Removal Of Chloride Ions Research Articles

Optimization of chloride ion removal from desulfurization wastewater by electrocatalysis progress: application of Box–Behnken design

Optimization of chloride ion removal from desulfurization wastewater by electrocatalysis progress: application of Box–Behnken design

Using layered double hydroxides and anion exchange resin to improve the mechanical properties and chloride binding capacity of cement mortars

Chloride-induced corrosion results in the deterioration of concrete structures. To resolve this issue, two types of synthetic layered double hydroxides (LDHs) 2D nanoflakes based on CaFe-NO3 and CaFeAl-NO3 and a strongly basic anion exchange resin (SBAER) were developed for removing chloride ions from simulated sea sand (SSS) mortars. We investigated the combined effect of SSS mortars blended with chloride adsorbents using the response surface methodology (RSM). A Box-Behnken Design (BBD) was used to discuss the independent variables (CaFe-NO3 LDHs, CaFeAl-NO3 LDHs, and SBAER) and evaluate the response of compressive strength and free chloride content concerning admixture content. Experimental results showed that the free chloride content of the samples decreased upon the addition of LDHs and SBAER due to a synergistic effect, which resulted in the formation of LDHs-Cl, [N+(CH3)3Cl−], Friedel’s salt (FS), and Kuzel’s salt (KS). The optimal range of the admixture content was determined to be 0.3–0.6 wt% CaFe-NO3 LDHs, 0.2–0.5 wt% CaFeAl-NO3 LDHs, and 0.2–0.5 wt% SBAER. In conclusion, LDHs and SBAER exhibited excellent chloride binding capacity, which makes them promising candidates for use as high-efficiency and stable chloride composite adsorbents in marine concrete.

Defect-rich heterojunction photocatalyst originated from the removal of chloride ions and its degradation mechanism of norfloxacin

Concentrated leachate (CL) contains typical high concentration of Cl−, and it is necessary to remove Cl− efficiently and even to achieve a high value-added product from the Cl− removal process. In this study, a Bi-contained upconversion glass–ceramic (GC) is firstly explored for ultra-efficient removal and utilization of Cl−, wherein the abundant porous structure is continuously formed in the Cl− removal process to further provide channels for the deep migration of Cl− and H+ to its inner Bi source. The high Cl− removal rates above 96% were all achieved over the best GC sample at the Cl− concentrations of 1300–13,000 mg/L, then the terminal BiOCl-based precipitates were directly collected as the near-infrared (NIR) GC photocatalysts, which possessed defect-rich heterostructure with excellent upconversion luminescence and electronic energy transmission properties. In the degradation of norfloxacin (NOR), high removal rates of 98%, 73%, and 36% were achieved under UV–Vis-NIR, Vis-NIR, and NIR irradiations. On a basis of the four possible NOR degradation pathways discussed, we found that the primary active species were attributed to O2·− and ·OH radicals under NIR and UV–Vis-NIR irradiations, respectively. Therefore, the Bi-contained GC will supply a new strategy for high-efficiency Cl− removal and value-added resource utilization.

Sulfate radical-based removal of chloride ion from strongly acidic wastewater: Kinetics and mechanism

Specific to strongly acidic wastewater, the traditional lime neutralization produces massive hazardous waste and present serious environmental risks. Thus, the recycling of purified wastewater after the contained contaminants being removed has been proposed. However, among these contaminants, chloride ion (Cl(-I)) is rather difficult to remove. This study proposes a new method to remove Cl(-I) using thermal activated persulfate (PS). Under optimized conditions, above 96% of initial Cl(-I) was removed from the actual wastewater, and the residual Cl(-I) was below 158 mg/L, which satisfies the requirement of Cl(-I) concentration for wastewater recycling. Furthermore, the mechanism was investigated. In the strongly acidic wastewater, the high concentration of H+ prompted the thermal activation process of PS through two pathways. (1) H+ prompted the transformation of S2O82- into HSO4- and SO4, and then into HSO5- that was finally transformed into ·OH and ·SO4− at above 70 ℃. (2) H+ prompted the production of ·OH through the transformation of ·SO4− into ·HSO4 and the cleavage of ·HSO4. The key step for Cl(-I) removal was identified as the formation of ·Cl or ·Cl2– from the oxidation of Cl(-I) by ·SO4− and ·OH, and their contribution ratios were estimated to be 67.4% and 32.6%, respectively.

Mechanistic study to investigate the injection of surfactant assisted smart water in carbonate rocks for enhanced oil recovery: An experimental approach

More than half of the world's discovered oil is held in carbonate reservoirs, most of which are naturally oil-wet fractured reservoirs. Oil Recovery efficiency can be improved noticeably if the rock wettability is changed from an oil-wet to a water-wet state. However, what factors control the wettability alteration are not clearly specified. In this study, a comprehensive mechanistic study is performed using different experimental tools to investigate the effects of active ions, non-active ions, CTAB, and different combinations of ions and CTAB on the sample rock's wettability. The results indicate that using CTAB and a smart water solution, in which the sodium and chloride ions are eliminated and the concentration of sulfate ions is increased, (SW-0NaCl-4SO42− + 1CTAB) reduced the contact angle to 43.58°. The zeta potential value of the oil-wet calcite powder increased from −61.12 to −7.6 mV after treatment with SW-0NaCl-4SO42− + 1CTAB. Moreover, the mean roughness value of oil-wet calcite powder increased from 5.02 to 25.89 nm after treatment with SW-0NaCl-4SO42− + 1CTAB. In fact, sulfate ions are capable of removing the strongly adsorbed carboxylic groups from the surface and changing the wettability of the calcite surface to a more water-wet state. Also, the cationic surfactant monomers tend to ionically react with carboxylic groups and separate them from the calcite surface. Moreover, the removal of sodium and chloride ions also leads to significant changes in the wettability. The imbibition results showed that the change of wettability from an oil-wet to a more water-wet state results in a critical increase in oil recovery efficiency during imbibition of distilled water into the calcite rock slice. High oil recovery efficiency can be obtained by optimizing the smart water solution composition and using a proper concentration of surfactant.

Removal of chloride ions from acidic solution with antimony oxides

This study aims to investigate the removal of Cl- from acidic solution with antimony oxides. The effects of the adsorbent type, reaction time, reaction temperature, Sb/Cl mole ratio and acidity on adsorption performance and the regeneration of loaded adsorbent were systematically studied. The results shows that Sb2O3·xH2O has the highest adsorption rate (97.64%) among Sb2O3·xH2O, Sb2O5·xH2O, Sb2O4·xH2O and Sb2O3 in the solution containing 1.25mol/L H2SO4 under the condition of Sb/Cl mole ratio 3:1 and stirring for 2h at room temperature, and the concentration of Cl- in the acid solution can be reduced to 280mg/L. Then the residual Sb in the adsorbed solution can be decreased from 48.21mg/L to 16.09mg/L by C-SbA which is made by Sb2O5·xH2O. The C-SbA which has been used can be reused after calcining at 400℃ for 2h. The loaded adsorbent was completely regenerated by adding it into NaOH or Na2CO3 solution whose pH is equal or more than 9.5 according to S/L ratio 1:6g/mL and was stirred for 0.5h at room temperature. The Cl- in the regenerated solution was crystallized and precipitated in the form of NaCl without evaporation and concentration according to the common ion effect of Na+, and the purity of NaCl was more than 99%.

Enhanced elution of chloride ions from incinerator bottom ash

Recycling of the incinerator bottom ash, which is discharged from solid waste treatment plants, is important since the landfilling capacity is limited, and if it is left untreated, it would generate a great environmental burden. Besides, the incinerator bottom ash has a similar chemical composition to that of cement and therefore it can be used as a substitute raw material in cement manufacturing. This recycling method would, in turn, reduce the consumption of natural resources, such as limestone and clay. Generally speaking, a high concentration of chloride leads to severe corrosion of steel, which can damage the reinforced concrete structure. The removal of chloride ions from the ash should, therefore, be carried out in advance to use it as a raw material for cement production. Thus, this study aims to find an effective method for eluting chloride ion from the incinerator bottom ash for recycling. One of the main findings of this work was that the residual chloride concentration in the incinerator bottom ash was reduced to 1.70 g/kg, eluting 87.78% of initial Cl concentration, when the ash was washed with an acetic acid solution (concentration: 1.5 mol/L) saturated with CO2 micro-bubbles.

Copper nanowire array as highly selective electrochemical sensor of nitrate ions in water

Contamination of water with nitrate ions is a significant problem that affects many areas of the world. For this reason, European legislation has set the maximum permissible concentration of nitrates in drinking water at 44 mg/L. Thus, it is clear that a continuous monitoring of nitrate ions is of high technological interest but it must be rapid, easy to perform and directly performable in situ. In this work we have developed a nanostructured sensor based on array of copper nanowires obtained with the simple method of galvanic deposition. The nanostructured sensors have a very short response time with a detection limit less than 10 μM. Different interfering species were tested finding a negligible effect except for the chloride ions. However, this problem has been solved by removing chloride ions from the water through a simple precipitation of chloride compounds with low solubility. Nanostructured sensors were also used to analyze real water samples (rain, river and drinking water). In the case of drinking water, we have measured a concentration of nitrate ions very close to the that measured by conventional laboratory techniques.

Electroflotation Extraction of Sparingly Soluble Rare-Earth Compounds in a Multicomponent Mixture from Aqueous Solutions Containing Chloride Ions

The electroflotation extraction of sparingly soluble rare-earth compounds from aqueous solutions containing chloride ions was studied. At pH in the range 5–9, the recovery did not exceed 15%. The influence of various organic additives on the efficiency of electroflotation was also investigated. When the SUPERFLOC C-494 cationic flocculant was introduced in the system at pH 9, the recovery was 74%. The maximum recovery of sparingly soluble compounds of all elements of the multicomponent system was observed at pH 7 after addition of SeptaPAV (c) (α = 97–98%) and PEO-1500 (n) (α = 86–98%). The efficiency of the process remained high at a high NaCl concentration (100 g/L) in the presence of surfactants and flocculants. It was shown that electroflotation makes it possible to effectively extract sparingly soluble compounds of a mixture of rare-earth metals both from wash waters when washing rare-earth precipitates to remove chloride ions and from the (NaCl) salt solutions of filtrates.

A recyclable polydopamine-functionalized reduced graphene oxide/Fe nanocomposite (PDA@Fe/rGO) for the enhanced degradation of 1,1,1-trichloroethane

The removal of chlorinated hydrocarbons through heterogeneous catalysts from groundwater has become a valuable approach. However, the synthesis of a highly efficient and persistent material especially for trichloroethane (TCA) removal is still immature. In this study, we prepared polydopamine (PDA) embedded Fe/rGO nanocomposite via pH-induced polymerization of dopamine for the degradation of TCA in sodium percarbonate (SPC) system. The experimental outcomes revealed that PDA decorated Fe/rGO not only enhanced the TCA degradation (98%) more economically but also strengthened the stability and recyclability of catalyst compared to bare Fe/rGO. The TEM, XRD, FTIR, XPS and VSM analyses declared the successful preparation of magnetically separable PDA@Fe/rGO nanocomposite. Furthermore, a higher degradation rate of probe compounds in PDA@Fe/rGO/SPC system indicated that PDA decoration improved the formation of active species due to autoxidation of dopamine and reducing capability of PDA. The impact of solution matrix on PDA@Fe/rGO performance elucidated the effect of various species on degradation. The GCMS, TOC analysis and dechlorination experiments validated the formation of non-toxic products and reasonable TOC and chloride ions removal. The PDA@Fe/rGO catalyst can be recycled for six consecutive cycles retaining a 76% along with abundant availability of Fe2+ and Fe3+ species validated using XRD and XPS analysis. The enhanced remediation capacity and improved recyclability of PDA@Fe/rGO nanocomposite can serve as a shining star for the practical application of TCA removal in groundwater.

Electrochemical and photoelectrochemical approaches for the selective removal, recovery, and valorization of chloride ions

Anthropogenic activities such as the use of water softeners and road deicers have artificially increased the Cl− concentration in freshwater resources, threatening sustainable water ecosystems worldwide. Currently, there is no energy-efficient and sustainable method to selectively remove Cl− from water to regulate the Cl− concentration in water treatment processes. In this study, we report new electrochemical and photoelectrochemical strategies that can not only selectively remove Cl− but also recover and valorize Cl− to Cl2, HOCl, and ClO−. These methods are based on the use of Bi as a Cl-storage/release electrode for the construction of Cl-removal and Cl-recovery cells. We demonstrate the operation of proof-of-concept electrochemical and photoelectrochemical cells where the Cl− storage/release reactions are coupled with various reactions to generate electricity, fuels, and chemicals.

Treatment of acidic wastewater via fluoride ions removal by SiO2 particles followed by phosphate ions recovery using flow-electrode capacitive deionization

A new process for the treatment of phosphoric acid industry wastewater is proposed. The technique comprises the following major steps: (1) selective removal of fluoride ions via reaction/adsorption with SiO2-containing particles; (2) microfiltration; and (3) flow electrode capacitive deionization (FCDI) for selective separation of phosphate ions. Three different silica-based materials were tested (quartz send, glass beads and fly ash) and F- removal from initial concentration of 4.1 gr/l to undetectable level was achieved using fly ash & quartz sand mixtures (FA-QS). Fluoride adsorption by FA-QS resulted in pH reduction to pH≈1.0, at which the phosphate system in the wastewater shifts towards the H3PO4 form as a dominating species. These uncharged species could be efficiently separated from Cl- and SO42- ions electrochemically using a single-electrode FCDI process. FCDI operated with a single electrode (5 %wt activated charcoal powder) at a constant voltage of 1.2 V resulted in 90% selective separation of phosphorous with the complete removal of sulfate and chloride ions. The results, therefore, indicated that the new process can be effectively used to minimize the risk posed by the wastewater, while enabling the recovery of valuable phosphorus.

MXene/Activated-Carbon Hybrid Capacitive Deionization for Permselective Ion Removal at Low and High Salinity.

Two-dimensional, layered transition metal carbides (MXenes) are an intriguing class of intercalation-type electrodes for electrochemical applications. The ability for preferred counterion uptake qualifies MXenes as an attractive material for electrochemical desalination. Our work explores Ti3C2Tx-MXene paired with activated carbon in such a way that both electrodes operate in an optimized potential range. This is accomplished by electrode mass balancing and control over the cell voltage. Thereby, we enable effective remediation of saline media with low (brackish) and high (seawater-like) ionic strength by using 20 and 600 mM aqueous NaCl solutions. It is shown that MXene/activated-carbon asymmetric cell design capitalizes on the permselective behavior of MXene in sodium removal, which in turn forces carbon to mirror the same behavior in the removal of chloride ions. This has minimized the notorious co-ion desorption of carbon in highly saline media (600 mM NaCl) and boosted the charge efficiency from 4% in a symmetric activated-carbon/activated-carbon cell to 85% in a membrane-less asymmetric MXene/activated-carbon cell. Stable electrochemical performance for up to 100 cycles is demonstrated, yielding average desalination capacities of 8 and 12 mg/g, respectively, for membrane-less MXene/activated-carbon cells in NaCl solutions of 600 mM (seawater-level) and 20 mM (brackish-water-level). In the case of the 20 mM NaCl solutions, surprising charge efficiency values of over 100% have been obtained, which is attributed to the role of MXene interlayer surface charges.

Investigation of the Adsorption Efficacy in Removal of Chloride Ions by Synthesized magnesium–aluminum hydroxide from Zanjan Lead &Zinc Industry wastewater

Investigation of the Adsorption Efficacy in Removal of Chloride Ions by Synthesized magnesium–aluminum hydroxide from Zanjan Lead &Zinc Industry wastewater

Energy projection of the seawater battery desalination system using the reverse osmosis system analysis model

Water-stressed countries have been shifting their sources of clean water from inland freshwater to seawater. This led to a comprehensive exploration of seawater desalination processes to address water scarcity; however, membrane processes have expensive operational costs and high energy consumption. In this regard, this study presented a novel energy self-sufficient desalination system design that incorporates rechargeable seawater batteries as an additional energy storage system. Experimental data were projected using the reverse osmosis system analysis model to determine the configuration that achieved the lowest energy consumption and highest charging rate. The results show that the seawater battery achieved a satisfactory desalination performance with >90% and 74%−82% removal of sodium and chloride ions from actual water samples, respectively. Among the configurations, using ultrafiltration as pretreatment and applying 1.8 mA as initial current yielded the lowest energy consumption (1.35 kWh/m3) and the highest energy charging rate (1.01). Compared to the conventional reverse osmosis desalination plants (2.83 kWh/m3), the seawater battery-desalination system has a huge potential in addressing the major disadvantages of current desalination technologies.

Silver‐Triggered Activity of a Heterogeneous Palladium Catalyst in Oxidative Carbonylation Reactions

AbstractA silver‐triggered heterogeneous Pd‐catalyzed oxidative carbonylation has been developed. This heterogeneous process exhibits high efficiency and good recyclability, and was utilized for the one‐pot construction of polycyclic compounds with multiple chiral centers. AgOTf was used to remove chloride ions in the heterogeneous catalyst Pd‐AmP‐CNC, thereby generating highly active PdII, which results in high efficiency of the heterogeneous catalytic system.

Silver-Triggered Activity of a Heterogeneous Palladium Catalyst in Oxidative Carbonylation Reactions.

A silver‐triggered heterogeneous Pd‐catalyzed oxidative carbonylation has been developed. This heterogeneous process exhibits high efficiency and good recyclability, and was utilized for the one‐pot construction of polycyclic compounds with multiple chiral centers. AgOTf was used to remove chloride ions in the heterogeneous catalyst Pd‐AmP‐CNC, thereby generating highly active PdII, which results in high efficiency of the heterogeneous catalytic system.

Experimental Study on Chloride Ion Removal in High-Salt Wastewater System

Chlorine is usually present in the environment in an ionic state, is highly mobile and difficult to degrade. High-chlorine wastewater can corrode buildings and affect the growth of animals and plants. Therefore, how to solve the environmental problem of high concentration of chloride ions well and effectively has drawn the intensive attention of the society. In this paper, chloride ion is removed from wastewater with the method of coprous chloride precipitation, and investigation is made on the effects of pH, temperature, amount of precipitant, titration time and reaction time on the removal efficiency of chloride ions. The results show that: when nCuSO4:nNa2SO3:nNaCl: n(ascorbic acid) =1.3:1.1:1: 0.01, and reaction pH is 3, temperature is 80 °C, titration time of sodium sulfite is 20min, reaction time after titration is 30min, the chloride ion has the optimal removal efficiency. SEM method is used for the characterization of the precipitates formed by the reaction. The results show that the experimentally produced complex cuprous chloride is irregular polyhedron with uneven particle size.

Influence of cation types on the stability of bound chloride ions in cement mortar simultaneously under electric field and SO42− attack

Destabilization and release of bound chloride ions in reinforced concrete structures can cause accelerated corrosion of steel bars, posing an attendant risk to the durability of the whole structure and this problem is exacerbated by the combined effect of SO42− and electric field. In this paper, electrochemical chloride removal (ECR) method was used to remove chloride ions from mortar specimens and the influence of four cations (Mg2+, Ca2+, Na+ and K+) on the stability of bound chloride ions in cement mortars simultaneously under an electric field and SO42− attack was investigated. The results showed that bound chloride ions were prone to converting into free chloride ions under the combined effect of electric field and SO42− attack. Moreover, divalent cations (Mg2+ and Ca2+) exerted a more negative effect on the stability of bound chloride ions than monovalent cations (Na+ and K+). X-ray diffraction (XRD) analysis and thermal gravimetric and differential thermal gravimetric (TG-DTG) analysis demonstrated that the destabilization of bound chloride ions under an electric field was mainly attributed to the decomposition of the C-S-H gels and Friedel’s salts. Findings from this research shed new light on the fate of bound chloride ions in reinforced concrete structures under an electric field in chloride-sulfate coexistence environments.

Selective removal of chloride ions by bismuth electrode in capacitive deionization

Common methods in capacitive deionization (CDI) for selective removal are derived from membrane separation mechanism or size-based intercalation mechanism. In this study, based on the electrochemical activity of bismuth (Bi) material to chloride ions (Cl−) and inertness to sulfate ions (SO42−), Bi electrode is used as anode in CDI to selectively remove Cl− ions from mixed NaCl and Na2SO4 solution. Through the reaction with Bi, Cl− ions are stored in bismuth oxychloride (BiOCl). Results show that Bi electrode exhibits selectivity for Cl− over SO42− with a selectivity coefficient of more than 1.5 in solutions with mole ratio of Cl− to SO42− larger than 1. The selectivity coefficient is greatly dependent on the mole ratio of Cl− to SO42− and increases when the ratio rises. In solution with a fixed Cl−/SO42− mole ratio, higher applied voltage and prolonged time result in higher Cl− ion removal capacity, but not necessarily better selectivity. The highest selectivity coefficient of 4.5 is achieved in 8.5 mM NaCl and 1.1 mM Na2SO4 mixed solution at voltage of 1.6 and 2.0 V after charging for 1 h. These results demonstrate that Bi electrode can selectively remove Cl− ions from mixed solution with a relatively lower concentration of SO42− ions, which provides new insights into ion separation and selective removal by CDI.