Effective Dissolution of Tin Using Electrolytically Oxidized Alkaline Solution

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Tin (Sn) is used as solder and plating in electronic devices, and its recycling is becoming increasingly important. Hydrometallurgical processes can be performed using small-scale plants without consuming large amounts of energy. Considering the strongly amphoteric nature of Sn, its dissolution (or corrosion) with alkaline solution (pH ~14) is an attractive technique for its selective extraction from various secondary resources. Sn and its alloys exhibit high corrosion resistance, and appropriate oxidants are required for their efficient dissolution. Recently, the iodate ion (IO3 −) was reported to be one of the most effective oxidants for dissolving Sn into alkaline solutions without much heating.When Sn and its alloys are immersed in the IO3 −-containing solution, their dissolution rates decrease with increasing consumption of the oxidant (i.e., the reduction of IO3 − ions to iodide ions (I−)). To overcome this, in this study, we propose to regenerate the consumed IO3 − using electrolysis, as illustrated in Figure 1. A KI-added 1 M NaOH solution were kept in an electrolytic cell with a cation exchange membrane and then electrolyzed at ~20 °C using graphite as the anode and nickel as the cathode. After electrolysis, the concentrations of the IO3 − and I− ions in the solution were analyzed by liquid chromatography. The results showed that the I− ions can be anodically oxidized to IO3 − ions with a current efficiency of near 100%. Furthermore, when the metallic Sn samples were immersed in the anode compartment of the cell during or after electrolysis, they dissolved rapidly. The results obtained in this study indicate that the dissolution and extraction of Sn using IO3 −-containing alkaline solutions can be achieved more efficiently by combining with electrolysis. Figure 1