Abstract: A rapid method for forming vitreous carbon foams from flexible polyurethane foams having membranes dividing contiguous cells, which faithfully reproduces the geometry of the uncarbonized polyurethane foams, by infusing the polyurethane foams with substantially unresinified or unpolymerized furfuryl alcohol which is capable of resinification at temperatures above room temperature is described. An important step in the method which permits rapid carbonization without cracking and which is essential to faithful foam geometry reproduction is the substantial removal of the liquid non-infused furfuryl alcohol from the polyurethane foam surfaces after the infusion or swelling step. The carbonized foam is in the form of vitreous, disordered or glassy carbon and is particularly useful for corrosive and/or high temperature applications such as insulation, corrosion resistant chemical processing components and the like.

Abstract: Waste gas containing sulfur oxide (SO.sub.x) and nitrogen oxide (NO.sub.x) is mixed with an ozone-containing gas to have the value x of NO.sub.x fall in the range of 1.2 to 2.5 and thereafter brought into contact with an aqueous solution containing sulfuric acid, nitric acid and an iron compound to be deprived of SO.sub.x and NO.sub.x. To the solution with which the waste gas has been brought into contact, air or oxygen is added to effect oxidation of the part of said oxides still remaining therein in an unoxidized state and regenerate the activity of the iron compound functioning as a catalyst. Part of the solution to which the addition of air or oxygen has been made is recycled as the solution for the purpose of contact with waste gas.