Precipitation Of Silver Chloride Research Articles

Waste from Argentometric Determination of Chloride as a Source of Silver in the Synthesis of p‐Hydroxybenzoic Acid Capped Silver Nanoparticles

AbstractThis paper describes the utilization of waste from the argentometric determination of chloride in a chemistry teaching laboratory as a source of silver for the synthesis of p‐hydroxybenzoic acid capped silver nanoparticles (AgNPs). All white and red‐brick precipitates in the waste were first separated from the liquid and converted to silver chloride precipitate by washing the precipitates using hydrochloride acid 0.1 M. The silver chloride precipitate was then converted to diammineargentate complex ion by dissolving it into an ammonia solution. The conversion was successfully conducted by using 50 moles of ammonia for every mole of silver chloride. The formation of AgNPs was optimum by applying diammineargentate complex ion and p‐hydroxybenzoic acid solutions at a molar ratio of 1 : 10. The formed AgNPs showed a yellow color and absorption peak at around 420 nm with an average particle size of 26.4 nm. The as‐synthesized AgNPs were stable at least 16 weeks of storage, indicating that p‐hydroxybenzoic acid did not only act as a reducing agent but also play a role as a capping agent.

Effects of Different Application Times of Silver Diamine Fluoride on Mineral Precipitation in Demineralized Dentin.

Silver diamine fluoride (SDF) is a cost-effective method for arresting active dental caries. However, the limited cooperation of patients may lead to an SDF application time that is shorter than the recommended 1–3 min for carious lesions. Therefore, the aim of this study was to assess the effect of different application times of SDF on the degree of mineral precipitation in demineralized dentin. Demineralized dentin specimens from permanent maxillary molars were treated by applying 38% SDF for 30, 60, or 180 s. Water was applied in the control group. The specimens were immersed in simulated body fluid for 2 weeks, and the mineral precipitation in demineralized dentin was then analyzed using FTIR-ATR, SEM-EDX, and synchrotron radiation X-ray tomographic microscopy (SRXTM). The FTIR-ATR results showed a significant increase in mineral precipitation in the 180 s group after 1 week. However, after 2 weeks, the SRXTM images indicated comparable mineral density between the 30, 60, and 180 s groups. The precipitation of silver chloride and calcium phosphate crystals that occluded dentinal tubules was similar in all experimental groups. In conclusion, an application time of either 30, 60, or 180 s promoted a comparable degree of mineral precipitation in demineralized dentin.

Recovery of Silver from Solar Panel Waste: An Experimental Study

The aim of this study was to develop a recycling process to recover silver metal from solar panel waste. Experimental procedure consisted of mechanical/physical separation, leaching of silver from silicon wafer and precipitation to retrieve silver chloride (AgCl) precipitate. The precipitated AgCl was reduced to silver precipitate form which was subsequently heated up to produce silver metal. The leaching process was first conducted by using 4 M of nitric acid for 24 hrs. The silver-containing leached solution would then be added by sodium chloride solution to precipitate AgCl. The precipitate was filtrated out from the solution and was rinsed with water ready for further step. The rinsed precipitate was dissolved in water, then sucrose and sodium hydroxide were added to achieve precipitated silver. Finally, the precipitated silver was burned with acetylene gas to finally obtain silver metal. Base on the experiment the purity of silver metal of 99.98% can be achieved and by considering recycling of solar panel of 1,000 kg the recycling product of pure silver of 0.23 kg could be acquired.

Memristive response and electrochemical processes in polyaniline based organic devices

We investigated in details the redox mechanism of an electrochemical two-terminal solid-state device with memory, otherwise named organic memristive device (OMD), by varying the composition of solid polyelectrolytes, the doping agents of the conducting polymer, and the material of the gate electrode. The switching mechanism resulted dependent on the presence of a redox active polymer with high conducting and low conducting states, the presence of a redox counter-reaction, and the ability to transport ions between the polymer and electrolyte phases. The memristive response was observed in hydrochloric acid doped and silver gated devices. The crucial role of the chloride ions and of the silver wire as gate electrode for the promotion of electrochemical reactions is demonstrated. The redox reactions occurring in OMD, the silver dissolution process and the redox reactions of PANI result to be tuned by silver chloride precipitation and ion migration into/out of the polymer matrix to compensate the excess of charges inside the film. The dopant anions are released from polymer network during its oxidation and deprotonation process. Our results, giving rise to a more detailed understanding of the mechanisms involved in redox gated memory devices, provide also a better identification and important details about the requirements for the conducting polymer, the redox counter reaction, and the polyelectrolyte for optimizing the development and fabrication of organic solid-state nonvolatile memory devices. • The redox mechanism of a conductive polymer in a solid-state device was investigated. • Different formulations of polymeric blends as well as the electrode materials were considered. • The current rectification was observed without the presence of any cation in the polyelectrolyte. • The memristive response was due to chloride acid in silver gated devices.

Synthesis of SnO2 and Ag Nanoparticles from Electronic Wastes with the Assistance of Ultrasound and Microwaves

In this work, SnO2 and Ag nanoparticles were produced with a raw material nitric acid solution, which came from the leaching of printed circuit boards. First, a precursor of tin oxide was precipitated from the nitric acid solution by three different techniques: (I) conventional heating, (II) microwave irradiation, and (III) ultrasound treatment. Second, this precursor was transformed into tin oxide nanoparticles by heat treatment in a furnace. Third, hydrochloric acid was added to the nitric acid solution to induce the precipitation of silver chloride. Fourth, silver chloride was reduced to metallic silver nanoparticles in an ammonia solution using glucose syrup as both the reducing agent and the capping agent. The reduction reaction was carried out through (I) conventional heating, (II) microwave irradiation, and (III) ultrasound treatment. The nanoparticles were characterized by scanning electron microscope (SEM), x-ray diffractometer (XRD), infrared (IR)-spectroscopy, transmission electron microscope (TEM), ultraviolet (UV)-spectroscopy, and laser diffraction particle size analyzer.

Determination of chemical oxygen demand (COD) using an alternative wet chemical method free of mercury and dichromate

Worldwide, the standard methods for the determination of the important wastewater parameter chemical oxygen demand (COD) are still based on the use of the hazardous chemicals, mercury sulfate and chromium(VI). However, due to their properties they are meanwhile classified as “priority pollutants” and shall be phased out or banned in the frame of REACH (current European Chemical Law: Registration, Evaluation, Authorization and restriction of Chemicals) by the European Union. Hence, a new wet-chemical method free of mercury and chromium(VI) was developed. Manganese(III) was used as oxidant and silver nitrate for the removal of chloride ions. The quantification was performed by back titration of manganese(III) with iron(II) as done in the standard method. In order to minimize losses of organic substances during the precipitation of silver chloride, suspended and colloid organic matter had to be separated by precipitation of aluminum hydroxide in a first step. In these cases, two fractions, one of the suspended and colloid matters and a second of the dissolved organic substances, are prepared and oxidized separately. The method was tested with potassium hydrogen phthalate (KHP) as conventional COD reference substance and different types of wastewater samples. The oxidation of KHP was reproducible in a COD range of 20–500 mg/L with a mean recovery rate of 88.7% in comparison to the standard COD method (DIN 38409-41). Also in presence of 1000 mg/L chloride a recovery rate of 84.1% was reached. For a series of industrial and municipal wastewater samples a high correlation (R2 = 0.9935) to the standard method with a mean recovery rate of 78.1% (±5.2%) was determined. Even though the results of the new method are not 100% of the standard method, its high correlation to the standard method and reproducibility offers an environmentally benign alternative method with no need to purchase new laboratory equipment.

Predictability of silver nanoparticle speciation and toxicity in ecotoxicological media

The bioavailability of silver was controlled by chloride and proteins through complexation, precipitation and colloidal stabilisation of silver chloride.

Stripping voltammetry microprobe (SPV): Substantial improvements of the protocol

The recently introduced new electroanalytical protocol of stripping voltammetry microprobe (SPV) has been considerably improved with respect to analytical performance. The determination of the silver ions is shown to be possible by the precipitation of a solution of silver drops on an electrode surface, which is previously moistened with a solution of NaCl. The electrode thus modified, i.e., with the silver chloride precipitate on the surface, is introduced into a chloride electrolyte and is negatively polarized to reduce the silver salt to metallic silver. Whereas this reduction process produces only a broad signal, the following electrochemical oxidation of the silver metal back to AgCl provides a highly sensitive and narrow signal, which lends itself for analysis. The linear range for determination of silver ions following this protocol is 1.4×10−7 to 7.4×10−4molL−1 and the detection limit is 4.6×10−8molL−1.

The dissolution and biological effects of silver nanoparticles in biological media.

Silver ions and silver nanoparticles have a well-known biological effect that typically occurs in biological or environmental media of complex composition. Silver nanoparticles release silver ions if oxidizing species like molecular oxygen or hydrogen peroxide are present. The presence of glucose as a model for reducing sugars has only a small effect on the dissolution rate. In the presence of chloride ions, precipitation of silver chloride nanoparticles occurs. At physiological salt concentrations, no precipitation of silver phosphate occurs as the precipitation of silver chloride always occurs first. If the surface of a silver nanoparticle is passivated by cysteine, the dissolution is quantitatively inhibited. Upon immersion of silver nanoparticles in pure water for 8 months, leading to about 50% dissolution, no change in the surface was observed by transmission electron microscopy. A model for the dissolution was derived from immersion and dissolution experiments in different media and from high-resolution transmission electron microscopy. A literature survey on the available data on the dissolution of silver nanoparticles showed that only qualitative trends can be identified as the nature of the nanoparticles and of the immersion medium are practically never comparable. The dissolution effects were confirmed by cell culture experiments (human mesenchymal stem cells and neutrophil granulocytes) where silver nanoparticles that were stored under argon had a clearly lower cytotoxicity than those stored under air. They also led to a less formation of reactive oxygen species (ROS). This underscores that silver ions are the toxic species.

Sulfonated Water-Soluble N-Heterocyclic Carbene Silver(I) Complexes: Behavior in Aqueous Medium and as NHC-Transfer Agents to Platinum(II)

This report describes the synthesis of water-soluble silver(I) and platinum(II) complexes bearing sulfonated mono- or dianionic N-heterocyclic carbene ligands. Thus, treatment of the corresponding zwitterionic imidazolium derivative with silver(I) oxide in water afforded the light-sensitive bis(carbene) complexes Ag[Ag(NHC)2] (2Ag+), which were transformed into the stable salts Na[Ag(NHC)2] (2) by addition of sodium chloride. In contrast, the same reaction in dmso afforded mono(carbenes) of general formula Na[AgCl(NHC)] (3). The solvent-dependence of the reaction product can be rationalized on the basis of the equilibrium [AgCl2]− ↔ AgCl + Cl–. The precipitation of silver chloride is more favored in protic solvents than in aprotic solvents such as dmso, thus explaining the formation of bis(carbenes) in water. The formation of silver chloride may also promote the hydrolysis of silver NHC complexes under some conditions. The water-soluble platinum(II) complexes Na[PtCl2(dmso)(NHC)] were synthesized by using...

Metallic Silver from Leach Liquor: A New Approach for Silver Nano Metal Synthesis

The leach liquor of a low grade silver ore containing 0.5% Ag is used to produce two varieties of metallic silver following two routes. Route-I leading to silver mould by precipitating out silver chloride with 1.62g/L NaCl and later on roasting the silver chloride with Na2CO3 in 2:1 ratio at 1000°C for 2h. Route-II leading to silver nano metals by treating the leach liquor with 5% (v/v) hydrazine hydrate as reductant and 10mL of 0.01M sodium lauryl sulfate in 100mL of leach liquor as surfactant. The paper first time reports the production of silver nano metal from impure leach liquor. This is a new dimension to the conventional nano metal preparation. Silver is obtained in nature in its native form. Apart from coin making (ancient eras) and jeweler making, silver has its uses in various fields like electrical, thermal and pharmaceuticals due to its high electrical and thermal conductance’s and for its proficient antibacterial activity respectively. Extraction of silver deals with the leaching with different reagents like ferricyanide,1-3 cyanide,4-5 thiosulfate,6-8 thiourea,9-11 ferric ion,12 sulfate,13 nitric acid14-15 and chloride/hypochlorite.16 Ultrasound assisted leachings17-18 are also one of the recent trends. Silver is extracted from the leach liquor through electrochemical deposition, 19 electroseparation20 and precipitation.21 Synthesis of silver nano metal is one of the most upto-date investigations in today’s world due to its high applicability. Nano metals show amazing properties due to high surface to volume ratio. Nano clusters provide a potential platform to study atoms as well as bulk and looking towards both the sides being in the middle.22 Nano metallic particles have many such unique properties as compared to the bulk. Investigations so far have reported the preparation of silver nano particle synthetically from silver nitrate,23-26 silver diamine27-28 and silver thiosulfate.23 One thing to be noted here that all those silver nano particles are produced from high grade pure salts. This paper first time reports the preparation of metallic silver from a leach liquor of low grade silver ore containing 0.5% silver which would never be used for industrial silver production. Nano metal synthesis from a pure salt is in ease due to its purity and assurance of the absence of other ions. But synthesizing pure metal nano particles from a solution having varieties of ions is a challenging task. The advantages of producing silver nano metal from impure leach liquor are 1) it may suggest another method of metal extraction from the leach liquor apart from the conventional ones, 2) it would give a process to produce nano silver from leach liquor of various kind of silver ores and the secondary silver materials and 3) it will substitute the electrode position and electro separation thereby reducing the electrical energy. Moreover this paper also reports the production of metallic silver mould from route-I via precipitation of silver chloride followed by roasting and metallic silver nano powder via reduction method. (Chemical bonds between primary particles) state, since their

Localization of potential ion transport pathways in vesicular trichome cells of Atriplex halimus L.

The secreting glandular trichomes are recognized as an efficient structure that alleviates salt effects on Atriplex halimus. They are found on buds, young green stems, and leaves. They occupy both the leaf surfaces and give them a whitish color. Their histogenesis and ultrastructure were investigated in the third young leaves. They appear in early stage of plant development and its initiation continuous until just the leaf final development state. Each trichome contains two parts; a stalk which has high electron opacity, embedded in epidermal cells, and bears a second one which is unicellular, called bladder cell and has a low electron density. The bladder cell appears as a huge vacuole and the well-reduced cytoplasm which is pushed close to the wall, contains only a few organelles. Concurrently, the use of silver chloride precipitation technique shows that, in secretion process, salt follows a symplasmatic pathway which is consolidated by the presence of numerous plasmodesmata between the stalk cell(s), and the bladder one and the neighboring mesophyll cells. In addition, according to lanthanum-tracer study, salt can be excreted apoplastically. In fact, the heavy element can be transported via endocytosis vesicles, and by Golgi, endoplasmic reticulum, and lysosome (G.E.R.L.) network toward the storage vacuoles.

Water‐Soluble Arene Ruthenium Complexes Containing a trans‐1,2‐Diaminocyclohexane Ligand as Enantioselective Transfer Hydrogenation Catalysts in Aqueous Solution

AbstractThe cationic chloro complexes [(arene)Ru(H2N∩NH2)Cl]+ (1: arene = C6H6; 2: arene = p‐MeC6H4iPr; 3: arene = C6Me6) have been synthesised from the corresponding arene ruthenium dichloride dimers and enantiopure (R,R or S,S) trans‐1,2‐diaminocyclohexane (H2N∩NH2) and isolated as the chloride salts. The compounds are all water‐soluble and, in the case of the hexamethylbenzene derivative 3, the aqua complex formed upon hydrolysis [(C6Me6)Ru(H2N∩NH2)OH2]2+ (4) could be isolated as the tetrafluoroborate salt. The molecular structures of 3 and 4 have been determined by single‐crystal X‐ray diffraction analyses of [(C6Me6)Ru(H2N∩NH2)Cl]Cl and [(C6Me6)Ru(H2N∩NH2)OH2][BF4]2. Treatment of [Ru2(arene)2Cl4] with the monotosylated trans‐1,2‐diaminocyclohexane derivative (TsHN∩NH2) does not yield the expected cationic complexes, analogous to 1–3 but the neutral deprotonated complexes [(arene)Ru(TsN∩NH2)Cl] (5: arene = C6H6; 6: arene = p‐MeC6H4iPr; 7: arene = C6Me6; 8: arene = C6H5COOMe). Hydrolysis of the chloro complex 7 in aqueous solution gave, upon precipitation of silver chloride, the corresponding monocationic aqua complex [(C6Me6)Ru(TsHN∩NH2)(OH2)]+ (9) which was isolated and characterised as its tetrafluoroborate salt. The enantiopure complexes 1–9 have been employed as catalysts for the transfer hydrogenation of acetophenone in aqueous solution using sodium formate and water as a hydrogen source. The best results were obtained (60 °C) with 7, giving a catalytic turnover frequency of 43 h–1 and an enantiomeric excess of 93 %. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Turbidimetric determination of chloride in different types of water using a single sequential injection analysis system.

A sequential injection analysis system for the turbidimetric determination of chloride in different types of water is proposed. The determination is based on the reaction of chloride with silver ions and the subsequent measurement of the turbidity caused by silver chloride precipitation. In this method, the use of toxic reagents, such as mercury thiocyanate, commonly employed in most spectrophotometric techniques for chloride determination, is avoided. The main feature of the developed system is the use of a single configuration to carry out the determination over a wide concentration range (2-400 mg L(-1)) by changing only the aspirated sample volume. This characteristic allows the determination of chloride in ground, surface and wastewaters using the same manifold. In addition, a considerable saving of precipitating reagent is achieved due to non-continuous consumption. The results obtained with the developed system were statistically indistinguishable from those of the potentiometric titration reference method. Relative standard deviations for ten consecutive injections were lower than 3.7%, with a sampling frequency of between 55 and 57 determinations per hour.

A modified digestion procedure for analysing silver in environmental water samples

The low recovery of silver in the analysis of environmental water samples has been experienced for a long time. The major cause was postulated to be due to chloride in the sample that causes precipitation of silver chloride. A modified procedure in which the sample was taken to dryness during acid digestion was proposed to remove chloride. Analysing a surface water sample and a photographic wastewater sample validated this modified procedure.

High-throughput synthesis and screening of platinum drug candidates.

Platinum drugs play an important role in the treatment of cancer, but there is room for improvement. Here we present a new platinum drug-discovery strategy to identify compounds having efficacy equivalent to that of cisplatin with the expectation that some may increase the spectrum of treatable tumors and/or reduce dose-limiting toxicity. Platinum drug candidates were generated through the use of automated synthesis, taking advantage either of the trans effect or by using silver chloride precipitation to activate the starting materials. Reaction products were screened for activity in a high-throughput transcription assay and the most promising candidates characterized. Over 3,600 reaction products were screened for their ability to inhibit transcription of beta-lactamase in the BlaM HeLa cell line by monitoring cleavage of a lactam ring linking the two halves of a fluorescent resonance energy transfer (FRET) dye, CCF2/AM. From this screen, three reactions produced good candidates, and four species were identified among these reaction products. Three of the compounds, cis-[(isopropylamine)2PtCl2], cis-[(cyclobutylamine)2PtCl2], and cis-[ammine(cyclobutylamine)PtCl2], have been previously determined to be active cisplatin analogs. The fourth compound, cis-[ammine(2-amino-3-picoline)PtCl2], represents a new kind of antitumor drug candidate similar to ZD0473, a recently reported analog. The discovery of these compounds represents an important proof of principle that platinum anticancer drug candidates can be rapidly prepared and screened in this manner.

A new surface-enhanced Raman scattering substrate based on silver nanoparticles in sol-gel

We report for the first time the development of a new surface-enhanced Raman scattering (SERS)-active silver chloride silica–glass substrate prepared by using in situ precipitation of silver chloride particles in sol–gel films as a precursor for nanoparticles of silver. The controlled precipitation of silver chloride was achieved by the reaction of silver nitrate with trichloroacetic acid, which leads to a slow release of chloride ions. Silver chloride particles were reduced to silver nanoparticles by FeSO4·7H2O. The sol–gel films prepared exhibit good optical properties and induce a strong SERS effect for several model compounds, including cresyl fast violet and brilliant cresyl blue. Optimization studies of substrate preparation and coating conditions were performed and are discussed in detail. The performance of this new substrate compares favorably with those of previously developed silver-coated alumina substrates. The SERS spectra of other compounds of environmental and biological interest, such as 1−aminonaphthalene, 2−aminopyrimidine, pyridine and p$-aminobenzoic acid, were investigated to illustrate the usefulness of this novel type of SERS substrate for use in chemical and biological analysis. Copyright © 1999 John Wiley & Sons, Ltd.

Determination of trace metal impurities in high purity silver by two step selective precipitation separation followed by neutron activation analysis

A neutron activation analysis method for the determination of Au, Co, Cu, Fe, Hg and Zn in high purity silver materials with prior isolation of the analytes by a two-step selective precipitation separation from the silver matrix was developed. In the first step, the silver matrix was separated from the trace impurities of interest through the addition of hydrochloric acid to form a silver chloride precipitate. The principle of this separation is based on the extreme difference in the solubilities of the chlorides of silver and the trace elements of interest. In the second step, the trace elements remaining in the solution were subsequently coprecipitated with the Pb salt of pyrrolidine dithiocarbamate, Pb(PDC)2. The concentrations of six elements (Au, Co, Cu, Fe, Hg and Zn ) collected in the precipitate were determined by neutron activation analysis. Limits of detection of 0.001, 0.1, 0.08, 10, 0.1 and 1 µg g–1 for Au, Co, Cu, Fe, Hg and Zn, respectively, were obtained. The proposed method was validated by the analysis of NIST SRM 8171 Fine Silver and applied to the determination of metal impurities in two high-purity silver samples (EM9465 and EM9343).

Selective precipitation separation and inductively coupled plasma mass spectrometric determination of trace metal impurities in high purity silver.

A simple and rapid method for the determination of some trace element impurities in high purity silver, combining the isolation of analytes from the silver matrix with selective precipitation followed by ICP-MS determination was developed. On the basis of an extreme difference in the solubilities of the chlorides of silver and the other accompanying trace elements, silver can be separated completely through the addition of hydrochloric acid. The sample of silver was at first dissolved in 7 M nitric acid followed by addition of hydrochloric acid to remove the silver matrix by formation of a silver chloride precipitate, while leaving the trace element impurities in the solution, which was subsequently analysed by ICP-MS. Eleven elements (Al, Au, Cd, Co, Cu, Fe, Mg, Mn, Ni, Pb and Sn) were determined with good accuracy and precision. The limits of detection (based on the 3 sigma criterion) of these elements were 10(-1)-10(-3) ng g-1. The proposed method was successfully applied to the determination of metal impurities in high-purity silver samples (EM9465 and EM 9343) and validated by the analysis of NIST SRM 8171 (Fine Silver FS 14).

Growth kinetics of silver chloride precipitation in a Na2O-B2O3 glass investigated by means of small-angle X-ray scattering and transmission electron microscopy

The kinetics of silver chloride cluster formation in a sodium borate glass heat treated isothermally at different temperatures above the glass transition temperature has been studied with small-angle X-ray scattering (SAXS). It is established that the size distributions of particle number and particle volume have bimodal shapes, i.e. the system of AgCl droplets consists of two populations with significantly different mean radii. The bimodality of the size distribution functions is confirmed by results of transmission electron microscopy (TEM) even if different techniques of sample preparation are used. The resolution limits of the TEM techniques applied amount to 2 nm and are comparable with the smallest particle diameters detectable by the SAXS method. The evolution of the size distributions is discussed in the framework of the theories of nucleation, growth and Ostwald ripening.