to the zeolite. Because ammonia and ammonium exist in equilibrium in water (see Eq. 1 in Ammonia section), the removal of ammonium from the water also causes the ammonia concentrations to decline in order to re-establish the equilibrium. The reduction in ammonia concentrations results in reduced toxicity. 

Waste treatment - Clinoptilolite, ehabazite, mordenite, and phillipsite remove radioaetive Cs and Sr ° from nuelear waste streams and serve as eneapsulants for these isotopes to faeilitate solid waste disposal. Zeolites, partieularly elinoptilolite, are used in treating sewage and industrial waste streams to remove ammonia and heavy metals. Extracted ammonia is subsequently vented, reeovered for ehemieal use, or eonverted with sulfurie acid to ammonium sulfate fertilizer. 

The exchange process in zeolite is governed by two mechanisms namely mass transfer of the sorbate for exchange on the surface of zeolite and diffusion within the pores of the zeohtes for exchange with the mobile ion corresponding to the lower and higher concentrations of the zeolite dose, respectively. Waste water and flue gas treatment can be performed by application of zeohtes A, Y and a blend of zeolites 4A-X. The sludge and/or waste water which has initial pH ( 6.5-7.6) and different concentrations of arsenic (As), ammonia (NH4 ) and copper (Cu), can be treated by apphcation of proper zeohte dose (g/1). The removal efficiency of the zeolites for these ions is depicted in Fig. 7.2a, b [9, 11]. 

The applications of fly ash zeolites discussed in this chapter are summarized here in brief. Fly ash zeolites A, 4A, P and 4X are suitable for detergent builder and common substitute to phosphate builders. Other types of zeolites A, Y, P, Na-Pl, 4A, X, KM, Chabazite, Herschelite and Faujasite are effective for removal of heavy metals and ammonia from waste water. Zeolite A and Faujasite are proven cation exchange materials for removal of from sewage. Zeolite Na-P,... 

Where ammonia-based odours and fumes are present, synthetic media such as nonwoven polyester impregnated with activated carbon or zeolite can be used. These filters have proved useful for removing odours in nurseries or other child care facilities, hospitals and nursing homes, animal facilities, public restrooms and so on. 

In order to get the pore system of zeolites available for adsorption and catalysis the template molecules have to be removed. This is generally done by calcination in air at temperatures up to 500 °C. A careful study (ref. 12) of the calcination of as-synthesized TPA-containing MFI-type single crystals by infrared spectroscopy and visible light microscopy showed that quat decomposition sets in around 350 °C. Sometimes special techniques are required, e.g. heating in an ammonia atmosphere (ref. 13) in the case of B-MFI (boron instead of aluminum present) to prevent loss of crystallinity of the zeolite during template quat removal. 

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