Determination of Cr(III) and Cr(VI) in electroplating wastewater with p-amino-N, N-diethylaniline spectrophotometric method

In HCl solution of pH = l.0, Cr(III) and Cr(VI) can be separated and concentrated with CL-tributyl-phosphate (TBP) levextrel resin. Using p-amino-N, N-diethylaniline as coloring regent, a method for the determination of trace Cr(III)and Cr(VI) in electroplating wastewater with spectrophotometry was developed. The results show that the apparent molar absorptivity is 3.4 × 104 L·mol-1·cm-1 at 554 nm with the linear range of 0-1.6 mg/L. The detection limit for the determination of Cr(III)and Cr(VI) is 0.01 mg/L and 0.007 mg/L, respectively. The relative standard deviation is 4.4% and 2.6%, respectively, for the determination of 0.32 mg/L Cr(III) and 0.57 mg/L Cr(VI). The standard added recoveries for Cr(III) and Cr(VI) are 90.0%-102.0% and 97.5%-105.0%, respectively. The proposed method can be used to determine the content of Cr(III) and Cr(VI) in electroplating wastewater.