Improvement of Alumina Dissolution from the Mechanically Activated Dross Using Ultrasound-Assisted Leaching

Abstract

Aluminum dross results from the re-melting of used aluminum cans, and is a valuable resource containing alumina. In general, aluminum dross contains oxides of Al, Ca, Fe, Mg, Si and Ti and some salts. As a continuation of the previous work to recover pure alumina from the dross, the effect of employing ultrasound wave in the NaOH solution was investigated to improve the leaching percentage of alumina from the mechanically activated dross. The use of ultrasound improved the leaching percentage of alumina from 35% to 60% and resulted in a leaching solution where the purity of aluminate ion was 99%. Among the optimum conditions (5 M NaOH, 50 o C, 4 h, pulp density of 100 g/L and ultrasonic power 100 W), leaching time had a remarkable effect on the dissolution of alumina in the presence of ultrasound. The combined effect of ultrasound and the addition of CaCl 2 and organic acids to the NaOH solution was also investigated. Roasting of the black dross with CaCl 2 followed by ultrasound leaching did not improve the leaching percentage of alumina. The presence of organic acids in the NaOH solution increased the leaching percentage of alumina as well as silica, and thus was not favorable for recovering pure aluminate solution from the black dross.

A comprehensive review on the ultrasound-enhanced leaching recovery of valuable metals: Applications, mechanisms and prospects

“…Ultrasound-assisted leaching technology has been extensively applied to extract valuable metals from metal ores, such as vanadium-bearing shale [16] , [19] , chalcopyrite [26] , [49] , scheelite [25] , [50] , [51] , zinc oxide ore [30] , [52] , [53] , nickel laterite ore [17] , rare earth ore [29] , refractory gold ore [27] , [54] , [55] , [56] , [57] , [58] , uranium ore [59] , [60] , K-feldspar [31] , copper-bearing biotite [43] , refractory silver ore [61] , eudialyte [62] , quartz sand [63] , [64] , [65] , [66] , [67] , [68] , poly-metallic sulfide ore [13] , deep-sea nodules [69] , phosphorus-potassium associated ore [21] , sphalerite [32] , and magmatic rocks [70] . In addition, ultrasound-assisted leaching has also been developed with successful enhancement in the leaching efficiency of metals from secondary resources, including metallurgical residues [3] , [15] , [35] , [38] , [39] , [42] , [48] , [71] , [72] , [73] , [74] , [75] , [76] , [77] , [78] , [79] , [80] , [81] , [82] , [83] , [84] , [85] , [86] , spent catalysts [33] , [37] , …”

“…Li et al [137] reported that the leaching ratio of Al from quartz sand was increased from 12.22% to 42.25% with Na 2 CO 3 under ultrasound irradiation for only 25 min. Nguyen and Lee [79] also proposed the ultrasound-assisted NaOH leaching technique for the recovery of Al from aluminum dross, and it was obviously found that the leaching percentage of Al was improved from 35% to 60% with the use of ultrasound. In the meanwhile, researchers attempted to combine ultrasound with other processes to further improve the leaching recovery of Al.…”

Leaching of Rare Metals from Spent Petroleum Catalysts by Organic Acid Solution

“…Generally, the valuable metals in spent catalysts are recovered by leaching with either water after soda roasting or strong acid/base solutions 3,7,8) . The disadvantages of roasting followed by leaching are high consumption of energy 9) .…”