Arsenic removal from drinking water by a "loose" nanofiltration membrane

The dissolution of pure Cu, 90/10 and 70/30 Cu---Ni alloys and of Monel 400 in strongly aerated 0.1 m HCl is studied by the weight loss technique at 25°C and 60°C. All four materials behave in a similar manner. The weight-loss/time curves are formed by an initial, low rate, induction period representing the dissolution of Cu in the monovalent state, CuCl-2. The nickel of the alloys dissolves simultaneously, but in quantities higher than present in the solid metal. Air oxidizes Cu+ to Cu2+. When enough of Cu2+ accumulates in solution, the dissolution of Cu is auto-catalyzed through the reaction Cu+Cu2+ = 2Cu+. This conclusion is supported by the results of experiments in which extra Cu2+ ions are added to the solution. The rate of dissolution along the induction period increases and the period itself decreases and disappears as more Cu2+ ions are added to the acid. A rise in temperature accelerates the dissolution