NH4Cl Solution Research Articles

UHMWPE Modified by Halogenating Reagents: Study on the Improvement of Hydrophilicity and Tribological Properties

Three groups of ultra-high-molecular-weight polyethylene (UHMWPE) with optimum hydrophilicity were obtained by halogenation modification. They were immersed in a 15% KBr solution for 30 h, a 10% NH4Cl solution for 60 h, or a 15% NH4Cl solution for 60 h. The mechanism of hydrophilicity enhancement by halogenation modification was investigated by combining surface morphologies and energy spectrum analysis. Friction and wear tests were carried out to measure the friction coefficients of modified UHMWPE under different test conditions, and the wear volume and morphologies of the worn surfaces were studied to explore the friction and wear mechanism. The results showed that the best tribological properties were obtained when immersed in the 15% KBr solution for 30 h. Furthermore, the synergistic optimization effect of hydrophilicity enhancement on tribological properties was explained by the lubrication mechanism, as well as the influence of interfacial properties change on the wear mechanism. This study provides an experimental and theoretical basis for using halogenated UHMWPE.

Production of Nanoporous Zeolites Modified by Silver Ions with Antibacterial Properties

We study the effect of activation of clinoptilolite specimens by the solutions of HCl, H2SO4 , NaOH, and NH4Cl with their subsequent thermal treatment for the sorption capacity in silver ions. It is shown that the highest sorption capacity is observed for the clinoptilolite activated by a sodium-hydroxide solution. It was established that, in all cases, the increment of sorption capacity observed upon attainment of a temperature of 200°С is insignificant. The rate of sorption of silver ions by clinoptilolite preliminarily activated by reagents is higher than the initial rate (without activation) by an order of magnitude. We also established the influence of the temperature of treatment of chemically activated clinoptilolite on the sorption rate of silver ions. It was shown that their absorption by clinoptilolite occurs according to the mechanisms of ion exchange and sorption.

High-temperature thermodynamics of ZnO–NH4Cl–H2O system

On the basis of the principles of simultaneous equilibrium, conservation of mass, and aqueous electronic charge neutrality and the correspondence principle of ion entropy, the high-temperature thermodynamics of the ZnO–NH4Cl–H2O system was studied to predict solubility and construct Zn species distribution. The model was constructed precisely by using the MATLAB program. The total Zn2+ concentration in the solution was affected significantly by temperature and total ammonium concentration. ZnNH3Cl3− was the predominant species in the ZnO–NH4Cl–H2O system. The solubility of zinc diammine chloride in NH4Cl solution (>2 mol·L−1) in the temperature range of 303–353 K was determined using equilibrium experiments, which had results that agreed well with the theoretical value. The data and high-temperature thermodynamic model used in this paper are reliable.

Removal of ammonia nitrogen from water by mesoporous carbon electrode-based membrane capacitance deionization.

The removal of ammonia nitrogen from wastewater is always a focus in current water treatment. In this study, a combination of mesoporous carbon electrode and selective ion exchange membrane was used to assemble a membrane capacitor deionization system (MCDI). The optimal process parameters were determined as follows: the plate spacing was 1 mm, the voltage was 1.2 V, and the flow rate was 23.8 mL/min. Under the optimal conditions, the removal efficiency of ammonia nitrogen can reach more than 80%. The quasi-first order kinetics and Langmuir adsorption isotherm model can well describe the adsorption process of MCDI. The nature of physical adsorption between ammonia nitrogen cations and mesoporous carbon electrode was demonstrated by the calculation of activation energy and thermodynamic parameters. Moreover, 1500 mg/L NH4Cl, NaNO2, and NaNO3 solutions were tested respectively. The results showed that the removal efficiencies of NH4+, NO2-, and NO3- were 82.33%, 90.96%, and 97.73% respectively, indicating that MCDI is feasible to removal different forms of inorganic nitrogen from water.

Local structure of NH4Cl solution and its correlation with osmotic coefficient by molecular dynamics simulation and Raman spectroscopy

The NH4Cl aqueous solution ranging from 1.00 wt.% to 22.00 wt.% have been studied by molecular dynamic simulation, Raman spectroscopy and polarized Raman spectroscopy. Radial distribution function (RDF), diffusion property, structure of hydrogen bond network, excess Raman spectroscopy and non-coincidence effect (NCE) were obtained. The contact ion pairs of cation and anion appeared in NH4Cl solution of 15.00 wt.%, leading to fundamental changes in hydrogen bonds and the hydrated shell. The evolution of hydrogen bond with mass fraction in solution was described. The osmotic coefficient of NH4Cl aqueous solution was obtained by thermodynamic calculation, and its linear relationship with double donor single acceptor hydrogen bond (DDA-OH) was preliminarily summarized. Moreover, the experimental results are in good agreement with the simulation results.

Recovery of pure molybdenum and vanadium compounds from spent petroleum catalysts by treatment with ionic liquid solution in the presence of oxidizing agent

Nonaqueous solutions were employed to investigate the selective recovery of vanadium and molybdenum from the spent petroleum catalysts. In this work, commercial extractants such as D2EHPA, Alamine336 and Aliquat336, and an ionic liquid synthesized from Aliquat336 and D2EHPA, ALi-D2, were employed as a lixiviant and extractant for the target metal ions in the presence of oxidizing agent, H2O2. Among the 4 nonaqueous systems, ALi-D2 showed the best performance for the selective and effective leaching of vanadium and molybdenum over alumina, nickel and iron. The effect of several parameters on the leaching efficiency was also studied. Under the optimum conditions, the leaching percentage of vanadium and molybdenum was 74.6 and 89.6% in the first stage and 26.0 and 66.9% in the second stage by ALi-D2 system. Vanadium and molybdenum from the ALi-D2 loaded phase can be sequentially precipitated by NH4Cl and BaCl2 solutions in alkaline media. Precipitation percentage of vanadium were 94.2% and its purity was 99.5%, whereas that of molybdenum was 99.4% with 84.1% purity. A process was proposed for recovery of vanadium and molybdenum from the spent petroleum catalysts. Pure vanadium and molybdenum compounds can be recovered by this process with less burden to the environment.

Hydrometallurgical stepwise recovery of copper and zinc from smelting slag of waste brass in ammonium chloride solution

A new process for recycling zinc and copper from the smelting slag of waste brass was investigated in this study. The zinc and copper present in the smelting slag were dissolved in a ZnCl2–NH4Cl solution system. To recycle copper, the lixivium was purified by a novel method termed as electrochemistry and chemistry synergetic (ECS) purification. After deep purification of the ECS-treated lixivium by zinc powder cementation, zinc in the lixivium was extracted by electrowinning to obtain a zinc plate. The effects of the leaching temperature, reaction time, and liquid–solid ratio on the extraction percentages of zinc and copper were examined. The results revealed that the extraction percentages of zinc and copper were 88.37% and 90.85%, respectively, at a leaching temperature of 95 °C, reaction time of 90 min, and liquid–solid ratio of 8:1 mL/g. Further, effects of the current density, temperature, and reaction time on the recovery ratio of copper by ECS method were examined. The results revealed that 98.51% of copper could be extracted from the lixivium and that the purity of the extracted copper was 96.7% at a temperature of 70 °C and cathode current density of 75 A/m2 after a reaction for 4 h. In the deep purification process, 0.3 g/L zinc powder was used to completely remove impurities from the ECS-treated lixivium. In the zinc electrowinning process, a current efficiency of 95.79% was achieved at 70 °C and 400 A/m2; the purity of the obtained zinc product was greater than 99.95%, and the direct energy consumption was 2966.59 kW·h/t-Zn.

Chondroitin sulfate as a green corrosion inhibitor for zinc in 26% ammonium chloride solution: Electrochemical and surface morphological analysis

In the present investigation, Chondroitin sulfate (CS) has been tested as green as a corrosion inhibitor for zinc-carbon battery by using electrochemical impedance spectroscopy (EIS), electrochemical frequency trend modulation (EFTM) and potentiodynamic polarization (PDP) measurements. The calculated results suggest that inhibition efficiency is 98.9% at the optimum concentration (200 mg/L) in 26% NH4Cl solution at 308 K. The outcome of EIS indicates that the values of double-layer thickness increased as the CS concentration increased. EFTM suggests in the presence of CS corrosion rate and corrosion current decreased.PDP results reveal that the nature of CS adsorption is mixed with dominantly cathodic.CS adsorption on the zinc surface obeyed the El-Awady adsorption isotherm model. The magnitude of ΔGads supports the chemical nature of CS adsorption. The Scanning electron microscope (SEM), Energy dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS) study supports the presence of CS adsorbed film over the zinc surface.

Effect of cations in chloride solutions on low-temperature hydrolysis performances and mechanisms of Mg–Ca-based hydride

Hydrogen generation via hydrolysis can provide fuel cell with the on-site and controllable supply. However, the current hydrolysis materials that exhibit poor performances at low temperatures are not suitable for portable devices and military. In this study, influence of different cations (Na+, Ca2+, Mg2+ and NH4+) in chloride solutions on low-temperature (253, 263, 273, 283K) hydrolysis performances of Mg–Ca based hydride (MCH) and mechanisms of interaction are investigated. The results demonstrate that Mg2+ and NH4+ in chloride solutions significantly enhance the rate of hydrolysis reaction between MCH and water. In NH4Cl solution, MCH exhibits the best initial hydrolysis performance and the highest H2 yield, 1198 mL g−1(MCH) of H2 is generated within the first 5 min and the final conversion rate reaches 89% at 273 K. MCH displays the best hydrolysis dynamics in MgCl2 solution, where the activation energy is low, only 3.56 kJ mol−1. This can be attributed to the fact that the types of hydroxide products and the corresponding physical states with respect to the hydrolysis of MCH in various chloride solutions differ with the variations of OH− affinity toward Mn+ cations (i.e. pK/(n+1)) when pH values of chloride solutions are altered. Thus, different low-temperature hydrolysis performances can be observed. Above all, the remarkable low-temperature hydrolysis performances of MCH–MgCl2 and MCH–NH4Cl systems indicate that both systems are promising candidates for supplying H2 for the portable and military fuel cells at various remote locations, especially in areas with low temperatures.

Soft chemical deintercalation of silver from delafossites AgFeO2, and AgCrO2

Selective deintercalation of Ag+-ion from AgFeO2 and AgCrO2 with the use of dilute aqueous solutions of NH4Cl was achieved successfully. Based on the ICP analysis, the Ag: Fe and Ag: Cr ratios were 0.9:1 and 0.87:1 in the deintercalated sample of AgFeO2 and AgCrO2, respectively. Retention of both structure and the polytypes were noticed after deintercalation together with the reduction in their unit cell c-axis. Raman spectra of deintercalated samples confirmed the preservation of overall symmetry. XPS results confirmed the existence of Fe (III) and Cr (III) in the Ag+-ion deintercalated samples.

In situ assembly of PB/SiO2 composite PVDF membrane for selective removal of trace radiocesium from aqueous environment

A non-toxic and applicable surface-modified polyvinylidene fluoride (PVDF) membrane consisting of Prussian blue (PB) and aminating silica (A-SiO2) nanoparticles was fabricated for the selective removal of trace radionuclide cesium (Cs) from water. The modified membrane denoted as PB/A-SiO2/PVDF exhibited high selective removal of cesium with a high permeate flux of more than 800 L/h∙bar∙m2 in a wide pH range from 3 to 9. The adsorption experiments showed that the Langmuir isotherm model and the pseudo-second order model fitted well with the experimental results. The maximum adsorption capacity was 10.95 mg-Cs/g-membrane (i.e. 78.21 mg-Cs/g-PB sorbent on membrane) for the membrane at an initial Cs concentration of 50 mg/L. Based on the high Cs adsorption capacity of PB, the membrane could remove more than 97.5% Cs in the presence of the coexisting ions and organic matter for more than 10 h. The filtrated membrane could be effectively regenerated by NH4Cl, H2O2 and HNO3 solution with negligible decrease in removal efficiency after repeated use. With the high membrane flux and selective removal efficiency, the fabricated membrane can be potentially applied in Cs contaminated water treatment.

Transport Models of Ammonium Nitrogen in Wastewater from Rare Earth Smelteries by Reverse Osmosis Membranes

Wastewater from rare earth smelteries contains large amounts of ammonium nitrogen (NH4+-N), which causes severe environmental problems. In this contribution, the desalination efficiency of reverse osmosis (RO) was investigated in the treatment of NH4Cl or NaCl solutions from 0.1 to 40 g/L under different operating pressures with a commercial RO membrane. Experimental results showed that when an operating pressure above 30 bar is applied to the 5 g/L NH4Cl solution, the permeate was found to meet the discharge standards of NH4+-N. Compared to NH4Cl, the permeate fluxes of NaCl solutions were higher due to the higher net driving force and lower propensity to membrane fouling. Theoretical models indicate a linear relationship between water flux and the net driving force for both NH4Cl and NaCl solutions. On the contrary, a power function between the salt flux and concentration difference correlated well with the experimental data for salt transport. The equations for water and salt transport obtained by this work would provide a facile and practical means for predicting the membrane performance in design and optimization of RO processes for the treatment of wastewater from the rare earth industry.

Using highly concentrated chloride solutions to leach valuable metals from cathode-active materials in spent lithium-ion batteries

This study focused on the extraction of valuable metals from the cathode-active materials in spent lithium-ion batteries using a high-concentration chloride solution. The effects of the concentrations of ammonium chloride (NH4Cl), hydrochloric acid (HCl), and reductants such as hydrogen peroxide (H2O2) and urea (CO(NH2)2) on metal extraction and chlorine production were studied experimentally. The leaching mechanism was analyzed, and a leaching model was established. It was found that the addition of solid NH4Cl to an HCl solution significantly improved the metal extraction capability of the latter and reduced the formation of chlorine gas by 96.0% compared to that only using HCl. The activation energies for leaching Li, Ni, Co, and Mn were determined to be 30.4, 38.5, 30.6, and 38.2 kJ·mol−1, respectively. This study demonstrates an environmentally friendly method for recycling metal resources from cathode-active materials and furthers understanding of how NH4Cl inhibits chlorine production when leaching with mixed solutions of HCl and NH4Cl.

Rheology of Pastes Containing High-Volume Fly Ash and Their Permeability Because of Calcium Leaching Procedure in Ammonium Chloride Solution

Abstract This article presents the findings of a research program that concern the rheology of fresh paste containing high-volume fly ash and its permeability because of calcium leaching procedure after 90 days’ curing. In a fresh state, the combined influence of fly ash content and water addition time on Herschel–Bulkley parameters was investigated. The critical value of fly ash content and water addition time was defined. In a hardened state, ammonium chloride (NH4Cl) was chosen as the accelerate leachant based on the comparison of microscale effect of ammonium nitrate (NH4NO3) and NH4Cl solution as well as leaching mechanism establishment. At specified leaching durations, the leached depth and porosity and permeability coefficient of both sound and deteriorated paste specimens were tested. It was indicated that both the porosity increment and permeability coefficient increment have a linear relation to the square root of leached ratio. Additionally, the velocity of the porosity increment declines with fly ash content, whereas the velocity of permeability coefficient increment declines with fly ash content at first and increases slightly when the fly ash dosage ranges from 40 % to 60 %. It can be concluded that fly ash was effective in improving leaching resistance. Finally, the relevance of fresh and hardened behavior was proposed.

Hydrometallurgical recycling of palladium and platinum from exhausted diesel oxidation catalysts

An efficient reclamation of the precious metals remained in exhausted diesel oxidation catalyst (DOC) is desirable due to their high economic values and depletion of primary minerals. Aiming to the resource recovery from exhausted DOC, herein, HCl leaching followed by the selective precipitation of platinum and palladium has been investigated. The parameters like acid concentration (2.0–10.0 mol/L), H2O2 addition dosage (0.5–5.0 vol%), temperature (25–70 °C), time (10–180 min), and pulp density (5–20 wt./vol.%) were varied to determine the optimum condition of leaching. Experimental results revealed that the efficient formation of metal-chloro complexes was achieved by the addition of 3 vol% H2O2 with 8.0 mol/L HCl solution at 55 °C and 180 min of leach time that yielded approximately 94% palladium and 90% platinum into the leach liquor. Under the studied condition, the leaching process was found to be governed by a diffusion-controlled mechanism with the apparent activation energy of palladium and platinum was calculated to be 14.4 kJ/mol and 10.8 kJ/mol, respectively by following the logarithmic model. Subsequently, the leach liquor was processed to selectively recover platinum salt by adding a 300 g/L solution of NH4Cl, precipitating (NH4)2PtCl6. Palladium from platinum-depleted leach liquor was recovered by additional introducing NaClO3 crystals under heating, yielding red precipitates of (NH4)2PdCl6. The present process can potentially contribute to the circular economy of precious metals through the hydrometallurgical recycling of exhausted DOC.

Determination of Ultralow Level 135Cs and 135Cs/137Cs Ratio in Environmental Samples by Chemical Separation and Triple Quadrupole ICP-MS.

An analytical method was developed for the determination of ultralow level 135Cs in environmental samples by chromatographic separation of cesium with AMP-PAN and AG50W-X8 columns and sensitive measurement of cesium isotopes with triple quadrupole inductively coupled plasma mass spectrometry (ICP-MS/MS). Cesium was simply released by acid leaching using aqua regia from environmental solid samples and preconcentrated on AMP-PAN column. The cesium adsorbed on the column was effectively eluted with NH4Cl solution without dissolving the AMP. The excessive amount of NH4Cl in the eluate was removed by sublimation in the presence of small amount of LiCl. The remaining barium and other interfering elements such as Mo, Sn, Sb, and Li were efficiently removed using cation exchange chromatography (AG50W-X8). The decontamination factors of this procedure are above 4 × 107 for barium and 4 × 105 for molybdenum; the chemical yields of cesium are more than 85% for samples of less than 10 g. This method enables to separate cesium from large size of samples for the determination of ultralow level 135Cs, avoiding the problem of removal of a huge amount of Mo in the dissolved AMP. Intrinsic 137Cs in the environmental samples measured by gamma spectrometry before and after separation was used as internal isotope dilution standard for quantitative determination of 135Cs without complete release and recover of radiocesium. The interference of barium (135Ba and 137Ba) to the ICP-MS measurement of 135Cs and 137Cs was further suppressed to 8 × 10-5 by using N2O as the reaction gas in ICP-MS/MS at a flow rate of 0.7 mL/min, so a total suppression of 2 × 10-12 for Ba was achieved, making the isobaric interference of Ba isotopes to the measurement of 135Cs and 137Cs in environmental samples negligible. A detection limit of 9.1 × 10-17 g/g for 135Cs and 137Cs was achieved for 60 g samples. The developed method was validated by analysis of standard reference materials (IAEA-375, IAEA-330, and IAEA-385) and successfully applied for the determination of 135Cs concentrations and 135Cs/137Cs ratios in soil samples collected from Denmark, Sweden, and Ukraine. The 135Cs/137Cs isotopic ratios in Danish soil (2.08-2.68) were significantly higher than that from Sweden and Ukraine (0.65-0.71), indicating different sources of radiocesium. This work demonstrated the application of 135Cs/137Cs as a unique fingerprint for discriminating the sources of radioactive contamination and estimating their contribution to the total inventory, which will be useful for nuclear forensics and environmental tracer studies.

A newly synthesized green corrosion inhibitor imidazoline derivative for carbon steel in 7.5% NH4Cl solution

Corrosion and corrosion inhibition behaviors of steel Q-235 were studied in 7.5% NH4Cl solution with the newly synthesized inhibitor by potentiodynamic polarization together with tests of electrochemical impedance spectroscopy and weight loss measurements in 298–338 K temperature range. The new inhibitor 2-(2-heptadecyl-4, 5-dihydro-1H-imidazole-1-yl) ethanol (HDIE) is synthesized with the help of microwave radiations in solvent free conditions. The results showed that inhibition efficiency above 90% is achievable at 298 K with 0.5 mML−1 inhibitor concentration. The Adsorption studies revealed that HDIE follows Langmuir model and its adsorption mechanism was mixed-type with predominant effect on anodic half cell. It was seen from the EDS characterization of corroded steel surfaces that the HDIE retarded the corrosion by impeding the chloride attack. Quantum chemical calculations demonstrated that the imidazoline ring and hetero-atoms were active sites. Moreover, an inhibition mechanism was proposed on the basis of the quantum chemical calculations and experimental corrosion studies.

Square wave anodic stripping voltammetric determination of Hg(II) with N-p- chlorophenylcinnamohydroxamic acid modified carbon paste electrode

A new method has been developed for the electrochemical determination of Hg(II) with N-p-chlorophenylcinnamohydroxamic acid (CPCHA) modified carbon paste electrode by square wave anodic stripping voltammetry (SWASV). Hg(II) was accumulated on the electrode surface by the formation of the complex in an open circuit and the resulting surface was characterized by electrochemical reduction and stripping. The optimum voltammetric response was observed using a carbon paste composition of 7.5% (w/w) CPCHA and preconcentration time of 210 s in 0.1 M sodium acetate at pH 8 followed by electrochemical SWASV in 0.3 M NH4Cl solution at pH 4 at a reduction potential of -0.6 V. The voltammetric signals were linear in the range of 1-25 µM Hg(II) with a detection limit of 12.9 nM. The voltammetric response for six replicate measurements of 15 µM Hg(II) was reproduced with 3.8% relative standard deviation (RSD). Many coexisting metal ions had little or no effect on the determination of Hg(II). Five spiked samples of water were evaluated by using the developed method giving recoveries of Hg(II) in the range 98-105%.
 
 Bull. Chem. Soc. Ethiop. 2020, 34(1), 25-39.
 DOI: https://dx.doi.org/10.4314/bcse.v34i1.3

Mesoporous Intermetallic NiAl Nanocompound Prepared in a Molten LiCl Using Calcium Species as Templates

A novel mesoporous intermetallic NiAl nanocompound was successfully prepared at 600 °C in a molten LiCl with an assistance of CaH2. The obtained powder had a fine crystal structure assigned to a single phase intermetallic NiAl. The measured BET surface area was as high as 113.9 m2/g, originating from the mesopores (3.1 nm on average) and the unique crumpled morphology. Calcium species, such as CaH2, Ca(OH)2, CaO and CaCl2, could work as templates in alloying process and they were readily removable by NH4Cl solution rinsing afterwards. As far as we know, this paper is the first report of mesoporous metal aluminide with a defined crystal structure and a high surface area of >100 m2/g.

Formation of calcite in the presence of dissolved organic matter: Partitioning, fabrics and fluorescence

Dissolved organic matter (DOM) is omnipresent in natural waters and is commonly incorporated into carbonates. Records of DOM from speleothems (secondary carbonates found in caves) have often been interpreted to reflect groundwater DOM concentrations. However, the fidelity of these records is largely untested. An understanding of the relationship between dripwater and speleothem DOM is thus required to allow speleothems to be reliably used as archives of DOM concentration.We precipitated calcite (CaCO3) crystals from weak solutions of (NH4)2CO3, CaCl2 and NH4Cl. These solutions also contained peat DOM (from 0 to 15 mgC/L). Fluorescence 3D excitation-emission matrix (3D EEM) analysis showed a strong, positive correlation between [DOM] in the parent-solution, and [DOM] in the calcite. Calcite precipitation was reduced at high DOM concentrations, potentially indicating inhibition of crystallisation. Partition coefficient values showed that DOMaq was subtly preferentially incorporated into calcite.Scanning electron microscope images indicated that the crystal structures were heavily influenced by DOM adsorption with finer, smooth-faced, rhombohedral crystals forming in growth solutions with low aqueous [DOM] (0–5 mgC/L), and prismatic, ‘impure’ crystals produced at high aqueous [DOM] (10 and 15 mgC/L).Overall, our results indicate that authigenic carbonates are likely to faithfully record variations in aqueous [DOM] within the natural range of DOM concentrations in representative freshwater systems (caves, soil water), and that crystal habits are altered by aqueous [DOM] within their growth solutions.We also applied our findings to three flowstones collected from three New Zealand caves which vary in climatic, vegetation and hydrological regimes. We conclude that differences in initial aqueous [DOM] do indeed control incorporation of DOM into calcite, and thus 3D EEM fluorescence can be used to reconstruct original aqueous [DOM] from authigenic carbonates.