【正文】 cy of zinc and aluminum respectively using 3% H2SO4acid. It can be seen that at 45 Cand after 1 h both zinc and aluminum metals pletelygo into solution. It is also seen that at lower temperature or after shorter time the leached amount of thedissolved metals decreases.A separate set of experiments have been conducted toelaborate the eC128ect of acid concentration on the leaching percentage of these metals from the dross sample.Experimental conditions with respect to temperatureand time are maintained constant at the optimum levels.Table 1Metal content of zinc solder dross sampleMetal Tin Lead M Zinc TotalPercentage Table 2Xray diC128raction data for zinc solder dross sample, leaching residue and recovered pounds from the drossSample Main interplaner spaces, A ASTM cardno. Identified poundZinc solder sampe 40831 Zn 211486 ZnO 221034 (99Al2Oe)ZnO 40686 Pb 23331 Pb2O3 4673 (Sn)4U 251259 Sn2O3Residue after H2SO4leaching 361461 PbSO4 40686 Pb 331374 SnO2Produced aluminium carbonate 1483 Ca4Al2CO9.11H2OProduced zinc carbonate 30787 2.4H2OCrystalline zinc sulphate 12781 ZnSO4.H2OFig. 2. EC128ect of leaching time on leaching percentage of zinc from thedross using diC128erent sulphuric acid concentrations.Fig. 3. EC128ect of leaching time on leaching percentage of aluminumfrom the dross using diC128erent sulphuric acid concentrations.. Barakat/Waste Management 19 (1999) 503–507 505Results are shown in Fig. 7. It can be seen that acidconcentration does not aC128ect the leaching of tin or lead.It is worthy to note that aluminum leaching percentageis very small at acid concentration lower than 3%. Withhigher acid concentration (3%), plete leaching ofthe metal concerned is achieved. With zinc, the leachingpercentage increases gradually with increase in acidconcentration approaching plete metal dissolutionat acid concentration 3%.Fig. 8 demonstrates the eC128ect of pH on the precipitation recovery of zinc from solution as basic zinc carbonate. It can be seen that precipitation of zinc carbonatetakes place at pH 5 with recovery e ciency of about10%. The recovery e ciency increases gradually to% with increase of pH up to , this is followed bya drastic increase in the recovery amounting to % atpH . At higher pH values more than , the %recovery increases gradually with pH reaching a nearlyplete recovery for zinc at pH . This means thatthe suitable medium for zinc carbonate precipitation isnearly neutral.The purity of the obtained pounds was investigated by Xray diC128raction technique (data is shown inTable 2) besides chemical analysis. Mass balance for theinput and output products was calculated and nearly nolosses were observed.Fig. 5. EC128ect of leaching temperature on leaching percentage of zincwith 3% sulphuric acid at diC128erent times.Fig. 4. EC128ect of leaching time on leaching percentage of lead and tinfrom the dross using diC128erent sulphuric acid concentrations.Fig. 6. EC128ect of leaching temperature on leaching percentage of aluminum with 3% sulphuric acid at diC128erent times.Fig. 8. EC128ect of pH on the recovery percentage of zinc from solutionas basic zinc carbonate.Fig. 7. Leaching percentage of the metals from the dross as aC128ectedby sulphuric acid concentration at the optimum leaching parametersof time and temperature.506 . Barakat/Waste Management 19 (1999) 503–5074. ConclusionThe main finding of this work is that the metal content of a zinc solder dross sample co