ETHYLXANTHATE ADSORPTION AND KINETICS OF ADSORPTION ON LEAD MODIFIED GALENA AND SPHALERITE UNDER FLOTATION CONDITIONS
The effect of lead ions on the galena and sphalerite surface properties, ethylxanthate adsorption and kinetics of ethylxanthate adsorption in alkaline medium were studied for the possible use of recycled flotation water. The flotation tests and the zeta-potential measurements were carried out and correlated with the results of the infrared attenuated total reflection spectrophotometry (ATR–IR) and UV data. Lead adsorbed on the galena or sphalerite surface as Pb(OH) + and less as Pb 2+ reduces the collectorless galena floatability from pH 7 to 9.5, but has a strong activating effect on natural sphalerite floatability (in pH range 7.6–10.5). After collection of Pb-modified minerals with K-ethylxanthate both forms of lead ethylxanthate, monolayer Pb–EX (chemically adsorbed (EX) – ), and multilayer, physically adsorbed Pb(EX)2, were detected on the mineral surfaces. Sphalerite floated nearly 100% in the examined pH range, but galena floated better only from pH 8 to 9.5 (85–95%). The main surface reaction in pH range 8–9.5 is probably the ion-exchange reaction M–Pb–OH + (EX) – = M–Pb–EX +(OH) – (M – mineral), which contributes to the chemical adsorption of (EX) – as monolayer –Pb–EX, on the surface of either of the mineral. The reaction between Pb-treated mineral and (EX) – ion is the reaction of pseudo-first order (on Pb-modified galena – rate constant is k = 0.711 min –1 ; on Pb-modified sphalerite k = 0.102 min –1 ).