Caustic impregnated carbons

Bandosz, T.J., Bagreev, A., Adib, F., and Turk, A. (2000). Unmodified versus caustics-impregnated carbons for control of hydrogen sulfide emissions from sewage treatment plants. Environ. Sd. Technol, 34, 1069—74. 

Bagreev, A. and Bandosz, T.J. (2002). A role of sodium hydroxide in the process of hydrogen sulfide adsorption/oxidation on caustic-impregnated activated carbons. Ind. Eng. Chem. Res., 41, 672—9. 

The examples of carbons working as catalysts supports are discussed in the following chapters. The best known examples an whcdcritcs used for military filters [387], caustics [388], oxidants or copper impregnated carbons for desuHurization [389], transition metals impregnated carbons for removal of HCN [390] and reduction of nitric oxides [383, 391]. 

A process for impregnating black ash and white ash with carbonic acid, in ordor to convert the caustic and silicate of soda containad therein into carbonate, was... 

First NO is formed and then it is oxidized in the atmosphere to NOj. Since in combustion, the origin of nitrogen is not only from N-rich fuel but also from air supphed for oxidation, in the elimination of NO, postcombustion methods are important. So far the most effective technique has been selective catalytic reduction of NO . on various catalysts. When the activated carbons are used as removal media, the elimination process includes also adsorption combined either with oxidation or reduction. Oxidation usually leads to the formation of nitric acid whereas Nj is the product of NO, reduction. As in the cases of other pollutants addressed in this review, for NO, removal either unmodified or impregnated (caustics, catalytic metals) activated carbons have been used [101-114]. 

When char is impregnated with caustic soda or potash and heated above 500° C, an energetic reaction occurs33 which results in erosion of the carbon accompanied by an increase in adsorptive power.34 The process has a destructive effect on equipment, and caustic alkali by itself is seldom used commercially. 

Based on the above described chemistries of the adsorption/oxidation process either elemental sulfur, or sulfuric acid are the most likely products of surface reaction in the presence of air and water [60]. When hydrogen sulfide is adsorbed on unmodified activated carbons at elevated temperatures sulfur is the main product [73, 75, 76, 85, 89, 123]. Elemental sulfur is also deposited when activated carbons impregnated with caustic are used [61]. In the case of application of unmodified carbons as hydrogen sulfide adsorbents at ambient temperatures a... 

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