Patent ID: 9278871
Filing Date: 2016-03-08
CPC Classification: B01J,C02F

Claim Text:
1. A method of removing chromium from chromium-rich water, said method comprising the steps of: (a) providing an ion exchange resin comprising weak base anion exchange groups on a polymeric substrate; (b) flowing the chromium-rich water through the ion exchange resin at a flow rate and for a flow time such that chromate ions are removed from the chromium-rich water by a primary mechanism wherein the chromate ions are exchanged with counter ions of the weak base anion exchange groups without substantially overburdening an ion exchange capacity of the weak base anion exchange groups; (c) reducing a flow of the chromium-rich water through the ion exchange resin for a rest period, such that a secondary mechanism of chromium removal predominates, wherein chromium ions are removed from the weak base anion exchange groups and precipitated inside the ion exchange resin; and (d) repeating steps (b) and (c) for a number of cycles without replacing the ion exchange resin or substantially exceeding a total capacity of the ion exchange resin, wherein a pH of the chromium-rich water flowing into the ion exchange resin is greater than 5.5, and product water is obtained which contains a reduced amount of chromium relative to the chromium-rich water.