(Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy,
Chicago, 1991,368P)
H Liu, Y. Wu, A. Tan, J. Huang, J. Xu and X Zhao
Center for Process Analytical Chemistry, Central South University
of Technology, Changsha, P. P. China.
In zinc hydrometallurgical plant in China, germanium content in zinc sulfate purification solution directly affects the quality of cathode deposit and need to be controlled (lowered) to certain limit (0.05 mg/L) before elctrolysis.
An automatic system for the determination of trace germanium for the zinc sulfate purification process has been developed using a home-made on-line spectrophotometric analyzer which is based on flow injection analysis and microcomputer techniques. The colorimetric system used is salicyl fluorome (SAF) in the presence of surfactant p-octyl polyethylene glycoophenyl ether (OP) under 1M HCl acidity. The influence of sample turbidity is overcome by a dual-wavelength approach. In order to obtain enough sensitivity, a 5-cm flow cell is used and the pump is stopped for 20 seconds before the measurement of absorbance.
Since instrument zeroing and standard calibration can be performed automatically, instrument shift and the variation in the experiment conditions are compensated adequately and reliable results can be obtained for a relative long period of time without any attendence.
An analysis including zeroing, calibration, measurement of absorbance and calculation can be completed in 4 minutes (in 2 minutes without calibration). A sample containing 0.04 mg/L germanium was analyzed every 30 minutes in 24 hours and 48 data were obtained with the mean at 0.0392 g/L and a relative standard deviation of 2.3%. The system is fast, sensitive, selective and reliable enough for the process monitoring of germanium in zinc hydrometallurical plant.
* This work was partly supported by ZhuZhou Smelter.