A spectroelectrochemical investigation of the influence of sodium diisobutyldithiophosphinate on silver dissolution in aqueous cyanide

Polarization studies have been carried out to determine the influence of diisobutyldithiophosphinate (DIBDTPI) on the dissolution of silver in cyanide solutions at pH 11. DIBDTPI was found to inhibit dissolution at concentrations similar to those used when this compound is applied as a flotation collector. The inhibition efficiency in 10(-2) mol dm(-3) CN- was found to increase with increase in DIBDTPI concentration in the range 10(-6)-10(-4) mol dm(-3), and with increase in time of exposure of the silver to the DIBDTPI solution. The inhibition efficiency found for 10(-4) mol dm(-3) DIBDTPI in quiescent 10(-2) mol dm(-3) CN- solution at 23 degreesC was 64.6% and 95.0% for exposure times of 10 min and 2 h, respectively. These values are significantly less than those found previously for 2-mercaptobenzothiazole under the same conditions. Surface enhanced Raman spectroscopy showed that inhibition was associated with adsorption of DIBDTPI displacing cyanide from the silver surface. Voltammetry at 0.5 mV s(-1) indicated that adsorption of DIBDTPI involves charge transfer.