Water purification from chromium ions in a diaphragm electrolyzer

In the production of rocket and space technology electrochemical processes are applied that is the reason of pollution of wastewater with metal ions. The strict requirements of the environmental authorities do not allow dumping sewage waste water containing metal ions which concentration exceeds the maximum permissible values directly into water bodies or sewerage. The greatest difficulty is water treatment from hexavalent chromium. Proposed methods for purification of hexavalent chromium - electrocoagulation method, the method galvanokoagulyatsii, sorption methods, combined methods have drawbacks, such as significant power consumption, a considerable consumption of soluble metal anode passivation anodes need for large excesses of reagent (iron salts), large quantities of sludge and the complexity of its dehydration, high cost and scarcity of sorbents, high consumption of reagents for regeneration and other sorbents. Water purification from chromium using a non-diaphragm electrolyzers with soluble iron anode diaphragm electrolyzers are used to change the active reaction and the redox potential of the medium. We present experimental setup with coaxial arrangement of electrodes and an inert diaphragm separating the water, the calculation time of the ion migration from the cathode to the anode chamber. Anion concentration of chromium was determined by atomic absorption spectroscopy. The initial concentration of the anion of the chromium in the cathode chamber is equal to 892 mg / l, final - 669 mg / liter. The degree of purification of water by chromium is 25 %. Insufficient degree of purification can be explained by the following factors: the migration of chromium anions from the cathode chamber into the anode space occurs opposite directional diffusion flux due to the appearance of a gradient of concentration of anions with increasing concentration of like charged anions in the anode chamber increases the Coulomb repulsion force, which limits the influx of anions anode chamber. Since the waste water engineering plants contain less than 0.5 mg / L chromium, the distance between the like-charged ions causing considerable repulsive force decrease. In this connection it should expect an increase in the degree of purification and the proposed method can be used for purification of wastewater from metal ions to the maximum permissible concentration.