Rapid determination of nitrate in city water by a combined coppered cadmium column reduction-spectrophotometric method; with special reference to the removal of heavy metals released in laboratory waste waters

Abstract

For the routine analysis of treated and untreated city waters for nitrate, use of coppered cadmium column was tested to facilitate the rapid reduction of nitrate and the subsequent determination. As an activation procedure for used columns treatment of the column (once a day) with a mixture of hydrochloric acid [10-4 M]-EDTA(disodium salt) [0.08%] turned out to be effective enough to permit the subsequent 5 runs of the reduction process. Repeated five determinations of respective 4 and 20 µg NO3-N were accomplished in this way with the accuracy of 88 to 105%, the precision being also comparable with those attainable by the conventional salicylic acid method. We used 10 columns simultaneously, thus accomplishing 50 determinations of nitrate a day. With respect to the removal of cadmium and copper ions released in laboratory waste waters, several methods were examined. Coprecipitation with ferric hydroxide best functioned for this purpose. When the effluent contained EDTA as well as the heavy metals, sulfide precipitation in 0.2 N hydrochloric acid media proved to be effective, but a treatment involving the destruction of EDTA with permanganate and the subsequent coprecipitation with ferric hydroxide was more attractive, because of its simplicity and effectiveness. Whichever methods are applied, they allowed the level of heavy metals after the treatment to decrease down to the permissible concentration in the waste in Japan (Cd 0.1 ppm, Cu 3.0 ppm). © 1979, The Japan Society for Analytical Chemistry. All rights reserved.