gold recovery
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2022 ◽  
Vol 429 ◽  
pp. 132283
Author(s):  
Ivan Korolev ◽  
Pelin Altinkaya ◽  
Mika Haapalainen ◽  
Eero Kolehmainen ◽  
Kirsi Yliniemi ◽  
...  

2022 ◽  
Vol 32 (1) ◽  
Author(s):  
Yu-Fong Huang ◽  
Szu-Ling Chou ◽  
Shang-Lien Lo

AbstractRecycling of waste printed circuit boards (PCBs) has attracted increasing attention because of its high annually produced amount and high content of gold. In this study, gold recovery from waste PCBs was carried out by using the processes including microwave pyrolysis, acid leaching, solvent extraction and oxidative precipitation. The leaching efficiency of copper was approximately 95% when using a lixiviant composed of sulfuric acid and hydrogen peroxide, and the leaching efficiencies of gold were approximately 59, 95 and 95% by using thiourea, thiosulfate and aqua regia, respectively. The gold ions contained in the leachate previously produced by the leaching processes were not satisfactorily extracted by using organic solvents including di-(2-ethylhexyl)phosphoric acid, tributyl phosphate, dibutyl carbitol and trioctylamine, so the leachate was decided to bypass solvent extraction and directly apply to the oxidative precipitation process. By using the oxidants of hydrogen peroxide and perchloric acid, the precipitation efficiencies of gold were approximately 95 and 99%, and the final recovery rates were approximately 90 and 93%, respectively. The high recovery rates of gold can be attributable to the use of microwave pyrolysis that prevents the loss of gold caused by shredding and grinding processes. In addition, perchloric acid can provide higher selectivity for gold recovery than hydrogen peroxide. The maximum processing capacity of microwave pyrolysis of waste PCBs would be approximately 1.23 kg. The gold recovered from 1 t of waste PCBs can be sold for approximately USD 10,000, and thus the return on investment can be as high as approximately 1400%.


2021 ◽  
pp. 32-36
Author(s):  
O. S. Bryukhovetsky ◽  
A. G. Sekisov ◽  
A. V. Rasskazova ◽  
A. Yu. Lavrov
Keyword(s):  

2021 ◽  
pp. 128073
Author(s):  
Yanli Chen ◽  
Zhiwen Li ◽  
Rui Ding ◽  
Tingting Liu ◽  
Huijuan Zhao ◽  
...  

Minerals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1343
Author(s):  
Zhong-Sheng Huang ◽  
Tian-Zu Yang

Most studies conducted have focused on the pulp density, Fe3+ concentration and sulfuric acid concentration, etc., of bio-oxidation, and few have reported on the influence of different bio-oxidation methods on kinetics. In this study, a comparative investigation on refractory gold concentrate by batch and continuous bio-oxidation was conducted, with the purpose of revealing the kinetics influence. The results showed that improving the removal rates of the gold-bearing pyrite (FeS2) and arsenopyrite (FeAsS) yielded the best results for increasing gold recovery. The removal rates of S, Fe and relative gold recovery linearly increased when compared to the second-order equation increase of the As removal rate in both batch and continuous bio-oxidation processes. The removal kinetics of S and Fe by continuous bio-oxidation was 12.02% and 12.17% per 24 h day, approximately 86.64% and 51.18% higher than batch bio-oxidation, respectively. The higher removal kinetics of continuous bio-oxidation resulted from a stepwise increase in microbe growth, a larger population and higher dissolved Fe3+ and H2SO4 concentration compared to a linear increase by batch bio-oxidation. The cyanidation gold recovery was as high as 94.71% after seven days of continuous bio-oxidation, with the gold concentrate sulfur removal rates of 83.83%; similar results will be achieved after 13 days by batch bio-oxidation. The 16sRNA sequencing showed seven more microbe cultures in the initial residue than Acid Mine Drainage (AMD) at genus level. The quantitative real-time Polymerase Chain Reaction (PCR) test showed the four main functional average microbe populations of Acidithiobacillus, Leptospirillum, Ferroplasma and Sulfobacillus in continuous bio-oxidation residue as 1.08 × 103 higher than in solution. The multi-microbes used in this study have higher bio-oxidation activity and performance in a highly acidic environment since some archaea co-exist and co-contribute.


Minerals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1316
Author(s):  
Cindy Cindy ◽  
Ryotaro Sakai ◽  
Diego M. Mendoza ◽  
Kojo T. Konadu ◽  
Keiko Sasaki

Environmentally friendly pretreatment of double refractory gold ores (DRGO) to improve gold recovery without emitting pollutant gas is challenging. Sequential biotreatment, including iron-oxidizing microorganisms to decompose sulfides, followed by the enzymatic decomposition of carbonaceous matter, was recently developed. The effect of acid washing by 1 M HCl for 24 h between two bioprocesses was evaluated using a real double refractory gold ore from the Syama mines, Mali, which includes 24 g/t of Au and 5.27 wt % of carbon with a relatively higher graphitic degree. The addition of the acid washing process significantly improved gold recovery by cyanidation to yield to 84.9 ± 0.7% from 64.4 ± 9.2% (n = 2). The positive effects of acid washing can be explained by chemical alteration of carbonaceous matter to facilitate the accessibility for lignin peroxidase (LiP) and manganese peroxidase (MnP) in cell-free spent medium (CFSM), although the agglomeration was enhanced by an acid attack to structural Fe(III) in clay minerals. Sequential treatment of DRGO basically consists of the oxidative dissolution of sulfides and the degradation of carbonaceous matter prior to the extraction of gold; however, the details should be modified depending on the elemental and mineralogical compositions and the graphitic degree of carbonaceous matter.


2021 ◽  
Author(s):  
L.V. Semushkina ◽  
◽  
S.M. Narbekova ◽  

The aim of the work is the flotation processing of gold-containing tailings using composite flotation (CF) agents. According to the results of chemical analysis, the studied tailings sample contains 0.39 g/t gold. The main part of the initial tailings sample is represented by rock-forming minerals such as quartz, clinochlore, microcline, tremolite, albite, calcite, and muscovite. According to the results of the rational analysis, 39.50% of gold is in the hard-to-recover form with quartz; 28.87% is in the form of fine-grained gold; 31.63% is in intergrowths with sulfides and rocks. The optimum reagent scheme of flotation processing of tailings was chosen: degree of regrinding of 95% of grade -0,074 mm, consumption of sodium butyl xanthate of 100 g/t, consumption of foaming agent T-92 of 30 g/t. Under the chosen reagent scheme the gold-containing concentrate containing 6,4 g/t gold at the recovery of 49,68% was obtained. Preliminary regrinding of tailings allows to increase the gold recovery in the blanks concentrates by 27.96%. The reagent scheme of flotation of gold-containing tailings with the application of composite flotation (CF) agent was tested. A composition of sodium butyl xanthate and reaeflot was used as a composite flotation reagent for the improvement of gold extraction from flotation tailings. Application of composite flotation (CF) agent pre-treated on the dispersant increases gold recovery into gold-containing concentrate by 4.65%, in comparison with the basic collector sodium butyl xanthogenate. Consumption of flotation agent CF is reduced by 20%.


2021 ◽  
Vol 1 (7) ◽  
pp. 35-44
Author(s):  
Sergei I. Evdokimov ◽  
◽  
Tatiana E. Gerasimenko ◽  

Research objective is to address an up to date task of developing the technology of associated gold recovery from complex ore. Object of research is the gold-bearing copper-pyrite ore. Gold was recovered in laboratory conditions with the use of gravity methods of mineral separation. Research tools. Rational modes of machinery operation have been determined through mathematical planning of experiments including the obtained results processing by mathematical and statistical methods. Methods of research. Gold was recovered in the grinding-classification circuit based on a seriesinstalled short-cone hydrocyclone, a jigging machine and a shaking table. Research results. The developed jig mode differs from the existing ones by the closed-circuit of jig machine chambers: from the feed of the second (in the direction of the light fraction travel) jig chamber, the light fraction (tailings) and undersize product – fraction with the increased content of accessory minerals (rough concentrate) are separated. The rough concentrate in the second chamber is directed to the first chamber of the machine, where the finished jig concentrate is obtained in the form of an undersize product. The light fraction moves from the first chamber to the second and is removed from the machine through the tail board. When fine-tuning the heavy fraction of jigging on a shaking table, it is recommended to mix 1/2 part of the initial feed of the tables with the rough concentrate isolated from the other 1/2 of the original feed. The new jigging mode and the scheme of concentration on the tables provide an increase in the gold content in the initial feed of the apparatus, which is the reason for a decrease in gold losses with the tails of the gravity circuit. Research relevance. Gold recovery increment by 4.77% was obtained due to the use of all three recommended scientific and technical measures, namely sands concentration in a short head cone crusher on a jig, switching the jig chambers to a closed circuit, and jet motion of concentrates on shaking tables. Scope of the results. The results should be applied when concentrating ore containing free (amalgamable) gold, as well as gold-bearing pyrite.


Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 2010
Author(s):  
Kin-ya Tomizaki ◽  
Tatsuki Tonoda ◽  
Shungo Teramura ◽  
Haruka Okazaki ◽  
Takahito Imai ◽  
...  

The separation and recovery of noble metals is increasingly of interest, in particular the recovery of gold nanocrystals, which have applications in medicine and industry. Typically, metal recovery is performed using liquid–liquid extraction or electrowinning. However, it is necessary to develop noble metal recovery systems providing high selectivity in conjunction with a one-pot setup, ready product recovery, and the use of dilute aqueous solutions. In prior work, our group developed a selective gold recovery process using peptides. This previous research showed that RU065, a nonapeptide containing an anthracene moiety (at a concentration of 2.0 × 10−4 M), is capable of selective reduction of HAuCl4 to recover gold from a solution of HAuCl4 and H2PtCl6, each at 5.0 × 10−5 M. However, peptide molecules are generally costly to synthesize, and therefore it is important to determine the minimum required structural features to design non-peptide anthracene derivatives that could reduce operational costs. In this study, we used RU065 together with 23 of its fragment peptides and investigated the selective precipitation/recovery of metallic gold. RU0654–8, a fragment peptide comprising five amino acid residues (having two lysine, one L-isoleusine, and one L-alanine residue (representing six amide groups) along with an L-2-anthrylalanine residue) provided an Au/Pt atomic ratio of approximately 8, which was comparable to that for the full-length original RU065. The structural features identified in this study are expected to contribute to the design of non-peptide anthracene derivatives for low-cost, one-pot selective gold recovery.


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