Typical UV–visible spectra of ethyl xanthate adsorption and desorption
on Cp at different pulp potentials are shown in Fig. 2. A 38 ppm sodium
ethyl xanthate stock solution was prepared and analysed as a
baseline. Two absorbance peaks were observed at 301 nm and 226 nm
corresponding to xanthate [23–25]. After the initial 150 g of ground
Cp was added to the 38 ppm xanthate solution, it was conditioned for
5 min prior to the collection of an absorbance spectrum (Fig. 2-(2)).
The peaks at wavelengths 301 nm and 226 nm disappeared indicating
the adsorption of xanthate on to the Cp surface.When Ehwas decreased
to−100 mV a peak at 301 nm corresponding to xanthate and a peak at
346nmcorresponding to perxanthate [26,4]were observed (Fig. 2-(3)).
These results showthe removal of xanthate fromCp surface at reductive
potentials. As the Eh of the slurry was further decreased to −200 mV,
the concentration of xanthate desorbed from Cp surface was increased.
Adsorption and desorption of xanthate at different potentials as
measured by UV–vis spectra are tabulated in Table 1.