High Concentration Of Chloride Ions Research Articles

Electrochemical redox treatment of denitrification in coastal secondary effluent using Ti/IrO2 anode

In northern coastal industrial park, inlet of the wastewater treatment plant (WWTP) had the characteristics of low carbon source and high chloride ion concentration, which resulted in its poor biodegradability. In this case, the experiment explored an electrochemistral method to remove nitrogen. Cathodic potential, Ti/IrO2 was confirmed as the anode and − 1.6 V was taken as the potential in order to remove nitrate-N. The findings include: when the initial chloride ion was 2000 and 3000 mg/L, the effect on the removal difference of nitrogen was slight. When the electrolysis time was 60 min, ammonia-N was removed completely, nitrite-N concentration kept 1 mg/L approximately. The ammonia-N removal efficiency went up with the increasing cathodic potential, and was completely removed in different water samples, but nitrate-N removal showed an opposite result. The production amount of nitrite-N was the least at − 1.6 V. As the pH increased, ammonia-N and nitrate-N’s removal efficiency went up first and then down, the removal effect was the best at pH being 9, Nitrite-N was less influenced by pH. After optimizing the raw water sample, Nitrate-N and TN removal efficiency were significantly increased, but the nitrite-N almost kept constant.

Use of Alternative Water Resources in Copper Leaching Processes in Chilean Mining Industry—A Review

Due to the significant growth of the world population, the accelerated growth of economic industries in various countries, and improved living conditions, freshwater consumption has increased dramatically and is currently under critical pressure. Its good use and rationing are essential. Even though mining is an industry that consumes much less water than other industries, such as agriculture, surrounding communities are constantly questioned. This occurs mainly because mining deposits are generally found in arid areas where freshwater is scarce, forcing government authorities to regulate water use in mining processes more severely. Faced with this scenario, the mining industry has innovated the use of seawater and wastewater from processes for its production processes. In addition, various projects are under development to construct desalination plants and water impulsion systems of the sea; therefore, it is expected that seawater and/or wastewater in mining will continue to grow in the coming years. Among the main challenges faced in the use of these water resources in mining is: (i) the close relationship that exists between the use of seawater and energy consumption, transferring the problem of water scarcity to a problem of energy cost overruns; (ii) generation of greater integration between the use of water and sustainable energy; and (iii) brine management is economically expensive and technically challenging and, therefore, most desalination plants discharge untreated brine directly into the sea, causing an environmental impact. On the other hand, regarding the use of these water resources in leaching processes, there are very positive results for the dissolution of copper from sulfide minerals, where the wastewater from desalination plants presents better results than seawater due to its higher concentration of chloride ions, allowing it to work at higher redox potential values in order to increase copper dissolution. This manuscript is a bibliographic review in which finally, it is concluded that it is feasible to incorporate wastewater from water desalination plants in heap leaching processes for copper sulfide ores, as long as the cost of transfer from water desalination plants to mining sites can be supported.

High Selectivity Electrocatalysts for Oxygen Evolution Reaction and Anti-Chlorine Corrosion Strategies in Seawater Splitting

Seawater is one of the most abundant and clean hydrogen atom resources on our planet, so hydrogen production from seawater splitting has notable advantages. Direct electrolysis of seawater would not be in competition with growing demands for pure water. Using green electricity generated from renewable sources (e.g., solar, tidal, and wind energies), the direct electrolytic splitting of seawater into hydrogen and oxygen is a potentially attractive technology under the framework of carbon-neutral energy production. High selectivity and efficiency, as well as stable electrocatalysts, are prerequisites to facilitate the practical applications of seawater splitting. Even though the oxygen evolution reaction (OER) is thermodynamically favorable, the most desirable reaction process, the four-electron reaction, exhibits a high energy barrier. Furthermore, due to the presence of a high concentration of chloride ions (Cl−) in seawater, chlorine evolution reactions involving two electrons are more competitive. Therefore, intensive research efforts have been devoted to optimizing the design and construction of highly efficient and anticorrosive OER electrocatalysts. Based on this, in this review, we summarize the progress of recent research in advanced electrocatalysts for seawater splitting, with an emphasis on their remarkable OER selectivity and distinguished anti-chlorine corrosion performance, including the recent progress in seawater OER electrocatalysts with their corresponding optimized strategies. The future perspectives for the development of seawater-splitting electrocatalysts are also demonstrated.

Synergistic Effect of Different NaCl Concentrations on the Initial Corrosion of Q235 Steel under a Simulated SO2 Environment

AbstractThe synergistic effect of chloride ions and industrial corrosive gases in the atmosphere intensifies metal corrosion. Therefore, the study of this corrosive behavior and its effects on metals in complex environments is crucial. In this study, the wet/dry cyclic corrosion test, under a constant deposited salt, was used to simulate atmospheric corrosion conditions. In addition, the methods of corrosion weight gain, dynamic potential polarization curves, electrochemical impedance spectroscopy, and other analyses were used to explore the mechanism and law of Q235 steel with different corrosion times in different coastal‐industrial atmospheric environments. The corrosion pattern of Q235 steel and the composition of the rust layer were further investigated through X‐Ray Diffractometer analysis and Scanning Electron Microscope observations. The results show that the content of Fe3O4 decreases at higher chloride ion concentrations and the content of α‐FeOOH increases in later stages of corrosion.

Evaluation of Physicochemical Characteristics and Carbonate Equilibria System of the New Calabar River, Choba, Rivers State, Nigeria

Carbonate equilibrium helps to critically determine the degree or level of pollution and its possible source. In this study the physicochemical properties and carbonate equilibria system of the New Calabar River, Choba, Rivers State, Nigeria was evaluated using standard techniques by analyzing the pH, total dissolved solid, bicarbonate ion, sulphate ion, chloride ion, total alkalinity and total hardness of five samples collected from strategic points along the River. Data obtained show that the pH ranged 5.93-6.33, while TDS values varied from 4770mg/l to 5280mg/l. The total alkalinity of the sample 1, sample 2, sample 3, sample 4 and sample 5 analyzed and their results are 70mg/l, 68 mg/l, 66 mg/l, 73 mg/l and 60.5 mg/l respectively. The total hardness of sample 1, sample 2, sample 3, sample 4 and sample 5 collected from the New Calabar River and the results are 913mg/l, 904 mg/l, 942 mg/l, 933 mg/l and 939 mg/l. The sulphate ion concentration for sample 1, sample 2, sample 3, sample 4 and sample 5 are 519.20mg/l, 510.5mg/l, 552mg/l, 543mg/l and 549.00mg/l, while the Chloride concentration varied from 3390.5 mg/l to 4,802 mg/l mg/l. Result indicated that all physiochemical parameters apart from total alkalinity was not within the WHO guidelines or standard and the river shows presence of weak acid deposits but very high concentration of chloride ion which indicates higher degree of organic pollution and also acidic in nature. Thus, the river poses a health risk to the rural communities who rely primarily on them as the only source of domestic water supply.

Laser Additively Manufactured Iron-Based Biocomposite: Microstructure, Degradation, and In Vitro Cell Behavior.

A too slow degradation of iron (Fe) limits its orthopedic application. In this study, calcium chloride (CaCl2) was incorporated into a Fe-based biocomposite fabricated by laser additive manufacturing, with an aim to accelerate the degradation. It was found that CaCl2 with strong water absorptivity improved the hydrophilicity of the Fe matrix and thereby promoted the invasion of corrosive solution. On the other hand, CaCl2 could rapidly dissolve once contacting the solution and release massive chloride ion. Interestingly, the local high concentration of chloride ion effectively destroyed the corrosion product layer due to its strong erosion ability. As a result, the corrosion product layer covered on the Fe/CaCl2 matrix exhibited an extremely porous structure, thus exhibiting a significantly reduced corrosion resistance. Besides, in vivo cell testing proved that the Fe/CaCl2 biocomposite also showed favorable cytocompatibility.

Same site, different corrosion phenomena caused by chloride: The effect of the archaeological context on bronzes from Sujialong Cemetery, China

The corrosion of archaeological bronzes is a complex process, and different corrosion phenomena can occur even within the same site, while previous studies paid little attention. Different corrosion phenomena can be observed on bronzes unearthed from Sujialong Cemetery, Hubei, China; in particular, some bronzes exhibit severe bronze disease, which is an uncommon phenomenon in Hubei bronzes. Multiple analysis methods were used to identify the corrosion products on the bronzes and to clarify the corrosion mechanisms. The results showed that the different corrosion phenomena were associated with the tomb microenvironment in different areas of the cemetery, which was confirmed by a spatial analysis of the whole cemetery; the outbreak of bronze disease was closely related to the presence of high chloride ion concentrations in the tomb environment and poor preservation conditions after excavation. The different corrosion phenomena are related to the archaeological contexts of the bronzes (especially microenvironments), which have been investigated only superficially in the past.

Degradation of chloroaniline in chemical wastewater by ionizing radiation technology: Degradation mechanism and toxicity evaluation

Chloroaniline is a typical organic pollutant in chemical wastewater, which cannot be effectively removed in conventional wastewater treatment processes. In this study, ionizing radiation was used as advanced treatment process to degrade 2-chloroaniline (2-CA). The results showed that 10 mg/l of 2-CA could be completely degraded at 1 kGy. The required dose for completely degrading 2-CA by radiation increased when its initial concentration increased. Solution pH affected 2-CA degradation by changing the radiation-chemical yield of reactive species. Chloride ions (10 and 100 mM) had not obvious influence on 2-CA degradation. Hydrogen radicals, hydrated electrons and hydroxyl radicals, all contributed to the degradation of 2-CA, but with different degradation mechanisms. Hydrogen radicals and hydrated electrons could initiate reductive dechlorination of 2-CA, while hydroxyl radicals can degrade 2-CA by hydroxylation. 6-amino-1,4-cyclohexadiene and chlorobenzene were the main intermediate products of 2-CA degradation in the hydrogen radicals or hydrated electrons dominant process; while o-hydroxyaniline and nitroso-chlorobenzene were the main intermediate products in the hydroxyl radicals dominant process. The solution toxicity after radiation treatment varied with the initial concentration of 2-CA and the absorbed dose. In the actual chemical wastewater, 2-CA can be effectively removed by radiation, even in the presence of high concentration of chloride ions (about 2800 mg/l). The solution toxicity of actual wastewater decreased with the increase of adsorbed dose. This study provided an insight into the 2-CA degradation by radiation, and demonstrated that radiation could be an alternative option for the treatment of chloroaniline-containing chemical wastewater.

Analysis of Poultice-Based Desalination of a Nineteenth Century Brick and Stone Cathedral after the Event; A Longitudinal Study of Surface Chloride Readings

St George’s Cathedral in Perth was consecrated in 1888 and constructed using hand-made bricks and limestone. After 120 years of exposure to salt-laden winds, rising salty water and leaky roofs significant deterioration due to salt efflorescence and water penetration necessitated an $18 million AUD restoration program in 2002. Before accepting the heritage architect’s proposal to replace all the worst damaged brick and stone elements, surface chloride activity mapping of the affected areas was conducted. The survey found that the worst decay was associated with high chloride ion concentrations, with a maximum value of 10,000 ppm on a brick buttress and 7,600 ppm on a stone colonnade on the west front. After four months of treatment, the Westox Cocoon papier-mâché pulp poultice had lowered the surface chloride readings to 10 ± 5 ppm on the bricks and stone. Ten years after the work, a series of tests were conducted on salt-damaged reference stone and bricks to find formulae for converting surface chloride readings into weight percent extractable chloride concentrations. This data was then retrospectively applied to the treated cathedral fabric to estimate how much chloride had been removed. Without the poultice treatment, large sections of the original fabric would have been lost.

Removal of chloride ions from a copper leaching solution, using electrodialysis, to improve the uranium extraction through ion-exchange

This study shows the technical feasibility to recover uranium from copper Pregnant Leaching Solutions (PLS) using ion-exchange, after a removal of chloride ions using the electrodialysis (ED) technique. The original copper PLS solutions came from the National Copper Corporation (CODELCO), from their hydrometallurgical operations, which contained high concentrations of chloride ions. These solutions contained average concentrations of 22 g/L chloride ions, pH 1.5 – 1.8 and 20 mg/L uranium. The high chloride contents made the uranium recovery technically unfeasible, because of the high volumes of chemical reagents needed to operate. To eliminate the chloride ions selectively, a modified electrodialysis (ED) process was developed. The ED process was made of a three–compartment cell. This system removed selectively the chloride ions, and replaced them with sulphuric ions, without modifying the composition of the copper PLS solution, to allow a continuous operation of the copper production plant. The ED process decreased the chloride content from 22 g/L to 6 g/L. Finally, static and dynamic load tests were performed for both the original PLS and the treated PLS, using 3 different anion-exchange resins: Dowex-1, Lewatit A365 and Lewatit MP62-WS. The loading capacity of the ion-exchange resins was increased 4 times approximately.

Electrochemical Corrosion Behaviour of Carbon Steel in Concrete with Metakaolin Admixture Exposed to Soil with High Concentration of Chloride Ions

Electrochemical Corrosion Behaviour of Carbon Steel in Concrete with Metakaolin Admixture Exposed to Soil with High Concentration of Chloride Ions

Influence of NaCl concentration on microbiologically influenced corrosion of carbon steel by halophilic archaeon Natronorubrum tibetense

The influence of NaCl concentration on microbiologically influenced corrosion (MIC) of Q235 carbon steel by the halophilic archaeon Natronorubrum tibetense was investigated by immersion tests and electrochemical measurements. An increase in NaCl concentration from 0 g/mL to 0.1 g/mL promoted the anodic dissolution of carbon steel and accelerated its corrosion, but MIC did not occur. A further increase in NaCl concentration to 0.2 g/mL led to MIC in inoculated medium, and the occurrence of the MIC resulted in further aggravation of carbon steel corrosion. Once the NaCl concentration reached 0.3 g/mL, the high concentration of chloride ions greatly interfered with the adsorption of dissolved oxygen and the attachment of N. tibetense cells to the surface of carbon steel, thus reducing the corrosion rate of carbon steel and inhibiting the MIC.

High concentrations of sodium and chloride ions have opposing effects on the growth of the xerophyte Pugionium cornutum under saline conditions

AbstractBackground: The research on plant salt tolerance has mainly focused on Na+, but Cl− has been relatively neglected. Previous studies have found that the xerophyte Pugionium cornutum, an important forage grass in the arid and semi‐arid regions of northwestern China, could synergistically accumulate high quintiles of Na+ and Cl− in its shoots under NaCl treatments. However, the separate effects of these ions on the adaptation of P. cornutum to saline conditions have not been investigated.Aims: In this study, the response of P. cornutum to Na+ and Cl− was analyzed.Methods: Four‐week‐old seedlings were treated with additional 50 mM NaCl, Na+‐specific solution containing 50 mM Na+ with a mix of , H2 , and as counter anions, and Cl−‐specific solution containing 50 mM Cl− with a mix of K+, Ca2+, and Mg2+ as counter cations.Results: Compared with the normal growth condition irrigated with Hoagland solution, the Na+‐specific solution severely impaired the growth and photosynthesis of P. cornutum due to the high accumulation of Na+ in shoots and the deterioration of tissue K+ homeostasis; while the Cl−‐specific solution significantly increased shoot fresh and dry biomass. The Cl−‐specific solution could also increase the turgor pressure in leaves for enhancing osmotic adjustment, which should be mainly attributed to the large accumulation of Cl−, since the concentrations of other ions, including K+, Mg2+, Ca2+, H2 , and , in tissues under Cl−‐specific treatment were maintained at the same levels as those observed under the normal condition.Conclusions: P. cornutum displays an excellent tolerance to moderate Cl− but not to Na+, and the large accumulation of Cl− should play a positive role in stimulating the growth of P. cornutum under salt stress.

Groundwater flow and chloride transport modeling of the alluvial aquifer of lower Soummam Valley, Béjaia, North-East of Algeria

Resulting from lithological conditions and anthropogenic activities as fertilizers use and wastewater discharge, high concentrations of chloride ions were revealed in both surface water and groundwater in Lower Soummam valley, situated in the North-Eastern of Algeria. Using geological, hydrogeological and geochemical data, a conceptual model was designed in order to improve understanding of chloride mass movements within the aquifer. A groundwater flow using PMWIN, coupled with a solute transport numerical model using MT3D code was run. Following a steady state stress period, four transient stress periods were added in order to simulate groundwater level evolution from 2011 to 2030. Groundwater withdrawals, providing from the National Plan of Water, were increased and vertical recharge rate was progressively reduced. Respecting an optimal management of water resources suitable for arid and semi-arid watersheds, successive tests have been conducted in order to mitigate the influence of high pumping rates and low recharge conditions. Recognized as a major term in water budget, water inflows from lateral boundaries representing 54.4%. At the river–aquifer interface, water was exchanged in both upward and downward representing 18% of the total amount of inflow. In coherence with experimental data, simulations indicate an impact of exchange fluxes across the river-aquifer interface. The Cl model simulations show a substantial decrease of Cl loads. According to good hydraulic properties, 90% of simulated wells show a gradual decline in their calculated concentrations, almost located on El Kseur-Oued Ghir pathway. Simulation results could be integrated in the future water resource management plan of Soummam Valley. Such a predictive model, it will be used to lay down water quality restoration strategy.

Transient Dynamics of Archaea and Bacteria in Sediments and Brine Across a Salinity Gradient in a Solar Saltern of Goa, India.

The microbial fluctuations along an increasing salinity gradient during two different salt production phases – initial salt harvesting (ISH) phase and peak salt harvesting (PSH) phase of Siridao solar salterns in Goa, India were examined through high-throughput sequencing of 16S rRNA genes on Illumina MiSeq platform. Elemental analysis of the brine samples showed high concentration of sodium (Na+) and chloride (Cl–) ions thereby indicating its thalassohaline nature. Comparison of relative abundance of sequences revealed that Archaea transited from sediment to brine while Bacteria transited from brine to sediment with increasing salinity. Frequency of Archaea was found to be significantly enriched even in low and moderate salinity sediments with their relative sequence abundance reaching as high as 85%. Euryarchaeota was found to be the dominant archaeal phylum containing 19 and 17 genera in sediments and brine, respectively. Phylotypes belonging to Halorubrum, Haloarcula, Halorhabdus, and Haloplanus were common in both sediments and brine. Occurence of Halobacterium and Natronomonas were exclusive to sediments while Halonotius was exclusive to brine. Among sediments, relative sequence frequency of Halorubrum, and Halorhabdus decreased while Haloarcula, Haloplanus, and Natronomonas increased with increasing salinity. Similarly, the relative abundance of Haloarcula and Halorubrum increased with increasing salinity in brine. Sediments and brine samples harbored about 20 and 17 bacterial phyla, respectively. Bacteroidetes, Proteobacteria, and Chloroflexi were the common bacterial phyla in both sediments and brine while Firmicutes were dominant albeit in sediments alone. Further, Gammaproteobacteria, Alphaproteobacteria, and Deltaproteobacteria were observed to be the abundant class within the Proteobacteria. Among the bacterial genera, phylotypes belonging to Rubricoccus and Halomonas were widely detected in both brine and sediment while Thioalkalispira, Desulfovermiculus, and Marinobacter were selectively present in sediments. This study suggests that Bacteria are more susceptible to salinity fluctuations than Archaea, with many bacterial genera being compartment and phase-specific. Our study further indicated that Archaea rather than Bacteria could withstand the wide salinity fluctuation and attain a stable community structure within a short time-frame.

A High‐sensitivity and Enzyme‐free Clenbuterol Sensor using SWCNT Arrays Prepared with a One‐pot Method Comprising Gold Nanoparticles and Cl−

AbstractWe describe a novel enzyme‐free sensor for clenbuterol (CLE) prepared by a simple electrochemical method. A new method to detect clenbuterol hydrochloride was developed by single‐walled carbon nanotubes (SWCNTs) arrays and gold nanoparticles (AuNPs)‐Cl− complex. SWCNT arrays modified glass carbon electrode (GCE) was first prepared by one‐pot method with cyclic voltammetry.Then AuNPs were deposited on the SWCNT arrays and complexed with a high concentration of chloride ions (0.1 mol/L). The as‐fabricated SWCNT arrays/AuNPs senor have showed an excellent sensitivity in CLE detection with lower detection limit (0.5 ng/L) and wider linear range (1–800 ng/L). Its high performance can be attributed to the high catalytic activity of SWCNT arrays and the special absorption of CLE on AuNPs. The surface morphology of the electrode was analyzed by atomic force microscopy, X‐ray photoelectron spectroscopy and SEM. This work offers a new method for the synthesis of SWCNT arrays and a novel avenue for CLE detection. The modified electrode was stable with 98.5 % of its initial current response after remained one month, it was used to detect CLE in human urine, animal tissues and food with satisfactory results.

Modeling the corrosion of steel casing and the damage of well cement in a borehole system

This paper presents the effect of chloride-induced corrosion in an underground borehole system, specifically considering the steel casing and further damage to the surrounding cement. In the past four decades, oil well cement has been successfully used for underground construction. However, high concentrations of chloride ions gradually degrade the functionality and durability of well cement. Gasses and liquids can leak from deterioration caused by chloride ions, and thus motivate this study. The chemo-mechanical coupling diffusion model and a classical fracture mechanics model are applied. The model is validated with OPC concrete corrosion data from literature, and then applied to well cement using experimentally obtained material property data. The time when crack initiation, peak pressure, and complete fracture is reached in the model of the cement sheath provides a quantification of the expected service life of the borehole system.

Effects of the α/γ-Phase Ratio on the Corrosion Behavior of Cast Duplex Stainless Steel

The effects of the α/γ-phase ratio on pitting corrosion initiation and growth in cast duplex stainless steel were studied, including the preferential dissolution of the two phases inside the pits, using pitting potential measurement and potentiostatic polarization measurement with a high concentration of chloride ions and a low pH. The initiation of pitting was not dependent on the α-phase ratio. The γ phase preferentially dissolves when a high potential in the active dissolution region is applied, and the α phase preferentially dissolves when a low potential is applied. In addition, with an increase in α-phase ratio, the potential range where the α phase preferentially dissolves enlarged toward the higher potential side. The growth rate of stable pitting increased with the α-phase ratio. Dissolution of the α phase increased with an increase in the α-phase ratio. This phenomenon is presumably caused by the decreased amount of Cr in the α phase, resulting from the increased α-phase ratio, as well as by Cr depletion around Cr nitrides.

Individual and additive stress impacts of Na+ and Cl‾ on proline metabolism and nitrosative responses in rice

It is well-established that plants accumulate high concentrations of sodium (Na+) and chloride (Cl‾) ions when subjected to salinity stress. However, little is known about individual or relative toxic impacts of these ions and whether they exert additive impacts under NaCl. Most of the investigations have historically been directed to decode Na+-toxicity, and as a result deeper understandings about Cl‾-toxicity are lacking. In this study, the extent to which sodium and chloride ions contribute in inducing nitrosative responses and proline metabolism is shown in two rice cultivars, one tolerant (Panvel-3) and one sensitive (Sahyadri-3). Equimolar (100 mM) concentrations of Na+, Cl‾ and NaCl (EC ≈ 10 dSm−1) reduced biomass production in both the cultivars in following manner NaCl > Na+>Cl‾. Na+ and NaCl treatments displaced K+, however, the tolerant cultivar maintained low Na+/K+ levels. Hyper-accumulation of Na+ may apparently be attributed for the reduced plant growth and biomass accumulation, and higher lipid-peroxidation. Nitric oxide and nitrate reductase were more responsive to NaCl followed by Na+ and Cl‾, respectively. The expression patterns of key-genes involved in proline biosynthesis and degradation confirmed the involvement of proline in better performance of salt tolerant cultivar under stresses, with higher responsiveness to NaCl and then Na+ and Cl‾ treatments. Principal component analysis revealed correlations in proline metabolism and nitrosative responses under ionic stresses and confirmed the closeness of NaCl and Na+ stresses. Overall, amongst the individual ions, Na+ induced higher toxicity than Cl‾ and both these ions exerted additive stress impacts under NaCl treatment.

Experimental and theoretical characterization of commercial nanofiltration membranes for the treatment of ion exchange spent regenerant

This work presents a joint experimental and simulation campaign aimed at characterizing two nanofiltration membranes (TS80 and NF270) in the presence of a multi-ionic water solution simulating the spent regenerant of cationic ion exchange resins employed for water softening. We identified the membrane parameters, which allowed for predicting the performances through the Donnan Steric Pore Model with Dielectric Exclusion. A good agreement between model and experimental trends of rejection as a function of the applied pressure was observed (error < 15%). The analysis of trans-membrane fluxes and exclusion coefficients showed that dielectric exclusion was the crucial mechanism for the ionic partition. In fact, the lower pore dielectric constant found for TS80 justified the higher rejections to divalent cations with respect to NF270. Moreover, negative charge densities were found for both membranes, because of the high concentration of chloride ions in the feed, which likely adsorbed onto the membrane. However, it was observed that the experimental rejections did not change significantly with the feed pH. This result, in line with the minor role of the Donnan exclusion resulting from the model, suggested that the membrane performances were not much affected by the charge density at high feed ionic strengths (~1 M).