Surface, Adsorption, and Catalytic Studies

Surface unsaturation in microcrystalline carbons, as measured by the fixation of bromine from aqueous solution, is thought to arise from the elimination of acidic C02-complexes, the elimination of two moles of complex generating one ethylenic bond. This is said to be a definite quantity characteristic of a carbon, and it can be enhanced by surface oxidation (treatment with potassium persulphate) followed by evacuation. 

The effect of methylation (treatment with a solution of diazomethane in ether) on the properties of oxidized charcoals has been found to be to enhance by ca. 50% the degree of adsorption of anions from hydrochloric acid solutions. This is thought to be due to the reduction of molecular oxygen on the carbon surface by the acid, which is not observed in the case of untreated oxidized carbon. 

An interesting application of the adsorption properties of carbons involved an attempt to remove mercury from atmospheric pollutants using sulphurized charcoal at 150 °C. The extent of mercury removal from the contaminated streams increased with increasing sulphur content, strongly suggesting that the mercury reacts with the sulphur present on the carbon surface to form mercuric sulphide. 

---