Removal Of Chloride Research Articles

Mechanical–transport–chemical modeling of electrochemical repair methods for corrosion‐induced cracking in marine concrete

AbstractReinforced concrete structures exposed to marine environments often experience chloride ingress, reinforcement corrosion, and corrosion‐induced cracking. The electrochemical repair method is a promising concrete rehabilitation technique with advantages of non‐destructive and economic performance in crack repair, chloride removal, and corrosion protection, which is particularly suitable for structures exposed to marine environments. This work presents an innovative methodology for modeling the mechanical, transport, and chemical process during electrochemical treatment for marine concrete structures. The entire process from concrete cracking up to repairing can be successfully reproduced and digitally visualized. The first sub‐model calculates the corrosion‐induced cracking process at the mesoscopic level with the consideration of local mechanical variances of concrete composites. Then, a reactive transport sub‐model is established to reveal the interactions and electrochemical reactions among various species of ions. A crack repair sub‐model is built to visualize the moving interface between chemical deposition and crack surface. Through combining the three sub‐models, the interconnected influencing factors in practical engineering can be quantitively investigated. The calculation results show that, compared with electrolyte concentration, the influence of current density on crack closure rates are more obvious. Other factors such as steel reinforcement diameter and crack distribution pattern, which have not been previously reported are highlighted. These findings can guide the application of electrochemical repair in practical engineering.

Removal of hydrogen chloride from simulated coal gasification fuel gases using honeycomb-supported natural soda ash

In this study, we examined the HCl absorption performance of cheap natural soda ash loaded on a honeycomb support as a hot-gas cleanup method. Air-blown and oxygen-blown coal gasification fuel gases were used to simulate the gas composition. The effect of fuel gas composition on the HCl removal performance of the prepared absorbent was studied. It was found that the removal performance in an inert atmosphere was maintained in the presence of H2. On the other hand, the performance deteriorated in the presence of CO due to carbon deposition from the disproportionation reaction of CO. When CO2 was added to the CO, carbon deposition was suppressed in the air-blown gas and the HCl removal performance recovered. The performance recovery for an oxygen-blown gas was smaller than that for an air-blown gas. However, when the amount of CO2 added to the oxygen-blown gas was increased, the removal performance improved. The HCl removal performance of the absorbent was dependent on the initial HCl concentration and treatment temperature in the following order: 2000 ppm < 1000 ppm < 500 ppm, and 400 °C < 600 °C ≈ 500 °C. Recycled absorbents were prepared by loading natural soda ash once again on the recovered honeycomb supports that had been washed with water. Their HCl removal performance was similar to the fresh absorbent regardless of air-blown or oxygen-blown gasification. Thus, honeycomb supports were recyclable.

A visible-light-driven photocatalytic fuel cell/peroxymonosulfate (PFC/PMS) system using blue TiO2 nanotube arrays (TNA) anode and Cu-Co-WO3 cathode for enhanced oxidation of organic pollutant and ammonium nitrogen in real seawater

Antibiotics (or pharmaceuticals) and inorganic nitrogen may coexist in mariculture wastewater, adversely affecting food safety and coastal ecology. Advanced treatment of marine wastewater is of great significance. In this study, simultaneous removal of refractory berberine chloride (BC) and ammonium nitrogen (NH4+-N) was firstly achieved in a visible-light-driven marine photocatalytic fuel cell/peroxymonosulfate (PFC/PMS) system. The modified blue TiO2 nanotube arrays (TNA) anode and Cu-Co-WO3 cathode bridged photo-electrocatalysis, sulfate radical-based oxidation and catalytic chlorination, benefiting both pollutant removal and fuel cell electricity generation. Under optimized conditions (double photoelectrodes, 2.5 mM PMS, R = 500 Ω), the system had an open circuit voltage of 0.57 V, removing 95% of BC and NH4+-N, meeting the discharge standard of mariculture. Natural-sourced CODMn, and inorganic nitrogen in simulated mariculture wastewater were also efficiently removed with power generation. The mechanism involving (photo-)electrocatalytic chlorination and PMS-chlorination theoretically supports the application/optimization of integrated electrochemical technologies for marine pollution control.

Biodesalination and treatment of raw hypersaline produced water samples using indigenous wastewater algal consortia

Indigenous microalgae consortia present in domestic wastewater, were acclimatized to three real produced water (PW) samples collected from different oil fields. PW, a byproduct of oil mining and extraction, is hypersaline and toxic. Therefore, progressive adaptation mechanism was applied for acclimatization in a steadily decreasing dilutions of PW. After acclimatization, algae consortia were used for biodesalination and treatment of PW. The acclimatization lag phase was longer when the dilutions were reduced. The predominant species present in the consortia were Chlorella. One PW sample (onshore with largest initial salinity) showed the earliest adaptation (13 days) at lowest dilution. Chloride and salinity removal efficiencies of 25% and 22% were achieved, respectively, along with significant decrease in total dissolved solids (TDS) and conductivity in the different samples. The same PW sample showed highest removal of chloride (25%, from initial 53 g/L to final 40 g/L) and COD (44%). Another PW sample showed highest removal of salinity (22%), electrical conductivity (9%), TDS (20%) and total organic carbon (26%), as well as highest increase in alkalinity (86%). Removal efficiencies were minimum in the last PW sample which also showed less adaptability to the same dilution ratio of other two PW samples.

Ecosafety Screening of Photo-Fenton Process for the Degradation of Microplastics in Water

Microplastic pollution is receiving increased attention due to the realization of its hazards to aquatic and human life. Researchers across the globe are attempting to remove microplastics before its entry into the ecosystem. Therefore, the present work focused on the removal of microplastic from water and studied the potential risks for marine organisms and the ecosystem. The removal of model microplastics, polypropylene (PP) and polyvinyl chloride (PVC), has been studied by using photo-Fenton process. ZnO nanorods coated with SnOx(x &amp;lt; 2) layer and decorated with zero valent iron (Fe0) nanoparticles was used as heterogeneous catalyst for the removal of the microplastics in continuous water flow device. The obtained results demonstrated that high degradation efficiency of PP and PVC microplastics was achieved in a relatively short time and more than 95% of the average particle volume was reduced after 1 week of irradiation. The environmental impact of the photo-Fenton process of the microplastics degradation was investigated by using an ecotoxicological approach. An ecosafety screening has been performed through a series of experiments (bioassays) under controlled conditions, testing water samples after the photo-Fenton degradation of microparticles using a lab scale device. The ecotoxicological impact has been investigated by applying a battery of certified bioassays (UNI EN ISO/EPA standardized techniques) on aquatic organisms at different trophic levels (bacteria, algae, invertebrates). The results obtained on the three model organisms (A. fischeri, P. subcapitata, and D. magna) revealed no toxic effect for samples collected both before and after the photo-Fenton process, thus showing the absence of toxic by-products development during the degradation process.

Dehydrochlorination study of plasticized poly(vinyl chloride) contianing modified titanium dioxide, cerium stearate, organotin and β-diketone complex after long-term storage

Understanding the influence of additives on the dehydrochlorination of plasticized poly(vinyl chloride) (PVC) from the source and long-term storage is an attractive topic. In this work, the effects of folic acid modified nano titanium dioxide (FANT), cerium stearate, organotin and β -diketone compound additives on the dehydrochlorination of plasticized PVC and long-term storage were investigated using conductivity measurements. The results showed that the induction time of hydrogen chloride removal of plasticized PVC (C-1) containing composite stabilizer at 200 °C were 243% higher than those of the control (S1). After storage, the heat stability of the control decreased significantly. Instead, the induction time and stability time of plasticized PVC containing FANT, cerium stearate, organotin and β- diketone composites were significantly enhanced at 200 °C. The thermal stability sequence from difficult to easy for removal of hydrogen chloride was : 3.0 phr (1.90% wt) (C2) >1.0 phr (0.64% wt) (C1) > 5.0 phr (3.17% wt) (C3) with FANT. It is inferred that this is due to the FANT’s hydrogen bonding van der Waals force and the complexation reaction of variable valence metal Ce+3/Ce+4 with C-Cl bond in PVC polymer molecule. The induction time (min) of hydrogen chloride removal at 200 °C before and after storage is as follows: C-20 (71.9) > C-10 (70.6) > C-1 (60.7) > C-3 (57.2) > C-30 (52.7) > C-2 (49.9) > S1 (25.3) > S10 (19.7). The critical temperature for hydrogen chloride removal by the composite film is around 210 °C. If the content of FANT increased to 3.17%, the intermolecular force and repulsive force in PVC system offset each other, indicating that the increase of FANT content will lead to the increase of repulsive force with PVC. A certain amount of FANT, cerium stearate, organotin and β- diketone composites has a significant synergistic effect on the thermal stability of PVC.

Chloride removal capacity and salinity tolerance in wetland plants

Deicing with sodium chloride maintains safe roads in the winter, but results in stormwater runoff with high chloride (Cl−) content that causes various downstream problems. Chloride-rich water risks contaminating groundwater, shortening the lifespan of concrete and metal constructions, and being toxic to aquatic organisms. Current stormwater treatment methods are unable to remove Cl−, but wetland plants with high chloride uptake capacity have potential to decrease Cl− concentrations in water. The aim was to identify suitable plant species for removing Cl− from water for future studies on phytodesalination of water, by comparing 34 wetland plant species native to Sweden in a short-term screening. Additionally, Carex pseudocyperus, C. riparia, and Phalaris arundinacea was further compared as to their salinity tolerance and tissue Cl− concentration properties. Results show that Cl− removal capacity, tissue accumulation, and tolerance varied between the investigated species. Removal capacity correlated with biomass, dry:fresh biomass ratio, water uptake, and transpiration. The three tested species tolerated Cl− levels of up to 50–350 mg Cl− L−1 and accumulated up to 10 mg Cl− g−1 biomass. Carex riparia was the most Cl-tolerant species, able to maintain growth and transpiration at 500 mg Cl− L−1 during 4 weeks of exposure and with a medium removal capacity. Due to a large shoot:plant biomass ratio and high transpiration, C. riparia also had high shoot accumulation of Cl−, which may facilitate harvesting. Phalaris arundinacea had the highest removal capacity of the investigated species, but displayed decreased growth above 50 mg Cl− L−1. From this study we estimate that wetland plants can remove up to 7 kg Cl− m−2 from water if grown hydroponically, and conclude that C. riparia and P. arundinacea, which have high tolerance, large biomass, and high accumulation, are suitable candidates for further phytodesalination studies.

Organic Chlorides in Petroleum Crude Oil: Challenges for Refinery and Mitigations

AbstractCrude oils contain chloride impurities, including some organic components termed as ‘organic chloride'. Owing to the high dissociation energy of the C‐Cl bond, organic chlorides are very difficult to remove during the desalting process unlike inorganic chloride salts. Failure to properly remove organic chlorides could have a significant adverse effect on petroleum refinery equipment in terms of corrosion during crude oil processing. Therefore, stringent specification of organic chlorides is being maintained throughout the refining process to avoid corrosion‐related incidents. Generally, a guard bed column is used for the removal of organic chlorides in the downstream of the refining process. Guard bed columns are comprised of metal oxide‐based components that operate at a very high temperature. In contrast, a phase transfer catalyst (PTC)‐based process for organic chloride removal at the upstream of the refining process is established up to lab‐scale and with model compounds only. This review is aimed to highlight the technical challenges associated with organic chloride contamination in refining processes and plausible methods and techniques available for smooth refining operations.

Carbonation treatment of gasification fly ash from municipal solid waste using sodium carbonate and sodium bicarbonate solutions

In recent years, slagging-gasification technology has received increasing attention in treating municipal solid waste (MSW). Compared with conventional incineration, the higher temperature in the slagging-gasification process optimizes its residue composition, and gasification fly ash (GFA) is the only unreused solid residue. Although GFA is a potential civil engineering material, its high content of heavy metals, chlorides, and sulfates hinders its practical use. Moreover, although carbonation has proven to immobilize heavy metals in incineration fly ash, the conventional gas carbonation method cannot remove chlorides and sulfates. In this study, sodium bicarbonate (NaHCO3) treatment was studied to treat GFA for the first time, and sodium carbonate (Na2CO3) was used for comparison. Different concentrations of NaHCO3 and Na2CO3 solutions were used to treat the GFA, and comprehensive tests were conducted on the treated samples. The results indicated that NaHCO3 treatment was effective in immobilizing Pb, Zn, Cu, and Ni in GFA, while Na2CO3 treatment could not effectively immobilize Pb and Zn. Both NaHCO3 and Na2CO3 promoted the removal of chlorides and sulfates in GFA. The wastewater from the NaHCO3 treatment contained fewer heavy metals compared with those from water washing or Na2CO3 treatment, benefitting its treatment or reuse.

The application of multiple advanced chloride removal methods to synthesized Friedel’s salt and municipal solid waste incineration bottom ash

To recycle municipal solid waste incineration bottom ash as a cement raw material, it is important to reduce the Cl concentration in the ash. However, the reduction of chlorides by washing only has limited success due to the presence of insoluble Friedel’s salt (FS) in the ash. Although some studies on the decomposition of FS and the application of advanced chloride removal methods to bottom ash have been reported, few studies have compared the effects of different removal methods. Moreover, due to the complex ash composition, it is also necessary to compare the effects on different ashes and pure FS. Therefore, in this study, we applied five advanced chloride removal methods to synthesized FS and two types of bottom ash (FS-High and FS-Low), and compared the effects. For both FS and bottom ash, all methods promoted chloride dissolution more than washing only. For FS, aging was the most effective method, with a Cl removal ratio of 73%. In contrast, for ash FS-High, aging increased the Cl removal ratio to 80% and decreased the Cl content to 2800 mg/kg. The FS-derived peak observed in an X-ray diffraction analysis disappeared following aging. For ash FS-Low, acid washing increased the Cl removal ratio to 64% and decreased the Cl content to 1800 mg/kg. The treatment with the highest removal ratio in each ash had the lowest pH. There was a significant correlation between pH and the Cl removal effect. The Cl remaining after the application of the methods was likely associated with Na.

A numerical study of chloride migration in concrete under electrochemical repair

Electrochemical repair (ECR) is one of the most effective methods of removing chloride from offshore engineering structures to improve their durability. The diffusion of chloride and electrochemical migration are key stages in this process. In this work, a new numerical chloride migration–diffusion model was established using the Nernst–Planck equation. The distributions of free chloride ions in concrete in the stages of free chloride diffusion and ECR were simulated and the effects of the external potential and cathode position on ECR efficiency were analysed. The results showed that ECR can effectively remove chloride ions from concrete. After 12 weeks of ECR, the chloride removal efficiency was more than 66%. With an increase in the repair time, the ECR efficiency decreased gradually. In the initial stage of ECR, the chloride concentration on the rebar surface decreased rapidly. After 4 weeks of ECR, the chloride concentration tended to stabilise. The ECR efficiency also improved with an increase in external potential increases, with the chloride concentration on the reinforcing bar surface decreasing rapidly. When cathodes are set on both sides of the concrete, the ECR time should be extended and the external potential should be increased to achieve a better repair effect.

Chloride accumulation in aboveground biomass of three macrophytes (Phragmites australis, Juncus maritimus, and Typha latifolia) depending on their growth stages and salinity exposure: application for Cl- removal and phytodesalinization.

Anthropogenic activities can be the source of saline solid wastes that need to be treated to reduce their salt load to meet the purposes of reuse, valorization or storage. In this context, chloride remediation can be achieved using high-salt accumulating plants. However, there is very limited information on the comparative potential of different species in the same environment, and only scarce data concerning their efficiency as a function of growth stage. In order to rationalize these selection criteria, three macrophytes i.e., common reed (Phragmites australis), sea rush (Juncus maritimus), and cattail (Typha latifolia), were cultivated at two growth stages (6-months old and 1-year old) for 65 days in Cl− spiked substrates (from 0 up to 24 ‰ NaCl). The plants’ survival and potential capacity for removal of Cl− from substrates and accumulation in shoots were investigated. For the three studied species, mature and juvenile plants display a high tolerance to salinity. However, mature specimens with higher shoot biomass and Cl− contents are capable of greater chloride removal than juvenile plants. The sole exception is P. australis which displays just the same phytoremediation potential for both mature and juvenile specimens. Moreover, P. australis has the lowest potential when compared with other species, being 1.5 and 3 times lower than for J. maritimus and T. latifolia. When considering the plant growth and the shoot biomass production, chloride removal rates from the substrate point that mature J. maritimus should preferentially be used to design an operational chloride remediation system. The results highlight the relevance of considering the growth stage of plants used for Cl− removal.Highlights1) Mature and juvenile specimens of J. maritimus, P. australis, and T. latifolia have high salinity tolerance in solid media spiked up to 24 ‰ NaCl.2) Mature plants have generally better Cl− removal and phytoremediation performances than juvenile specimens.3) J. maritimus is the most effective species for chloride phytoremediation with high survival and high Cl− sequestration in shoots.4) T. latifolia has high Cl− removal in shoots and good remediation capacities but also shows sign of stress.5) P. australis shows low Cl− sequestration and is a poor candidate for chloride remediation from substrate.Supplementary InformationThe online version contains supplementary material available at 10.1007/s11356-021-17591-3.

Preparation of MgX/Al2O3-Y sorbent for highly efficient simultaneous removal of hydrogen fluoride and hydrogen chloride under low-temperature environment

ABSTRACT In this study, a series of Mg-modified γ-Al2O3 sorbents have been introduced to simultaneously remove HCl and HF in a low-temperature environment. These sorbents were prepared by impregnation, and the effects of Mg loading amount and calcination temperature on the performance of the sorbent were investigated. The optimal sorbent (modified by 15 wt% Mg and calcined at 400℃, Mg15/Al2O3-400) exhibited the highest adsorption capacity of all the sorbents tested, 37.89 mg(HF)•gsorbent −1 and 34.54 mg(HCl)•gsorbent −1, respectively. Taking into account an excellent HF(HCl) capacity of the Mg15/Al2O3-400, these sorbents are very promising HF(HCl)sorbents usable in a low-temperature environment. The role of MgO loaded on γ-Al2O3 was investigated by Brunauer−Emmet−Teller (BET) method, X-ray diffractometer (XRD), scanning electron microscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), temperature-programmed desorption of CO2 (CO2-TPD), and thermogravimetric analysis (TG-DTG). The results revealed that MgO acted as a ‘leading role’ to promote the adsorption activity of the sorbents. BET analysis demonstrated that the Mg modification process did not seriously change the pore type of the γ-Al2O3. CO2-TPD results revealed that the calcination temperature will significantly affect the number and strength of the basic sites on the surface of the sorbent. In addition, XRD and XPS analysis indicated that the consumption of MgO and the accumulation of reaction products on the surface and pores are the main reasons for the deactivation of the sorbent.

Chloride Removal of Calcium Aluminate Cements: Reaction and Physicochemical Characteristics

Chloride Removal of Calcium Aluminate Cements: Reaction and Physicochemical Characteristics

Layered double hydroxide coated electrospun carbon nanofibers as the chloride capturing electrode for ultrafast electrochemical deionization

Slow desalination kinetics and poor durability of the electrodes are two key limitations of electrochemical deionization (EDI) that are considered to be the next generation of capacitive desalination (CDI). Herein, we report the design of a high-efficiency chloride removal electrode material for accelerating the desalination kinetics and concurrently improving the durability of EDI, which is based on coating NiMn-Cl layered double hydroxides (LDHs) on the surface of electrospun carbon nanofibers (CNFs@LDHs). The salient features of the as-developed CNFs@LDHs are that applying layer-structured LDHs with abundant redox-active sites to accelerate the pseudo-capacitive ion storage via fast ion intercalation/deintercalation, and leveraging the rigid CNF backbone to strengthen its durability by preventing the potential aggregation of LDHs. As expected, the CNFs@LDH based EDI system displays an ultrafast desalination rate of 0.51 mg g−1 s−1 and outstanding long-term stability (only 10.66 % desalination capacity reduction after 35 cycles), which is achieved without sacrificing its excellent desalination capacity (72.04 mg g−1). This work could be inspirational for the future design of ultrafast yet durable EDI approaching industrial desalination applications.

Investigation of dielectric heating method of zinc-containing materials for chlorides removal

The technological development of the world community makes it necessary to resolve the issues of the produced industrial residues utilization. Worn-out galvanized metal cars, ceilings and other metal structures require orderly utilization. Utilization of galvanized scrap may be carried out in Electric Arc Furnaces (EAF) to obtain intermediate steel and EAF dust. Electric Arc Furnaces dus contains zinc, so it is used as a secondary raw material for the production of metallic zinc. Waelz oxides are formed in Waelz kilns, after the primary processing of EAF dust. Waelz oxide contains halides that must be removed first. Halides may be removed by heating to temperatures of about 1000°C. Dielectric (microwave) heating is a promising and environmentally friendly method for material processing. Microwave heating is carried out without burning natural gas, which leads to decrease of waste gases volume. The work experimentally confirmed the possibility of zinc-containing materials heating at electromagnetic emission exposure. The duration of products heating up to the temperature of 1000°C was 128 - 188 s. The residual content of chloride ions in the calcined products is less than 0.05 wt%.

CO2 capture and ions removal through reaction with potassium hydroxide in desalination reject brine: Statistical optimization

Previous studies have investigated the overall performance of the modified Solvay process based on a new alkaline compound, namely, KOH. Preliminary results have confirmed its high reactivity and effectiveness in capturing CO2 and managing reject brine. In this study, parametric sensitivity analysis has been carried out to optimize the operating conditions and thereby maximize CO2 capture and ions removal from high-salinity brines. Response surface methodology (RSM) analysis using the central composite design (CCD) approach was implemented to statistically determine the impact of important operating conditions, including KOH concentration (30–110 g/l), CO2 gas flow rate (400–1600 ml/min), gauge pressure (1–3 barg), and temperature (10–50 °C) on key response process output variables, such as CO2 uptake and ions reduction. The importance of these parameters and their interactions were confirmed by employing analysis of variance (ANOVA) approach at a confidence level of 95% (p < 0.05). These analyses demonstrated that under the optimized conditions of a temperature of 10 °C, gauge pressure of 2.1 barg, CO2 gas flow rate of 848.5 ml/min, KOH concentration of 110 g/l, and an inert mixing particle volume fraction of 15%, a maximum CO2 uptake value of 0.58 g/g KOH, maximum sodium (Na+) removal of 44.1%, chloride (Cl−) removal of 40.1%, calcium (Ca2+) removal of 100%, and magnesium (Mg2+) removal of 99.8% were achieved. The characterization of the collected solid products at optimum conditions revealed the production of valuable and useful products, particularly sodium and potassium bicarbonates, in addition to KCl.

Comparison of bismuth ferrites for chloride removal: Removal efficiency, stability, and structure

The chloride (Cl−) ions in wastewater are difficult to remove, since there is a lack of effective and recyclable chloride removal agents. In this study, the bismuth ferrites (BFO) are first explored as chloride removal agents, and their oxidation or precipitation effects on the Cl− removal are studied. In the BFO samples, the crystal phases of BiFeO3 and Bi2FeO4 have very limited contributions to the Cl− removal, while the enhanced removal ability is exhibited with the increase of Bi25FeO40. When the mass percentage of Bi25FeO40 reaches 70%, high Cl− removal efficiencies of 80–90% are achieved, which even exceeds 95% for pure Bi25FeO40. The morphology and structure characterizations reveal that the excellent Cl− removal performance of Bi25FeO40 is determined by its unstable chemical structure due to the sharing of Bi5+ and Fe3+ ions in the tetrahedral positions. The density of states and electron localization function of Bi25FeO40 demonstrate that its Fe and O bonding is weaker than those of BiFeO3 and Bi2FeO4, resulting in the easier breaking of the Fe3+/Bi5+-O bonds to release Bi5+ ions, which have oxidation ability for the formation of OH and Cl radicals to enhance the Cl− removal efficiency.

Sorption of HCl from an Aromatic Hydrocarbon Mixture Using Modified Molecular Sieve Zeolite 13X.

In this study, the removal of chlorides, especially HCl, from an aromatic hydrocarbon mixture composed of benzene, toluene, xylenes, and ethylbenzene has been studied. Molecular sieve zeolite 13X as such and exchanged with different amounts of alkali and alkaline earth metal ions has been used as an adsorbent. Different techniques like inductively coupled plasma-optical emission spectroscopy, X-ray powder diffraction, N2 adsorption–desorption for Brunauer–Emmett–Teller surface area and pore volume, and scanning electron microscopy were utilized to analyze all of the adsorbents. The effect of varying concentrations of alkali and alkaline earth metal cations and process parameters like temperature and flow rate on the removal of HCl has been studied by performing the adsorption breakthrough experiment. The main objective of this study is to determine the precise concentration of exchangeable ions and the optimum temperature, pressure, and feed flow rate at which the adsorbent exhibits the highest capacity toward the sorption of chloride species from an aromatic hydrocarbon stream. The maximum chloride sorption capacity was observed at T = 100 °C, P = 35 kg/cm2, and a liquid hourly space velocity (flow rate) of 2 h–1 when the molecular sieve zeolite 13X (NaX) exchanged with 0.6 wt % Ca2+ and 1 wt % Mg2+ cations was used as an adsorbent.

Unprecedented biodesalination rates–Shortcomings of electrical conductivity measurements in determining salt removal by algae and cyanobacteria

Phormidium keutzingianum performed biodesalination of brackish water (10 g/L). The electrical conductivity (EC) was measured to evaluate the salt concentration over 80 days of cyanobacterial inoculation. Anion concentrations were measured using ion chromatography to estimate salt removal. EC-based measurements showed ∼8–10% removal efficiency in the first 20 days. However, the removal efficiency based on chloride ion concentration showed ∼40% removal in the same time frame. The pH increase was observed with growth of algal biomass. The increasing pH proposes the formation of hydroxyl and carbonate ions. Sulfuric acid was added at day 110 to neutralize them. At pH 4, the EC reduced significantly to about ∼37% confirming the chloride removal. EC should not be used to measure salt reduction as it is an obscure parameter, and therefore, EC is not the best choice to measure salinity removal using algae. Some recently published studies used only EC to estimate biodesalination, and it is anticipated that salt removal is misrepresented in those studies.