Carbon adsorbents oxidation treatment

Accent [Aqueous carbon compound effluent treatment] A process for oxidizing organic contaminants in aqueous streams by catalyzed oxidation with sodium hypochlorite. The catalyst is promoted nickel oxide, which retains active oxygen at its surface, as well as adsorbing the organics. Developed by ICI Katalco and first offered in 1998. 

Figure 3. Breakthrough plots of TBB (dry or wet airstream) on different carbons after different treatments such as freezing-thawing with water adsorbed in different media or pre-adsorbed water, oxidizing (labelled Ox) and reduction (Re).

Possibility of combination of removal by adsorption and catalytic conversion in a separate step. Solid catalysts may act as adsorbent to remove pollutants present in diluted wastewater emissions, and act as catalysts to catalyse the conversion of adsorbed substances during a regeneration step . This allows much better process energy use than wet (catalytic) oxidation for diluted wastewater. Also active carbon can be functionalized with a catalysF to allow its regeneration by oxidative treatment at much lower temperatures (around... 

Activated carbon reacts with oxidants commonly used in drinking water treatment. Furthermore, activated carbon adsorbs oxygen from air during storage and dissolved oxygen... 

The oxidation of coal is of considerable interest as a means of modifying the physical and chemical properties of the coal. In particular, the caking of the coal on carbonization may be reduced or prevented by oxidation treatment. The degree of oxidation is important, about 1% of oxygen being adsorbed on, or combined with, the coal. It may be estimated by chemical analysis or trial carbonization, but for the control of oxidation plant, a more rapid indication is required of any departure from the correct operating conditions. 

Adsorption by carbon, which is one of the oldest adsorption methods used, has been reviewed and evaluated for the preconcentration of trace metals (794). Many authors have discussed the preparation of activated charcoal and carbon from a wide variety of usually local sources. The applications to water treatment are far too numerous to mention other than a few. Jo (795) carbonized a resin and a gum and hydrated the residue above 600 C to produce an adsorbant selective for cadmium(II). Kuzin et al, 196) used deashed active carbon and oxidized carbon for the quantitative sorption of copper, lead, zinc, and nickel from nearly neutral solutions containing 1-2 M alkali-metal halide. Pearson and Siviour (797) converted the metal-ion species to amine complexes before adsorbing these onto carbonaceous materials such as brown charcoal char or cellulose. Mercury vapor can be removed from a solution by reduction followed by passage of a nitrogen stream and adsorption by activated charcoal (798). Activated carbon, which had been oxidized with nitric acid, has been used to extract several metals including divalent nickel, cadmium, cobalt, zinc, manganese, and mercury from fresh water, brine, and seawater (799, 200). 

Activated carbon adsorbents generally show very little selectivity in the adsorption of molecules of different size. However, by special activation procedures it is possible to prepare carbon adsorbents with a very narrow distribution of micropore size and which therefore behave as molecular sieves. The earliest examples of carbon molecular sieves appear to have been prepared by decomposition of polyvinylidene dichloride (Saran) but more recently a wide variety of starting materials have been used. Most commercial carbon sieves are prepared from anthracite or hard coal by controlled oxidation and subsequent thermal treatment. The pore structure may be modified to some extent by subsequent treatment including controlled cracking of hydrocarbons within the micropore system and partial gasification under carefully regulated conditions. ... 

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