Initial NaCl Concentration Research Articles

Dendrite Pattern Formation of Sodium Chloride Crystal.

A variety of crystal structures is found in nature, not only equilibrium structures reflecting molecular structures, but also non-equilibrium structures which depend on the physicochemical conditions occurring during the crystal growth. In this paper, we focus on the dendrite structure of sodium chloride (NaCl) formed by the simple evaporation of an aqueous NaCl solution. The characteristics of the growth structures were measured as a function of the initial concentration of NaCl. In addition, the crystal growth process was measured using optical microscopy. As a result, the growth rate was not constant but was found to oscillate over time and synchronize with the wetting of the crystal. Our observations indicate that dendrite structures are more easily generated at higher initial concentrations. The detailed mechanism for dendrite pattern formation is still under investigation.

Simulating fouling impact on the permeate flux in high-pressure membranes

Porous high-pressure membranes have been widely used for saline water desalination. However, fouling (concentration polarization) extensively reduces permeate flux in reverse osmosis (RO) and/or nanofiltration (NF) modules. Fouling arises from pore blocking, organic adsorption, cake formation, inorganic or biological precipitation reducing water flux. Herein, we investigated the effect of feed water with various NaCl concentrations on fouling of RO and/or NF and the permeate water flux. A parabolic (or diffusion) partial differential equation (PDE) was used to model salt concentration profile or gradient inside the membrane. Subsequently, the numerical PDE equation, solved by the forward finite difference (FFD) explicit method, estimated flux decline rates resulted from NaCl fouling. It was found that salt accumulation occurs at the feed-side with a noticeable decrease in flux as fouling increases. Previous works reported similar findings as those identified from our analysis: (1) fouling increases with feed concentration and surface roughness, (2) fouling becomes intensified with higher pressure and flux, (3) fouling from long operation times can reduce flux by 65% within 24 h, (4) NaCl fouling can decrease flux rates by 70% (67-22 LMH) for brackish water with an initial concentration of 10000 ppm, and (5) reversible organic fouling may be avoided from lowering flux rates below the membrane critical flux. Results showed fouled RO modules would decrease flux rates from the increased surface polarization, where reverse flow (negative flux) was estimated for feed-side accumulations >10000 ppm for waters with an initial NaCl concentration of 10000 ppm and average diffusivity of 1.3×10-6 cm2/s.

High-cell-density fed-batch cultivations of Vibrio natriegens

ObjectivesWith generation times of less than 10 min under optimal conditions, the halophilic Vibrio natriegens is the fastest growing non-pathogenic bacterium isolated so far. The availability of the full genome and genetic engineering tools and its ability to utilize a wide range of carbon sources make V. natriegens an attractive host for biotechnological production processes. However, high-cell-density cultivations, which are desired at industrial-scale have not been described so far.ResultsIn this study we report fed-batch cultivations of V. natriegens in deep-well plates and lab-scale bioreactor cultivations at different temperatures in mineral salt medium (MSM). Upon switching from exponential glucose to constant glucose-feeding cell death was induced. Initial NaCl concentrations of 15–18 g L−1 and a temperature reduction from 37 to 30 °C had a positive effect on cell growth. The maximal growth rate in MSM with glucose was 1.36 h−1 with a specific oxygen uptake rate of 22 mmol gCDW−1 h−1. High biomass yields of up to 55 g L−1 after only 12 h were reached.ConclusionsThe shown fed-batch strategies demonstrate the potential of V. natriegens as a strong producer in industrial biotechnology.

Multi-walled vanadium oxide nanotubes modified 3D microporous bioderived carbon as novel electrodes for hybrid capacitive deionization

Herein, a promising rationally-designed, high surface area multi-walled vanadium oxide nanotubes (VOx NTs) with a large interlayer spacing (6.5 Å) has been demonstrated as a cathodic dopant for efficient hybrid capacitive deionization (c-HCDI). The VOx NTs enhanced the surface charge of the 3D microporous graphene-like carbon, derived from natural palm tree (CNPT), as verified by Raman profiles and potential of zero charge measurements. The CDI batch-fashion testing has been performed using large surface area electrodes (6 × 7 cm2) and 135 ml of saline NaCl electrolyte. Interestingly, the used c-HCDI showed high salt adsorption capacity (SAC) of 25.0 mg/g for 6 mM NaCl at 1.6 V compared to the symmetric capacitive deionization configuration (s-CDI) that is only sustaining 16.0 mg/g. Besides, the cell demonstrates efficient stable SAC regardless of the initial feed concentration (1.6–25 mM) of NaCl. The charge efficiency of the c-HCDI markedly raised by around 25% over s-CDI for 5 mM NaCl, indicating the improved permselective manner of sodium ion diffusion/intercalation at the VOx NTs/CNPT cathode. Most importantly, the c-HCDI demonstrates a superior salt adsorption retention of 94.7% after 50 successive charge/discharge cycles compared to s-CDI that showed a decline of 7% after only 15 cycles. The Improved surface charge and wettability together with the pseudocapacitive storage manner of the cathode composite illustrate the synergism obtained via the hybrid configuration..

Dimensionally stable anode (Ti/RuO2) mediated electro-oxidation and multi-response optimization study for remediation of coke-oven wastewater

Electrochemical oxidation by means of dimensionally stable anodes (Ti/RuO2) was executed for the simultaneous elimination of various pollutants (such as COD, phenol, cyanide, and ammonia, etc.) from simulated and real coking-wastewater. A multiparameter variation study was also performed to investigate the operating range of certain operational parameters (such as pH, electrolyte, current density (CD), and H2O2 as a catalyst) and their effects on removal efficiencies of COD and rest of the pollutants of wastewater. To investigate the visual, morphological & elemental features of electrodes FE-SEM and EDX studies were performed before and after the treatment of wastewater. The electrochemical behavior was explored through cyclic voltammetry analysis. Moreover, the degradation and mineralization performance of organic material in wastewater was also investigated through LC-MS and total organic carbon (TOC) studies, respectively. A mathematical equation (model) was also developed to represent the multi-parameter optimization study using central composite design (CCD) through response surface methodology software (RSM tool). At the end of the process, the COD (90.13%), phenol (99.34%), cyanide (96.23%), and ammonia (94.43%) were eliminated within 180 min of reaction at optimum initial pH, NaCl (electrolyte), current density (CD), and H2O2 concentration of 8.0, 1.6 g/L, 24 mA/cm2 and 0.030 M, respectively.

Electrochemical mineralization of abattoir wastewater with continuous system

This study aims to determine the effects of initial pollutant concentration level (1/1–1/4), flow rate (10–40 mL/min), NaCl concentration (0.1–1 M), pH (3–9) and current density (4.73–23.67 mA/cm2) parameters on the removals of total suspended solids, total organic carbon, chemical oxygen demand, total nitrogen and color for economic treatment of cattle-abattoir wastewater using mesh-type Ti/Pt anodes with continuous EO system. Total suspended solids, total organic carbon, chemical oxygen demand, total nitrogen and color analyses were carried out according to photometric method, catalytic oxidation method, closed reflux colorimetric method, nitrogen cell test method and platinum–cobalt method, respectively. The effluent chloride levels were analyzed according to the argentometric titration method. According to results, all operational parameters had an impact on removal efficiencies but the most effective parameters on energy consumption were NaCl concentration and applied current density. Although two possible system conditions were determined according to removal efficiencies the operating conditions with the lowest energy consumption are considered to be optimal. The optimum operating conditions were determined as NaCl concentration of 1 M, CD of 4.73 mA/cm2, initial pH of 7.03, reaction temperature of 25 °C and FR of 10 mL/min. Under these conditions removal efficiencies (%) for total suspended solids, total organic carbon, chemical oxygen demand, total nitrogen and color were found as; 98.28, 93.03, 97.44, 95.53 and 99.80, respectively. The energy consumption values were calculated as 2.42 kWh/kg COD and 19.43 kWh/m3. The approximate cost to treat 1 m3 wastewater was calculated as $ 6.43. The kinetic behavior abided by a pseudo-first-order model.

Optimization of Cadmium Adsorption by Magnetic Graphene Oxide Using a Fractional Factorial Design.

Graphene materials have attracted increasing interest in water remediation. In this study, magnetic graphene oxide (MGO) was prepared through the modified Hummers method and the adsorption behaviors of cadmium were investigated. Firstly, the sorption kinetics, isotherms, as well as the effects of pH were investigated. Then, fractional factorial design (FFD) was used to optimize the effects of pH, temperature, time, initial concentration of cadmium ion and NaCl on cadmium adsorption. The results indicate that MGO could effectively remove cadmium ions from an aqueous solution and the sorption data could be described well by pseudo-second-order and Freundlich models, showing that the adsorption rate of cadmium ions on MGO is multilayer adsorption and dominated by the chemical adsorption. According to the FFD results, the maximum adsorption capacity of cadmium ions was 13.169 mg/g under the optimum condition of pH value 8, 45 °C, contact time 60 min, initial cadmium concentration of 70 mg/L and NaCl concentration of 100 mg/L. Higher levels of the pH value, temperature and initial cadmium concentration are beneficial to the adsorption process. These results are important for estimating and optimizing the removal of metal ions by MGO composite.

Role of the Wild Carob as Biosorbent and as Precursor of a New High-Surface-Area Activated Carbon for the Adsorption of Methylene Blue

Wild carob (WC), an abundant and unused lignocellulosic waste in Algeria, has been used as an inexpensive biosorbent for the elimination of methylene blue (MB) from the aqueous solution and as a precursor for the preparation of a new activated carbon by chemical activation with ZnCl2 (ACWC). The adsorbent materials were characterized by N2 physisorption, SEM/EDX, FTIR spectroscopy and isoelectric point (pHpzc) measurements. The adsorption performance of WC and ACWC was estimated for MB at different adsorption variables, such as solution pH (2–11), MB initial concentrations (25–200 mg L−1), time (0–1500 min), adsorbent dose (0.25–2.00 g L−1), temperature (10–40 °C) and NaCl concentration (0.0–0.5 M). The obtained results indicate that WC has an acidic surface due to the presence of carboxyl and phenol groups that play an important role in the fixation of cationic dye molecules, obtaining a maximum monolayer adsorption capacity of 84 mg g−1 at natural pH (7.5) and 40 °C. However, this adsorption performance was much higher in the case of the ACWC sample (218 mg g−1). From the equilibrium data, the Freundlich, Langmuir, Sips and Redlich–Peterson isotherms parameters of both samples were calculated and compared. For WC, the experimental data fitted well with Redlich–Peterson, Langmuir and Sips isotherm models, while in the case of ACWC they were best represented by the Redlich–Peterson and Sips isotherms. The adsorption kinetics data were found to follow the pseudo-second-order model for WC and the pseudo-first-order model for ACWC. The thermodynamic parameters suggest that, for both materials, the process was endothermic and spontaneous in the range of temperatures studied.

Treatment of oil and grease in wastewater using Electrocoagulation (Dept. C (Public Works ) )

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COMPARATIVE PERFORMANCE OF SCREEN AND SHEET CATHODES IN DECOLORIZATION OF ACID RED 14 BY ELECTROCOAGULATION

This study investigated the efficiency of decolorization of Acid Red 14 dye solution using screen cathode and compare the results with sheet cathode by electrocoagulation. A simple electrochemical cell was performed with horizontal mild steel iron disc anode and vertical stainless steel cylindrical cathodes (screen or sheet). Process duration, agitation speed, current density, initial dye concentration and electrolyte NaCl concentrations were the variables studied. It was found that screen cathode was more effective than sheet cathode. . For dye solution with 50 ppm and agitation speed 100 rpm after 18 min, 86 % color removal was achieved on using screen cathode, while 77 % color removal was achieved on using sheet cathode. The higher efficiency of screen cathode is attributed to the fact that screen acts as turbulence promoter and generate high turbulence intensity.

Ice Confinement-Induced Solubilization and Aggregation of Cyanonaphthol Revealed by Fluorescence Spectroscopy and Lifetime Measurements.

When an aqueous salt solution freezes, a freeze-concentrated solution (FCS) separates from the ice. The properties of the FCS may differ from those of a supercooled bulk solution of the same ionic strength at the same temperature. The fluorescence and lifetime characteristics of 6-cyano-2-naphthol (6CN) were studied in frozen NaCl solutions in order to provide insight into the solution properties of the FCS. While the photoacidity of 6CN in an FCS is similar to that in solution, several anomalous behaviors are observed. Fluorescence spectra indicate that the solubility of 6CN is significantly enhanced in the FCS (50 mM or higher) compared to that in the bulk NaCl solution where the solubility limit is 250 μM. The high solubility induces the aggregation of 6CN in the FCS, which is not detected in bulk solutions. This trend becomes marked as the initial NaCl concentration decreases and the FCS is confined in a small space. The fluorescence lifetimes of 6CN in the FCS support the spectroscopy results. In addition to the species identified by fluorescence spectroscopy, excimers are assigned from lifetime measurements in the FCS. The excimer formation is also a result of the enhanced solubility of 6CN in the FCS.

Removal of malachite green, a cationic textile dye using Amberlite polymeric resins

ABSTRACT Malachite green dye was removed using three different polymeric resins (Amberlite XAD7, Amberlite 120H and Amberlite IRA67). Equilibrium and kinetic experiments were carried out to determine the effect of contact time (0–120 min), resin dose (0.05–0.4 g), initial dye concentration (10–50 mg/L), temperature (303–323 K), pH (2–12) and NaCl concentration (0.5–50 g/L) on the adsorption capacity of all the resins. With an increase in the resin amount, a sharp decrease in the adsorption capacity was observed. The removal efficiency of dye was found to be 98.29% with IRA67, 99.27% with XAD7, and 98.66% with IR120H after 120 min. Temkin isotherm matched equilibrium data for XAD7 and IR120H, whereas Freundlich isotherm model best described the results for IRA67, pH, temperature and NaCl did not affect the removal efficiency significantly. Kinetic data were well fitted with pseudo-second order rate kinetics. All the three resins were regenerated using 1 M NaOH solution showing good reusability.

DESALINATION OF CHLORIDE-SULFATE BRACKISH WATER WITH AN ELECTRODIALYZER WITH IMPROVED DESIGN

It has been studied that the process of desalination and preconcentration of imitates of brackish chloride-sulfate water with electrodialyzer with improved designs provides high efficiency: it was found that at a current density of 1.0 A/dm2 for 63–105 min, simulate with an initial concentration of NaCl of 4.3 can be desalted — 8.6 g/dm3 to a chloride-water content below the MPC level in drinking water while concentrating brines to110.7–135.8 g/dm3. When SO42– ions are introduced into the initial solution, a decrease in the content of Cl– ions and an increase in the content of SO42– ions in the dilute are observed due to the intensification of the competing transfer of the latter through the ion-exchange membrane. In this regard, in order to achieve the MPC of these ions in drinking water, the duration of the electrodialysis process should be increased. Ref. 12, Fig. 3, Tab. 2.

Nitrogen and sulfur co-doped NaTi2(PO4)3/hole graphene composite as high-performance electrosorption electrodes for hybrid capacitive deionization

In this study, a nitrogen and sulfur co-doped sodium titanium phosphate/hole graphene (N,S-NTP/rHGO) was synthesized by one-step hydrothermal method using thiourea as N/S source. The microstructure characterization confirms that N and S heteroatoms have been integrated into the graphene skeleton. The electrochemistry and electrosorption properties of the N,S-NTP/rHGO electrodes were investigated for hybrid capacitor deionization (HCDI). The results indicate that the specific capacitance of N,S-NTP/rHGO electrodes can reach 530.46 F g−1 at a scan rate of 0.2 mV s−1, which is 33.8% higher than that of the sample without doping. Moreover, the HCDI cell based on the N,S-NTP/rHGO-2 shows a high desalination capacity of 36.87 mg g−1 and a rapid ion removal rate of 0.66 mg g−1 s−1, which is more than twice as high as the sample without doping (0.3 mg g−1 s−1) at an initial NaCl concentration of 800 mg L−1 and applied voltage of 1.4 V. Further, the N,S-NTP/rHGO electrode exhibits excellent regeneration ability. Therefore, this study suggests that as-prepared N,S-NTP/rHGO composite exhibits a great potential application for high-performance HCDI systems.

Ion removal performance and enhanced cyclic stability of SnO2/CNT composite electrode in hybrid capacitive deionization

Hybrid capacitive deionization (HCDI) is developed based on capacitive deionization (CDI) for water treatment, which combines CDI with a battery system. Developing the high-performing battery electrode materials is a significant point for HCDI. Herein, SnO2/CNT was fabricated according to hydrothermal method, which was denoted as SnO2/CNT-H, after calcination, the obtained product was denoted as SnO2/CNT-HC. The as-prepared SnO2/CNT-HC was used in HCDI system for the first time, which demonstrated a salt adsorption capacity of 9 mg g−1 and ultrafast salt adsorption rate of 2.5 mg g−1 min−1 at 500 mg L−1 initial NaCl concentration. The SnO2/CNT-HC electrode also had a good cyclic stability of keeping 120 % of salt adsorption capacity after 100 adsorption-desorption cycles at 1.0 V and 500 mg L−1 NaCl solution. Moreover, when this system was used to study the adsorption-desorption performance for different cations (Li+, K+ and Ca2+) and anions (F−, NO3− and SO42−), the phenomenon was revealed that the cation adsorption capacity of Li+ > K+ > Ca2+ captured by SnO2/CNT-HC and the anion adsorption capacity of F− > NO3− > SO42− adsorbed by activated carbon. These results show that SnO2/CNT-HC should be one of realistic electrode materials for HCDI.

ZINC HYDROXIDE NANOPARTICLES-MODIFIED CLAY FOR ULTRASOUND-ASSISTED REMOVAL OF METHYLENE BLUE

The objective of the present work was to introduce a novel adsorbent with high adsorption potential toward methylene blue by decorating montmorillonite clay (MMT clay) with Zn(OH)2 nanoparticles (Zn(OH)2 NPs). The adsorbent was characterized structurally by FE-SEM and FTIR techniques. Central composite design response surface methodology was applied to optimize experimental variables including adsorbent dosage, pH, initial MB concentration, NaCl concentration, and sonication time. A modified quadratic model was used to establish a relationship between the removal percent of MB and the experimental variables. F value of 74.99 and squared correlation coefficient of 0.96 confirmed the significance and reliability of the model. Under the optimum conditions of pH 8.0, sonication time 3.5 min, adsorbent dosage 73 mg, analyte concentration 7.5 mg L-1, and electrolyte concentration (2 % w/v), the removal percentage of 99.3 0.70 % were attained. Freundlich isotherm was agree well with the adsorption isotherm data. The adsorption kinetic was best described by pseudo second order kinetic model. Thermodynamic study of the MB uptake on the sorbent shows the spontaneous (.G = -13.45 -34.15 kcal mol-1 in the temperature range of 15 45 C). These results infer that Zn(OH)2 NPs MMT clay can be applied as a new, low cost adsorbent in adsorbing MB from aqueous solution.

Role of liquid water in the formation of O3 and SOA particles from 1,2,3-trimethylbenzene

Aromatic volatile organic compounds (VOCs) are highly reactive in the formation of ozone (O3) and secondary organic aerosols (SOA). 1,2,3-trimethylbenzene (123-TMB) is an aromatic VOCs which is directly emitted to the atmosphere by motor vehicle exhaust emissions and the evaporation of solvents. In this study, a series of smog chamber experiments were conducted to compare the formation of O3 and SOA particles from photooxidation of 1,2,3-TMB by UV radiation, under various humidity conditions and NOx control conditions, in the presence and absence of NaCl seed particles. At a relative humidity of 86%, the hygroscopic growth factor (GF) of SOA generated from 123-TMB was 1.044. Conversely, with increasing liquid water content (LWC) from 0 to 85.0 μg m−3, O3 concentrations decreased from 468 ppb to 323 ppb and the yield of SOA increased from 3.0 to 14.7%, with initial NaCl concentrations of 11.0 ± 0.7 μg m−3. FT-IR results show that with increasing LWC, the major contributors to SOA were identified as alcohols and hydrates. These findings indicate that liquid water is an important factor in the formation of O3 and SOA.

Production of polyhydroxyalkanoates on waste frying oil employing selected Halomonas strains

The aim of this work was to study the potential of selected Halomonas species for conversion of waste frying oil into polyhydroxyalkanoates (PHA). In total nine Halomonas strains were experimentally screened for their capability of PHA production. Among them, Halomonas neptunia and Halomonas hydrothermalis were identified as potent PHA producers. Initial concentration of NaCl was identified as parameter influencing PHA yields as well as molecular weight of the polymer. In addition, H. hydrothermalis was capable of biosynthesis of a copolymer of 3-hydroxybutyrate and 3-hydroxyvalerate P(3HB-co-3HV). When valerate was utilized as a precursor, the 3HV fraction in the copolymer reached high values of 50.15 mol.%. PHA production on lipid substrates by Halomonas has not been reported so far. Bearing in mind all the positive aspects of employing extremophiles in industrial biotechnology, H. hydrothermalis seems to be a very interesting halophilic strain for production of PHA using lipid substrates.

Porous carbon material prepared from Na2EDTA and its performance in capacitive deionization process

Porous carbon materials were synthesized by a simple one-step pyrolysis of disodium ethylenediamine tetraacetate (Na2EDTA) under different temperature (650, 750 and 850 °C). Several characterization technologies were employed to evaluate the as-synthesized samples. Cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy tests were carried out to study the electrochemical property of the samples. The capacitive deionization (CDI) performance of the three samples-based electrodes was investigated and compared. The obtained results showed that pyrolysis temperature played a key role in the formation of the final products with different pore structure and heteroatom content, such as nitrogen and oxygen. Electrochemical performance measurement revealed that 750 °C sample exhibited the highest specific capacitance, the smallest diffusive resistance and charge-transfer resistance, and good conductivity. The salt electrosorption capacity of 750 °C samples were 8.02 mg g−1 at a low initial concentration of NaCl solution (25 mg L−1) and 27.75 mg g−1 at a high initial concentration of NaCl (500 mg L−1). The outstanding CDI performance of 750 °C material can be contributed to its high specific surface area and suitable pore structure. As a low-cost and processable precursor, Na2EDTA exhibited promising application prospect in large-scale CDI process.

Cationic selectrodialysis for magnesium recovery from seawater on lab and pilot scale

In view of its multiple applications the selective recovery of Mg2+ from seawater can be very interesting. For this purpose, cationic selectrodialysis (cSED), which uses a conventional electrodialysis stack that is supplementary equipped with monovalent selective cation-exchange membranes, was used. Initially, various parameters were investigated on lab scale using synthetic seawater. The results pointed out that a lower current density resulted in a higher Mg2+ concentration in the product. A higher unwanted Mg2+ concentration was obtained in the brine when the initial concentration of NaCl in the product was lowered. Subsequently, it was demonstrated that the treatment of real North Sea water with cSED was technologically feasible during a short-term batch experiment on lab scale. In a next phase, a cSED pilot plant was operated in a stable way in a long-term feed and bleed experiment in which the Mg2+ content of the North Sea water that was used as initial product was at least doubled. However, the Ca2+ concentration in the product also increased. This might reduce the applicability of the recovered product. From this research it is concluded that cSED is a promising and attractive technology to recover Mg2+ from seawater.