DETERMINATION OF TOTAL AMMONIA AND CARBON-DIOXIDE IN LIQUORS FROM THECARON PROCESS FOR NICKEL EXTRACTION

We have developed a two-channel flow-injection analysis (FIA) system f or determination of total ammonia and total carbon dioxide in leaching solutions used in the hydrometallurgical Caron process for nickel ext raction. Total alkalinity is measured from the spectrophotometric resp onse at 592 nm using a reagent composed by acetic acid and bromophenol blue. A stronger alkalinity is also determined in the same FIA system using a boric acid-cresol red reagent and monitoring the absorbance a t 572 nm. In both cases calibrations were performed by non-linear regr ession. In the samples from the Caron process, strong alkalinity is a direct measure of the total ammonia concentration, whereas total carbo n dioxide is computed from the difference between total and strong alk alinity. The results obtained are compared with those obtained by pote ntiometric titrations and linear modified Gran's functions. Insignific ant differences were found for both synthetic and real samples with re levant ammonia/carbon dioxide ratios. The set-up allows a sampling rat e of 120 samples h(-1). The repeatability, measured as relative standa rd deviation, was lower than 1.7% for ammonia and lower than 14% for c arbon dioxide determinations.