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PubMed1984

[Indications and contraindications for systemic gold therapy].

At the current state of the art a comparison of gold salts and other therapeutic modalities in terms of their risk-benefit ratios clearly shows chrysotherapy to have a place in the treatment of active rheumatoid arthritis. Factors supporting the use of gold salts as base-line drugs for active rheumatoid arthritis include the extensive experience accumulated with chrysotherapy as a basic antirheumatoid treatment and the potential of gold salts to halt joint destruction. The application of gold salts in the treatment of juvenile chronic polyarthritis and psoriatic arthritis rests on the same rationale. Further studies are needed to establish the place of gold salts in ankylosing spondylitis and chronic Reiter's syndrome. Contraindications include diseases of organs likely to be the site of disastrous side effects on gold administration as well as disseminated lupus erythematosus and arthritis in the presence of colitis. Experiences with systemic gold therapy will, no doubt, be expanded in many a respect by the availability of an oral dosage form. Whatever the indication of gold salts a thorough understanding of clinical rheumatology, a complete mastery of the technique and consistent, meticulous patient monitoring are paramount if treatment is to be beneficial.

Anti-Inflammatory Agents↗
PubMed1980

A review of the colloidal gold marker system.

Colloidal gold can be used as a particulate marker for the detection and localization of target molecules by various modes of microscopy (light and fluorescent microscopy, scanning and transmission electron microscopy) using both direct and indirect labeling approaches. Several techniques are available for the preparation of gold markers in a size range of 5nm to 150nm, their mean size and shape characteristics and absorption spectra varying with particle size. Under appropriate conditions, colloidal gold will bind macromolecules by non-covalent electrostatic adsorption with little change in the specific activity of the bound macromolecule. This interaction is influenced by a number of factors including ionic concentration, pH conditions (in correlation with the protein pI values) and protein stabilizing levels. Presence of reactive protein on probes can be demonstrated and quantitated by direct and indirect radioactive binding assays and agglutination assays. These assays provide convenient procedures for characterizing stability, and behaviour in storage, of gold probes. Stability of gold probes under conditons where competing proteins are present, under freeze-thaw cycles and under SEM preparation conditions have been evaluated in this paper. Some of the basic procedures in the application of gold probes to cell labeling are briefly discussed together with certain limitations of the colloidal gold marker system. A bibliography of gold probe cell labeling studies is included.

Animals↗
PubMedDate not supplied

Gold nephropathy.

The early use of gold in medicine and dentistry dates back to the ancient Chinese and Egyptians. The discovery in 1890 that gold salts were toxic in vitro to tubercle bacilli led to the extensive treatment of tuberculosis with gold salts in the first three decades of this century. Eventually, gold therapy was extended to arthritis and lupus erythematosus, because of the belief that these diseases were forms of tuberculosis. Because of its beneficial effect particularly on active rheumatoid arthritis, chrysotherapy has remained one of the most widely used treatments of rheumatoid arthritis for the past half century. Toxicity of gold salts includes hypersensitivity reaction of skin and mucous membranes, bone marrow depression, and nephrotoxicity. The nephrotoxic clinical manifestations are renal insufficiency, proteinuria and hematuria, and the nephrotic syndrome. The pathologic changes are tubular degeneration, acute tubular necrosis or immune complex glomerulonephritis. The justification that any of these possible changes are the result of gold therapy rests clinically upon the time relationship of gold therapy and the renal symptoms, and pathologically upon the presence of gold inclusions (aurosomes) in proximal tubular epithelial cells. Aurosomes can at times be visualized by light microscopy, are usually seen by electron microscopy, and can be identified by microprobe analysis. Their pathology will be illustrated and pathogenic mechanisms discussed.

Arthritis, Rheumatoid↗
PubMed1995

[A case of interstitial pneumonia in polymyositis difficult to distinguish from gold pneumonitis].

Rheumatoid arthritis was diagnosed in a 48-year-old woman. She received a gold compound, and 4 weeks after the start of that therapy, interstitial pneumonia appeared. Findings from a muscle biopsy, and high serum CPK and LDH levels indicated that she suffered from polymyositis rather than rheumatoid arthritis. The result of a drug lymphocyte stimulation test (DLST) for the gold compound was more than 200%. Because the usefulness of the DLST for the gold compound in the diagnosis of gold pneumonitis is not thoroughly established, the DLST was also done in patients with rheumatoid arthritis who were receiving the gold compound without side effects, and in normal subjects. Many of the rheumatoid arthritis patients and some of the normal subjects had a positive response to the gold compound. Therefore a positive response on the DLST for the gold compound does not always support the diagnosis of gold pneumonitis.

Antirheumatic Agents↗
PubMed1995

[Gold salt alveolitis in 3 patients with rheumatoid arthritis].

BACKGROUND: When the characteristic symptoms for an interstitial pulmonary disease arise in patients with rheumatoid arthritis, a drug-induced alveolitis should be considered in the differential diagnosis. In such cases, the administration of the drug and gold salts should be stopped. PATIENTS AND METHODS: The cases of three patients with rheumatoid arthritis (RA) who had been treated with gold salts for 2 months (A), 23 months (B), and 36 months (C) are presented. The total dose of sodium aureothiomalate amounted to 280 mg for patient A, 1150 mg for patient B, and 2190 mg for patient C. Clinical signs, X-rays of the lungs, pulmonary function tests, and laboratory tests were evaluated for the three patients while, for patient A BAL as well as provocation tests were additionally performed before and after therapy. In this case, the histological picture of the lungs is presented; biopsies were taken during the first BAL. RESULTS: The clinical complaints of all 3 patients were similar, with the alveolitis being observed as diffuse in one case and above all in the upper regions in two cases on radiology. This led to differing degrees of diffusion disorders in the lungs. In patient A, the diagnosis was made in the stage of progressive fibrotic alveolitis and was treated with D-penicillamine. All 3 patients received steroids over 3-6 months and the gold salts were stopped. Because of the long duration and doubtful differential diagnosis for patient A with either rheumatoid lung or gold salt alveolitis, a provocation test with sodium aureothiomalate was performed. All 3 patients had blood eosinophilia while, in case A, a thrombopenia was also found. CONCLUSIONS: A gold salt alveolitis can occur as a side effect of gold salts in addition to skin vasculitis and hematological disorders. When the gold salt administration is not stopped a fibrotic alveolitis can develop. The provocation test can be diagnostically useful to distinguish between a rheumatoid lung and gold salt alveolitis.

Aged↗
PubMed1975

[The significance of gold serum level determinations during chrysotherapy in rheumatoid arthritis (author's transl)].

The determinations of gold levels in serum of patients with rheumatoid arthritis allow an exact monitoring of chrysotherapy. The atomic absorption spectrophotometry turned out to be superior for clinical use when compared with the neutron activation analysis. Under the conventional gold therapy serum levels increase with repetitive application achieving on maintenance therapy levels, which are in some cases under the recommended levels for effective therapy. The comparison of the clinical response of prolonged gold applications and serum levels revealed for instance that recurrent acute episodes of arthritis are more often with levels of 0.5 ppm or less, than with levels of 1.0 ppm or more. To what extent high dose therapy can increase the efficiency of chrysotherapy should still be determined, it should however be considered that with increased gold levels also more adverse reactions are to be expected. The predominant indication to determine serum gold level in the case of rheumatoid arthritis is the lack of any response to gold application. The serum gold level determination allows to differentiate between insufficient dosage and total ineffectivity of gold.

Arthritis, Rheumatoid↗
PubMed1998

Cytotoxic effects of gold(III) complexes on established human tumor cell lines sensitive and resistant to cisplatin.

Gold(III) complexes, isostructural and isoelectronic with platinum(II) complexes, are potentially attractive as anticancer agents. We have synthesized a group of square planar gold(III) complexes, all containing at least two gold-chloride bonds in cis-position, and tested their in vitro cytotoxicity on a panel of established human tumor cell lines. Remarkably, all these compounds showed significant cytotoxic effects. In particular, the complexes containing the salycilaldiminate ligand induced tumor cell growth inhibitory effects comparable to or even greater than cisplatin. All gold(III) complexes substantially retained their antitumor potency against two cisplatin-resistant tumor cell lines (CCRF-CEM/R leukemia and A2780/R ovarian carcinoma); only minimal cross-resistance with cisplatin was observed. When considering the mechanism of action, it is reasonable to assume that the cytotoxicity of these gold(III) complexes derives from DNA binding. Preliminary spectroscopic results are consistent with this hypothesis; indeed, circular dichroism experiments show that both the salycilaldiminate- and the pyridine-containing gold(III) complexes bind calf thymus DNA in vitro and alter reversibly its B-type solution conformation. These results, however, must be treated with caution; solution studies indicate that gold(III) compounds are poorly stable under physiological conditions, possibly implying that, when injected, only a small amount will reach, unchanged, the DNA target. The results of our investigations are discussed in the perspective of future work on the cytotoxic and antitumor properties of gold(III) compounds.

Antineoplastic Agents↗
PubMed2001

Gold as an oral corticosteroid sparing agent in stable asthma.

BACKGROUND: Patients with chronic severe asthma are often dependent on the long term prescription of oral corticosteroids. The use of steroids is associated with serious side effects. Physicians treating such patients continue to search for alternative therapies that reduce the need for chronic dosing with oral steroids. Gold compounds are immunosuppressive agents and have benefits in the treatment of a number of inflammatory disorders. They have therefore been identified as an potentially useful agents in the treatment of chronic severe asthma both in terms of possible efficacy and as steroid sparing agents. OBJECTIVES: The objective of this review was to assess the effects of adding gold to oral steroids in the treatment of chronic steroid dependent asthmatics. SEARCH STRATEGY: The Cochrane Airways Group trials register and reference lists of identified articles were searched. SELECTION CRITERIA: Randomised trials looking at the addition of gold compared to placebo in adult steroid dependent asthmatics. DATA COLLECTION AND ANALYSIS: Trial quality was assessed and data extraction was carried out by two reviewers independently. Study authors were contacted for missing information. MAIN RESULTS: Three trials fulfilled the criteria for inclusion in the review and a total of 376 patients were recruited into these studies. Data from 311 patients could be analysed. There was a small but significant treatment effect for gold in terms of steroid dose reduction (Peto Odds Ratio 0.51, 95% confidence intervals 0.31,0.83). No meta-analysis could be done for measures of lung function although overall there were few changes suggesting a positive benefit for gold. There were trends suggestive of adverse effects but no significant changes for gold treated patients with respect to proteinuria (Peto Odds Ratio 1.4, 95% confidence intervals 0.6, 3.3) dermatitis/eczema Peto Odds Ratio 2.1, 95% confidence intervals 0.9, 4.7). REVIEWER'S CONCLUSIONS: The changes seen in these trials are small and probably of limited clinical significance. Given the side effects of gold and necessity for monitoring the use of gold as a steroid sparing agent in asthma cannot be recommended.

Adrenal Cortex Hormones↗
PubMed2005

Alkylthiol gold nanoparticles in sol-gel-based open tubular capillary electrochromatography.

A novel open-tubular capillary electrochromatography (OTCEC) column was prepared by immobilizing dodecanethiol gold nanoparticles on prederivatised fused-silica capillary columns with sol-gel technology. 3-Mercaptopropyl-trimethoxysilane (MPTMS) was selected as sol-gel precursor to develop a sol-gel layer on the inner wall of the capillary, prior to assembly of dodecanethiol gold nanoparticles onto the generated sol-gel layer through specific interaction between the gold nanoparticles and surface terminating thiol groups. The electrochromatographic behaviour of the sol-gel gold nanoparticle capillary was compared with a gold nanoparticle capillary prepared via MPTMS surface functionalisation, through variation of the percentage of the organic modifier, pH, and separation voltage. Efficient separation for a "reversed-phase" test mixture of thiourea, naphthalene, and biphenyl and for selected polycyclic aromatic hydrocarbons (PAHs) was obtained on the sol-gel based gold nanoparticle capillaries. OTCEC separations of three selected drug substances (propiophenone, benzoin, and warfarin) were also demonstrated. Scanning electron microscopy was used for the characterization of the sol-gel gold nanoparticle capillary surface. The results confirm that dodecanethiol gold nanoparticles, bound on the sol-gel-based inner layer of fused-silica capillary, can provide sufficient solute-bonded phase interactions for OTCEC with reproducible retention as well as characteristic reversed-phase behaviour.

Journal Article↗
PubMed2004

Have traditional DMARDs had their day? Effectiveness of parenteral gold compared to biologic agents.

This review tries to answer the question of whether in the face of the recently introduced biologics conventional disease-modifying antirheumatic drugs (DMARDs) can still be recommended in the treatment of rheumatoid arthritis (RA). We start with an overview of the oldest conventional DMARD, injectable gold (Au), which was introduced in the treatment of RA in the 1920s. The effect of gold is directed at a number of different sites of the immune system. A significant improvement of clinical and biochemical disease activity parameters as well as an inhibition of X-ray progression has been shown in many studies. Head-to-head comparisons between gold and high-dose methotrexate (MTX) demonstrated no significant difference but some advantages for gold. Since trials comparing biologics with gold will never be performed, an indirect comparison was done by analyzing the results of trials with gold with those with biologics. Conclusions from such comparisons have to be drawn with caution especially since the methodology for performing trials has changed with time. We selected four trials with gold (two open, one placebo-controlled, and one comparison with MTX) and five trials with biologics (three placebo-controlled, one dose escalation study, and one comparison with MTX). In all these trials baseline data regarding swollen joint count (SJC), erythrocyte sedimentation rate (ESR), and C-reactive protein (CRP) were roughly comparable and, with the exception of interleukin (IL)-1 RA, demonstrated a similar improvement of over 50% already after 6 months [with faster onset with tumor necrosis factor (TNF)-alpha blockade]. American College of Rheumatology (ACR) response data were not available for the older gold trials. European League Against Rheumatism (EULAR) response criteria could be calculated for the Au/MTX trial and were-for these compounds-only slightly inferior to the results with adalimumab. X-ray response is especially difficult to compare across studies. Although an inhibition with Au and MTX could be demonstrated, this occurred-similar to corticosteroid treatment-earlier and more pronounced with TNF-alpha blockers. We confirm the statement of Weinblatt that the most modern DMARDs do not appear to be much better than the oldest one indicating that conventional DMARDs are not outdated. Therefore, a sufficient trial of conventional DMARDs should precede the introduction of treatment with the very expensive biologics.

Antirheumatic Agents↗
PubMed2005

Gold nanoparticles prepared using polyethylenimine adsorbed onto montmorillonite.

Polyethylenimine-modified montmorillonite (N-MMT) was used to prepare gold nanoparticles, where the montmorillonite (MMT) acted as a solid support to retain the conformation of polyethylenimine (PEI), and the amino groups of PEI were used simultaneously to both complex and reduce the gold ions. From the results of X-ray diffraction, it is apparent that the reduction of gold ions occurs primarily on the MMT surface. In the presence of MMT, the formation of a flattened configuration on the clay instead of stretched-out ethylenimine segments of PEI results in the formation of smaller gold particles. With a higher acidification ratio, the recharging of the MMT surface with positive ammonium ionic sites of PEI is likely to prevent the flocculation of clay and thus facilitate the reduction of gold. The rate of gold reduction with N-MMT is faster at low pH values, this being in contrast to the usual trend observed for the reduction of gold ions. The use of PEI adsorbed onto MMT has been shown to be able to act simultaneously as both a protective template and as a reducing agent, thereby greatly simplifying the process for preparing gold nanoparticles.

Journal Article↗
PubMed2003

Morphological change of gold-dendrimer nanocomposites by laser irradiation.

Gold-dendrimer nanocomposites are prepared in aqueous solutions in the presence of poly(amidoamine)dendrimers (PAMAM) (generation 3 and 5) or poly(propyleneimine)dendrimers (PPI) (generation 3 and 4) by wet chemical NaBH(4) method. Thus prepared gold-dendrimer nanocomposites are irradiated by laser at 532 nm. UV-vis absorption spectroscopy and transmission electron microscopy reveal that the gold nanoparticles grow with the laser irradiation time as well as the fluence of the laser; in particular, the gold nanoparticles prepared at lower concentrations of PAMAM dendrimer as well as lower generations of PAMAM grow significantly. On the other hand, in the case of PPI dendrimers, the gold nanoparticles hardly grow by irradiation. In addition, dynamic light-scattering measurements show that the laser irradiation markedly promotes the association of the gold-PAMAM G3 dendrimer nanocomposites compared to that of the gold-PAMAM G5 dendrimer nanocomposites, while the sizes of association for the gold-PPI G3, G4 dendrimer nanocomposites hardly change by laser irradiation.

Journal Article↗
PubMed2003

Electrochemical properties of DNA-intercalating doxorubicin and methylene blue on n-hexadecyl mercaptan-doped 5'-thiol-labeled DNA-modified gold electrodes.

Interactions between DNA-intercalating molecules, methylene blue (MB) and doxorubicin (DOX), and gold surface modified by various DNA species and n-hexadecyl mercaptan (HDM) were investigated by cyclic voltammetry (CV). Hydrophilic DOX was completely blocked by the HDM film from contacting the gold electrode whereas hydrophobic MB could readily partition into the film. Unlabeled single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) underwent non-specific adsorption on gold surface but the adsorbed DNA can be partially displaced by HDM. Thiol-labeled ssDNA and dsDNA adsorbed on gold surface via both thiol-gold linkage and non-specific interactions between DNA strands and gold. The non-specific interactions could be interrupted by the addition of HDM, forming a mixed monolayer containing both HDM and DNA attached to the gold surface at 5'-thiol termini. The presence of ssDNA and dsDNA in the monolayer facilitated the redox reaction of MB and DOX on the modified electrode. Both MB and DOX diffuse along the ssDNA in the ssDNA-containing monolayers, and they additionally intercalate into the dsDNA in the dsDNA-containing monolayers. No sufficient evidence is shown to indicate that an organized monolayer is formed by the thiol-labeled dsDNA on gold surface, and that the redox reactions of MB and DOX were carried out by electron transfer through DNA helix.

Adsorption↗
PubMed2004

Multichannel electrochemiluminescence of luminol in neutral and alkaline aqueous solutions on a gold nanoparticle self-assembled electrode.

The electrochemiluminescence (ECL) behavior of luminol on a gold nanoparticle self-assembled electrode in neutral and alkaline pH conditions was studied under conventional cyclic voltammetry (CV). The gold nanoparticle self-assembled electrode exhibited excellent electrocatalytic property and redox reactivity to the luminol ECL system. In neutral solution, four ECL peaks were observed at 0.69, 1.03, -0.45, and -1.22 V (vs SCE) on the curve of ECL intensity versus potential. Compared with a bulk gold electrode, two anodic and one cathodic ECL peaks were greatly enhanced, and one new cathodic ECL peak appeared. In alkaline solution, two anodic ECL peaks were obtained at 0.69 and 1.03 V, which were much stronger than those on a bulk gold electrode. These ECL peaks were found to depend on gold nanoparticles on the surface of the electrode, potential scan direction and range, the presence of O(2) or N(2), the pH and concentration of luminol solution, NaBr concentration, and scan rate. The emitter of all ECL peaks was identified as 3-aminophthalate by analyzing the ECL spectra. The spatial distribution of the luminol ECL peaks on the gold nanoparticle self-assembled electrode was studied by CCD. The surface state of the gold nanoparticle self-assembled electrode was characterized by scanning electron microscopy (SEM) and UV-visible reflection spectra. The mechanism for the formation of these ECL peaks has been proposed. The results indicate that the gold nanoparticle self-assembled electrode could lead to novel ECL properties, and strong luminol ECL in neutral and alkaline solutions could be obtained on such an electrode, which is of great analytical potential.

Journal Article↗
PubMed2004

New riches in carbaporphyrin chemistry: silver and gold organometallic complexes of benzocarbaporphyrins.

The NH-N-NH-N core of the porphyrin system represents one of the best studied and most versatile platforms for coordination chemistry. However, the replacement of one or more of the interior nitrogens with carbon atoms would be expected to diminish the ability of these systems to form metallo derivatives considerably. Despite this expectation, carbaporphyrinoid systems have been shown to form stable organometallic derivatives. Although azuliporphyrins and benziporphyrins act as dianionic ligands, benzocarbaporphyrins are trianionic ligands. Treatment of five different meso unsubstituted benzocarbaporphyrins and two different meso tetraarylbenzocarbaporphyrins with excess silver(I) acetate afforded 65-97% yields of the corresponding silver(III) organometallic derivatives. The insertion of silver metal was confirmed by mass spectrometry and X-ray crystallography. The UV-vis spectra showed a strong Soret band at wavelengths between 437 and 451 nm, together with a series of Q-type bands at longer wavelengths. The new metallo carbaporphyrins demonstrate the presence of a strong diatropic ring current in their proton NMR spectra, and carbon-13 NMR spectroscopy indicates that the derivatives retain a plane of symmetry. The reaction of meso tetraaryl carbaporphyrins with gold(III) acetate afforded the related gold(III) complexes, and these also showed strongly porphyrin-like aromatic characteristics. The UV-vis spectra for the gold complexes again showed a strong Soret band between 437-439 nm, but a secondary band near 400 nm is somewhat intensified for the gold species compared to the spectra for the related silver(III) meso tetrasubstituted carbaporphyrins. The ring currents observed for the gold(III) complexes by proton NMR spectroscopy were comparable to those of the silver(III) derivatives, implying that both series have similar macrocyclic conformations. Cyclic voltammetry was performed on two different carbaporphyrins, their silver(III) derivatives, and a gold(III) complex. The silver complexes display a reversible cathodic wave that is assigned to the Ag(III/II) couple. However, the gold porphyrinoid gave a value for the reductive wave that could be due to a gold(III/II) couple or a ligand-based process.

Journal Article↗
PubMed2003

Oxygen adsorption on hydrated gold cluster anions: experiment and theory.

The discovery that supported gold clusters act as highly efficient catalysts for low-temperature oxidation reactions has led to a great deal of work aimed at understanding the origins of the catalytic activity. Several studies have shown that the presence of trace moisture is required for the catalysts to function. Using near-atmospheric pressure flow reactor techniques, we have studied humidity and temperature effects on the reactivity of gas-phase gold cluster anions with O2. Near room temperature, the humid source produces abundant gold-hydroxy cluster anions, Au(N)OH(-), and these have a reversed O2 adsorption activity: Nonreactive bare gold clusters become active when in the form Au(N)OH(-), while active bare clusters are inactive when -OH is bound. The binding energies for the stable structures obtained from density functional calculations confirm fully these findings. Moreover, the theory provides evidence that electron-transfer induced by the binding of a OH group enhances the reactivity toward molecular oxygen for odd anionic gold clusters and suppresses the reactivity for the even ones. The temperature dependence of O2 addition to Au(3)OH(-) and Au(4)(-) indicates deviations from equilibrium control at temperatures below room temperature. The effects of humidity on gold cluster adsorption activity support the conclusion drawn for the mechanism of O2 adsorption on "dry" gold cluster anions and provides insight into the possible role of water in the enhanced activity of supported gold cluster catalysts.

Journal Article↗
PubMed2005

Gold nanoparticles with different capping systems: an electronic and structural XAS analysis.

Gold nanoparticles (NPs) have been prepared with three different capping systems: a tetralkylammonium salt, an alkanethiol, and a thiol-derivatized neoglycoconjugate. Also gold NPs supported on a porous TiO(2) substrate have been investigated. X-ray absorption spectroscopy (XAS) has been used to determine the electronic behavior of the different capped/supported systems regarding the electron/hole density of d states. Surface and size effects, as well as the role of the microstructure, have been also studied through an exhaustive analysis of the EXAFS (extended X-ray absorption fine structure) data. Very small gold NPs functionalized with thiol-derivatized molecules show an increase in d-hole density at the gold site due to Au-S charge transfer. This effect is overcoming size effects (which lead to a slightly increase of the d-electron density) for high S:Au atomic ratios and core-shell microstructures where an atomically abrupt Au-S interface likely does not exist. It has been also shown that thiol functionalization of very small gold NPs is introducing a strong distortion as compared to fcc order. To the contrary, electron transfer from reduced support oxides to gold NPs can produce a higher increase in d-electron density at the gold site, as compared to naked gold clusters.

Journal Article↗
PubMed2006

An investigation of gold adsorption from a binary mixture with selective mesoporous silica adsorbents.

Gold-selective adsorbents were prepared from mesoporous MCM-41 silica by grafting organic amine groups (i.e., RNH2, R2NH, and R3N; R=propyl). NH2-MCM-41, NRH-MCM-41, and NR2-MCM-41 displayed strong affinity for gold and at 1 mmol/g loading adsorbed 0.40, 0.33, and 0.20 mmol/g of gold. Copper and nickel were not adsorbed on these adsorbents. Grafting surface chemical moieties introduces heterogeneity on an otherwise uniform MCM-41 pore surface and metal adsorption is best described by the Freundlich adsorption model. A series of binary adsorption equilibrium studies with NH2-MCM-41 containing 2.2 mmol RNH2/g shows that NH2-MCM-41 adsorbs only gold from solutions containing copper and nickel with an adsorption capacity of 0.6 mol of Au/mol of RNH2 (1.1 mmol of Au/g of NH2-MCM-41). Copper and nickel were not adsorbed by NH2-MCM-41 regardless of the solution concentration, composition, and pH (i.e., 2 to 4) in the presence of gold. The LeVan and Vermeulen adsorption model based on a single component Freundlich isotherm and corrected for the anion effect accurately predicted the binary adsorptions. The adsorbed gold was completely recovered by a simple acid wash and the recovered gold solution is 99% pure. The regenerated NH2-MCM-41 remained 100% selective for gold removal and exhibited the same adsorption capacity even after several uses.

Journal Article↗