recoveryofmetalvaluesfromzincsolderdross-外文文獻(xiàn)(已修改)
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【正文】 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。 Acid leaching。 Zinc。 Aluminum。 Lead。 Tin。 Recovery。 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 behind a toxic slagwhich is disposed in land fill. The hazardous eC128ects ofsuch toxic materials on man’s health, such as damage ofkidney tissue and interfering with the central nervoussystem and the brain are well known [1,2].DiC128erent hydrometallurgical processes have been investigated for recovery of zinc, aluminum, lead and tin andtheir salts from waste materials such as dross, dust, slag,etc. Christian and Joseph [3] studied the recovery of Zn,Pb,Al, Cr, Ni or Sn from wastes. They used acid leachingand subsequent electrochemical or chemical oxidationwith an oxidizer such as air, oxygen, H2O2or KHS2O8with precipitation of the metals as hydroxides. Leachingwith HCl or H2SO4, selective precipitation, dissolution,cementation and electrolysis were used for metal recoveryfromwastematerialscontainingzincandlead[4]. Metalliclead and ZnCO3were recovered after leaching withHCl, while metallic zinc and PbSO4were recovered afterleaching with H2SO4. Myerson and Cudahy [5] studiedthe recovery of Zn, Cu, Pb, Sn and Cd by leaching withH2SO4followed by neutralizing the acidic solution withZnO or Zn(OH)2and cementing the final products tothe metal values. Thiele et al. [6] used 1–5 M H2SO4forrecovery of aluminum and zinc. Zinc was recoveredfrom solution as: zinc sulfate by vaporization and crystallizatio
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