Zinc solder dross containing 14.8 percent Sn, 16.3 percent Pb, 0.41 percent Al and 64.5 percent Zn was leached with 3 percent H_2 SO_4 at 45 deg C for 1 hour. Zinc and aluminum went into solution, whereas lead and tin remained with the residue. Aluminum was selectively precipitated as calcium aluminum carbonate by treating the sulphate leachate with limestone at pH 4.8. Zinc sulphate solution was either evaporated to obtain zinc sulphate crystals or precipitated as basic zinc carbonate at pH 6.8. The undissolved lead and tin were leached with 5M hot hydrochloric acid. The major part of lead chloride (approx = 73 percent ) was separated by cooling the leached products down to room temperature. From the soluble fraction, tin was recovered as hydrated tin oxide by alkylation with caustic soda at pH 2.4, while the remaining lead was separated at pH 8.5 as lead hydroxide. A process flowsheet had been suggested which involved two-stage hydrometallurgical treatment. Parameters affecting the recovery efficiency of the suggested method such as temperature, time, pH and acid solid stoichiometric ratio were investigated. Results obtained revealed that the optimum leaching conditions were achieved by using 20 ml of 3 percent H_2SO_4 acid I g dross for 1 hour at 45 deg C. Recovery efficiency of the metal salts was 99.1 percent, 99.4 percent, 99.6 percent and 99.5 percent for Zn, Al, Pb and Sn respectively. Recovery efficiency was related to the solubility of the concerned salts under the given experimental conditions.
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