Comparison of Lead Alloy Anode and DSA Titanium Anodes in Metal Electrowinning

Comparison of Lead Alloy Anode and DSA Titanium Anodes in Metal Electrowinning

Lead alloys are not dimensionally stable, since they slowly dissolve in electrolytes, leading to problems such as changes in the gap between the anode and cathode and product contamination by lead. Dimensionally stable anodes have brought considerable improvements to the field of electrowinning which includes:
(i) lower half-cell potential,
(ii) use of higher current densities,
(iii) lower gas bubble effect through special anode designs,
(iv) no loss of anode material, thus keeping the electrolyte pure,
(v) no contamination of cathode deposits
(vi) high current efficiency, and simple cell constructions.

The success of DSA anodes has been attributed to the chemical stability that allows them to maintain nearly constant dimensions during the life of the anode even when operating in environments with very low pH values. DSA anodes have been reported to have consumption rates as low as 1 mg/amp. yr due to their stability, and thus can be operated at high current densities (greater than 200 A/m2). High current densities result in high yields of metal deposits. DSA technology can result in up to 20-25% power savings compared to the lead counterparts.

In the search for the most suitable DSA-type electrode for oxygen evolution in acidic solutions, scientists examined the microstructural properties, electrocatalytic activity, and anodic stability. They found that Ti/IrO2 -Ta2O5 was the best electrode for oxygen evolution in acidic media. The anode was associated with high catalytic activity and service life. The service life of Ti/IrO2−Ta2O5 with 70 mol % IrO2 was estimated to be 5−10 years in electroflotation applications.
 
Although the reduction of the oxygen overvoltage via the use of DSA anodes may be expensive, continuing advances in anode materials and further increases in energy costs will undoubtedly lead to the wider acceptance of anodes having low oxygen overpotential such as DSA anodes in copper electrowinning. DSA-type electrodes show good technological performance and their success is due to desirable features such as high stability of the active coating, good overall performance under mild conditions, high conductivity, and commercial availability.

The energy consumed in the electrowinning of metals accounted for a substantial portion of the overall cost of metal production. Since 50-60% of the energy is consumed in the anode reaction alone, the appropriate anode selection is crucial. Science carried out an experiment comparing a dimensionally stable anode and an antimonial lead anode in 200 g/l sulphuric acids and found that the anode potential for the lead alloy anode was much higher than that of the DSA anode.