Determination of Ni in Nickel Laterite Ores by Ammonium Persulfate-Dimetylglyoxime Spectrophotometry

A spectrophotometry has been developed for determination of Ni content in nickel laterite ores. The sample was dissolved by mixed acids of HCl, HNO3, HF and HClO4 with appropriate proportions. After being completely dissolved, the salt was dissolved with 50% HNO3. Ni2+ and was oxidized to Ni4+ by ammonium persulfate in a NaOH medium. Ni4+ reacted with dimetylglyoxime to form a soluble red-wine complex compound which was measured by spectrophotometry to obtain the Ni content. Interferences of other matrix elements in the nickel laterite ores were eliminated by using potassium sodium tartrates as the masking agent. Experimental conditions including pH value, sequence of adding reagents, reagent consumption and coloration time were studied. Under the selected experimental conditions, the linear range was 0-2.0 μg/mL, and the limit of detection was 0.1 mg/g. The determination results were in agreement with those obtained by Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES). The relative standard deviations (RSD) were 0.75%-1.69% and the recoveries for Ni were 95.4%-102.7%. The experimental results indicate that this method is stable and reliable, and it can be applied to rapidly and accurately determine Ni in nickel laterite ores.