Synthetic Brine Solution Research Articles

Spray-coated porous photothermal layer on PTFE membranes for robust anti-scaling and solar membrane distillation

This paper presents a novel spray-coating procedure for the deposition of a photothermal carbon black (CB) coating, embedded in poly(vinyl alcohol) (PVA), onto polytetrafluoroethylene (PTFE) membranes for solar membrane distillation (MD) in complex, scale-inducing waters. To maintain water flux after coating, lithium nitrate (LiNO3) was added as a pore former, which resulted in a porous PVA-CB coating after elution. The performance of the PTFE/PVA-CB membranes was evaluated for a range of PVA, CB, and LiNO3 concentrations using a synthetic brine solution. Results showed that adding the hydrophilic PVA-CB increased the scaling resistance of the membrane compared to bare PTFE. Increasing the PVA loading on the membrane resulted in a decrease in water flux that could be mitigated by the addition of a pore former; however, at high (5 %) LiNO3 concentration, the high porosity increased the scaling propensity of the PTFE/PVA-CB membrane. The optimal coating condition (1.5 % PVA, 0.75 % CB, 1 % LiNO3 applied at a wet coating thickness of 55 μm) was stable over a range of operating conditions and able to use simulated sunlight as a driving force for MD desalination. Therefore, the membranes developed in this work show promising performance for off-grid solar desalination of high scaling potential waters.

Membrane crystallization for recovery of lithium carbonate crystals: Study on process parameters and salts effect for Li2CO3-NaCl-KCl-LiCl solutions

In this work, membrane crystallization (MCr) process was employed for recovery of lithium carbonate (Li2CO3) crystals from synthetic brine solutions. First, the effect of the main operating conditions in MCr, including feed temperature (40, 50, and 60 °C) and flowrate (0.81, 1, and 1.3 L/min) was investigated on the crystallization of Li2CO3 in a binary solution. Next, the effect of main inorganic salts in the brine solutions (i.e., NaCl, KCl, and LiCl) and the mixture of them on the MCr performance and crystallization of Li2CO3 were investigated. In-line microscope, light microscope, scanning electron microscope, and X-ray diffraction test were used to observe the crystallization and characterize the obtained crystals. The obtained results revealed that feed temperature is the main parameter to dominate the nucleation and crystal formation and growth. Thus, the higher the feed temperature, the faster the crystal formation and the larger the crystals. The average crystal size increased from 9.59 to 30.51 μm, when the feed temperature increased from 40 to 60 °C, respectively. However, smaller crystals were observed with adding NaCl and KCl to the solution. Moreover, none of the operating parameters nor the salts additives did affect the crystals shape and the obtained Li2CO3 crystals possess needle-like shape.

Gypsum Seeding to Prevent Scaling

Eutectic freeze crystallization (EFC) is a novel separation technique that can be applied to treat brine solutions such as reverse osmosis retentates. These are often a mixture of different inorganic solutes. The treatment of calcium sulphate-rich brines using EFC often results in gypsum crystallization before any other species. This results in gypsum scaling on the cooled surfaces of the crystallizer, which is undesirable as it retards heat transfer rates and hence reduces the yield of other products. The aim of this study was to investigate and understand gypsum crystallization and gypsum scaling in the presence of gypsum seeds. Synthetic brine solutions were used in this research because they allowed an in-depth understanding of the gypsum bulk crystallization process and scaling tendency without the complexity of industrial brines. A cooled, U-shaped stainless-steel tube suspended in the saturated solution was employed as the scaling surface. This was because a tube-shaped surface enabled the introduction of a constant temperature cold surface in the saturated solution and most industrial EFC crystallizers are constructed from stainless steel. Gypsum seeding was effective in decreasing the mass of scale formed on the heat transfer surface. The most effective seed loading was 0.25 g/L, which reduced scale growth rate by 43%. Importantly, this seed loading is six times the theoretical critical seed loading. The seeding strategy also increased the gypsum crystallization kinetics in the bulk solution, which resulted in an increase in the mass of gypsum product. These findings are relevant for the operability and control of EFC processes, which suffer from scaling problems. By using an appropriate seeding strategy, two problems can be alleviated. Firstly, scaling on the heat transfer surface is minimised and, secondly, seeding increases the crystallization kinetics in the bulk solution, which is advantageous for product yield and recovery. It was also recommended that the use of silica as a seed material to prevent gypsum scaling should be investigated in future studies.

Selective Removal of Barium and Hardness Ions from Brackish Water with Chemically Enhanced Electrodialysis

The use of a nonconventional water resource for energy and industrial applications often requires extraction of low-level undesirable ions from matrices of benign dominant ions. In this study, the selective extraction of Ba2+ and Mg2+ from synthetic brine solutions was evaluated using strong acid cation-exchange membranes modified with the surface deposition of macrocyclic molecules including crown ethers and calixarenes. Compared to the bare membrane, vinylbenzo-18-crown-6 (VB18C6) and calix[4]arene-amended membranes showed increased selectivity for Ba2+ and Mg2+ with respect to the dominant ion (Na+) by up to fourfolds, with the calix[4]arene-modified membrane achieving more selective separation than VB18C6. Optimal selectivity was achieved at a moderate-to-high current density (3.1–6.3 mA/cm2), which was attributed to the alleviation of transport limitation in the boundary layer by the surface modification. Amendment of a calix[4]arene derivative with a crown-6 “boot strap” and two carboxylic groups resulted in reduced selectivity due to the formation of strong complexes with divalent ions. These results show that surface deposition of ion sequestrants can be a versatile approach to improve the membrane’s selectivity; however, the performance is sensitive to feed water salinity, current loading, and the macrocycle-ion chemistry, where there is a trade-off between ion affinity and mobility.

Liquification of 2,2,4-trimethyl-1,3-pentanediol into hydrophobic eutectic mixtures: A multi-criteria design for eco-efficient boron recovery

New genres of ionic liquids and deep eutectic solvents (DES) have recently emerged as eco-efficient “designer’s solvents”. Herein, we report the liquification of the water soluble diol 2,2,4-trimehtyl-1,3-pentanediol (TMPD) into a novel hydrophobic DES with thymol or menthol, where the intrinsic supercooling properties of the constituents yielded eutectic mixtures with a wide liquid window and superior capabilities for boron extraction. The design framework of the TMPD-based DESs considered multiple criteria in which the trade-offs between the solvents’ properties, its boron extraction efficiency and leachability to the aqueous phase were thoroughly mapped. Formation of stable TMPD-boric acid complexes provided exceptional selectivity towards boron extraction from a synthetic brine solution. The performance of TMPD-based DESs was verified over various extraction parameters, with a single-stage extraction efficiency of ~ 98%, sustained stability over a wide pH range (2 – 8) and reusability over multiple regeneration cycle. This remarkable performance of the newly developed DESs associate the role of the TMPD as both a DES constituent and an active boron extractant, which disregards the use of hazardous organic diluents.

High purity recovery of magnesium and calcium hydroxides from waste brines

Direct disposal of concentrate brines, generated by many industrial sectors, causes serious environmental concerns. An industrial sector that produces high concentrate brines is softening water industry, in particular during the regeneration of ion exchange resins. These brines are mainly rich in sodium, magnesium and calcium chlorides, thus, their regeneration, by removal/recovery of magnesium and calcium, can be a valuable option to turn the brine into a source of minerals and reduce disposal costs and environmental concerns. In this regards, one of the goals of EU-funded ZERO BRINE project is to develop a treatment chain for the valorization and regeneration of spent brines from water softening plants. The treatment chain consists of Nanofiltration, crystalization and evaporation to regenerate spent brines and recover high purity magnesium and calcium hydroxides. In this work, a wide experimental campaign was carried out to recover high purity magnesium and calcium via selective chemical precipitation of relevant hydroxides adding by injection of an alkaline solution in two consecutive steps at controlled pH. Precipitations were performed using synthetic brine solution, mimicking the retentate produced by nanofiltration, some of them were carried out considering a pre-treatment step to remove bicarbonate ions.

Green corrosion inhibitor for oilfield application II: The time–evolution effect on the sweet corrosion of API X60 steel in synthetic brine and the inhibition performance of 2-(2-pyridyl) benzimidazole under turbulent hydrodynamics

Time–evolution study of 2-(2-pyridyl) benzimidazole (2PB) as CO2 corrosion inhibitor for API X60 steel under hydrodynamic conditions in a synthetic brine solution has been undertaken. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) techniques were employed for this study. The results indicate that 2.56 mM of 2PB could provide up to 88.3 % inhibition efficiency after 12 h at 4000 rpm in the synthetic brine solution. The addition of 0.14 mM thiobarbituric acid (TBA) significantly enhances 2PB performance to 95.6 % using PDP. ATR-IR, SEM and optical image characterizations confirm that 2PB adsorption suppresses the localized corrosion of the steel.

CO2-enriched brine injection’s impact on mechanical properties of a sandstone specimen

CO2 capture and geological sequestration is one of the most practical and efficient methods of mitigating anthropogenic CO2 emissions. Due to the uncertainties associated with CO2 injection into deep saline reservoirs, the interaction between the host rock and the injected CO2 needs to be better understood as it can lead to considerable pore-structure changes. The geochemical reactions, especially mineral dissolution, can compromise the mechanical properties of the reservoir rock, which consequently threatens the reservoir stability and integrity. Therefore, it is crucial to capture the variation of mechanical properties of the reservoir rock upon CO2 injection. In this study the variation of elastic properties (e.g. Young’s modulus, shear modulus, bulk modulus, and Poisson’s ratio) of a brine-saturated sandstone specimen upon injecting CO2-enriched brine is investigated. The elastic properties of the specimen were initially characterized through multi-stage elastic (MSE) test before injecting the CO2-enriched brine. Then, the synthetic brine solution was enriched with CO2 and injected into the brine saturated sandstone specimen. The mechanical test results revealed that a significant mechanical weakening occurred upon injecting CO2-enriched brine into the sandstone specimen. This mechanical degradation can be attributed to the dissolution of calcite and clay minerals. The results from this study indicated that the mechanical deterioration of reservoir rock during CO2 injection should be considered through the entire CO2 sequestration process (i.e. site selection, injection operation, and post-injection monitoring).

Kinetics-Controlled Separation Intensification for Cesium and Rubidium Isolation from Salt Lake Brine

The separation efficiency of cesium (Cs(I)) and rubidium (Rb(I)) from a synthetic brine solution containing potassium (K(I)) was improved via a kinetics-controlled strategy. Specifically, 4-tert-butyl-2-(α-methylbenzyl) phenol (t-BAMBP) dodecane solution was partially saponified by NaOH solution first and then was directly used in extraction without adjusting the pH of the feed solution to exceed 13. Compared to the traditional process, much higher separation factors of Cs(I) and Rb(I) over K(I) (βCs/K = 1550.7, βRb/K = 45.2) were gained due to the enhanced kinetics differences during ion exchanges. In addition, the consumption of NaOH was reduced by 70–97%, and a large amount of strong alkaline wastewater was avoided because of the recyclability of NaOH saponifying agent. For synthetic brine solution containing high concentration K(I), 99.1% Cs(I) and 86.5% Rb(I) were recovered after three-stage extraction. The novel process showed a bright prospect for the extraction of Cs(I) and Rb(I).

Solvent extraction of cesium and rubidium from brine solutions using 4-tert-butyl-2-(α-methylbenzyl)-phenol

A comprehensive study on the separation of cesium and rubidium from potassium with 4-tert-butyl-2-(α-methylbenzyl)-phenol (t-BAMBP) from a synthetic brine solution containing 20mg/L Cs, 200mg/L Rb and 5g/L K was conducted. The effects of alkalinity, t-BAMBP concentration, temperature, A/O ratio on extraction were investigated. It was found that the best conditions to extract cesium and rubidium were using 30% t-BAMBP concentration with 0.1M NaOH feed solution alkalinity under room temperature, for example 22°C, at an A/O ratio of 1. Under these conditions, the separation factor of cesium and rubidium over potassium were found to be 139 and 11, respectively. The kinetics of both extraction and stripping were fast with equilibrium reached within 2min. All extracted cesium and rubidium and 93% potassium were stripped with 0.1M HCl at an A/O ratio of 1:1 in a single contact. A batch continuous test with 5 extraction stages was conducted under these conditions. It was found that over 99% cesium and rubidium were extracted with 19.4% potassium co-extracted. The concentration ratios of potassium over cesium decreased from 216 in the feed solution to 42 in the loaded organic solution and that of potassium over rubidium from 22 to 4.3, resulting in a decrease in concentration ratios of potassium over cesium and rubidium by about 5 times. Further work should target to test feed solution containing sodium and to improve extraction efficiency and selectivity of the extraction system.

Development of poly(aspartic acid-co-malic acid) composites for calcium carbonate and sulphate scale inhibition

Polyaspartic acid (PSI) is suitable for the inhibition of inorganic scale deposition. To enhance its scale inhibition efficiency, PSI was modified by reacting aspartic acid with malic acid (MA) using thermal polycondensation polymerization. This reaction resulted in poly(aspartic acid-co-malic acid) (PSI-co-MA) dual polymer. The structural, chemical and thermal properties of the dual polymers were analysed by using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry and gel permeation chromatography. The effectiveness of six different molar ratios of PSI-co-MA dual polymer for calcium carbonate and calcium sulphate scale inhibition at laboratory scale batch experiments was evaluated with synthetic brine solution at selected doses of polymer at 65–70°C by the static scale test method. The performance of PSI-co-MA dual polymer for the inhibition of calcium carbonate and calcium sulphate precipitation was compared with that of a PSI single polymer. The PSI-co-MA exhibited excellent ability to control inorganic minerals, with approximately 85.36% calcium carbonate inhibition and 100% calcium sulphate inhibition at a level of 10 mg/L PSI-co-MA, respectively. Therefore, it may be reasonably concluded that PSI-co-MA is a highly effective scale inhibitor for cooling water treatment applications.

A combined approach for the management of desalination reject brine and capture of CO2

Water desalination plants produce huge amounts of reject brine, which are usually sent back to the sea, where they could, in the long run, result in detrimental effects on the aquatic life as well as the quality of the seawater in the area. In this study, a new approach for the management of desalination reject brine and capture of CO2, where ammoniated brine is reacted with carbon dioxide, has been investigated. The effects of reaction temperature, reaction time, and excess ammonia were assessed. Carbon dioxide was used either as a pure gas or a mixture of 10% CO2 in methane. The experimental results indicated that the optimum reaction temperature was about 20°C and the optimum NH3/NaCl ratio was 2 for synthetic brine solutions and 3 for actual reject brine. The proposed process proved to be effective in reducing the CO2 concentration in a CO2–CH4 gas mixture by more than 90%. The solubility of sodium bicarbonate was found to play a key role in the removal of sodium. The results indicated that the new approach can reduce the salinity of reject brine and, at the same time, contribute to the reduction CO2 emissions.

Investigations of organic inhibitors for silica scale control from geothermal brines–II

In an effort to find alternatives to brine acidification for control of siliceous scale deposition in geothermal resource production facilities, a second series of laboratory screening tests with new organic inhibitors has been conducted. In the first series of tests, organic inhibitors, usually consisting of dispersants and phosphino-carboxylic acid mixtures, were examined for silica scale control activity [Gallup, D.L., 2002. Investigations of organic inhibitors for silica scale control in geothermal brines. Geothermics 31, 415–430]. The present study consisted of screening additional inhibitor formulations obtained from seven different manufacturers in a laboratory pressure reactor using a synthetic brine solution. Several of the organic inhibitors yielded promising scale deposition results. Similar to the initial series of tests, brine acidification always out-performed the organic inhibitors. Acid precursors also appear to be acceptable alternatives to strong acids as a means of limiting corrosion, transportation risks and safety/handling issues.

Evaluation of capillary electrophoresis for determining the concentration of dissolved silica in geothermal brines

The determination of silica concentrations in geothermal brines is widely recognized as a difficult analytical task due to its complex chemical polymerization kinetics that occurs during sample collection and chemical analysis. Capillary electrophoresis (CE) has been evaluated as a new reliable analytical method to measure silica (as silicates) in geothermal brines. Synthetic and geothermal brine samples were used to evaluate CE methodology. A capillary electrophoresis instrument, Quanta 4000 (Waters–Millipore) coupled with a Waters 820 workstation was used to carry out the experimental work. The separation of silicates was completed in ∼5.5 min using a conventional fused-silica capillary (75 μm i.d. × 375 μm o.d. × 60 cm total length). A hydrostatic injection (10 cm for 20 s at 25 °C) was employed for introducing the samples. The carrier electrolyte consisted of 10 mM sodium chromate, 3 mM tetradecyltrimethyl-ammonium hydroxide (TTAOH), 2 mM sodium carbonate, and 1 mM sodium hydroxide, adjusted to a pH 11.0 ± 0.1. Silicates were determined using an indirect UV detection at a wavelength of 254 nm with a mercury lamp and with a negative power supply (−15 kV). A good reproducibility in the migration times (%R.S.D. ∼ 1.6%) based on six non-consecutive injections of synthetic brine solutions was obtained. A linear response between silica concentration and corrected peak area was observed. Ordinary (OLR) and weighted (WLR) linear regression models were used for calculating silica concentrations in all samples using the corresponding fitted calibration curves. The analytical results of CE were finally compared with the most probable values of synthetic reference standards of silica using the Student's t-test. No significant differences were found between them at P = 0.01. Similarly, the atomic absorption spectrometry (AAS) results were also compared with the most probable concentrations of the same reference standards, finding significant differences at P = 0.01.

Determining the Distribution of Pu, Np and U Oxidation States in Dilute NaCl and Synthetic Brine Solutions

The effect of iron powder (Fe0) on the reduction of Pu(VI),Np(V), and U(VI) was investigated in dilute NaCl and synthetic brines. Thetotal concentrations and oxidation states of the actinides in these solutionswere monitored as functions of pC H +, Eh, and time using techniques includingVis/Near IR absorption spectrophotometry, solvent extraction, activity counting,and inductively coupled plasma spectroscopy-mass spectrometry (ICP-MS). Whenconcentrations were too low and the oxidation states could not be directlydetermined by spectrophotometry or solvent extraction, comparing the measuredconcentrations with the solubility of reference systems helped to define thefinal oxidation states. In general, the reduction was more rapid, and couldproceed further, in the dilute NaCl solution than in the brine solutions.The experimental observations can be summarized as follows: (1) in the diluteNaCl solutions (pC H + 7 to 12), all three actinides, Pu(VI), Np(V) and U(VI),were reduced to lower oxidation states (most likely the tetravalent state)within a few days to a few months in the presence of Fe0; (2) insynthetic brines containing Fe0 (pC H + 8 to 13), the reductionof Pu(VI) was much slower than in the dilute NaCl solution. The dominant oxidationstate of Pu in the brine solution was Pu(V), the concentration of which wascontrolled by the electrochemical potential and could probably be representedby a heterogeneous redox reaction PuO2 . xH2O(s) PuO2 + +e —; (3) in synthetic brines containing Fe0 (pC H + 8 to 13), Np(V) was probably reduced to Np(IV) and precipitatedfrom the solution; (4) in synthetic brines containing Fe0 (pC H+ 8 to 13), no significant reduction of U(VI) was observed within 55 days.

Ultraviolet spectroscopic evidence for polynuclear lead (II) complexes in synthetic Red Sea brines

The Pb complexes in a synthetic brine solution with a composition comparable to that of the Atlantis II Deep 56°C Brine have been identified by UV absorption spectroscopy. The important species at ambient temperatures are PbCl 2− 4 and Pb(OH)BrCl 2 2−. At 56°C the former complex partially dissociates to form lower chloro complexes while the latter undergoes halide exchange reactions forming Pb(OH)Br 2Cl 2−. Evidence has also been found for the following polymeric lead hydroxo complexes: Pb 4(OH) 4Cl 4, Pb 6(OH) 3Cl 12 and Pb 3(OH) 12Cl 4. The predominant polynuclear complex in the brine, Pb 4(OH) 4Cl 4, tends to dissociate at 56°C to form lower polymeric species. The formulation of the limiting binary chloro complex as PbCl 4 2− rather than PbCl 6 4− is supported by the reflectance spectrum of Cs 4PbCl 6.

Emission Spectrometric Determination of Barium, Boron, Iron, Manganese, and Strontium in Oilfield Waters Using a Plasma Arc

Studies of the concentration and distribution of the mineral content in subsurface oilfield waters aid in locating water-pollution sources, determining water compatibilities, determining the origin and distribution of oilfield waters and petroleum, and exploring for petroleum and other minerals. An emission-spectrographic method using a plasma arc to determine B, Ba, Fe, Mn, and Sr in oilfield waters was developed. Variations in brine composition were reduced by use of a synthetic brine solution. Less than 1 mg/liter of each ion can be detected. Synthetic and natural oilfield waters containing the subject ions were mixed with various organic solvents and the internal standard. Relative intensities of their emission lines were determined using each of 10 solvent systems.