We modified a rapid method for determining carbonate content and applied to some iron and steel slags. One gram of pulverized slag sample is weighed into an air-tight plastic bag fitted with stop cock and heat-sealed. The bag is evacuated to remove air, 35 mL of 0.7 mol/L iron(III) chloride and 200 mL of air are introduced through the stop cock and the contents are allowed to react for 20 min with occasional shaking. Carbon dioxide content of the air inside the bag is determined with the aid of carbon dioxide detector tube. The carbonate content of the sample is calculated by summing the amount of carbon dioxide in the air phase and that dissolved in the solution, the latter is calculated by using the Henry’s law. The method was successfully applied to an air aged converter slag sample and samples taken from slag-paved woodland paths. The carbonate content ranged from 0.26 to 0.83 mol/kg. The paving materials that had been exposed to the atmospheric air and soil air contained more carbonate.
Spent zinc-carbon batteries and alkaline batteries contain manganese dioxide, but they are buried in landfill sites without being recycled in Japan. Manganese dioxide is nobler than metal copper. The contact between both materials causes galvanic interactions, and manganese dioxide acts cathode to be reduced while copper reacts as anode to be oxidized. We have investigated the galvanic leaching of copper in shredded printed circuit boards using manganese dioxide recovered from spent zinc-carbon batteries. The dissolution of copper was enhanced in the presence of manganese dioxide in sulfuric acid solution with pH 1.0. The extraction yield of copper was 90% in the presence of manganese dioxide in 8 hour leaching while 16% of copper dissolved in the absence. Effects of factors such as pH, amount of manganese dioxide and temperature on the leaching of copper were also examined.