Alternative Lixiviants to Cyanide for Leaching Gold Ores

Toward Eco‐Friendly E‐Waste Recycling: New Perspectives on Ozone‐Assisted Gold Leaching

“…[57] Complexing agents like halide anions promote gold dissolution. [13] While chlorides, bromides, and iodides were initially considered in this work, both bromide and iodine were rejected due to safety concerns. Even at low concentrations, these halide anions can be oxidized at lower potentials than chlorides and released in significant amounts, such as bromine and iodine, which are hazardous.…”

“…[9] Thiosulfate is an excellent alternative to cyanide, with high selectivity toward gold and very mild conditions. [10][11][12][13] However, the current technologies do not make this approach economically viable. The thiosulfate-based gold leaching processes are still far from large-scale application because the overall gold recovery is generally lower than in other commonly used processes and the reagent consumption is high.…”

“…The most commonly employed complexing agents are Cl À and Br À in acidic media, while cyanide and thiosulfate anions promote dissolution in alkaline media. [7,13,[40][41][42][43][44] Our group has extensively studied platinum and gold dissolution by examining the influence of potential, pH, temperature, and the presence of halides on both anodic and cathodic dissolution from polycrystalline samples. [45][46][47] The dissolution is also affected by the size of gold nanoparticles (NPs).…”

Challenges and opportunities in the recovery of gold from electronic waste

“…Other alternatives to cyanide include halide leaching, whereby the strong oxidants Cl 2 or Br 2 are generated in situ , either electrochemically or by reaction between sulfuric acid and hydrochloric or hydrobromic acid or a halide salt, with the latter reported as effective in copper leaching. 47,62,63 Other oxidants such as O 2 , Cu( ii ), Fe( iii ) or nitric acid are also used in addition to halides, 53 and the non-toxic ammonium persulphate is reported to have greater lixiviant properties than potassium or sodium persulphate. 64 More recently, synergistic mixtures of N -bromosuccinimide (NBS, a strong oxidant) with pyridine (py, an effective complexing ligand) have been found to offer a cheap and low-toxic route to selective gold leaching ( Fig.…”

Eco-friendly and rapid extraction of gold by in-situ catalytic oxidation with N-bromosuccinimide

“…In fact, Br 2 had been utilized for gold extraction since the end of the XIX century [ 23 ]. However, the leaching environment is acidic and Br 2 is volatile, corrosive and toxic, which is not conducive to its development [ 9 , 22 , 27 ]. Its application as an alternative to cyanide has been downplayed due to its hazard and extreme difficulty in storing or transporting under safe conditions [ 23 ].…”