Chinese Bio-oxidation Gold Extraction Technology Reaches International Advanced Level

In Liaoning, Hunan, Guangxi, Guizhou, Gansu, Sichuan, Anhui, Jilin and other provinces in China, there is a wide occurrence of metal quantity over 1000 tons of refractory gold ores, principally because of low gold recoveries and become ＂stay mine＂. Features of refi＇actory gold ores are： gold in micro-particles or a microscopic state that is wrapped in pyrite, presence of arsenopyrite and other sulfide minerals or disseminated in the crystal lattice of sulfide minerals; harmful impurity elements such as arsenic, carbon, mercury, antimony, copper with high content are closely related with the gold, and these elements affect the contact reaction between the gold and solvent extraction, making the recovery of the gold extraction process low. In the past 20 years, overseas countries have developed the application of the roasting oxidation method, hot acid （alkali） oxidation, bacterial oxidation and flash chlorination oxidation technology to solve this problem.Among these, biological oxidation has developed rapidly in the domestic market and gold enterprises abroad because of its low investment in infrastructure, low production costs, less environmental pollution, simple process and easy control, etc.

Study on gold concentrate leaching by iodine-iodide

Gold extraction by iodine-iodide solution is an effective and environment-friendly method. In this study, the method using iodine-iodide for gold leaching is proved feasible through thermodynamic calculation. At the same time, experiments on flotation gold concentrates were carried out and encouraging results were obtained. Through optimizing the technological conditions, the attained high gold leaching rate is more than 85%. The optimum process conditions at 25℃ are shown as follows： the initial iodine concentration is 1.0%, the iodine-to-iodide mole ratio is 1：8, the solution pH value is 7, the liquid-to-solid mass ratio is 4：1, the leaching time is 4 h, the stirring intensity is 200 r/mim, and the hydrogen peroxide consumption is 1%.

LEACHING GOLD BY LOW CONCENTRATION THIOSULFATE SOLUTION

The effects of the concentrations of thiosulfate,copper and ammonia on the extraction of gold from sulfide gold concentrate have been studied.The results show that it is possible to reduce thiosulfate concentration.More than 95%of the gold could be extracted by a 0.2 mol/L thiosulfate leaching solution in two hours under suitable conditions.Therefore,the process of washing the residue was simplified,and the consumption and loss of thiosulfate carried by the washing residue were reduced.

Effect of mechanical activation on thiosulfate leaching of gold from complex sulfide concentrate

The use of mechanical activation to enhance gold recovery from a CuPbZn complex sulfide concentrate was investigated. The effects of milling time, ball size, sample to ball ratio and milling speed on thiosulfate leaching were studied. Under optimum conditions of milling time 1 h, ball size 20 mm, sample to ball ratio 1/15 and mill speed 600 r/min, nearly 78% of sample is amorphized, particle size decreases from d100=30 μm to d100=8 μm, specific surface area increases from 1.3 m2/g to 4.6 m2/g and gold recovery enhances from 17.4 % in non-activated sample to 73.26 %.

The efficacy of a novel tomato extracts formulation on skin aging and pigmentation:A randomized,double-blind,parallel-controlled trial

Background:Oxidative stress is a significant factor in skin aging and pigmentation,which can be precipitated by various circumstances.Antioxidants and tyrosinase inhibitors,such as carotenoids,yeast extract(glutathione),sodium hyaluronate,astaxanthin,and niacin,can individually protect the skin against aging through distinct mechanisms.These mechanisms potentially enhance the skin barrier and improve signs of aging and pigmentation.However,the synergistic effects of these compounds,as found in a golden tomato extract formulation,have been scarcely explored.Objective:To evaluate the effects of an orally administered formulation on the skin aging and pigmentation.Material and Methods:In this study,a randomized,double-blind,parallel-controlled trial was conducted,utilizing the WONDERLAB?Tomato Niacinamide beverage.Out of all participants,62 volunteers completed the experiment and were included in the statistical analysis.Results:The results indicated that after eight weeks of consuming the research product,there were no significant changes in the skin indicators within the placebo group.In contrast,the treatment group receiving the sample formulation exhibited a 35.63%increase in stratum corneum hydration and a 29.39%reduction in transepidermal water loss(TEWL),suggesting enhanced skin hydration.Visual assessments revealed improvements in skin color and gloss index by 15.03%and 11.41%,respectively,in the treatment group.Furthermore,the skin gloss and individual typology angle(ITA)value increased by 18.59%and 6.36%,respectively,leading to a lighter skin tone.Significant enhancements were also observed in skin pigmentation,color uniformity,and redness.After eight weeks of intervention with the sample,blood levels of superoxide dismutase(SOD)and glutathione peroxidase(GPx)increased,while malondialdehyde(MDA)levels decreased.Conclusion:These findings confirm that continuous intake of the tomato extract formulation over eight weeks effectively improved the volunteers'skin whitening and hydration,and visibly brightened skin tone through an antioxidant mechanism.

STUDIES ON THE EXTRACTION MECHANISM OF GOLD (Ⅲ) FROM HYDROCHLORIC ACID MEDIUM BY TRIPHENYLPHOSPHINE OXIDE (TPPO)

In studies on the extraction chemistry of gold, the extractants of alcohols, ethers, ketones and amines are widely used. The neutral extractants tributylphosphate (TBP) and trioctylphosphine oxide (TPPO) have been widely applied. A few experiments on the synthesis of solid complexes of transition metal ions with TPPO have been car-

Solid-phase extraction gold from alkaline cyanide solution with quaternary ammonium surfactant

The solid-phase extraction（SPE） technique applied to the extraction of organic compound was creatively used as the extraction of inorganic gold in the paper.Two types of techniques were proposed and explored,namely the SPE and the liquid–liquid extraction（LLE） of the quaternary ammonium surfactant [cetytrimethyl ammonium bromide（CTMAB）,cetyl pyridine bromide（CPB）,benzyl dimethyl dodecyl ammonium chloride（BDMDAC）,and dodecyl trimethyl ammonium chloride（DTMAC）].The surfactant could react with Au（CN）2^- to form the ionic complex,and the compound could be extracted by SPE column of reversed-phase bonded silica gel.Hence,a new method of SPE was proposed to extract gold with these features of the high selectivity,the reliability,and the simplicity.The experimental result shows that the recovery rate of gold is more than 98 %,and the solid-phase extraction column is not easily damaged and it can be repeatedly used.The new method can be used as the extraction process of gold from alkaline cyanide solution as well.Besides,the paper also puts forward a new process of gold extraction.

Green-synthesized gold nanoparticles from Plumeria alba flower extract to augment catalytic degradation of organic dyes and inhibit bacterial growth

Bio-inspired eco-friendly gold nanoparticles were synthesized by a green method using aqueous Plume- ria alba flower extract （PAFE）. The use of 1% and 5% concentrations of PAFE resulted in two different sizes of P. alba gold nanoparticles, PAGNPsl and PAGNPs2, with surface plasmon resonance （SPR） peaks at 552 and 536 nm, respectively. Size-controlled formation of gold nanoparticles was indicated by the SPR shift observed with increasing concentration of PAFE. The accurate size and morphology of PAGNPs I and PAGNPs2 were determined by transmission electron microscope （TEM） analysis is found to be 28 ＋ 5.6 and 15.6 4-3.4 nm, respectively, and those are spherical in shape. The antibacterial activity of PAGNPsl and PAGNPs2 was tested against Escherichia coil; the small-sized PAGNPs2 exhibited better antibacterial activity with a 16-mm zone of inhibition at a concentration of 400 txg/mL. Furthermore, the catalytic activity of PAGNPsl and PAGNPs2 was analyzed on six hazardous dyes; PAGNPs2 exhibited more pro- nounced catalytic activity than PAGNPsl. Among all of the dyes, 4-nitrophenol was most rapidly degraded to 4-aminophenol by PAGNPs2 within 5 min. The mechanism of catalysis in the presence of PAGNPsl and PAGNPs2 can be described as an electron transfer process from donor NaBH4 to an acceptor. The facile green synthesis of such eco-friendly nanoparticles in bulk suggests this method has potential industrial applications.

Intracellular biosynthesis of Au and Ag nanoparticles using ethanolic extract of Brassica oleracea L. and studies on their physicochemical and biological properties

In this present study, we reported broccoli （Brassica oleracea L.） as a potential candidate for the synthesis of gold and silver nanoparticles （NPs） in green chemistry method. The synthesized metal nanoparticles are evaluated their antimicrobial efficacy against different human pathogenic organisms. The physico-chemical properties of gold nanoparticles were analyzed using different analytical techniques such as a UV-Vis spectrophotometer, Field Emission Scanning Electron Microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and a Fourier Transform Infrared spectrophotometer. In addition, gold and silver NP antimicrobial efficacy was checked by disc diffusion assay. UV-Vis color intensity of the nanoparticles was shown at 540 and 450 nm for gold and silver nanoparticles respectively. Higher magnification of the Field Emission Scanning Electron Microscopy image shows the variable morphology of the gold nanoparticles such as spherical, rod and triangular shapes and silver nanoparticles were seen in spherical shapes. The average spherical size of the particles was observed in 24- 38 nm for gold and 30-45 nm for silver NPs. X-ray diffraction pattern confirmed the presence of gold nanopartides and silver nanoparticles which were crystalline in nature. Additionally, the functional metabolites were identified by the Fourier Transform Infrared spectroscopy. IR spectra revealed phenols, alcohols, aldehydes （sugar moieties）, vitamins and proteins are present in the broccoli extract which are accountable to synthesize the nanoparticles. The synthesized gold and silver NPs inhibited the growth of the tested bacterial and fungal pathogens at the concentration of 50 μg/mL respectively. In addition, broccoli mediated gold and silver nanoparticles have shown potent antimicrobial activity against human pathogens.