電解法による希薄溶液からのクロム酸イオンの回収

抄録

The recovery of chromate ions from dilute solutions in low voltage electrolysis has been investigated in relation to the effects of diaphragm components and applied voltages. Mixtures of SiO₂ and Al₂O₃ powders and several kinds of porous refractory tubes were used as diaphragm materials. A netlike cathode was used in close contact with the diaphragm in order to remove the chromate ions quickly out of the cathode solution as they were formed. The chromate concentration in the cathode solution decreased logarithmically to the lower limit when the voltage of more than 6 volts was applied. The chromate ion elimination rates increased parabolically in the range of 6-20 volts but were not affected appreciably by the voltage more than 20 volts. The rates were independent of the diaphragm component in the Al₂O₃ range of 0-60% but decreased with increasing ratio of more than 60% Al₂O₃. The lower limit of chromate concentration was less than 3ppm for diaphragms consisting of less than 60% Al₂O₃ and increased with increasing Al₂O₃ content of more than 60%. Chromate ions can be thus recovered electrolytically from dilute solutions in a short time by use of the diaphragm containg more than 40% SiO₂ and in the range of 20-30 volts.