# Study of Oxidative-Reductive Potential Changes in the Enrichment of Oxidized Polymetallic Ores
## 2 Materials and Methods
\begin{table}
\begin{tabular}{l c} \hline \hline
**Mineral/Phase Group** & **Content (\%)** \\ \hline Sulfide minerals (total): & 0.37 \\ \hline Galena (PbS) & 0.16 \\ \hline Sphalerite (ZrS) & 0.12 \\ \hline Copper sulfide minerals (e.g., Cu\({}_{2}\)S) & 0.04 \\ \hline Pyrite (FeS\({}_{2}\)) & 0.05 \\ \hline Oxidized phases (total): & 6.47 \\ \hline Oxidized and residual lead compounds & 0.89 \\ \hline Oxidized and insoluble zinc compounds & 1.07 \\ \hline Iron oxides (goethite, hematite) & 4.51 \\ \hline Silicate minerals (total): & 84.39 \\ \hline Mica group minerals & 53.44 \\ \hline Quartz (SiO\({}_{2}\)) & 30.95 \\ \hline Other phases (calcite, etc.) & 8.77 \\ \hline Total & 100.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Results of the X-ray phase composition. Figure 1: Results of the X-ray phase composition of the ore sample. As seen in Table 3, the ore's valuable components are unevenly distributed across size fractions. A substantial proportion of lead (about 32% of Pb) and zinc (\(\sim\)15% of Zn) are found in the finest fraction (\(\sim\)0.045 mm), even though that fraction represents only \(\sim\)16.8% of the mass. The coarsest fraction (-2 + 1 mm) contains a large share of both metals (around 28.6% of Pb and 32.7% of Zn in about 39.8% of the mass). The intermediate fractions contribute the rest. These data indicate that a significant amount of lead, in particular, is concentrated in the fines, which often consist of oxidized lead compounds liberated from the gangue upon crushing. The relatively low grades of Pb and Zn in all fractions (all below 2% Zn and 1% Pb) reflect the overall low tenor of the ore and the diluting effect of the abundant gangue. The ore sample preparation for the study was carried out using the wet grinding method with a laboratory ball mill featuring a rotating axis (MShL-7; 40 ML, \"Mekhanobr-Tekhnika\", St. Petersburg, Russia). For subsequent flotation tests, the optimal grinding fineness of \(-\)0.071 mm, with 70% passing, was determined. Flotation tests were conducted using tap water, and the results of the analysis are presented in Table 4. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Particle Size**} & \multirow{2}{*}{**Yield, \%**} & \multicolumn{2}{c}{**Content, \%**} & \multicolumn{2}{c}{**Recovery, \%**} \\ \cline{3-6}  & & **Zn** & **Pb** & **Zn** & **Pb** \\ \hline \(-2+1\) & 39.78 & 0.58 & 0.65 & 32.67 & 28.59 \\ \hline \(-1+0.5\) & 18.48 & 1.11 & 0.77 & 29.37 & 15.76 \\ \hline \(-0.5+0.2\) & 14.73 & 0.49 & 0.50 & 10.29 & 8.23 \\ \hline \(-0.2+0.1\) & 6.45 & 0.67 & 0.88 & 6.17 & 6.32 \\ \hline \(-0.1+0.071\) & 1.99 & 1.10 & 1.80 & 3.12 & 3.99 \\ \hline \(-0.071+0.045\) & 1.79 & 1.49 & 2.68 & 3.81 & 5.34 \\ \hline \(-0.045+0\) & 16.78 & 0.61 & 1.70 & 14.57 & 31.77 \\ The initial sample & 100.0 & 0.70 & 0.90 & 100.0 & 100.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Granulometric composition of the ore sample (crushed to 2 mm), with zinc and lead distribution across size fractions. Figure 2: Characteristics of sphalerite and galena inclusions. Spl—sphalerite, Chp—chalcopyrite, Cv—covellite, Gn—galena. The water analysis indicates moderately hard water (total hardness \(\sim\)9.8 \({}^{\circ}\)dH, with calcium and magnesium present) and near-neutral pH. Floration concentration was carried out using standard laboratory mechanical flotation machines of the Mekhanobr type (FML-3) (St. Petersburg, Russia), with cell volumes of 3 and 1.5 L. The impeller diameter was 70 mm, the air intake rate through the impeller was 0.07 L/s, and the froth scraper rotation frequency was 0.25 s\({}^{-1}\). The ore pulp density in flotation was about 30% solids by weight (specific gravity of the ore \(\sim\)2.70 g/cm\({}^{3}\)).