Initial Gold Research Articles

Physical and chemical evolution of a Pleistocene marginal marine gold paleoplacer deposit, southern New Zealand

Pleistocene placer gold accumulation in coastal sediments during fluctuating Pleistocene sea levels and active tectonic uplift in southern New Zealand provides a well-constrained model for processes that have affected paleoplacers formed in similar settings in older rocks, going back to the Archean. Initial gold concentration occurred > 200 ky ago on exposed sandy beaches, where sand-blasting processes deformed fluvially-transported (~200 km) flakes into toroids, dumbells and spheroids. This gold was recycled into younger gravel-bearing sediments < 30 m thick during subsequent uplift (>50 m) with negligible morphological changes during < 10 km of fluvial transport. Most of the gold accumulated in basal fluvial gravels hosted in channels incised into gabbroic basement. Groundwater in the sedimentary sequence was derived from rain with marine aerosols and had the composition of dilute sea water. This low-temperature groundwater interaction has altered mafic clasts and immediately underlying basement to clays dominated by smectites and kaolinite, with some clay cementation. Groundwater alteration occurred under a wide range of redox and pH conditions that were lithologically controlled, principally by permeability contrasts at the centimetre to metre scale. Hence, oxidised waters produced clays impregnated with ferric iron oxyhydroxide, and reduced waters generated authigenic pyrite. Some of this pyrite was subsequently oxidised with localised acidification. Micron scale dissolution of gold via chloride, thiosulphate and bisulphide ligands led to authigenic gold impregnation of clays. Basal gravels contain clasts that have been pervasively clay-altered, partially clay-altered, and only incipiently clay-altered, attesting to repeated fluvial reworking to basement of the channelised sediments, and progressive gold concentration.

Full Factorial Design for Gold Recovery from Industrial Solutions.

Gold is one of the precious metals with multiple uses, whose deposits are much smaller than the global production needs. Therefore, extracting maximum gold quantities from industrial diluted solutions is a must. Am-L-GA is a new material, obtained by an Amberlite XAD7-type commercial resin, functionalized through saturation with L-glutamic acid, whose adsorption capacity has been proved to be higher than those of other materials utilized for gold adsorption. In this context, this article presents the results of a factorial design experiment for optimizing the gold recovery from residual solutions resulting from the electronics industry using Am-L-GA. Firstly, the material was characterized using atomic force microscopy (AFM), to emphasize the material’s characteristics, essential for the adsorption quality. Then, the study showed that among the parameters taken into account in the analysis (pH, temperature, initial gold concentration, and contact time), the initial gold concentration in the solution plays a determinant role in the removal process and the contact time has a slightly positive effect, whereas the pH and temperature do not influence the adsorption capacity. The maximum adsorption capacity of 29.27 mg/L was obtained by optimizing the adsorption process, with the control factors having the following values: contact time ~106 min, initial Au(III) concentration of ~164 mg/L, pH = 4, and temperature of 25 °C. It is highlighted that the factorial design method is an excellent instrument to determine the effects of different factors influencing the adsorption process. The method can be applied for any adsorption process if it is necessary to reduce the number of experiments, to diminish the resources or time consumption, or for expanding the investigation domain above the experimental limits.

Adsorption of gold in gold-thiosulfate solution onto a quartz surface

Experimental research and quantum chemical calculations were used to study the adsorption of gold-thiosulfate ions on a quartz surface from a solution. The adsorption rate of gold-thiosulfate ions from a quartz-containing solution was 9.52% when a stirring time of 30 min, a stirring speed of 500 r·min−1, a 30% quartz mass ratio in the slurry, and an initial gold concentration of 56.50 mg·L−1 were used. Fourier-transform infrared spectroscopy (FTIR) and energy-dispersive X-ray spectroscopy (EDS) were used to study the interaction mechanism of quartz and gold-thiosulfate ions in the gold-containing solution. The results showed that quartz and gold-thiosulfate underwent both physical and chemical adsorption in solution under different conditions. The CASTEP module in Materials Studio was used to perform quantum chemical calculations. The band structure, density of states, and Mulliken population analysis of the optimized quartz crystal structure showed that the p orbital of quartz was the most active. The calculated adsorption energy of gold-thiosulfate onto the (101) surface of quartz was −386.70 kJ·mol−1. The calculated S2–O36 distance was 1.628 Å, and the S3–O44 distance was 1.622 Å. The results of the Mulliken charge population analysis and bond population analysis showed that gold-thiosulfate ions adsorbed via the formation of relatively stable bonds on the (101) surface of quartz. Some gold was adsorbed by quartz when thiosulfate was used to leach gold ore, which affected the extraction of gold. These results indicate that quartz has the ability to “rob” gold during the thiosulfate gold leaching process, thereby affecting the leaching efficiency.

Stealthiness and Hematocompatibility of Gold Nanoparticles with Pre-Formed Protein Corona.

Studies have established that a serum protein corona pre-formed around gold nanorods (NRs) could be exploited for loading photosensitizers and chemotherapeutics to result in efficient cell kill in vitro with an extremely low dose. In this study, we further demonstrated that pre-forming a serum protein corona (PC) around citrate-capped NRs (NR-Cit) to form NR-PC conferred them stealth property and high hematocompatibility similar to the common strategy of PEGylating NRs, which would otherwise not be able to evade the immune system. Specifically, the NR-PC caused minimal complement activation with significantly lower formation of the terminal complement complex SC5b-9 measured in human serum containing NR-PC, and this resulted in low uptake by phagocytic U937 monocytes of 5.9% of the initial gold dose compared to 55.8% of NR-Cit. In addition, NR-PC exhibited very low hemolytic activity of less than 0.2% hemolysis with no observable effect on RBC morphology as opposed to 0.6% for NR-Cit at the same concentration of 1 nM NRs. Furthermore, we showed that the high hematocompatibility and stealth property of NR-PC were maintained even after the loading of small molecules, photosensitizer Chlorine e6 (Ce6), into the protein corona, thus further establishing the potential clinical relevance of exploiting the inevitably formed serum protein corona on nanoparticles as an effective delivery vector for small molecular therapeutics.

Effective utilization of calcined MgAl-layered double hydroxides for adsorption of gold (I) thiosulfate complexes

Layered double hydroxides (LDHs) have been widely used to remove anions from water owing to their ability to exchange interlayer anions. In this study, LDHs synthesized by coprecipitation method were used as raw materials to produce calcined layered double hydroxides (CLDH), in order to investigate the adsorption of gold (I) complexes from a thiosulfate solution. The effects of solution pH, adsorption temperature, initial gold concentration, and thiosulfate concentration on the adsorption of Au(S2O3)23- by the CLDH were systematically studied. The results showed that the adsorption of Au(S2O3)23- by the CLDH is a very fast endothermic process, and that the adsorption equilibrium can be reached in 2 h. More than 85% of Au(S2O3)23- could be recovered over a wide gold concentration range. Increasing the initial gold concentration resulted in faster and more efficient CLDH adsorption of Au(S2O3)23-, the cumulative adsorption capacity of activated carbon for gold was 11.8 mg/g. The adsorption followed pseudo-second-order kinetics and was well described by the Freundlich model. The adsorption mechanism involves the CLDH adsorbing Au(S2O3)23- species in an anionic solution based on the memory effect, which restores its original layered structure. The Au(S2O3)23- loaded CLDH (CLDH-Au) could be recycled by elution with CO32-. The present results reveal that the recovery of gold ions from a thiosulfate leaching solution using CLDH has good application prospects in gold hydrometallurgy.

Assessment of the Possibility of Hydrometallurgical Processing of Low-Grade Ores in the Oxidation Zone of the Malmyzh Cu-Au Porphyry Deposit

The geochemical features of the ores present in the oxidation zone of the gold-copper Malmyzh mineral deposit are characterized. This deposit is located in the the Nanaian region of the Khabarovsk Territory in the Russian Federation, and a technological assessment of ores present was carried out. The initial gold content in the oxidized ore is 0.1–1.2 ppm, and the leachability of gold from different size fractions by hot cyanide revealed the fact that the ore is not refractory and characterized by increased cyanide consumption. The results demonstrated a high gold content in fine size fractions. Different leaching reagents were applied for oxidized ore testing. These reagents were used both for oxidative pretreatment and leaching process. Activation of solutions was carried out by electrolysis and UV radiation. Different reagent combinations were tested in laboratory with the highest gold recovery (94%) provided by the chloride system with peroxide-sulfuric pretreatment of the oxidized ore. The same reagent combination resulted in 91–94% gold recovery during the column leaching of crushed (−10 mm) ore.

Inductively coupled plasma optical emission spectroscopy as a tool for evaluating lateral flow assays.

Lateral flow assays (LFAs) are immunochromatographic point-of-care devices that have greatly impacted disease diagnosis through their rapid, inexpensive, and easy-to-use form factor. While LFAs have been successful as field-deployable tools, they have a relatively poor limit of detection when compared to more complex methods. Moreover, most design and manufacturing optimization is achieved through time- and resource-intensive brute-force optimization. Despite increased interests in LFA manufacturing, more quantitative tools are needed to study current manufacturing protocols and therefore, optimize and streamline development of these devices further. In this work, we focus on a critical LFA component, colloidal gold conjugated to a detection antibody, one of the most commonly used reporter elements. This study utilizes inductively coupled plasma optical emission spectroscopy (ICP-OES) in conjunction with a lateral flow reader to quantitatively analyze colloidal gold distributions at the read-out test and control lines, as well as residual gold on the conjugate pad and other flow through regions. Our goals are to develop a more rigorous understanding of current LFA designs as well as a quantitative understanding of shortcomings of operational characteristics for future improvement. To our knowledge, this is the first time that ICP-OES has been used to study the initial distribution of colloidal gold on an unused LFA and its redistribution after a test is performed. Using three different brands of commercially available malaria LFAs, gold content was measured within each section of an LFA at varying parasite test concentrations. As expected, the total mass of gold remained unchanged after LFA use; however, the total mass of initial gold and its redistribution varied among manufacturers. Importantly, there are also some inherent inefficiencies that exist in these commercial LFA designs; for example, only 30% of the total gold deposited onto Brand A LFAs binds to the test and control lines, sections of the test that contain interpretable signal. Using information gathered with this method, future devices could be more purposefully engineered to focus on improved binding efficiency, resulting in reduced costs, improved limit of detection, and diminished test-to-test and manufacturer-to-manufacturer variability.

Evidence of coalescence sum rule in elliptic flow of identified particles in high-energy heavy-ion collisions

The major goal of high-energy heavy-ion collisions is to study the properties of the deconfined quark gluon plasma (QGP), such as partonic collectivity. The collective motion of constituent quarks can be derived from the anisotropic flow measurements of identified hadrons within the coalescence framework. Based on published results of elliptic flow (v2), we shall test the coalescence sum rule using K±, p, p¯, Λ and Λ¯, and further extract v2 values for produced u(d, u¯, d¯), s and s¯ quarks, as well as transported u(d) quarks in 10-40% Au+Au collisions at sNN=7.7, 11.5, 14.5, 19.6, 27, 39 and 62.4 GeV. We also attempt to link the v2 difference between π− and π+ to the different numbers of u and d quarks in the initial gold ions, and to relate the v2 measurements of multi-strange hadrons to the formation times of ϕ, Ω± and Ξ+.

Controlling the morphology of poly(ethyleneimine)/gold nanoassemblies through the variation of pH and electrolyte additives

Recent investigations have revealed very promising analytical and medical applications of poly(ethyleneimine) (PEI) capped gold nanoparticles (Au NPs). One simple way for their synthesis utilizes the dual nature of PEI molecules, which can simultaneously act as reducing and stabilizing agents via their amine groups. However, the formation mechanism of these kinds of NPs as well as the dependence of their morphology and charge on the pH and electrolyte additives has not been explored yet. In the present paper, the role of these factors on the PEI assisted one-pot synthesis of gold nanoassemblies was studied systematically using IR and UV–Vis spectroscopy as well as DLS, electrophoretic mobility and TEM techniques.It was shown that these nanomaterials cannot be considered as simple PEI coated Au NPs. Instead, the gold particles are embedded in a rather specific polymer matrix, the structure of which ranges from a slightly cross-linked, positively charged thin polymer layer at low pH, to an extended, negatively charged and coherent amorphous polymer film in alkaline medium, provided that adequate type and concentration of supporting electrolyte is also present. These observations were rationalized through the unique pH and salt dependent mechanism of the initial gold(III)/amine complexation and that of the subsequent oxidation and cross-linking processes of the PEI molecules. This crucially determines the following nucleation and growth as well as the morphology, charge and size of the polymer entrapped gold NPs. The presented results may have important implications in novel applications of gold nanoassemblies.

Gold recovery from cyanide-starved glycine solutions in the presence of Cu using a molecularly imprinted resin (IXOS-AuC)

The synergistic leaching system using glycine as the main lixiviant with low levels of cyanide as a catalyst has been shown to be an effective approach to leach gold‑copper ores and concentrates, allowing the consumption of cyanide to be remarkably reduced. The recovery of gold from the synthetic cyanide-starved glycine leachate in the presence of copper has been investigated using. It was found that the adsorbed copper was mostly cuprous cyanide. The effects of [CN−]:[CuT] and [Gly]: [CuT] molar ratios were not significant on the adsorption of gold and copper using IXOS-AuC resin. The gold recovery increased, while the copper recovery decreased with the increasing initial gold concentration. The equilibrium and kinetics studies were undertaken, and the experimental adsorption equilibrium and rate data showed an excellent fit using the Freundlich isotherm and pseudo-second-order models respectively. Elution tests showed that the loaded copper can be selectively pre-eluted over gold by 0.4 M NaCN at pH 11.5. Gold can be effectively eluted by either acidic thiourea or alkaline thiocyanate. The multi-cycle adsorption/elution tests showed that the resin can be effectively regenerated by both acidic thiourea and alkaline thiocyanate, with an insignificant decrease in adsorption and elution efficiency over 3 adsorption/elution cycles. From SEM analysis, the change of surface morphology of the resin was not significant after adsorption and the adsorption/elution cycles.

OXYGEN REDUCTION ON THE SURFACE OF Fe3O4&amp;Au NANOCOMPOSITES

Functional materials based on ferromagnetics and noble metals are attractive due to their unique optical, catalytic and magnetic properties. Nowadays these materials find their application in various fields of science and technology: medicine, biotechnology, chemistry, physics and energy sector. The aim of the present work is to study the electrochemical characteristics of the oxygen reduction on the surface of Fe3O4&amp;Au nanocomposites. The formation of the composite particles took place on the surface of a rotating steel disk which was in contact with HAuCl4 aqueous solution and air. Initial gold concentration was varied from 0.2 to 10.0 mg/l. Oxygen reduction was studied on a floating gas diffusion electrode (pressed carbon black P803 + 30 % PTFE) with surface, modified by prepared Fe3O4&amp;Au nanocomposites, in 1 M KOH solution at 20 ºC. Electrochemical measurements were carried out using a PI-50-1.1 potentiostat.&#x0D; Tafel slopes of the stationary polarization curves ∂E/∂lgj of oxygen reduction on the electrode modified by composites formed at с(Au3+) from 0.2 to 5.0 mg/l lay in the ranges: b1 = 0.048 – 0.060 V, b2 = 0.119 – 0.131 V. When nanocomposites were obtained at с(Au3+) from 7.0 to 10 mg/l these values were: b1 = 0.042 –0.061 V, b2 = 0.079 – 0.105 V. It was concluded that oxygen reduction mechanism is multistep and includes formation of the hydrogen peroxide as intermediate. Obtained b1 and b2 values indicate that electrode process me-chanism changes when current density grows.&#x0D; The largest exchange current (8.51∙10–3 A/g) was achieved when electrode was modified by composite formed at с(Au3+) = 1.0 mg/l, whereas when the composite formed at с(Au3+) = 10.0 mg/l was used, the j0 value was smallest. Perhaps, the increase in the initial Au3+ concentration during nanocomposite formation led to an increase in the number of separate gold clusters on the surface of Fe3O4 nanoparticles and to raise of composite catalytic activity. But when с(Au3+) exceeded 1.0 mg/l the core-shell Fe3O4&amp;Au composites with compact gold shell were formed. Such coreshall composites had lower catalytic activity in the oxygen reduction than composites with separate gold clusters on the surface of Fe3O4 particles.

Comparison of Adsorption Properties of Activated Carbons with Different Crops Residues as Precursors for Gold Cyanide Recovery: An Iranian Gold Industry Guide

Adsorption of gold cyanide on three types of Activated Carbons (ACs) has been investigated in batch and column adsorption conditions. Applied ACs have been derived from different crops precursors i.e., coconut shell (CAC), peach stone (PAC), and walnut shell (WAC). As peach stone and walnut shells are abundant agricultural residues in Iran, the activated carbons produced from these precursors are economically preferable for the gold recovery process. The ACs were characterized using FTIR, SEM, BET, and Wet-Bed Compaction Hardness analyses. Batch equilibrium adsorption data were analyzed using the Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models. Freundlich isotherm was in better agreement with the equilibrium data and the maximum adsorption capacity (40.8 mg/g) was tabulated for CAC. Adsorption kinetics was also modeled using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. The PAC recorded the highest removal rate in the light of better agreement of the pseudo-second-order model. Fixed-bed column experiments were carried out at different initial gold concentrations (30, 50 mg/L) to determine the characteristics of the breakthrough curves. The maximum bed capacity (37.55 mg/g) was obtained for CAC. Three dynamic adsorption models including, Thomas, Yoon–Nelson, and Adam–Bohart,were applied to describe the breakthrough curves. Both Thomas and Yoon–Nelson models were in appropriate agreement with the experimental column adsorption data. This research introduces peach stone as a promising precursor considering availability, technical features, and economical aspects for the production of AC for gold recovery from cyanide leach solutions. Results are also conducive for gold mining industries to select the appropriate activated carbon.

Studies of enrichment of sulfide and oxidized ores of gold deposits of the Aldan shield

The paper presents the analysis of studies of the enrichment of sulfide and oxidized ores in Yakutia deposits. The ore of the deposit is a mixture of primary, mixed and oxidized ores. The main useful component of the studied ore samples is gold with a content of 1.5 to 2.8 g/t, the silver content is low – 5-17 g/t. Ore minerals are represented by sulfides, among which pyrite predominates. The total sulfide content does not exceed 3-5 %. The presence in the ore of free and associated gold with a grain size from fractions of a micron to 1.5 mm. Gold is represented by nuggets in intergrowth with sulfides and also forms independent inclusions. Ores are classified as easily cyanidable.&#x0D; It was found that the content of amalgamable gold is 10-49, the share of cyanidable gold ranges from 66.67-91, the share of refractory gold is 9.0-33.33 %, which in absolute amount equals to 0.24-0.8 g/t. The extraction of gold in gravitation concentrate varies depending on the gold content in the ore and the yield of concentrate and for ores with a gold content of 1.5-2.8 g/t from 40 to 60 %. The direct cyanidation of all studied ore samples established the possibility of extracting gold into solution up to 86.7-92.9 %, the gold content in cyanidation cakes is 0.2-0.3 g/t. Investigations of the gravitation concentrate by the method of intensive cyanidation showed that with an initial gold content of ~ 500 g/t, up to 98.9 % is extracted into the solution. The gold content in intensive cyanide cakes will be 6-15 g/t. A set of studies carried out by the authors of the article at various institutes showed that it is advisable to process ore from the deposit using cyanidation technology with preliminary gravitational extraction of gold.

In-situ reduction of gold thiosulfate complex on molybdenum disulfide nanosheets for a highly-efficient recovery of gold from thiosulfate solutions

Thiosulfate leaching is widely considered an alternative and nontoxic technique for cyanidation in gold hydrometallurgy; however, the main problem with this technique is the difficulty in recovering gold from pregnant solutions. Here, we report that a simple and accessible material, molybdenum disulfide nanosheets, can effectively in-situ reduce and recover gold from pregnant solution based on its semiconducting properties. The results of the in-situ reduction showed that the gold-thiosulfate complex([Au(S2O3)2]3−) can be reduced to elemental gold particles with a particle size of 130–320 nm. The origin of the in-situ reduction of gold might be derived from the photo generated electrons released by molybdenum disulfide. The 1866.762 mg∙g−1 recovery capacity of gold on molybdenum disulfide from a 100 mg∙L−1 initial gold solution, which is 1000 times the recovery capacity of modified activated carbon, further demonstrates that molybdenum disulfide is a superior gold recovery material. Moreover, the removal of ~99% gold from gold-loaded MoS2 indicates the recyclability of MoS2 in gold recovery. Based on these results, it is obvious that molybdenum disulfide nanosheets is an excellent material to recover gold from gold-thiosulfate complexes. Besides, the application of molybdenum disulfide to gold recovery can simplify the traditional thiosulfate leaching process.

Geology and pyrite sulfur isotopes of the Suoluogou gold deposit: Implication for crustal continuum model of orogenic gold deposit in northwestern margin of Yangtze Craton, SW China

Since the crustal continuum model was proposed mainly based on the variation of mineralization and alteration features of hypozonal, mesozonal, to epizonal deposits, genetic relationship between the different types in one ore belt still requires research. This issue was addressed by the research on the Suoluogou mesozonal orogenic gold deposit and its comparison with the hypozonal orogenic gold deposit in northwestern margin of Yangtze craton. Gold mineralization in Suoluogou is controlled by the bends of roughly EW-trending brittle fault developed in the Late Triassic strata, and it is associated with quartz, sericite, chlorite, carbonate, and sulfide alteration. Pyrite and arsenopyrite are the predominant sulfide mineral, with minor amounts of chalcopyrite, sphalerite, and galena. Four paragenetic stages are divided based on crosscutting relationship and mineral assemblage, including the pre-mineralization stage (stage Ⅰ), the hydrothermal quartz-sulfide stage (stage Ⅱ) and carbonate-quartz-sulfide stage (stage III), and the post-mineralization carbonate-pyrite stage (stage Ⅳ). The δ34S values for pyrite in stage Ⅱ vary from 6.01% to 8.59‰, and those in stage III are from 0.96% to 4.62‰. The decrease of δ34S value from stage Ⅱ to III is explained to the result of the isotope fractionation during separation of oxidised sulfur species in the brecciated space. The sulfide δ34S values in the initial gold mineralization stage of the Suoluogou deposit are similar to those of regional hypozonal orogenic deposit with derivation from metasomatized mantle in the craton margin. This similarity suggests that the mesozonal and hypozonal gold deposits formed in different depths of a crustal continuum model for the deposits sharing similar subcrustal source.

Gold extraction via cyanide leaching using alkaline-based empty fruit bunch activated carbon

This research is carried out to extend the knowledge on the modernized method of modifying the physical and structural properties of empty fruit bunches (EFB), a low-cost, highly accessible and abundant agricultural waste in Malaysia, for gold adsorption process. To complete this aim, EFB was modified by using an alkaline-based chemical to improve the surface area, porosity volume and surface chemistry of sorbents. The structure of the empty fruit bunch is characterized by using characterization techniques such as Thermogravimetric analysis (TGA) and Energy-Dispersive X-ray spectroscopy. The gold solution was prepared by mixing gold with a sodium cyanide solution to undergo a leaching process for 24 hours. The solution was then used for the adsorption experiment. The performance of the alkaline-based EFB-AC to separate gold from the cyanide leaching solution was further studied on the effect of contact time, pH and agitation rate. The gold adsorption capacity achieved by the alkaline-based EFB-AC was measured by calculating the difference between the initial and final gold concentrations using Atomic Absorption Spectrometry (AAS). The maximum gold adsorption capacity findings of contact time, pH, and agitation rate were found to be 2.5 hours, pH of 10 and 60 rpm, respectively. This study reveals that the alkaline-based EFB-AC has the potential to extract gold as an alternative activated carbon in the gold adsorption process.

Forward Appraisal of Potential Gold Content of Dredge and Sluice Tailings Dumps at Placers in Russia’s Far East

A brief appraisal of probable gold in dredge and sluice tailings dumps at placers in Russia’s Far East is given. In terms of mining waste piles and operating placer mines in the Khabarovsk Territory, Jewish Autonomous Province, Amur and Magadan Regions, a probable gold content of dredge and sluice tailings dumps is predicted. The calculation used different combinations of estimation parameters: loss, initial gold content, fineness of gold sand. It is shown that the probable gold content varies quantitatively and qualitatively as function of combination of the estimation parameters. The tough, optimistic, realistic and unrealistic scenarios of prospects for secondary gold extraction from dredge and sluice tailings are presented.

Screening for acquired latent tuberculosis in rheumatoid arthritis patients on tumor necrosis factor inhibition therapy in Southern California.

There are no studies assessing the development of latent tuberculosis infection (LTBI) in patients on tumor necrosis factor inhibitors (TNFα-I) in high TB prevalence areas of the USA. Our objective was to assess the rate of LTBI development in rheumatoid arthritis (RA) patients on TNFα-I therapies in San Bernardino and Riverside Counties of California, high TB prevalence areas in the US. Data were extracted from the electronic health record for 217 adult RA patients across three health centers from January 2010 to January 2017 who have had at least 1year of TNFα-I use and negative initial QuantiFERON Gold status. Demographics, TNFα-I type, duration of use, TB risk factors, QuantiFERON results, rates of re-screening, TB test seroconversion, and its association with drug use and other factors were assessed. Of the 217 patients, 115 (53%) received baseline and annual screening for LTBI. LTBI was diagnosed in 9.4% (10) of patients. Four patients were on infliximab, three on golimumab, two on adalimumab, and one on etanercept. Hispanic patients tended to have a greater than 200% increase in odds of seroconversion compared to non-Hispanic patients. Infliximab and golimumab were associated with a 92% and 400% increase in odds of seroconversion, respectively. The LTBI developed in 9.4% of the patients. This is higher than what is reported for previous US studies. Screening for LTBI in the US should take into consideration TB prevalence, ethnicity, drug type, and duration of use. For our local population and similar populations, annual screening should be practiced. Key Points • Although patients on TNFα inhibitor (TNFα-I) therapy are at high risk of latent tuberculosis infection (LTBI), few studies report the rate of LTBI in patients living in high prevalence areas of the US. • The rate of LTBI was 9.4% in patients on TNFα-I therapy in Southern California. The risk of seroconversion was higher in patients of Hispanic ethnicity and also higher for those on infliximab and golimumab compared to those on other TNFα-I therapies. • Screening guidelines for LTBI screening on TNFα-I should consider local TB prevalence, drugs used, duration of use and ethnicity for cost efficient, and optimal healthcare.

Intensification of sorption-reduction coupled gold biorecovery process through microbial surface modification: effect on gold sorption and reduction.

Biorecovery is emerging as a promising approach to retrieve gold from various sources, while its efficiency is usually restricted by the limited functional groups on natural microbial biomass surface. This study aims to intensify Pycnoporus sanguineus boosted sorption-reduction coupled gold biorecovery process via microbial surface modification. Results showed that grafting polyallylamine hydrochloride onto P. sanguineus biomass surface increased amino group content on microbial biomass surface from 1.29 to 2.81mmol/g. When applying modified biomass to gold biorecovery with initial gold concentrations of 1.0, 2.0 and 3.0mM, biosorption equilibrium time shortened to the 12.5%, 37.5% and 41.7% of those obtained with pristine biomass, and sorption rate constants correspondingly increased to 11.2, 3.1 and 3.7 folds as well. Maximum sorption capacity increased 30% and the affinity between biomass and gold enhanced heavily after microbial surface modification. Meanwhile, microbial surface modification favored gold reduction and gold nanoparticles (AuNPs) formation. The change of microbial biomass morphology from smooth surface with some branched structure to layered stacking structure with many pores and the increase of amino group content on microbial biomass surface were the main impetus for the gold bioreocovery process intensification.

Synthesis of Precision Gold Nanoparticles Using Turkevich Method.

Gold nanoparticles (AuNPs) exhibit unique size-dependent physiochemical properties that make them attractive for a wide range of applications. However, the large-scale availability of precision AuNPs has been minimal. Not only must the required nanoparticles be of precise size and morphology, but they must also be of exceedingly narrow size distribution to yield accurate and reliable performance. The present study aims to synthesize precision AuNPs and to assess the advantages and limitations of the Turkevich method—one of the common chemical synthesis technique. Colloidal AuNPs from 15 nm to 50 nm in diameter were synthesized using the Turkevich method. The effect of the molar ratio of the reagent mixture (trisodium citrate to gold chloride), the scaled-up batch size, the initial gold chloride concentration, and the reaction temperature was studied. The morphology, optical property, surface chemistry, and chemical composition of AuNPs were thoroughly characterized. It was determined that the as-synthesized AuNPs between 15 nm and 30 nm exhibit well-defined size and shape, and narrow size distribution (PDI < 0.20). However, the AuNPs became more polydispersed and less spherical in shape as the particle size increased.