recoveryofmetalvaluesfromzincsolderdross-外文文献(编辑修改稿)

recoveryofmetalvaluesfromzincsolderdross-外文文献(编辑修改稿)内容摘要：

analysis and Xray diC128raction data for thesolder dross sample are shown in Tables 1 and 2respectively. From Table 1 it is seen that zinc is themajor ponent of the dross (%) while aluminumis the minor element (%). The total metal content isequal to about 96%, the remaining percentage (4%)exists as metal oxides as shown from Xray data.Figs. 2–4 illustrate the eC128ect of leaching time on theleaching of the concerned metals into solution usingH2SO4acid of diC128erent concentrations at diC128erent temperatures. In Fig. 2 it can be seen that leaching of zincincreases with increase of acid concentration, pleteleaching of zinc was achieved by using 3% H2SO4acidfor 1 h at 60 or 80 C. It can also be seen that theleaching e ciency is less sensitive to time and temperature parameters as pared to acid concentrationeC128ect. This can be explained as follows: zinc can easilydisplace the hydronium ions of the reacting acid due tothe higher electrode potential value of zinc ( volt)and this promotes dissolution of zinc in the attackingacid more readily. The reaction is thus a function of theFig. 1. Flowchart of the recovery of valuable salts of zinc, aluminum,lead and tin from zinc solder dross.504 . Barakat/Waste Management 19 (1999) 503–507(H+) concentration. By plotting a graph between acidconcentration and the weight of both the leached andundissolved metals in the leaching solution under theconditions used in this work (the graph is not given) itwas found that acid dissolution is kiically zero orderreaction. In Fig. 3, the leaching percentage of aluminumwith 1 and 2% acid is very poor (%). Completeleaching for aluminum is only achieved with 3% acidconcentration at 60 C for 1h.Zn H2SO4! ZnSO4 H2 1 2Al 3H2SO4! Al2SO4 3 3H2 2 Fig. 4 illustrates the leaching e ciency of lead and tinas aC128ected by leaching time. It is seen that the majoramount of lead (%) and all the tin content of thedross were kept as a residue in the leaching solution.From the Xray data shown in Table 2, it can be seenthat the residue was posed of metallic lead, leadsulphate and tin dioxide. This is due to the lower attackof the concerned metals with dilute H2SO4. However,the oxide fraction of lead reacts with the acid to formlead sulphate.Figs. 5 and 6 show the eC128ect of leaching temperatureon the leaching e ciency 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 2.4H2OCrysta。