Ammonium Carbonate Solution Research Articles

The Enhancement of Enargite Dissolution by Sodium Hypochlorite in Ammoniacal Solutions.

The dissolution of both copper and arsenic from a copper concentrate was investigated in oxidative ammonia/ammonium solutions at moderate temperatures and atmospheric pressure. The main parameters studied were temperature, pH, concentrations of different ammonia salts, the presence of sodium hypochlorite, pretreatment with sodium chloride, and curing period. In all ammoniacal solutions studied, increasing the temperature enhanced the dissolution of copper, but the dissolution of arsenic remained marginal. Mixing the copper concentrate with sodium chloride and leaving it to rest for 72 h before leaching in ammoniacal solutions significantly increased the dissolution of copper and slightly increased the dissolution of arsenic from the concentrate. A maximum of 35% of Cu and 3.3% of As were extracted when ammonium carbonate was used as the lixiviant. The results show relatively rapid dissolution of the concentrate with the addition of sodium hypochlorite in ammonium carbonate solution, achieving a dissolution of up to 50% and 25% of copper and arsenic, respectively. A copper dissolution with a non-linear regression model was proposed, considering the effect of NaClO and NH4Cl at 25 °C. These findings highlight the importance of using the correct anionic ligands for the ammonium ions and temperature to obtain a high dissolution of copper or arsenic. The results also showed that the curing time of the packed bed before the commencement of leaching appeared to be an important parameter to enhance the dissolution of copper and leave the arsenic in the residues.

Reversible pH Responsive Aggregation Behavior of Size-Controlled Calcium Carbonate Composite Nanoparticles by Phytic Acid in Aqueous Solution.

Composite colloidal nanoparticles were prepared by a carbonate controlled-addition method in the presence of phytic acid, in which an aqueous ammonium carbonate solution was added into an aqueous solution of phytic acid and CaCl2. The number-average particle size of the colloidal particles was 76 ± 18 nm formed by using the molar ratio [phytic acid]/[Ca2+] = 0.5 from the complexation time of 1 h. The composite nanoparticles were stable for more than 5 days in the suspension under the quiescent condition. After isolation of the nanoparticles by ultrafiltration, the dried samples could be redispersed in water. Effects of the complexation times of the aqueous solution of phytic acid and CaCl2 and the molar ratio ([phytic acid]/[Ca2+]) were studied. Increasing the concentration of the calcium reagents as well as increasing the complexation times increased the particle sizes. The minimum and maximum average particle sizes of 29 and 142 nm were obtained. The plot of the transmittance at 350 nm of the aqueous solution of the dispersion against pH values after addition of 0.05 M HCl for 6 h showed that, by gradually increasing turbidity with decreasing pH from 9.6 to 7.3, precipitates were recognized at below pH 7.5, and turbidity decreased with further decreasing pH beyond 7.2. Dynamic light scattering analysis showed that the particle diameters increased from 90 to 200 nm with decreasing pH from 9.6 to 7.2. When increasing the pH from 6.2, the precipitate was redispersed and the turbidity increased to a pH of 7.4. No precipitates were observed above a pH of 7.4. These results suggest that the present phytic acid stabilized nanoparticles exhibit pH-dependent reversible precipitation and redispersion without degradation under slightly acidic conditions.

Recovery of Copper from Ammoniacal Leachates by Ion Flotation

Sulfidic copper–lead–zinc tailings can pose a significant environmental threat, ranging from generation of acid mine drainage (AMD) to dam failures. On the other hand, they can also be considered as low-grade ore resources for zinc and copper provided that novel economically feasible metal extraction and metal recovery techniques are developed. Due to the low metal concentrations in these resources, the leaching will generate dilute leachates from which metal recovery is a challenge. Ion flotation is a foam separation technique capable of recovering metal ions from dilute aqueous leachates. In this paper, ion flotation was applied to separate copper from ammoniacal leachates of microwave-roasted sulfidic tailings samples. The sulfidic tailings were first roasted at 550 °C for 60 min, for the oxidation of sulfide minerals to more easily soluble sulfates using microwave-assisted irradiation as heating source. The microwave-roasted material was then leached with a mixture of ammonia and ammonium carbonate solutions. The optimum leaching efficiencies of zinc (86%) and copper (75%) were obtained under the following conditions: liquid-to-solid ratio = 10 mL g−1, T = 90 °C, [NH3 + NH4+] = 4 mol L−1, NH3:NH4+ = 2:1, t = 5 h. From the generated pregnant leach solution, it was possible to selectively separate 85% of copper to the foam phase by ion flotation, with sodium dodecyl sulfate (SDS) surfactant, as colloidal copper(II) tetraamine dodecyl sulfate under the optimized conditions: [SDS]total = 5.85 mmol L−1, [EtOH] = 0.5 % (v/v), ttotal = 5 h, flotation stages = 3. The zinc that remained in the solution after ion flotation was recovered by precipitation (95%) as basic zinc carbonate.Graphical AbstractCopper and zinc extraction by ammoniacal leaching from microwave-roasted Cu-Zn-Pb sulfidic tailings followed by recovery of copper and zinc by ion flotation and precipitation.

Kinetic and Thermodynamic Evaluation of the Uranium (VI) Stripping from Alamine-336 in the Presence of Iron (III)

An economic process was developed via the batch scale for the uranium (VI) stripping in the presence of iron (III) from loaded alamine-336 by ammonium carbonate solution. The optimum conditions were assessed for the uranium (VI) stripping using the central composite design method, which is a subset of response surface methodology. The R-squared, U (VI), and Fe (III) stripping percentages with a value of equal 0.989, 72.61%, and 0.1% were obtained, respectively in the optimum conditions of the U (VI) and Fe (III) stripping from loaded alamine-336. The optimum stripping conditions led to the obtaining of the ammonium carbonate concentration equal to 0.64 mol/L, the phase ratio of 0.8 (O/A), the temperature of 53 , the contact time of 2510 seconds, and the shaking speed of 1100 rpm. Moreover, the stripping kinetics, equilibrium constant, and thermodynamic data were determined to describe the nature of the U (VI) and Fe (III) stripping from loaded alamine-336 by the ammonium carbonate solution. The temperature-dependent data showed that the U (VI) stripping was an endothermic process.

Synthesis and characterization of two-dimensional (2D) nanosheet zinc aluminum layered double hydroxide (Zn/Al LDH) via an alkali-free route

The effect of different molar ratios on the synthesis of zinc aluminium layered double hydroxide (Zn/Al LDH) via an alkali-free route was carried out in this research. This method was prepared by mixing zinc nitrate solution, aluminium nitrate solution, and ammonium carbonate solution at a constant pH of 8.5 with a spanning ratio of Zn to Al from 4:1, 3:1, and 2:1. The XRD patterns showed crystal nanostructure of Zn/Al LDHs was successfully formed. The lattice parameters (a and c) were slightly increased with the increasing of Zn/Al molar ratio. A larger hexagonal platelet is observed in the SEM image align with the high molar ratio of Zn/Al synthesized. The same trend has been observed in the FTIR spectra.
 
 Keywords: Zn/Al LDH, alkali-free route, different molar ratio, XRD, SEM, FTIR

Synthesis and characterization of NiO colloidal ink solution for printing components of solid oxide fuel cells anodes

A synthesis of NiO colloidal ink solution for printing of the main anode component of solid oxide fuel cells (SOFCs) by commercial printer was shown in the work. The ink was synthesized by a single step chemical reaction of the dissolved nickel nitrate hexahydrate and ammonium carbonate solution with the addition of Triton X-100 surfactant. Results revealed that the obtained ink was stable for at least 4 months contained almost the same NiO nanoparticles with the size at the range of 7–9 nm. These nanoparticles structural and morphology investigation was conducted by high resolution transmission electron microscopy (HR-TEM), Raman spectroscopy and selected area electron diffraction (SAED) analytical methods. Detected rheological properties of the ink revealed that materials for anode in SOFC can be deposited using a commercial printer followed by calcination at 900 °C. Processes occurred during calcination were investigated by TGA and DSC analytical techniques. Finally, the printed coating was subjected to the investigation using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM).

Use of Carbamide Nitrate in the Hydrometallurgy of Uranium

The influence exerted by carbamide nitrate additive in the extractive refining of uranium on the capacity of the extractive agent (23% TBP in an organic diluent), completeness of uranium re-extraction from a saturated extractive agent, and residual concentration of uranium in the nitrate raffinate was examined. Nitrate-carbamide and nitrate solutions containing uranyl nitrate [UO2(NO3)2] obtained in the dissolution of concentrated uranium oxide (U3O8) were used in experiments. The re-extraction of uranium was performed with acidified water at pH 3. It was found that the capacities of the extractive agent for uranium are comparable for the nitrate-carbamide and nitrate solutions, which makes it possible to use carbamide nitrate as an agent for salting-out of uranyl nitrate. The residual concentration of uranium in the raffinate after a carbamide denitration does not exceed 13.6–14.1 mg/L. A solution of ammonium carbonate also provides a complete solid-phase re-extraction of uranium from the extractive agent saturated in the nitrate-carbamide solution. There is no accumulation of carbamide nitrate in the technological cycle at an acidity of the starting solution equal to 0.4–0.6 M. The stability temperature is calculated for the system under study. A process of hydrolysis of carbamide nitrate to ammonium nitrate at an elevated pressure is suggested. The resulting solution can be used, after an acidity correction, as a desorbing agent in the sorption refining of uranium in the technology of underground leaching of uranium.

Hydrothermally Synthesized Spherocobaltite Nano-Particles

Spherocobaltite, CoCO3, or cobalt carbonate is a mineral of calcite group. It finds applications in high-performance Li-ion batteries, as an animal feed trace elements, and also used as a precursors to synthesize cobalt oxide. In this study, spherocobaltite nano-particles are synthesized by hydrothermal method using cobalt sulphate solution and ammonium carbonate solution in the ratio of 1:3.The mixture was then transferred into a 100 ml Teflon-lined autoclave and heated at 140 °C for 4 h. The final sample is recovered by centrifugation redispersion cycle. The hexagonal crystal structure is confirmed by powder XRD, and the average crystallite size is determined by Scherrer’s formula and Williamson-Hall method, which is found to be within 14 nm. The presences of Carbon, Oxygen and Cobalt were confirmed by EDAX analysis. The TEM image suggests spherical morphology of the nano-particles. The FT-IR spectrum confirms the presence of functional groups such as O-H and C-O. The TGA curve suggests that the material starts dehydrating first and then decomposes in to cobalt oxide at 390o C temperature. The impedance and dielectric studies are carried out within 20 Hz to 2 MHz range at room temperature. The complex impedance and modulus plots are drawn and exhibiting the grain effect only. The VSM data taken at room temperature and low temperatures from 20 K to 300 K suggests a paramagnetic nature of the sample.

Production of high quality ammonium uranyl carbonate from “uranyl nitrate + carbonate” precursor solution

The purpose of this study is to investigate production of high quality ammonium uranyl carbonate (AUC) from “uranyl nitrate + ammonium bicarbonate”, or “uranyl nitrate + sodium carbonate” precursor solutions, by controlled injection of ammonium carbonate solution which could be applicable in material testing reactor (MTR) fuel production plant for recycling of rejected uranium oxide powder. The experimental observations revealed: at pHs higher than 6, precipitation proceeds with formation of no intermediate, thus ensuing a better morphology and size distribution of the AUC products. The results of scanning electron microscopy, X-ray diffraction, particle size analysis, and uranium content analysis showed that precipitation of AUC in the sodium carbonate medium was slow and incomplete (with a yield around 40%); and quality of the precipitate and morphology of its particles could not meet the required criteria. In contrast, ammonium bicarbonate medium resulted in the AUC crystals with suitable morphology and appreciable particle size distribution. In the latter case, precipitation was fairly well modelled by simple “diffusion-reaction” model. Application of the supersaturated ammonium bicarbonate solution for precipitation resulted in the following advantages over the sub-saturated solution: 1) higher yield of uranium precipitation, 2) smaller size of AUC particles (dmean≈86 μm compared to 112 μm for sub-saturated), 3) lower degree of crystals agglomeration, 4) lesser formation of cracks on the surface of U3O8 particles, which are prepared as the products from AUC. The final U3O8 powder, after sintering and milling, appears to be smooth and rounded, and was qualified for MTR fuel plate fabrication.

Preparation of spherical cobalt carbonate from cobalt sulfate solution

Abstract A precursor of cobaltous dihydroxycarbonate was firstly prepared by precipitation reaction of cobalt sulfate solution and ammonium carbonate solution, and then a hydrothermal process for the precursor was conducted to obtain the spherical cobalt carbonate with low sulfur content. The experimental results show that the feeding method, final pH value of the precipitation reaction slurry and the concentration of the cobalt sulfate solution have obvious effects on the sulfur content, morphology and particle size distribution of the precursor. The sulfur content of the precursor is 0.0115 wt.% under the optimized conditions. The hydrothermal treatment with temperatures of 125−150 °C can transform the precursor of cobaltous dihydroxycarbonate into spherical cobalt carbonate and decrease the sulfur content to 0.0030 wt.% in the obtained product.

Structural, magnetic and dielectric studies of siderite nano-particles synthesized by hydrothermal method

Siderite or ferrous carbonate [Formula: see text] is a well-known mineral and finds applications in various fields such as dietary supplement to treat anemia and in petroleum drilling fluids for [Formula: see text] removal. The FeCO3 nano-particles are synthesized by hydrothermal method using aqueous solutions of iron sulfate, ascorbic acid and ammonium carbonate with a molar ratio of 1:1:3, respectively, and heating at [Formula: see text]C for 1.5 h in Teflon-lined stainless steel autoclave. The recovered sample is characterized by several techniques. The powder XRD indicates the hexagonal crystal system and the average crystallite size of 17.32 nm are obtained from the Scherrer’s formula and 18.98 nm is obtained from the Williamson and Hall formula. The TEM images suggest the spherical nature of the nano-particles. The EDX confirms the elemental presence of iron, carbon and oxygen. The impedance and dielectric studies are carried out within 20 Hz–2 MHz range at room temperature. The complex impedance plot, i.e. the Nyquist plot, is composed of one semicircle indicating the contribution from the grain only. The Jonscher’s power-law is applied to AC conductivity data. The VSM data at room temperature and at low temperature, i.e. 20–300 K range, suggests a weak antiferromagnetic nature of the sample.

Influence of ammonium salts on the interaction of fluoroquinolone antibiotic drug with sodium dodecyl sulfate at different temperatures and compositions

The interaction between sodium dodecyl sulfate (SDS) and an antibiotic drug, ciprofloxacin hydrochloride (CPFH) has been carried out by conductometric measurement at various temperatures from 298.15 K to 318.15 K. The critical micelle concentration (cmc) values of SDS/SDS+CPFH mixture were attained to be reduced in the electrolytes medium. The effect on the cmc reduction is higher in case of ammonium carbonate than ammonium chloride. The cmc values of SDS/SDS+CPFH mixture follow U-shaped behavior with temperature in water and ammonium chloride and reversed U-shaped in ammonium carbonate solution. In the existence of CPFH, the cmc of SDS reduces in aqueous medium but enhances in the electrolytes medium. The extent of micelle ionization (α) was found to be enhanced with the increase of concentration of CPFH in aqueous medium and in ammonium chloride medium at a lower temperature. The α values follow inverted U-shaped in ammonium carbonate medium. The estimated values of ΔGmo for distinct SDS, as well as SDS+CPFH mixtures, were obtained to be negative in entire cases illustrating the spontaneity of micellization. The magnitudes of ΔHmo, ΔSmo and thermodynamic parameters of transfer have been evaluated and discussed in details.

Double Purification Technique for Crude Yellowcake: Selective Dissolution of Impurities and Liquid-Liquid Extraction from Acetate Media

Innovated two-stage technique was developed for the uranium purification starting from Egyptian crude yellowcake. Preliminary purification using urea-tetrahydrofuran system allowed removal of large amounts of undesirable gangues. The second purification stage using acetate aqueous liquor/Alamine 308 solvent extraction system allowed removal of the remaining gangues from the semirefined cake. The maximum loading capacity of the organic solvent was 42 gU L-1 after five contacts between the two phases under the optimized conditions: 10% solvent concentration in kerosene, 5 min shaking time, aqueous feed pH 0.25, and 1 : 1 organic to aqueous ratio. Uranium stripping was done using ammonium carbonate solution. The final purified uranium peroxide cake (66.2% U) of nuclear purity, meeting the ASTM C788-03 standard, was obtained from the stripping solution after hydrogen peroxide precipitation.

Monophosphine‐substituted diiron azadithiolate complexes: New syntheses, characterization and electrochemical properties

Investigating the synthesis and properties of diiron azadithiolate complexes is one of the key topics for mimicking the active site of [FeFe]‐hydrogenases, which might be very useful for the design of new efficient catalysts for hydrogen production and the development of a future hydrogen economy. A series of new phosphine‐substituted diiron azadithiolate complexes as models for the active site of [FeFe]‐hydrogenases are described. A novel and efficient way was firstly established for the preparation of phosphine‐substituted diiron azadithiolate complexes. The reaction of Fe2(μ‐SH)2(CO)6 and phosphine ligands L affords the intermediate Fe2(μ‐SH)2(CO)5L (A). The intermediate reacts in situ with a premixed solution of paraformaldehyde and ammonium carbonate to produce the target phosphine‐substituted diiron azadithiolate complexes Fe2[(μ‐SCH2)2NH](CO)5L (1a–1f) (L = P(C6H4–4‐CH3)3, P(C6H4–3‐CH3)3, P(C6H4–4‐F)3, P(C6H4–3‐F)3, P(2‐C4H3O)3, PPh2(OCH2CH3)). Furthermore, reactions of the intermediate A with I‐4‐C6H4N(CH2Cl)2 in the presence of Et3N give the phosphine‐substituted diiron azadithiolate complexes Fe2[(μ‐SCH2)2NC6H4–4‐I](CO)5L (2a–2e) (L = P(C6H4–4‐CH3)3, P(C6H4–3‐CH3)3, P(C6H4–4‐F)3, P(C6H4–3‐F)3, P(2‐C4H3O)3). All the complexes were fully characterized using elemental analysis, IR and NMR spectroscopies and, particularly for 1a, 1c–1e, 2a and 2c, single‐crystal X‐ray diffraction analysis. In addition, complexes 1a–1f and 2a–2e were found to be catalysts for H2 production under electrochemical conditions. Density functional theory calculations were performed for the reactions of Fe2(μ‐SH)2(CO)6 + P(C6H4–4‐CH3)3.

Recovery of vanadium using an aqueous two-phase system consisting of poly (ethylene glycol) 2000 and sodium sulfate

An environmentally friendly approach was reported for recovering vanadium (V) from aqueous media with aqueous two-phase system (ATPS) formed by poly (ethylene glycol) 2000 (PEG2000) and sodium sulfate with octadecyl amine ethoxylate ethers as extractants. The effect of aqueous pH, the type of extractants and phase-forming salts, vanadium concentration and extracting temperature on the extraction performance of vanadium was investigated. The researched results indicated that the extraction rate of vanadium has remarkable relationship with vanadium species in aqueous phase, and the selected extractants can extract efficiently vanadium from salt-rich to PEG200-rich phase. The initial and equilibrium pH in aqueous phase has no relationship with vanadium concentration, and there is no new covalent bond generation between polyvanadate anion and extractant in PEG 2000-rich phase by FTIR, which can be deduced that polyvanadate anion is extracted into PEG 2000-rich phase due to the electrostatic attraction interaction between protonated extractant and polyvanadate anion. Adding chloride and nitrate in aqueous two-phase system could remarkably decrease the extraction rate of vanadium, and then sulfate is in favor of extracting vanadium. The extraction rate of vanadium decreases with increasing temperature from 40.0 °C to 60.0 °C, which showed the phase transfer of vanadium from salt-rich phase to PEG2000-rich phase is exothermal, resulting from the difference of interaction energy among all compositions in aqueous two-phase system. The vanadium can be easily separated out from the solution containing Fe(III), Co(II), Ni(II), Cu(II), Zn (II), Al(III), Cr(III) and Mn(II) under the suitable conditions. The stripping rate and precipitation rate of vanadium can be easily achieved to 90% and 80%, respectively, in single stage stripping with ammonium carbonate solution as stripping agent and phase-forming salt.

The Use of Super Base CaO from Eggshells as a Catalyst in the Process of Biodiesel Production

The use of heterogeneous catalysts in the biodiesel production process provides advantages because it is easier in the catalyst separation process. One type of heterogeneous catalyst that can be used is CaO. The raw materials for CaO are abundant in nature and can be obtained from various sources including agricultural waste such as eggshells. The alkalinity level of CaO can be increased to super baser CaO through the activation process of CaO by using an ammonium carbonate solution. Super base CaO which is used as a catalyst for transesterification reaction in the production of biodiesel made from palm oil. This research was carried out by varying the reaction time starting from 1, 2 and 3 hours. The highest yield was obtained at 3 hours reaction time of 93.92%. The results of the analysis of the physical properties of biodiesel obtained density in the range 853-854 kg/m3, kinematic viscosity 3.24-3.26 mm2/s (cSt), saponification number 193-201 mg-KOH/g biodiesel and acid number 0.3-0.7 mg-KOH/g. These characteristics meet the biodiesel quality standards based on Indonesian National Standard (SNI) 04-7182-2015. Thus the use of super base CaO from eggshells can be used as a catalyst in the process of biodiesel production.

Indirect determination of chlorine and fluorine in eye shadow by ion chromatography after an eco-friendly sample preparation method based on combustion reaction

A powerful and efficient method for indirect determination of chlorine and fluorine in eye shadow is described in this work. The presence of these elements should be controlled in eye cosmetics because of its allergenic properties. The proposed method combines the analyte volatilization from eye shadow based on combustion reaction and the indirect determination of Cl and F by ion chromatography as chloride (Cl−) and fluoride (F−). To achieve better combustion conditions as well as to improve the volatilization of Cl and F from the sample matrix (which is mostly inorganic), microcrystalline cellulose was evaluated as a volatilization aid. The central composite rotatable design was used to optimize the sample mass and volatilization aid mass to be used in the microwave-induced combustion. Afterward, water or ammonium carbonate solutions (50, 100 or 150 mmol L−1) were evaluated for Cl and F absorption. Using the selected conditions (200 mg of eye shadow, 400 mg of microcrystalline cellulose, and water as absorbing solution) recoveries for Cl and F were 100 ± 8% and 106 ± 7%, respectively. Moreover, a mixture containing the certified reference material MESS-4 (marine sediment), microcrystalline cellulose and the sample was prepared by microwave-induced combustion, and no significant difference was observed between the result obtained for Cl (11,269 ± 325 mg kg−1) and the certified value (13,100 ± 4400 mg kg−1). The proposed method showed suitable trueness, precision (the repeatability and the intermediate precision was always lower than 7%) and limits of detection (LODs) for Cl (60 mg kg−1) and F (20 mg kg−1). Extraction of Cl and F from eye shadow assisted by ultrasound was also evaluated; however, the Cl and F recoveries were not quantitative and the LODs were considerably high. To the best of our knowledge, this is the first work demonstrating a reliable method for multielement determination in eye shadow, which is safe, presents low generation of laboratory effluents and may be considered an efficient approach for routine analysis in cosmetic industry.

Gd/Sm-Pr Co-Doped Ceria: A First Report of the Precipitation Method Effect on Flash Sintering.

In this work, ceria-based ceramics with the composition Gd0.14Pr0.06Ce0.8O2-δ and Sm0.14Pr0.06Ce0.8O2-δ, were synthesized by a simple co-precipitation process using either ammonium carbonate or ammonia solution as a precipitating agent. After the calcination, all of the produced samples were constituted by fluorite-structured ceria only, thus showing that both dopant and co-dopant cations were dissolved in the fluorite lattice. The ceria-based nanopowders were uniaxially compacted and consequently flash-sintered using different electrical cycles (including current-ramps). Different results were obtained as a function of both the adopted precipitating agent and the applied electrical cycle. In particular, highly densified products were obtained using current-ramps instead of “traditional” flash treatments (with the power source switching from voltage to current control at the flash event). Moreover, the powders that were synthesized using ammonia solution exhibited a low tendency to hotspot formation, whereas the materials obtained using carbonates as the precipitating agent were highly inhomogeneous. This points out for the first time the unexpected relevance of the precipitating agent (and of the powder shape/degree of agglomeration) for the flash sintering behavior.

Aqueous carbonation of MgSO4 with (NH4)2CO3 for CO2 sequestration

AbstractMineral carbonation is an important technical option for the effective reduction of CO2 emissions. Natural magnesium‐containing minerals, such as serpentine and blast furnace slag (BFS), have recently been used for CO2 storage with an indirect carbonation route using ammonium sulfate. In this study, the effects of the feeding mode and process parameters on the magnesium conversion, product phase, and morphology during the aqueous carbonation of MgSO4 with ammonium carbonate solution were investigated in detail. The results showed that the carbonation ratio with a parallel feed was higher than the forward and reverse feed by about 3–5% with a limited reaction time, and the product size was more uniform. The phase and morphology of the products were affected significantly by the temperature. The highest carbonation ratio appeared at 40°C because only 75% of magnesium was carbonated if hydromagnesite was produced. When the mole ratio of (NH4)2CO3 to MgSO4 was 2:1 and the concentration of magnesium sulfate was higher than 0.4 mol·L−1, the carbonated products contain ammonium magnesium carbonate, and the ammonia should be recovered by selective thermal decomposition. When the mole ratio decreased to 1.5:1, only nesquehonite appears with high crystallinity and uniform size. The optimized conditions were therefore selected as 40°C, a mole ratio of 1.5:1, and magnesium sulfate concentration of 0.7 mol·L−1. Under these conditions the carbonation ratio reached 88%. Additionally, the optimal initial pH of MgSO4 solution was 9.5 (the product was nesquehonite at low pH) while the hydromagnesite will be produced at higher pH (pH more than 10). © 2019 Society of Chemical Industry and John Wiley & Sons, Ltd.

Improvement in the Experiment of Corrosion of Carbon Steel in Ammonium Carbonate Solution

Improvement in the Experiment of Corrosion of Carbon Steel in Ammonium Carbonate Solution