Aqueous Magnesium Sulfate Research Articles

A kinetic and thermodynamic study of the removal of calcium and magnesium from aqueous solutions similar to those of complex sulphide flotation by the addition of sodium carbonate

ABSTRACT The use of recycled water in flotation has a negative impact on flotation of sulphide mineral species because these waters contain chemical species that affect the recovery and selectivity of the process. This study aims to study the reaction mechanism between aqueous calcium and magnesium sulphate contained in the water released by complex sulphide flotation process, and the carbonate ions added to the water as sodium carbonate (Na2CO3). The addition of Na2CO3 has been shown to have a positive effect on the recovery and grade of the final Pb-Cu concentrate obtained, but the reasons of this are not yet fully understood. The present study was conducted by adding Na2CO3 to a saturated gypsum solution containing Mg(II). Analytical techniques such as XRD, TGA and zeta potential measurements were used to characterise the obtained solids. It was observed that the addition of Na2CO3 favoured the precipitation of the Ca(II) as calcite and vaterite. The reaction kinetics was found to be of second-order. In the case of magnesium alone, the precipitates are amorphous. This study provides new information on the reaction mechanism between metal ions and carbonates. The information collected can help design processes for the removal of ions from flotation water.

A total scattering study of prenucleation structures in saturated aqueous magnesium sulfate - observation of extended clusters.

Through a combination of X-ray and neutron total scattering and Empirical Potential Structure Refinement (EPSR) we explore the prenucleation structures of saturated aqueous magnesium sulfate. The atomistic model we present reveals a system characterised by isolated octahedral aquo magnesium species Mg(H2O)6, magnesium sulfate pairs (Mg(H2O)5SO4) and extended clusters built from corner-sharing MgO6 and SO4 polyhedra. Many of these features are directly observed in the crystal structures of the known solid form hydrates, including isolated polyhedra, corner sharing chains and rings, and it is only for the extended 3D polyhedral networks of the lower hydrates (mono- & di-) that no proto structures are observed in 2M solution. Looking at the average first solvation shell of the sulfate anion we see a complex and flexible environment that commonly includes water molecules brought into proximity by a coordinated hydrated magnesium. What emerges is a high probability that 10 water molecules will be observed in a combined tetrahedral/octahedral arrangement with a further 7 taking up more dispersed positions giving an average coordination of 17. The tendency for ions to aggregate into clusters allows areas of bulk water to exist that exhibit subtle differences in structure to that of pure water.

The Effect of Some Components Changes of Aspergillus niger Culture Media on the Production of Lipase Enzyme

The current work aimed to study the effect of some component changes of Aspergillus niger culture media on the production of lipase enzyme. Media contained nitrogenous sources, ammonium nitrate, peptone, nitrate phosphate, mono-potassium phosphate, and aqueous magnesium sulfate. It was found that the isolation was unable to grow and produce lipase enzyme efficiently due to the presence of inorganic nitrogen sources. The highest value of the dry weight rate was realized while using ammonium chloride at concentration of 1.23 g/100 ml. Ammonium nitrate was the best source (treatment) compared to the rest of the sources at a concentration of 0.1 g/100 ml, where the dry weight was 1.28 g/100 ml, and the effectiveness of lipase was 22.86 U/ml. Adding peptone with the ammonium nitrate to the medium helped to raise the productivity of isolated fungus, where the dry weight reached 2.75 g/100 ml, while the lipase activity reached 36.93 U/ml. The biomass in the organic nitrogen sources medium reached (2.24 g/100 ml). The highest value of the dry weight of phosphate source media (KH2PO4) reached (2.87 g/100 ml) at a concentration (0.28 g/100 ml), achieving the best value of the lipase’s effectiveness (39.96 U/ml). Aqueous magnesium sulfate concentration media resulted in a sort increase in the fungus isolation biomass, as the highest biomass for aqueous magnesium sulfate media was (3.00 g/100 ml) at (0.05 g/100 ml) concentration.

Evaluation of Some Biological and Chemical Elements in Controlling Some Soil-borne Fungi and Stimulating Plant Growth

This study was conducted to evaluate the efficacy of the biocontrol fungi Chaetomium cupreum, Trichoderma viride, and Saccharomyces cerevisiae and some chemical nutrients that stimulate plant growth, such as calcium nitrate, ammonium phosphate, aqueous magnesium sulfate, copper and boron in controlling some common soil-borne pathogenic fungi and evaluating their role in stimulating plant growth. All the bioagents showed significant antagonistic efficiency In vitro against the pathogenic fungi Drechslera Halodes, Fusarium oxysporum, Fusarium solani, Macrophomina phaseolina, Pythium aphanidermatum and Rhizoctonia solani. Under greenhouse conditions, BC treatment composed of biological and chemical elements, achieved the highest germination rate for tomato, cucumber and cowpea seeds inoculated with the pathogenic fungi, and reached 95.83-100.00% compared to 36.67- 47.50% for the control treatment. BC treatment also excelled in reducing disease incidence and severity, as the disease rate reached 0% compared to 95.83-99.17 % for the inoculated control treatment, and without significant difference with the non-inoculated (healthy) control. In addition, the BC treatment produced 0 % disease severity rate as compared to 82.58-85.83% for the inoculated control, and without significant difference with non-inoculated control. Furthermore, the BC treatment was superior to the rest of the treatments in increasing dry weight of all the plant species tested. Keywords: Chaetomium cupreum, Trichoderma viride, Saccharomyces cerevisia, Soil-borne fungi, biological control.

Electrical Conductivity of Aqueous Magnesium Sulfate at High Pressure and Low Temperature With Application to Ganymede's Subsurface Ocean

AbstractGanymede has strong evidence of a subsurface ocean primarily composed of MgSO4. We conducted experimental measurements of the electrical conductivity of aqueous MgSO4 at 200–1,200 MPa and 243–295 K in a multianvil press, simulating the high‐pressure and low‐temperature (HPLT) conditions of Ganymede's subsurface ocean. A numerical model is proposed with logσ = − 3.1605+940.931/T+0.8986logc+2logΛ0 − log(5Λ0+2695c1/2), where σ is electrical conductivity in S/m, T is temperature in K, c is molar concentration in mol/L, and Λ0 is limiting equivalent conductance in S·cm2·equiv−1. We used this model to generate electrical conductivity curves up to 500 km deep in Ganymede and found that the values are lower than previously predicted. Our novel experimental methods demonstrate access to the HPLT environment of liquid samples that expands our ability for experimental simulation of icy ocean worlds in the outer solar system.

Quantifying Concentration Polarization \u2013 Raman Microspectroscopy for In-Situ Measurement in a Flat Sheet Cross-flow Nanofiltration Membrane Unit

In this work, the concentration polarization layer (CPL) of sulphate in a cross-flow membrane system was measured in-situ using Raman microspectroscopy (RM). The focus of this work is to introduce RM as a new tool for the study of mass transfer inside membrane channels in reverse osmosis (RO) and nanofiltration (NF) generally. Specifically, this work demonstrates how to use RM for locally resolved measurement of sulphate concentration in a cross-flow flat-sheet NF membrane flow cell with channel dimensions similar to commonly applied RO/NF spiral wound modules (channel height about 0.7 mm). Concentration polarization profiles of an aqueous magnesium sulphate solution of 10 gsulphate·L−1 were obtained at operating pressure of 10 bar and cross-flow velocities of 0.04 and 0.2 m·s−1. The ability of RM to provide accurate concentration profiles is discussed thoroughly. Optical effects due to refraction present one of the main challenges of the method by substantially affecting signal intensity and depth resolution. The concentration profiles obtained in this concept study are consistent with theory and show reduced CPL thickness and membrane wall concentration with increasing cross-flow velocity. The severity of CP was quantified to reach almost double the bulk concentration at the lower velocity.

Effect of waiting time on the water transport kinetics of magnesium sulfate aerosol at gel-forming relative humidity using optical tweezers.

With the loss of water, the amorphous gel states in aqueous magnesium sulfate (MgSO4) aerosol forms and results in nonequilibrium dynamics, owing to the extended time scales for diffusive mixing. The mass transfer resistance in MgSO4 aerosol droplets during evaporation or condensation is investigated using aerosol optical tweezers (AOTs) coupled with Raman spectroscopy. In addition, the kinetics of water transport during hydration and dehydration after different waiting time is studied. With the cyclic change of the relative humidity (RH) below gel-forming, the waiting time is varied to examine the effect of the duration of drying and humidifying on water transport kinetics during subsequent hydration and dehydration process. Apparent diffusion coefficients (Dap) of water molecules in the gel state after different waiting time are obtained. The results indicate that the duration of drying will affect water transport kinetics for subsequent humidifying process due to the different structure and composition in MgSO4 aerosol droplet at different ambient humidities. However, the duration of humidifying has little effect on water transport kinetics for subsequent drying process below gel-forming RH.

The effect of microwave on the crystallization process of magnesium carbonate from aqueous solutions

The effect of microwave on reactive crystallization is investigated with magnesium carbonate as the working substance. In the experiments, magnesium carbonate is precipitated by mixing aqueous magnesium sulfate and sodium carbonate solutions in a MSMPR crystallizer located in a microwave reactor. A population balance model along with crystallization kinetics is formulated to assess the influence of microwave energy input on nucleation, growth, agglomeration and breakage during crystallization process. A general high order moment method of classes (HMMC) framework is applied to solve the model numerically. The results show that crystallization kinetics parameters, including the nucleation rate constant (kn), the growth rate constant (kg), the exponent of growth rate (g) and the collision efficiency (Ψag) change significantly due to mass transfer enhancement in microwave field. Meanwhile, the exponent of nucleation (n) and the breakage rate constant (kbr) remain constant or only change slightly. It is further discovered that the crystal suspension attenuates the microwave effect during crystallization process.

Volumetric Properties of Tetra-n-butyl ammonium bromide in Aqueous Solutions of Magnesium sulphate in the Temperature Range 298.15 to 318.15K and under the Atmospheric Pressure

ABSTRACTDensity and sound speed measurements have been carried out for the ternary systems consisting of tetra-n-butyl ammonium bromide (TBAB) in 0.1 m aqueous magnesium sulphate heptahydrate (MgSO4.7H2O)-water over the full range of composition from T = 293.15 to 318.15 K by using volumetric method. Using this experimental data, various physical and thermodynamical parameters such as adiabatic compressibility, apparent molal compressibility, apparent molal volume, apparent and limiting partial molar volumes of the electrolytes and ions in these mixtures have been evaluated and split into respective ionic contributions. The results have been discussed in terms of ion–ion and ion–solvent interactions occurring between TBAB and aqueous MgSO4 solutions. Further, structure making/breaking behaviour of MgSO4 has been reported in terms of sign of the partial molar expansibility at infinite dilution.

Feasibility study of MgSO4 hydrate production by eutectic CO2 clathrate crystallization

A case study is presented using eutectic CO2 clathrate crystallization (ECC) as an alternative for eutectic freeze crystallization (EFC): a 3kg/s MgSO4·11H2O salt production from 17w% aqueous magnesium sulphate stream. Both processes were simulated using Aspen Plus 7.1® to calculate the major energy requirements.In EFC process the eutectic conditions inside the crystallizer was maintained at −4°C, 1bar. The total cooling required for the crystallizer was achieved by an ammonia cooling cycle. A total energy requirement of 671kW was calculated for the EFC process.In ECC process the eutectic temperature i.e. the operational conditions inside the crystallizer was kept at 6.5°C and 40bars. The CO2 fed into the crystallizer was used both as a refrigerant for direct cooling, and as a component for the crystallization of the CO2-clathrate. The clathrate produced in the crystallizer was decomposed and the heat of decomposition was used for condensation of part of the recompressed CO2. The residual compressed CO2 was condensed in a cooling cycle for re-use. In ECC process most of the energy was consumed by the compressors and pumps. The total energy requirement for the ECC process based only on the pumps and compressors was 535kW.In this preliminary study, based on energy requirements alone, the clathrate process shows a slightly favourable energy requirement over the EFC process. However, the clathrate process required a fresh stream (2.9tonnes/day) of liquid CO2, which will add to the ECC operating costs. In addition the capital and operational costs for the ECC process might be higher as the process is operated at high pressures (40bar) and requires more processing steps than the EFC plant. These facts make the ECC process less attractive for MgSO4–H2O system.

Ganymede׳s internal structure including thermodynamics of magnesium sulfate oceans in contact with ice

The large icy moons of Jupiter contain vast quantities of liquid water, a key ingredient for life. Ganymede and Callisto are weaker candidates for habitability than Europa, in part because of the model-based assumption that high-pressure ice layers cover their seafloors and prevent significant water–rock interaction. Water–rock interactions may occur, however, if heating at the rock–ice interface melts the high pressure ice. Highly saline fluids would be gravitationally stable, and might accumulate under the ice due to upward migration, refreezing, and fractionation of salt from less concentrated liquids. To assess the influence of salinity on Ganymede׳s internal structure, we use available phase-equilibrium data to calculate activity coefficients and predict the freezing of water ice in the presence of aqueous magnesium sulfate. We couple this new equation of state with thermal profiles in Ganymede׳s interior—employing recently published thermodynamic data for the aqueous phase—to estimate the thicknesses of layers of ice I, III, V, and VI. We compute core and silicate mantle radii consistent with available constraints on Ganymede׳s mass and gravitational moment of inertia. Mantle radii range from 800 to 900km for the values of salt and heat flux considered here (4–44mWm−2 and 0 to 10wt% MgSO4). Ocean concentrations with salinity higher than 10wt% have little high pressure ice. Even in a Ganymede ocean that is mostly liquid, achieving such high ocean salinity is permissible for the range of likely S/Si ratios. However, elevated salinity requires a smaller silicate mantle radius to satisfy mass and moment-of-inertia constraints, so ice VI is always present in Ganymede׳s ocean. For lower values of heat flux, oceans with salinity as low as 3wt% can co-exist with ice III. Available experimental data indicate that ice phases III and VI become buoyant for salinity higher than 5wt% and 10wt%, respectively. Similar behavior probably occurs for ice V at salinities higher than 10wt%. Flotation can occur over tens of kilometers of depth, indicating the possibility for upward ‘snow’ or other exotic modes of heat and material transport.

Amino acid hydration in aqueous magnesium and sodium sulfate solutions

We study the partial volumes of amino acids in aqueous magnesium and sodium sulfate solutions, which have a different effect on the structure of water, and calculate the structural parameters of hydrated complexes of NH 3 + and COO− groups: hydration numbers and water volumes inside and outside the hydration shell. The hydration numbers are given as a sum of the contributions of the interactions in the ternary (water-salt-amino acid) and binary (water-salt) systems.

Selective elution of nickel and cobalt from iminodiacetic acid cation exchange resin using ammoniacal solutions

Nickel and cobalt were eluted from iminodiacetic acid functionalized ion exchange resin by ammoniacal eluents. The highest recovery of nickel and cobalt was achieved using a mixture of aqueous ammonia, ammonium sulphate, and magnesium sulphate. The use of ammonium sulphate yielded a higher extent of nickel desorption than the use of ammonium carbonate. The presence of a divalent metal salt such as magnesium sulphate, calcium sulphate, or manganese sulphate was found to increase the extent of nickel desorption. Magnesium was found to be most suitable for this purpose. Nickel and cobalt on the resin are displaced by magnesium during this process. The selectivity of this elution process varies by metal. Aluminium and iron show little or no affinity for ammoniacal elution. Calcium and manganese desorb to a limited extent. The kinetics of nickel desorption in aqueous ammonia–ammonium sulphate–magnesium sulphate solution are slower than that of sulphuric acid elution. When resin loaded with magnesium is contacted with aqueous nickel sulphate, nickel sulphate will displace magnesium on the resin. This reaction occurs on a similar time scale as that of protonated resin.

Thermodynamic properties of aqueous MgSO4 to 800 MPa at temperatures from −20 to 100 °C and concentrations to 2.5 mol kg−1 from sound speeds, with applications to icy world oceans

Thermodynamic properties of aqueous magnesium sulfate solutions (MgSO4 concentrations to 2.5molkg−1) are reported in a previously unexplored regime of pressure and temperature. Solution densities (to a few hundred parts-per-million), specifics heats (to a few percent), and volumetric mixing parameters were determined to 800MPa in the temperature range from −20 to 100°C from sound speeds measurements. Equilibrium data extrapolate smoothly to temperatures below which liquids are stable, providing a basis for equilibrium freezing calculations. In more compressed water at high pressure, where electrostrictive effects are smaller, the partial molal volume at infinite dilution is positive and changes less with pressure, while the non-ideal contribution to the apparent molal volume is reduced. Ion–solvent and ion-ion contributions are small under all conditions, while solvent contributions to non-ideality show greater variation with pressure and temperature. In application to Ganymede, Callisto, and Titan, the current results suggest that concentrations of aqueous MgSO4 would be exist that would be denser than overlying ice and thus buoyantly stable at the ice VI-rock interface, or between overlying layers of ice VI–V or V–III. More generally, the current data and analysis provide a comprehensive framework that can guide investigations of other single and multi-component aqueous systems.

Hydration numbers and the state of water in hydration spheres of magnesium chloride and magnesium sulfate solutions

An equation for determining hydration numbers and molar adiabatic compressibilities has been derived by correct thermodynamic processing of a data set comprising ultrasound velocity, density, and isobaric heat capacity in aqueous magnesium chloride and sulfate solutions for concentrations ranging from very dilute solutions to the complete solvation boundary and temperatures of 273.15–323.15 K. One basic innovation of the derived equation consists in that it accounts for the dependence of solvation numbers on solution concentration and in that all changes experienced by the solution are associated with the solvation of a stoichiometric mixture of electrolyte ions or nonelectrolytes molecules.

Ion Association in Dilute Aqueous Magnesium Sulfate and Nickel Sulfate Solutions Under Hydrothermal Conditions by Flow Conductivity Measurements

Electrical conductivities of very dilute aqueous solutions of magnesium sulfate and nickel sulfate (∼ 10−3 mol·kg−1) were measured at temperatures from (398.15 to 548.15) K and from (398.15 to 498.15) K, respectively, with an alternating current (AC) conductivity flow cell at a pressure of 18.62 MPa. The resulting conductivity data were modeled using the Fuoss−Hsia−Fernández−Prini (FHFP) conductance equations together with the appropriate activity coefficient expressions, to obtain equilibrium constants for the ion association reactions: Mg2+(aq) + SO42−(aq) ⇌ MgSO4o(aq) and Ni2+(aq) + SO42−(aq) ⇌ NiSO4o(aq). The equilibrium constants KA for the two systems, which correspond to the formation of all types of ion pairs (solvent−solvent-separated, solvent-separated, and contact ion pairs), agree remarkably well with results calculated from solubility measurements at much higher concentrations. The results were described by the temperature-dependent equilibrium constant model to a precision of ± 0.03 in log KA.

Solvation of magnesium chloride and sulfate in aqueous solutions at 278.15–323.15 K

Isoentropy compressibilities of aqueous magnesium chloride and sulfate were determined based on precision measurements of ultrasound velocity, density, and isobaric heat capacity at low to high concentrations at 278.15–323.15 K. The hydration numbers h and the molar parameters of volume and compressibility were calculated based on thermodynamically correct equations for hydration complexes (Vh, βhVh), water in the hydration shell (V1h, β1hV1h), and the void containing a stoichiometric mixture of ions (V2h, β2hV2h). The h and βhVh values were found to be independent of temperature; the molar compressibility of the hydration sphere (β1hV1h) and the stoichiometric mixture of ions without a hydration shell (β2hV2h) were independent of the concentration under the stated conditions. The effect of the electrostatic field of ions on the temperature dependence of the molar volume of water in the hydration sphere was more significant than the effect of pressure on the temperature dependence of the molar volume of bulk water. This is attributed to changes in the dielectric constant of water in the vicinity of the electrolyte ions.

Theoretical study on the reactivity of sulfate species with hydrocarbons

The abiotic, thermochemically controlled reduction of sulfate to hydrogen sulfide coupled with the oxidation of hydrocarbons, is termed thermochemical sulfate reduction (TSR), and is an important alteration process that affects petroleum accumulations in nature. Although TSR is commonly observed in high-temperature carbonate reservoirs, it has proven difficult to simulate in the laboratory under conditions resembling nature. The present study was designed to evaluate the relative reactivities of various sulfate species in order to provide greater insight into the mechanism of TSR and potentially to fill the gap between laboratory experimental data and geological observations. Accordingly, quantum mechanics density functional theory (DFT) was used to determine the activation energy required to reach a potential transition state for various aqueous systems involving simple hydrocarbons and different sulfate species. The entire reaction process that results in the reduction of sulfate to sulfide is far too complex to be modeled entirely; therefore, we examined what is believed to be the rate limiting step, namely, the reduction of sulfate S(VI) to sulfite S(IV). The results of the study show that water-solvated sulfate anions SO 4 2 - are very stable due to their symmetrical molecular structure and spherical electronic distributions. Consequently, in the absence of catalysis, the reactivity of SO 4 2 - is expected to be extremely low. However, both the protonation of sulfate to form bisulfate anions ( HSO 4 - ) and the formation of metal-sulfate contact ion-pairs could effectively destabilize the sulfate molecular structure, thereby making it more reactive. Previous reports of experimental simulations of TSR generally have involved the use of acidic solutions that contain elevated concentrations of HSO 4 - relative to SO 4 2 - . However, in formation waters typically encountered in petroleum reservoirs, the concentration of HSO 4 - is likely to be significantly lower than the levels used in the laboratory, with most of the dissolved sulfate occurring as SO 4 2 - , aqueous calcium sulfate ([CaSO 4] (aq)), and aqueous magnesium sulfate ([MgSO 4] (aq)). Our calculations indicate that TSR reactions that occur in natural environments are most likely to involve bisulfate ions ( HSO 4 - ) and/or magnesium sulfate contact ion-pairs ([MgSO 4] CIP) rather than ‘free’ sulfate ions ( SO 4 2 - ) or solvated sulfate ion-pairs, and that water chemistry likely plays a significant role in controlling the rate of TSR.

Partial Molar Volumes of Some of α-Amino Acids in Binary Aqueous Solutions of MgSO4·7H2O at 298.15 K

The apparent molar volume, V o φ,2, of glycine, alanine, α-amino-n-butyric acid, valine and leucine have been determined in aqueous solutions of 0.25, 0.5 and 1.0 mol·dm −3 magnesium sulfate, and the partial specific volume from density measurements at 298.15 K. These data have been used to calculate the infinite dilution apparent molar volume, V o 2,m , group contribution of amino acids and partial molar volume of transfer, � trV o 2,m , from water to aqueous magnesium sulfate solutions. The linear correlation of V o 2,m for a homologous series of amino acids has been utilized to calculate the contributions of charged end groups (NH + , COO − ), CH2- groups and other alkyl chains of amino acids to V o 2,m . The results fortrV o 2,m of amino acids from water to aqueous magnesium sulfate solutions have been interpreted in terms of ion-ion, ion-polar, hydrophilic-hydrophilic and hydrophobic-hydrophobic group interactions. The values of the standard partial molar volume of transfer for the amino acids with different hydrophobic contents, from water to aqueous MgSO4 are in general positive, indicating the predominance of the interactions of zwitterionic/hydrophilic groups of amino acids with ions of the salt. The hydration number decreases with increasing concentration of salt. The number of water molecules hydrated to amino acids decreases, further strengthening the predominance of ionic/hydrophilic interactions in this system.

A theory on bubble-size dependence of the critical electrolyte concentration for inhibition of coalescence

The interaction of pairs of bubbles with equal diameters grown on adjacent capillaries in aqueous magnesium sulfate solutions is studied by varying electrolyte concentration and bubble diameter by Tsang, Koh and Koch [Y.H. Tsang, Y.-H. Koh, D.L. Koch, J. Colloid Interface Sci. 275 (2004) 290] (referred to as TKK hereafter). They find that the critical concentration to prevent coalescence, C t , increases as the equivalent diameter, d eq , decreases. In fact, C t is found to scale as d eq −1.2 . This dependence is stronger than that predicted by Prince and Blanch ( C t ∼ d eq −0.5 ) (referred to as PB [M.J. Prince, H.W. Blanch, AIChE J. 36 (1990) 1425] hereafter) on the basis of a postulation that lubrication pressure due to Marangoni stresses inhibit coalescence. TKK postulate instead that bubbles are stabilized by hydration structures. We further illustrate here that when hydration force term is added to the equation of motion of the film thinning process, predicted values of critical concentration are found to scale as d eq −1 . The current prediction shows a much better agreement with the experimental results than that proposed by PB. This suggests previous assumption that immobility of the interface by Marangoni effect as the dominant mechanism of inhibition of coalescence in an electrolytic solution is inaccurate [M.J. Prince, H.W. Blanch, AIChE J. 36 (1990) 1425, G. Marrucci, Chem. Eng. Sci. 24 (1969) 975].