Mechanism of synergistic pretreatment with ultrasound and ozone to improve gold and silver leaching percentage

Effective removal of As from a high arsenic-bearing ZnSO4 solution by ultrasonic enhanced ozonation in a one-pot method

“…To effectively oxidize both As(III) and Fe 2+ in a ZnSO 4 solution, the use of ozone, which possesses stronger oxidizing properties than oxygen, is an effective approach. Gui et al's study demonstrated that ozone oxidation can significantly enhance the leaching rates of gold and silver [31] . Fig.…”

“…Ultrasound (US) can improve the mass transfer and decomposition process of ozone in solution while also promoting the generation of free radicals. Therefore, it can significantly enhance the oxidation effect of ozone [31] . US refers to sound waves with a frequency greater than 20,000 Hz, which possess strong penetration abilities and propagate efficiently within liquids.…”

“…Gui et al demonstrated that the combination of US and ozone can significantly enhance the leaching rate of gold in refractory gold ores, increasing it from 49.1% to 93.5%. This is mainly attributed to US significantly suppressing the secondary inclusion layer caused by surface pyrite, refining the ore particle size, and reducing the reaction resistance [31] .…”

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] , …”

“…It is widely accepted that ultrasound can be classified into two types: (i) low frequency ranging between 20 kHz and 2 MHz, where acoustic cavitation is generated and applied to induce and enhance chemical reactions and processes [23] ; and (ii) high frequency sonic waves in the range of 2–10 MHz, which are principally adopted in the field of diagnostic [24] . In recent decades, the utilization of ultrasound for the leaching of metal ores [17] , [19] , [25] , [26] , [27] , [28] , [29] , [30] , [31] , [32] and secondary resources [15] , [33] , [34] , [35] , [36] , [37] , [38] , [39] , [40] , [41] has gained increasing attention in hydrometallurgical fields, due to the increased leaching recovery, shortened leaching time, and reduced reagent consumption, which are induced by the cavitation, mechanical, and thermal effect of ultrasound. As presented in Fig.…”