Ammonium Citrate Solution Research Articles

Investigation of the Leaching Kinetics of Zinc from Smithsonite in Ammonium Citrate Solution

In this study, the response surface method is used to develop a model for analyzing and optimizing zinc leaching experiments. An investigation into the leaching kinetics of smithsonite in ammonium citrate solution is also conducted. A model of kinetics is studied in order to represent these effects. The experimental data show that an increase in the solution temperature, concentration, and stirring speed has a positive impact on the leaching rate, while an increase in the particle size has a negative impact on it. The optimal experimental conditions consist of a leaching temperature of 70 °C, ammonium citrate concentration of 5 mol/L, particle size of 38 µm, and rotational speed of 1000 rpm. Under these optimal conditions, the leaching rate of zinc from smithsonite is 83.51%. It is speculated that the kinetic model will change when the temperature is higher than 60 °C. When the temperature is lower than 60 °C, the leaching process is under the control of the shrinking core model of the surface chemical reactions. The calculated activation energy of the leaching reaction is equal to 42 kJ/mol. The model of the leaching process can be described by the following equation: 1−1−x1/3=k0⋅(C)0.6181⋅r0−0.5868⋅SS0.6901exp⁡−42/RT]t. This demonstrates that an ammonium citrate solution can be used in the leaching process of zinc in smithsonite as an effective and clean leaching agent.

An invertebrate model in examining the effect of acute ferric iron exposure on proprioceptive neurons

Iron is an essential element for plant and animal life and is found in soil, fresh waters and marine waters. The Fe3+ ion is a vital prosthetic group and cofactor to mitochondrial electron transport complexes and numerous proteins involved in normal functioning. Despite its importance to life-sustaining processes, overexposure results in toxicity. For example, ferric iron (Fe3+) accumulation in the mammalian central nervous system is associated with various neurological disorders. Although current literature addresses the long-term effects of Fe3+ overload, fewer studies exist examining the effects of acute exposure. Using the blue crab (Callinectes sapidus), we investigate the effects of acute Fe3+ overload on proprioception within the propodite-dactylopodite (PD) nerve. For proprioceptive studies, 10- and 20-mM ferric chloride and ferric ammonium citrate solutions were used at 5- and 20- min exposure times. Exposure to 20 mM concentrations of ferric chloride and ferric ammonium citrate reduced excitability in proprioceptive neurons. Thus, Fe3+ likely blocks stretch-activated channels or voltage-gated Na+ channels. The depressive effects of Fe3+ are partly reversible following saline washout, indicating cells are not acutely damaged. Gadolinium (GdCl3, 1 and 10 mM) was used to examine the effects of an additional trivalent ion comparator. Gd3+ depressed PD nerve compound action potential amplitude while increasing the compound action potential duration. This study is relevant in demonstrating the dose-dependent effects of acute Fe3+ and Gd3+ exposure on proprioception and provides a model system to further investigate the mechanisms by which metals act on the nervous system.

Exploring kinetics, removal mechanism and possible transformation products of tigecycline by Chlorella pyrenoidosa

The accumulation of antibiotics in wastewater leads to broad antibiotic resistance, threating human health. Microalgae have been receiving attention due to their ability to remove antibiotics from wastewater. Tigecycline (TGC) is a broad-spectrum glycylcycline antibiotic. It has not been investigated for removal by microalgae. The removal kinetics of TGC by Chlorella pyrenoidosa were evaluated under different initial dry cell densities, TGC concentrations, temperatures and light intensity conditions. Approximately 90% of TGC could be removed when the TGC concentration was 10 mg∙L−1 and the initial dry cell density was more than 0.2 g∙L−1. A low value of TGC per g dry cell weight ratio led to a high removal efficiency of TGC. The initial dry cell density of microalgae was also critical for the removal of TGC. A high initial dry cell density is better than a low initial dry cell density to remove TGC when the ratio of the TGC concentration to dry cell weight are the same at the beginning of the cultivation. The removal mechanisms were investigated. Photolysis was a slow process that did not lead to removal at the beginning. Adsorption, hydrolysis, photolysis and biodegradation by microalgae were the main contributors to the removal of TGC. TGC was easily hydrolyzed under high -temperature conditions. Three transformation products of TGC by microalgae were identified. The stability of TGC was evaluated in water and salt solutions of citric acid, K2HPO4·3H2O and ferric ammonium citrate. TGC was stable in ultrapure water and citric acid solution. TGC was hydrolyzed in K2HPO4·3H2O and ferric ammonium citrate solutions.

Crystalline phase analysis and phosphorus availability after thermochemical treatment of sewage sludge ash with sodium and potassium sulfates for fertilizer production

Phosphorus rich sewage sludge ash is a promising source to produce phosphorus recycling fertilizer. However, the low plant availability of phosphorus in these ashes makes a treatment necessary. A thermochemical treatment (800–1000 °C) with alkali additives transforms poorly plant available phosphorus phases to highly plant available calcium alkali phosphates (Ca,Mg)(Na,K)PO4. In this study, we investigate the use of K2SO4 as additive to produce a phosphorus potassium fertilizer in laboratory-scale experiments (crucible). Pure K2SO4 is not suitable as high reaction temperatures are required due to the high melting point of K2SO4. To overcome this barrier, we carried out series of experiments with mixtures of K2SO4 and Na2SO4 resulting in a lower economically feasible reaction temperature (900–1000 °C). In this way, the produced phosphorus potassium fertilizers (8.4 wt.% K, 7.6 wt.% P) was highly plant available for phosphorus indicated by complete extractable phosphorus in neutral ammonium citrate solution. The added potassium is, in contrast to sodium, preferably incorporated into silicates instead of phosphorus phases. Thus, the highly extractable phase (Ca,Mg)(Na,K)PO4 in the thermochemical products contain less potassium than expected. This preferred incorporation is confirmed by a pilot-scale trial (rotary kiln) and thermodynamic calculation.

Low-temperature oxidation behavior and mechanism of semi-dry desulfurization ash from iron ore sintering flue gas

The low-temperature wet oxidation behavior of semi-dry desulfurization ash from iron ore sintering flue gas in ammonium citrate solution was investigated for efficiently utilizing the low-quality desulfurization ash. The effects of the ammonium citrate concentration, oxidation temperature, solid/liquid ratio, and oxidation time on the wet oxidation behavior of desulfurization ash were studied. Simultaneously, the oxidation mechanism of desulfurization ash was revealed by means of X-ray diffraction, Zeta electric resistance, and X-ray photoelectron spectroscopy (XPS) analysis. Under the optimal conditions with ammonium citrate, the oxidation ratio of CaSO3 was up to the maximum value (98.49%), while that of CaSO3 was only 8.92% without ammonium citrate. Zeta electric resistance and XPS results indicate that the dissolution process of CaSO3 could be significantly promoted by complexation derived from the ammonium citrate hydrolysis. As a result, the oxidation process of CaSO3 was transformed from particle oxidation to SO 3 2− ion oxidation, realizing the rapid transformation of desulfurization ash from CaSO3 to CaSO4 at low temperature. It provides a reference for the application of semi-dry desulfurization ash and contributes to sustainable management for semi-dry desulfurization ash.

Morphological, microstructural and magnetic characteristics of electrodeposited Ni-Fe-W-Cu alloy powders

Nanostructured Ni-Fe-W-Cu alloy powders were electrodeposited from an alkaline ammonium citrate solution on a titanium cathode. Powder particles were dendrite- and cauliflower-shaped. The dendritic particles had a high density of branches made up of interconnected globules. XRD analysis showed that the powder contained an amorphous matrix and FCC nanocrystals of the solid solution of Fe, W and Cu in Ni. As the deposition current density increased, the mean nanocrystal size decreased, and the mean value of internal microstrain and the total weight percent of Fe and Ni in the alloy increased. The powders deposited at higher current densities exhibited higher magnetization. During annealing at temperatures up to 460?C, the powders underwent short-range ordering, which caused an increase in magnetization, whereas at temperatures above 460?C, the magnetization decreased due to the formation of large FCC crystalline grains.

Re–Ni cathodes obtained by electrodeposition as a promising electrode material for hydrogen evolution reaction in alkaline solutions

Re–Ni cathodes catalytic activity towards hydrogen evolution reaction (HER) in the solution of sodium hydroxide is studied. Re–Ni coatings were deposited onto the surface of a copper substrate from ammonium-citrate solutions in the galvanostatic regime. The obtained deposits were examined by the complex of modern physical methods, namely: XPS, XRD, and SEM with X-ray microanalyzer. It was established that the full reduction of nickel species occurs during electrodeposition, while rhenium species electroreduction is incomplete. The obtained electrolytic deposits contained a high amount of hydrogen sorbed by them during electrodeposition. The increase in rhenium content in Re–Ni deposits caused the increase in their catalytic activity towards HER that was accompanied by Tafel slope decreasing. Heat treatment at 450 °C in vacuum resulted in a decrease in catalytic activity towards HER. It was suggested that high catalytic activity towards HER is caused by rhenium oxides included in the Re–Ni coatings. Heat treatment results in rhenium oxides reduction by sorbed hydrogen that causes a decrease in catalytic activity towards HER.

Detection of Metabolites in Cells through Surface-Assisted Laser Desorption/Ionization Mass Spectrometry

We have developed a surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) approach for detection of five targeted metabolites, glycine (Gly), alanine (Ala), phosphocholine (PCho), glucose (Glu), and glutathione (GSH), in cells. The optimal SALDI-MS condition for the quantitation of the analytes is 0.5 mM ammonium citrate solution (pH 5.0) containing 15 nM Au NPs. Using sucralose as an internal standard, this approach allows reproducible quantitation of Ala, Gly, Glu, GSH, and PCho down to 2.7, 8.9, 2.7, 5.2, and 29.3 μM, respectively. The concentrations of each analyte in the tested breast cancer cells (MCF7, MDA-MB-231) and the nontumoral counterpart (MCF10A) are different. This assay has been validated by the determination of the activities of two inhibitors (2-deoxy-d-glucose and D609) and an anticancer drug (paclitaxel) for the cells by simply monitoring the concentration changes of the five analytes. Our study clearly shows that this simple, sensitive, reproducible, and rapid SALD...

Carbon quantum dots-decorated nano-zirconia: A highly efficient photocatalyst

A unique and efficient composite material was synthesized by incorporating carbon quantum dots on to the surface of zirconia (ZrO2) nanoparticles. ZrO2 nanoparticles with an average diameter of 40 nm were synthesized by a sol-gel process with zirconium oxychloride as the precursor. Carbon quantum dots (CQDs) were synthesized via a facile method by calcining a solution of ammonium citrate. Synthesized CQDs suspended in absolute ethanol emitted a green glow under UV irradiation. A convenient one-step process involving mixing in absolute ethanol under sonication was adopted for the formation of CQD-decorated ZrO2 nanoparticles (CQDZ). The dried final composite was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Fourier transform infrared (FT-IR) spectroscopy. The photocatalytic performance of CQDZ was evaluated by quantifying the removal efficiency of methylene blue dye. CQDZ managed to remove methylene blue by 66.5%, 76.5%, 84.3% and 95.0% under UV-irradiation of 10, 20, 40 and 60 min respectively. Under the same experimental conditions, pure ZrO2 nanoparticles managed to remove only 34% of the dye under 60 min of UV irradiation. The produced composite showed promise as a formidable contender to be used in industrial dye removal from waste water.

Hydrogen Evolution on Catalytically Active Electrodeposited Ni–Re Alloy: Electrochemical Impedance Study

Hydrogen evolution reaction on the catalytically active Ni–Re alloy is studied by the method of electrochemical impedance. The alloy was fabricated by the electrodeposition from the ammonium—citrate solutions. The experiments were performed in the 0.1 M sodium hydroxide solution. Based on the analysis of equivalent circuits, it is found that the absorption of hydrogen atoms on the Ni–Re cathode is controlled by diffusion. The parameters of structural elements of equivalent electric circuits are calculated, and the effect of cathodic overpotential on these parameters is analyzed.

Deposition yield of nickel in alkaline bath for synthesizing Ni-63 beta source

Nickel (Ni) and Ni-63 films were synthesized by direct current electrodeposition. The composition of an alkaline electrolyte was ammonium citrate (25 g/l), hydrazine hydrate (25 g/l), and ammonium solution (25%) for adjusting the pH to 10. The acidic electrolyte at pH 4 was prepared using a full chloride bath. A higher deposition yield (92%) of the citrate electrolyte (pH 10) than 73% of acidic electrolyte (pH4) was measured using ICP. The deposition yield of radioactive Ni-63 in a citrate bath was also same as natural Ni in alkaline electrolyte. A newly prepared alkaline bath for the deposition of Ni-63 can be a solution for an extremely decreased radio-activity in the waste after plating.

Determination of Pb in environmental samples after cloud point extraction using crown ether

In the present study, a new cloud point extraction methodology based on the selective preconcentration and the extraction of stable lead in acidic conditions with 4′,4''(5'')-di-tert-butyldicyclohexano-18-crown-6 as a chelating agent was developed, optimized and validated. A mixture of Triton X-114 as non-ionic surfactant and CTAB as cationic surfactant was used to produce micellar structures that incorporate the chelating agent. Phase separation, induced by coacervation, was achieved by increasing the temperature of the system above the cloud point temperature. Pb extraction efficiency was maximized through an optimisation process where the effect of each parameter (i.e. non-ionic and ionic surfactant concentrations, pH, chelating agent concentration and cloud point temperature) on the chemical recoveries of Pb was assessed. Under optimum experimental conditions, the method reaches recoveries greater than 67% for Pb in a variety of complex matrices. In order to facilitate the quantification of Pb by plasma based instrumentations, a back-extraction procedure using aqueous solution of ammonium citrate were performed on the surfactant rich phase in order to reduce the effects on sample introduction and non-spectral interferences. LOD and LOQ of 0.8µgL−1 and 2.6µgL−1, respectively, were determined by ICP-OES for the complete procedure. Using the back-extraction approach, a preconcentration factor of 39 was achieved for an initial sample volume of 195mL. The ruggedness of the methodology was validated by determining Pb concentration in various environmental and biological samples.

Microwave and Ultrasound Augmented Leaching of Complicated Zinc Oxide Ores in Ammonia and Ammonium Citrate Solutions

Recovery of zinc from low grade zinc oxide ore is attempted with ammonia and ammonium citrate solutions augmented by microwave roasting and ultrasound radiation. The influence of the ammonia-ammonium ratio, roasting temperature, ultrasound power, and leaching time were assessed on the recovery of zinc. A maximum zinc recovery of 88.57% could be achieved at a roasting temperature of 673 K, leaching temperature of 298 K, stirring speed of 300 rpm, total ammonia concentration of 5 mol/L with an ammonium citrate concentration of 1.2 mol/L, liquid to solid ratio of 5:1, the ultrasound power was 600 W and the leaching time was 120 min. The enhancement in recovery with increases in the roasting temperature up to 673 K was attributed to the conversion of ZnCO3 to ZnO. The phases of mineral samples and the reaction residues were characterized by X-ray diffraction (XRD).

Micro-pattern Corrosion Screening on Bimetallic Corrosion for Microelectronic Application

The continued miniaturization of the integrated circuit, leading to minute dimensions (<10nm) in microelectronic architecture, can greatly accelerate the on chip corrosion into a severe reliability threat. Particularly, various interfaces between multilayered film stacks create dissimilar contacts with significant galvanic potential difference. This can promote on-chip corrosion under semiconductor processing conditions. In this paper, an efficient micro-pattern corrosion screening metrology combined with electrochemical and x-ray photoelectron scattering techniques, is utilized to study bimetallic corrosion and its inhibition in wafer cleaning solutions. Cu/Ru bimetallic contact was found to exhibit a higher corrosion rate than the Cu/Ta contact. In alkaline ammonium citrate solution, higher dissolved oxygen content significantly accelerated Cu corrosion. The increased alkalinity (pH>12) at Cu/Ru interface, caused by enhanced oxygen reduction reaction on Ru, is proposed to generate more NH3 for sustaining fast Cu corrosion. Effects of different plasma chemistries like CF4, CF4+O2, CH2F2, C4F8 and SF6 on the Cu corrosion in tetramethylammonium hydroxide (TMAH) were also investigated. Plasma treatments using higher fluorine content gases showed higher Cu corrosion rate in TMAH. Benzotriazole showed limited corrosion inhibition to plasma treated Cu/Ru micro-patterns in pH 14 TMAH solution. Contrastingly, pyrazole demonstrated as an effective corrosion inhibitor suppressing Cu corrosion rate down to the desirable < 1 A°/min level.

Removal of Radioactive Cesium from Soil by Ammonium Citrate Solution and Ionic Liquid

Removal of Radioactive Cesium from Soil by Ammonium Citrate Solution and Ionic Liquid

Electrodeposition of iron–molybdenum alloy from ammonium–citrate solutions and properties of produced materials

The structure and properties of Fe–Mo alloys is studied. It is shown that the iron–molybdenum alloys formed in the electrolysis are highly hydrogenated, and the content of hydrogen in them increases with increasing atomic fraction of molybdenum in the cathodic deposit. The kinetics of hydrogen evolution reaction in the alkaline solutions on the obtained materials is studied.

Recovery potential of German sewage sludge ash

Incineration of sewage sludge is expected to increase in the future due to growing concerns about the direct use of sludge in agriculture. Sewage sludge is the pollutant sink of wastewater treatment and thus loaded with contaminants that might pose environmental hazards. Incineration degrades organic pollutants efficiently, but since the ash is currently mostly disposed of, all valuable component like phosphorus (P) and technologically relevant metals present in the sewage sludge ash (SSA) are removed from the economic cycle entirely. We conducted a complete survey of SSA from German mono-incineration facilities and determined the theoretical recovery potential of 57 elements. German SSA contains up to 19,000t/a P which equals approximately 13% of phosphorus applied in the German agriculture in form of phosphate rock based mineral fertilizers. Thus, SSA is an important secondary resource of P. However, its P-solubility in ammonium citrate solution, an indicator for the bioavailability, is only about 26%. Treatment of SSA is recommended to enhance P bioavailability and remove heavy metals before it is applied as fertilizer. The recovery potential for technologically relevant metals is generally low, but some of these elements might be recovered efficiently in the course of P recovery exploiting synergies.

A novel separation process for detoxifying cadmium-containing residues from zinc purification plants

A novel separation process for detoxifying cadmium-containing residues arising from zinc hydrometallurgical processes has been developed. The solution of sulfuric acid and ammonium citrate ((NH4)3C6H5O7) is used as the lixiviant to partially extract copper and other metals from the residue at room temperature. Copper in the leachate is recovered by solvent extraction (SX) with LIX 973. Cobalt in the raffinate from the copper SX process is recovered by precipitation with α-nitroso-β-naphthol. Zinc remaining in the solution, at high concentrations, is further separated from cadmium by solvent extraction with P204 (di(2-ethylhexly)phosphoric acid, D2EHPA). The results show that around 50% of the copper and virtually all the zinc, cadmium and cobalt in the residue can be leached under the experimental conditions used here. Virtually all dissolved copper and cobalt can be recovered in the subsequent solvent extraction and precipitation processes. The presence of (NH4)3C6H5O7 could significantly facilitate the extraction of zinc by D2EHPA. More than 97% of the dissolved zinc can be recovered through a two-stage counter current solvent extraction process. After separating copper, cobalt and zinc, cadmium can easily be recovered from the solution either by cementation with zinc powder or by electrowinning, while the purified solution can be recycled back to the leaching process.

Preliminary studies on the valorization of animal flour ash for the obtainment of active glasses

Animal flour ash, rich in phosphorous, calcium and alkaline oxides, has been used to formulate (i) controlled-release fertilizers, since they manage to release the nutrient elements (P, K) at a low rate, and (ii) bioactive glasses.(i) Four formulations were tailored using different amounts of animal flour ash (35–48wt%), potassium carbonate (10–25wt%) and a fixed amount of glassy sand (40wt%) in order to get glasses and glass-ceramics. The materials were characterised from a chemical (XRF), crystallographic (XRD) and microstructural (SEM/EDS) point of view. Moreover, in order to check the ability to release the macro- and micro-nutrients, tests were conducted to determine the kinetics of glass dissolution in different media (2% citric acid solution, 1% hydrochloric acid solution and ammonium citrate solution). The results obtained allowed to confirm all samples show a very low solubility in water (less than 1%) and high values (>40%) of P, Ca, K and Na in the other media.(ii) The rich content of phosphorous and calcium oxides makes the animal waste-derived ash a potential low-cost raw material to produce bioactive glasses. The analysis was focused on a bioactive glass, named BG_Ca, whose composition comes from the standard Bioglass® 45S5, got by increasing as much as possible the CaO content to combine a controlled behaviour during processing and a good apatite-forming ability in a simulated body fluid (SBF).This preliminary investigation shows that animal flour ash is a versatile material, which may be successfully used for several applications as various as the production of fertilisers and the preparation of bioactive glasses.

Cross-section measurements for the formation of manganese-52 and its isolation with a non-hazardous eluent

Summary With respect to the production of no-carrieradded 52Mn nuclear reactions on natural chromium were investigated. Cross sections of the reactions natCr(p, x)48V, 48,49,51Cr, 52g,mMn were determined in the proton energy range of 7.6 to 45MeV. Additionally, production yields of 52g,mMn and 51Cr were measured in the energy range from 8.2 to 16.9MeV and therefrom the calculated saturation thick target yields were obtained as (2.55±0.31), (6.96±0.57), and (1.53±0.15) GBq/μA, respectively. For in vivo applications like PET, low toxicity is critical and sufficient activity of a radiolabelled compound mandatory. Thus, additional purification steps after separation of radionuclides and target materials have to be avoided. However, no isolation procedure has been reported in the literature so far where radiomanganese is directly obtained in a nonhazardous solution. Therefore a new separation procedure was developed utilizing the cation-exchange resin DOWEX 50W×8 (H+-form). 52gMn was quantitatively isolated from “bulk” chromium after 3 to 4 h in non-hazardous 0.067M ammonium citrate solution. Up to 99% of 52gMn activity was harvested within 10 to 15 mL eluent solution with no measureable 51Cr impurities.