Determination of Trace Nickel in Red Mud by Fluorescence Quenching of CdTe Quantum Dots

CdTe Quantum Dots (QDs) have the advantages of high fluorescence intensity and good stability. Using CdTe QDs as fluorescence probes to analyze samples containing complex substrates, the interference of metal elements must be effectively separated, and elements whose contents are lower than detection limits must be efficiently enriched. Thioglycolic acid (TGA) modified CdTe QDs of high fluorescence were prepared in aqueous solution using thioglycolic acid as a stabilizer. A new fluorophotometric method for the determination of trace nickel in red mud was developed based on the strong quenching effect that CdTe QDs fluorescence had been quenched by nickel ion in borax buffer solution (pH was 10.0). The suitable experimental conditions were as follows: CdTe quantum dot concentration was 3.0×10^-4 mol/L, reaction temperature was room temperature, and reaction time was 10 min. The relative fluorescence intensity of CdTe QDs was proportional to the concentration of nickel ions that ranges from 2.0×10^-7 to 7.8×10^-5mol/L, and the detection limit was 1.5×10^-7 mol/L. In order to substrate the main lower metal elements such as Fe³⁺, Co²⁺, and Cu²⁺, the nickel ion in filtrate was extracted and recovered with solvent of 25% N530-coal oil sulfonated. The recovery of the nickel was over 99%. The proposed method has been applied to the determination of trace nickel in red mud, the results were consistent with those obtained by catalytic spectrophotometry with the spiked recoveries of 98.3%-104.2%.