Technology of Producing of Sodium Hypochlorite from the Concentrate of Reverse Osmosis Systems

摘要

One of the modern methods of water demineralization and softening for domestic and drinking purposes as well as for its preparation in industrial production is a reverse osmosis. This demineralization method is peculiar for its concentrates that are formed due to reverse osmosis membranes and nanofiltration technologies, the utilization of which continues to be an unresolved problem. The article deals with the solution of such problem to utilize those concentrates, which are obtained using reverse osmosis and nanofiltration units. In this regard, it seems promising to reduce the volume of technological concentrate at the first stage by its repeated concentration according to nanofiltration - reverse osmosis scheme. After that, the nanofiltration concentrate containing predominantly divalent Ca~(2+), Mg~(2+) and SO_4~(2-) ions is subjected to reagent treatment in the following sequence: first stage with barium compounds and second stage with carbonate and sodium hydroxide. Such sequence allows separating from the solution at the first stage practically insoluble BaSO_4 with its precipitation in the 1st stage vortex reactor and, further precipitation of slightly soluble in alkaline medium CaCO_3 and Mg(OH)_2 in the Ⅱ stage reactor. These insoluble BaSO_4, CaCO_3 and Mg(OH)_2 salts thrown off the mass balance are finally dehydrated using a filter press and subjected to subsequent sale as a market product or raw material. The obtained solution of sodium chloride is concentrated by 3-stage reverse osmosis resulting in a 0.8-1.0% aqueous solution (8-10 g/l) of sodium chloride solution, a high-grade raw material for the production of electrolytic sodium hypochlorite with 4-6 g/l concentration by chlorine equivalent.