Uptake and recovery of gold by immobilized persimmon tannin

Some attempts were made to recover gold from aqueous systems using immobilized persimmon tannin. This adsorbent adsorbed gold from solutions containing hydrogen tetrachloroaurate(III) with high efficiency, whereas there was minimal adsorption from solutions containing gold(I) sodium thiomalate and sodium dicyanoaurate(I). The adsorption of gold was rapid, and was affected by the pH of the solution, temperature, external gold concentration and amount of adsorbent. Adsorbed gold was easily desorbed with 1 mol dm^?3 thiourea solution, indicating that immobilized persimmon tannin can be repeatedly re-used for the recovery of gold using adsorption-desorption cycles.     

A new synthetic route to molecularly imprinted ORMOSIL: Characterization and evaluation

A new strategy for synthesis of molecularly imprinted organically modified silica (MIORMOSIL) has been described. The MIORMOSIL was prepared by reacting vinyl acetate and 3-(trimethoxysilyl) propyl methacrylate, followed by condensation and hydrolysis with tetraethyl orthosilicate in the presence of caffeine. The ORMOSIL was characterized by SEM, FTIR, ²⁹Si MAS NMR, ¹³C MAS NMR, TGA, nitrogen adsorption/desorption and tested to extract analyte from coffee samples. The percentage recovery of caffeine 88 ± 5% (n = 9), limits of detection and quantification, 5.14 × 10^–4 and 1.71 × 10^?3 mmolL^?1 respectively, were achieved. Cross reactivity studies for theophylline and theobromine showed high recovery (77% and 82% respectively).

Abbreviations: HMIP: Molecularly Imprinted ORMOSIL; HNIP: non imprinted ORMOSIL; TMSPM: 3-(Trimethoxysilyl)propylmethacrylate     

The Uptake of Gold(I) from Ammonia Leaching Solution by Imidazole Containing Polymeric Resins

Abstract

The polymeric resins containing guanylthiourea, 1-methylimidazole, 2-mercapto-1-methylimidazole ligands have been synthesized from vinylbenzyl chloride-divinylbenzene copolymers and used in the removal of Au(I) from ammonium buffer and ammoniacal thiosulphate solutions. The best gold sorption from ammonium buffer that contains 100 g/dm³ NH₃ · H₂O and 5 g/dm³ (NH₄)₂SO₄, is reached in the case of 1-methylimidazole resin (2) (27.9 mg/g) and all three resins do not have a measurable sorption of copper(II) ammine complexes. The resins display a higher affinity towards gold(I) from ammoniacal thiosulphate solutions than from the ammonium buffer solution. The XPS analysis of gold loaded resins suggests the presence of gold at Au(I) oxidation state, most likely in the form of ionic pair Au(NH₃)₂ ⁺OH^? or neutral complex AuNH₃OH and as highly-dispersed metallic gold. The degree of gold desorption is about 50% using 1% potassium cyanide solution in 0.3% hydrogen peroxide solution. Resins retain their capacity towards gold in five consecutive sorption/desorption cycles.     

Chitosan-polyacrylamide graft copolymers prepared with gamma irradiation for gold cyanide adsorption

ABSTRACT

Cyanidation is one important process in gold mining industries that required proper methods for gold recovery. The present study aims to explore gold cyanide adsorption using chitosan-polyacrylamide graft copolymers synthesized by gamma irradiation. The effects of pH, gold cyanide concentration, and adsorption time were evaluated. The FTIR analysis shows that grafting of polyacrylamide onto chitosan has been obtained. The results indicated that pH value of 7 had the highest adsorption capacity. It was found that the adsorption capacity increases with increasing gold cyanide concentration and adsorption time. The maximum adsorption capacity was 10.18 mg/g at pH 7, gold cyanide concentration 100 ppm, and adsorption time 100 minutes. Adsorption kinetic studies were also carried out and the experimental data were highest fitted to a zero-order with the rate constant, i.e., 0.3327 ppm.min^?1. The Freundlich isotherm model was best suitable for this experiment. Recovery studies had been done with cyanide-NaOH and desorption for gold cyanide released from the adsorbent was obtained up to 18.70%. This research represents a promising application of chitosan-polyacrylamide graft copolymers for the gold adsorbent.     

Microfunnel magnetic stirring-assisted liquid–liquid microextraction method for determination of trace amounts of gold after optimization employing response surface methodology

ABSTRACT

A rapid, sensitive and simple technique was proposed for the preconcentration and determination of gold in the presence of N-methyl-N,N,N-trioctylammonium chloride (Aliquat 336) as ion pair forming agent employing microfunnel magnetic stirring-assisted liquid–liquid microextraction (MF-MSA-LLME) and flame atomic absorption spectrometry. Parameters were optimized by full factorial and Box-Behnken design. Under the optimum conditions, the calibration graph was linear in the range of 2.5–800.0 ng mL?¹ (r² = 0.998). Detection limit, enrichment factor and relative standard deviation were 0.6 ng mL?¹, 240.0 and 1.4% (n = 7, C = 100 ng mL^?1), respectively. This technique was successfully applied for the determination of gold in soil and water samples.     

Solvent Extraction of Gold(I) from Alkaline Cyanide Solution with Furfuryl Thioalcohol

A facile approach was designed to extract gold(I) from alkaline cyanide solution via a hydrometallurgy method. The performances of gold(I) extraction with furfuryl thioalcohol were investigated. The results revealed that gold(I) extraction increased with increasing extractant concentration and phase ratio but decreased with increase of pH value and god(I) concentration. The transfer speed of gold(I) between two phases was rather fast, and the extraction equilibrium could be established within 2 min. The extraction of gold(I) reached 92.7% with 15% (V/V) extractant. Gold(I) loaded in organic phase was stripped by NaOH solution, and stripping of gold(I) reached 90.2% with 0.08 mol · L^?1.     

Chemometric analysis of selective polyphenolic groups in Asparagus racemosus (Shatavar) root extracts by traditional and supercritical fluid (CO2) based extractions

ABSTRACT

Asparagus racemosus root extracts were prepared by supercritical fluid (CO₂), soxhlet, and maceration-based methods also with various pretreatments. Thereafter, these root extracts were analyzed by High-Performance Liquid Chromatography, along with the chemometric study of the disparate phenolic groups. Among these, supercritical fluid (CO₂) based extract has a larger number of polar compounds and the antioxidant activity (98.54 ± 0.22 µM Trolox equivalent mg^?1). It also has the best cell viability (94.37 ± 1.12%) and insulin release (0.82 ± 1.12 ng mL^?1) on β-pancreatic RINm-5F cells whereas, the best extractive yield (75.80 ± 3.44% w/w) was observed for pretreated aqueous soxhlet-based extract.     

A highly efficient method for concentrating DNA from river water by combined coagulation and foam separation

ABSTRACT

Both Escherichia coli and Enterococci were collected in foam within 7 min from 500 mL of bacteria-spiked water by coagulation and foam separation using ferric chloride and milk casein. These bacterial DNA isolated in the 100 µL of extract from the foam more than 87.5% recovery using the DNeasy PowerWater® Kit. To test this method with water from three natural rivers, 0.67–2.70 µg of DNA were concentrated in 100 µL of extract from 1,000 mL of river water. When the DNA extract was subjected to 16S rRNA gene sequencing analysis, information on the bacterial flora could be obtained.     

Gold Recovery from HCl Solutions using Cyphos IL‐101 (a Quaternary Phosphonium Ionic Liquid) Immobilized in Biopolymer Capsules

Tetraalkyl phosphonium chloride (Cyphos IL‐101), an ionic liquid (IL), was tested for gold recovery from HCl solutions: first in liquid/liquid extraction systems (using toluene and hexane as solvent) and in a second step, after being immobilized in a biopolymer composite matrix. SEM‐EDAX analysis was used for the characterization of the resins. The sorption capacity reached up to 140 mg Au(III) g^?1 in 1 M HCl solutions. Base metals that do not form anionic chlorocomplexes and nitrate or chloride ions (at 5 g L^?1) did not interfere with Au(III) binding. Gold binding probably occurs through the interaction of R₃R'P⁺ with AuCl₄ ^?. The kinetics of sorption was carried out varying agitation speed, metal concentration, IL content, and resin drying. Intraparticle diffusion played an important role on the control of sorption kinetics. Gold could be desorbed from the loaded IL‐impregnated resin using thiourea (in HCl solutions). The resin could be re‐used for at least 4 cycles. The resins are specially adapted for the recovery of gold from low metal concentrations.     

Preparative Isolation of Bioenhancer Loganetin from sf Alstonia scholaris by Fast Centrifugal Partition Chromatography

Fast centrifugal partition chromatography (FCPC) was successfully applied in the separation of close R f complex bioactive iridoid, loganetin directly from the ethyl acetate extract of Alstonia scholaris . The experiment was performed with a two-phase solvent system composed of methyl tert- butyl ether (MtBE)/ACN/Water (3:1.5:3 v/v/v) where the lower phase of the biphasic system, the aqueous layer containing 8 mM HCl, was the stationary phase, while the upper organic layer supplemented with 15 mM triethylamine TEA was designated as the mobile phase. From 1.5 g of EtOAc extract, 48 mg of loganetin (1) was obtained in 94.4% purity as determined by HPLC. The isolated compound (1) was characterized on the basis of its ¹ H, ¹³ C–NMR, and ESI-MS spectroscopic data. Although loganetin does not possess antibacterial activity of its own, but in combination, it appreciably reduces the minimum inhibitory concentration (MIC) of nalidixic acid (NA) against nalidixic acid resistant (NAREC) and nalidixic acid sensitive (NASEC) strains of Escherichia coli . Loganetin, a very common, inexpensive, and non-toxic natural product may finds its application in the antibacterial drug development for treating multidrug-resistant Gram negative infections.     

Dielectrophoretic Gold Particle Separation

Abstract

We present a novel process for gold particle separation from aqueous setup with a high separation efficiency and without any environmental risk. Dielectrophoresis (DEP), as the main mechanism of this separation process, is applied for the first time to separate gold even continuously from a raw mineral mixture. Electrothermal and high-pass-filter effects, occurring in DEP with water as liquid phase, were investigated and considered during the design of the separation process. The experimental results demonstrate that even ultra thin gold particles can be separated from a raw mineral mixture with an efficiency of up to 88% at an electric field of 32 kV/m and 200 kHz in continuous operation with specific fluid flow of about 400 m³/(m h).     

Preparative Isolation of Bioactive Nitrile Glycoside “Niazirin” from the Fruits of Moringa oleifera Using Fast Centrifugal Partition Chromatography

Fast centrifugal partition chromatography was successfully applied in the separation of bioactive constituent niazirin directly from the chloroform extract of Moringa oleifera. The experiment was performed with a two-phase solvent system composed of ethyl acetate/BuOH/water (6:0.5:4 v/v/v) in which the upper organic layer was used as stationary phase and lower aqueous phase was used as mobile phase. From 1 g of crude extract, 70 mg of niazirin was obtained in 94.8% purity as determined by HPLC. The total yield recovery was >94%. The isolated nitrile glycoside (niazirin) was characterized on the basis of its ¹H, ¹³C-NMR and ESI-MS data.     

Isolation of Trypsin from Bovine Pancreas Using Immobilized Benzamidine and Peptide CTPR Ligands in Expanded Beds

Abstract

Peptide CTPR and p‐amino benzamidine (PAB) immobilized on Streamline? were utilized as the chromatographic matrices for trypsin purification from bovine pancreas. By using a clarified pancreas extract, maximum capacity for CTPR‐Streamline was 47.4 mg/mL and for PAB‐Streamline 78.9 mg/mL while Kd values were 0.39 and 0.38 respectively. Dynamic capacity was 23.0 and 46.0 mg/mL for CTPR‐ and PAB‐Streamline respectively. When the purification process was applied to unclarified pancreas extract in the expanded‐bed adsorption mode, 80% trypsin recovery with a purification factor of 18.7 was achieved. Cationic and anionic trypsin obtained from the affinity column were separated by ion‐exchange chromatography.     

Micelle‐Mediated Extraction for Direct Spectrophotometric Determination of Trace Uranium(VI) in Water Samples

Abstract

The possibility of using Dibenzoylmethane (DBM) for uranium(VI) concentrating by the way of micellar extraction at cloud point temperature and later spectrophotometric determination was investigated. Under the optimum conditions, preconcentration of 50 mL of water samples in the presence of 0.2% (w/v) octylphenoxypolyethoxy ethanol (Triton X‐114), 2×10^?4 mol L^?1 DBM and 2×10^?3 mol L^?1 buffer solution (pH=9) gave a limit of detection 11 ng mL^?1, and the calibration graph was linear in the range of 15–300 ng mL^?1. The recovery under optimum working conditions was higher than 98%.

The proposed method has been applied to the spectrophotometric determination of uranium(VI) in natural water samples after cloud point extraction with satisfactory results.     

One Step Purification of Piperine Directly from Piper nigrum L. by High Performance Centrifugal Partition Chromatography

Abstract

In this study, a preparative high performance centrifugal partition chromatography (HPCPC) method for isolation and purification of the bioactive component piperine directly from the ethanol extract of Piper nigrum L. was successfully established by using n-hexane-ethyl acetate-methanol-water as the two-phase solvent system. The upper phase of n-hexane-ethyl acetate-methanol-water (6:5:6:5, v/v) was used as the stationary phase of CPC. Under the optimum conditions, 40 mg of piperine at 98.5% purity, as determined by HPLC, was yielded from 300 mg of the crude extract in a single CPC separation. The peak fraction of CPC was identified by ¹H NMR and ¹³C NMR.     

Vibrating screen printed electrode of gold nanoparticle-modified carbon nanotubes for the determination of arsenic(III)

A linear sweep anodic stripping voltammetric method using a carbon nanotube–gold nanoparticle-modified vibrating screen printed electrode for the determination of arsenic(III) is reported. The experiments were conducted with a 0.1 mol L^?1 solution of H₂SO₄ in order to estimate the electrode area related to gold oxide formation. The results showed a clear reduction peak at approximately +0.85 V corresponding to the reduction of the gold surface oxide with a superficial area of 0.089 cm². A vibrating motor was attached to the screen printed electrode to create a portable and autonomous system with enhanced mass transfer. The repeatability of the measurements was 2.4 % (n = 10) at the level of 0.5 mg L^?1 of arsenic(III) under the best instrumental operating conditions. The peak current was linearly dependent on the arsenic(III) concentration, thus allowing the construction of a linear analytical curve in the range from 10 to 550 μg L^?1 with the equation: ?I_p (μA) = 0.05 + 134.59 [As(III) (μg L^?1)], R² = 0.99. The obtained detection and quantification limits were 0.5 (3 SD) and 1.5 (10 SD) μg L^?1, respectively, using 120 s as the deposition time. It was shown that Cu(II) does not interfere in the detection of As(III) using the proposed method.     

Separation and Recovery of Silver(I) Ions from Base Metal Ions by Melamine‐formaldehyde‐thiourea (MFT) Chelating Resin

Abstract

Melamine‐formaldehyde‐thiourea (MFT) chelating resin were prepared using melamine (2,4,6‐triamino‐1,3,5‐triazine), formaldehyde, and thiourea and this resin has been used for separation and recovery of silver(I) ions from copper(II) and zinc(II) base metals and calcium(II) alkaline‐earth metal in aqueous solution. The MFT chelating resin was characterized by elemental analysis and FT‐IR spectra. The effect of pH, adsorption capacity, and equilibrium time by batch method and adsorption, elution, flow rate, column capacity, and recovery by column method were studied. The maximum uptake values of MFT resin were found as 60.05 mg Ag⁺/g by batch method and 11.08 mg Ag⁺/g, 0.052 mg Zn²⁺/g, 0.083 mg Cu²⁺/g and 0.020 mg Ca²⁺/g by column method. It was seen that MFT resin showed higher uptake behavior for silver(I) ions than base and earth metals due to chelation.     

Separation of Radiogallium from Zinc Using Membrane-Based Liquid-Liquid Extraction in Flow: Experimental and COSMO-RS Studies

ABSTRACT

A switch from batch to continuous manufacturing of gallium-68 (⁶⁸Ga) and ⁶⁸Ga-labeled pharmaceuticals can be advantageous, as it recycles isotopically-enriched zinc-68 (⁶⁸Zn), removes pre- and post-irradiation target manipulations, and provides scalability via dose-on-demand production. Herein we report efficient extraction of radiogallium (^66,67,68Ga = *Ga) from ZnCl₂/HCl solutions in batch and in flow using a membrane-based liquid-liquid separator. From 5.6 M ZnCl₂/3 M HCl, a 1/2 (v/v) diisopropyl ether (ⁱPr₂O)/trifluorotoluene (TFT) solvent extracts 76.3 ± 1.9% of *Ga and 1.9 ± 1.6% of Zn in flow using a single pass through. From 1 M ZnCl₂/6 M HCl, a 1/2 (v/v) n-butyl methyl ether (n-BuOMe)/TFT solvent extracts 95.7 ± 2.0% of *Ga and 0.005 ± 0.003% of Zn in flow. TFT plays a key role in controlling the interfacial tension between the aqueous and the organic phases, ensuring clean membrane-based separation. The process did not extract Cu, Mn, and Co but did extract Fe. Using HGaCl₄ and ZnCl₂ as the extractable species, the COSMO-RS theory predicts the solvation-driven extraction of Ga and Zn with a mean unsigned error of prediction of 4.0% and 3.4% respectively.     

Study of a Nanoparticle Charger Containing Multiple Discharging Wires in a Tube

Abstract

A unipolar charger containing multiple discharging wires in a tube (inner diameter: 50 mm) was developed and tested in order to increase the aerosol flow rate and the charging efficiency of nanoparticles. Four gold wires of 25 µm in diameter and 15 mm in length were used as the discharging electrodes to generate positive ions (N_i) from 2.72 × 10⁸ ions/cc to 3.87 × 10⁹ ions/cc in concentration at the discharging voltage of + 4.0 ～ + 10 KV. Monodisperse NaCl particles of 10 ～ 50 nm in diameter were used to test the charging efficiency and the particle loss of charged particles with different aerosol flow rates, corona voltages and sheath flow rates. The sheath air near the tube wall was found to increase the extrinsic charging efficiency, and the highest efficiency was obtained at + 6.0 KV discharging voltage, 10 L/min aerosol flow rate and 9 L/min sheath flow rate. The extrinsic charging efficiency increased from 10.6% to 74.2% when the particle diameter was increased from 10 to 50 nm. The TDMA (tandem differential mobility analyzer) method was used to determine the charge distribution and the mean charge per particle and it was found that the Fuchs charging theory corrected for the extrinsic charging efficiency matched with the experimental data very well.     

Selective Gold Recovery Using Orange Waste

Abstract

Orange waste was crosslinked with sulfuric acid to immobilize the hesperetin-like molecule. Au(III) was selectively recovered from hydrochloric acid, exhibiting the negligible affinity to other precious metals and base metal ions. The isotherm demonstrated that the maximum loading capacity on the crosslinked orange waste is approximately 10 mol/kg, suggesting that orange waste has a high possibility for commercial application for gold recovery.