【正文】 uld be recovered.The recovery processes included two stage sulphuric andhydrochloric acid leaching processes followed by selective precipitation and separation for the salts of theconcerned metals. The optimum leaching conditionswere achieved by using 20 ml of 3% H2SO4acid/g drossfor 1 h at 45 C. Aluminum was selectively precipitatedas calcium aluminum carbonate by treating the sulphateleachate with limestone at pH . Zinc sulphate solution was either dried to obtain zinc sulphate crystals orprecipitated as basic zinc carbonate at pH . Theundissolved lead and tin were leached with 5 M hothydrochloric acid. About 73% of lead content wasrecovered as pure lead chloride by cooling the leachedproducts down to room temperature. The remaininglead was recovered as lead hydroxide at pH . Tin wasrecovered as hydrated tin oxide by alkylation withcaustic soda at pH . Recovery e ciency of the metalsalts was , , and % for Zn, Al, Pb andSn respectively. The obtained products meet the standard specifications with relatively low costs. Pollutionhazards associated with pyrometallurgical treatmenteconomic with no accumulation of secondary waste.AcknowledgementsThe author is indebted to Prof. Koike, Mr. Takasakiand Mr. Okamoura, Mining College, Akita University,Japan, for their assistance in saving the equipment andchemicals of this work.References[1] Neshkov NS. Gig Truda 1971。 Lead。Recovery of metal values from zinc solder dross. Barakat*Industrial Wastes Laboratory, Extractive Metallurgy Deptartment, CMRDI, PO Box 87 Helwan, 11421, Cairo, EgyptAccepted 20 July 1999AbstractZinc solder dross containing % Sn, % Pb, % Al and % Zn was leached with 3% H2SO4at 45 C for 1 h. Zincand 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 . Zinc sulphate solution was either evaporatedto obtain zinc sulphate crystals or precipitated as basic zinc carbonate at pH . The undissolved lead and tin were leached with 5 Mhot hydrochloric acid. The major part of lead chloride ( 73%) was separated by cooling the leached products down to roomtemperature. From the soluble fraction, tin was recovered as hydrated tin oxide by alkylation with caustic soda at pH , while theremaining lead was separated at pH as lead hydroxide. A process flowsheet had been suggested which involved twostagehydrometallurgical treatment. Parameters aC128ecting the recovery e ciency of the suggested method such as temperature, time, pHand acid: solid stoichiometric ratio were investigated. Results obtained revealed that the optimum leaching conditions wereachieved by using 20 ml of 3% H2SO4acid/g dross for 1 h at 45 C. Recovery e ciency of the metal salts was , , and% for Zn, Al, Pb and Sn respectively. Recovery e ciency was related to the solubility of the concerned salts under the givenexperimental conditions. 1999 Elsevier Science Ltd. All rights reserved.Keywords: Solder dross。 Aluminum。 Separation1. IntroductionAbout 50 tons of zinc solder dross are accumulatedannually during melting processes of zinc metals in onepany. The waste material contains toxic heavymetals such as zinc and lead, it is generally treated bypyrometallurgical processes. This results in the release ofthe toxic fugitive particles of Pb and Zn in air as theypossess relatively low melting and boiling points. Thustotal solid particle (TSP.) limits will overweigh thestandard limit according to pollution laws. Pyrometallurgical treatments also left behin