Separation of cadmium ions and estimation of membrane transport parameters of a nanofiltration membrane (original) (raw)
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Transport coefficients and cadmium salt rejection in nanofiltration membrane
Desalination, 2004
Cadmium is one of the main toxic pollutants generated by industrial activities. Many methods have been used to remove cadmium from wastewater issued from these industries. In the present study removal of cadmium Cd(II) ions from aqueous streams was investigated through a nanofiltration membrane process. The retention was studied as a function of the counter-ions, the ionic force and pH. The transport through the TFCS membrane was described by irreversible thermodynamics. The well-known Speigler-Kedem model was applied in order to deter-mine phenomenological parameters σ and Ps respectively, the reflection coefficient of the membrane and the solute permeability of ions. The convective and diffusive parts of the mass transfer were quantified.
International Journal of Environmental Engineering, 2010
Performance of a thin-film composite polyamide nanofiltration membrane has been studied to separate cadmium ions from aqueous solutions. The operating variables studied are pressure, concentration and feed flowrate. It is observed that the solute rejection increases with increase in applied pressure and decreases with increase in feed concentration at constant feed flowrate. The maximum observed rejection of the metal ion is found to be 82.87 and 64.86% for feed concentration of 5 and 250 ppm, respectively. Cadmium ion rejection is sensitive to pH change. Membrane transport parameters and mass transfer coefficients are estimated using different models.
Chemical Engineering Journal, 2009
Heavy metals are important sources of environmental pollution and are non-degradable, and therefore, continue to exist in water. Membrane technology is one option for the separation of heavy metals from wastewater without generating any pollution load. This paper presents the binary heavy metals (cadmium and nickel) separation capability of a commercial nanofiltration membrane from aqueous solutions. The influence of applied pressure, feed solute concentration, feed flowrate, feed pH and nature of anion on the retention of cadmium and nickel ions is studied. It is observed that the rejection increases with increase in feed pressure and decreases with increase in feed concentration at constant feed flowrate. The maximum observed solute rejection of nickel and cadmium ions are 98.94% and 82.69%, respectively, for an initial feed concentration of 5 ppm. The NF membrane is characterized by using the Spiegler-Kedem model based on irreversible thermodynamics coupled with film theory. Boundary layer thicknesses, as well as the membrane transport parameters are estimated by using the Levenberg-Marquardt method. The estimated parameters are used to predict the membrane performance and found that the predicted values are in good agreement with the experimental results.
Journal of hazardous materials, 2010
Removal of heavy metals from wastewater is of critical importance due to their high toxicity and tendency to accumulate in living organisms. In the present work, performance of a nanofiltration (NF) membrane has been studied to separate cadmium and nickel ions from multicomponent aqueous solutions at different operating conditions. It is observed that the separation of cadmium and nickel ions increases with increase in applied pressure and decreases with increase in feed concentration at a constant feed flow rate. The maximum observed solutes rejection of cadmium and nickel ions are 80.57% and 85.27% for CdCl 2-NiCl 2-water system and 97.26% and 98.90% for CdSO 4-NiSO 4-water system, respectively, for an initial feed concentration of 0.005 g/L. This difference in rejection is due to the charge density of the anions. It is also observed that the order of solute rejection sequence is inversely proportional to the diffusion coefficient. The NF membrane is characterized by an irreversible thermodynamics (IT) based Spiegler-Kedem model, coupled with film theory. Boundary-layer thickness and membrane transport parameters are estimated using Levenberg-Marquadt method. The estimated parameters are used to predict the membrane performance and found that the predicted values are in satisfactory agreement with the experimental results.
Model assessment of a nanofiltration membrane for the removal metal ions from simulated wastewater
Journal of Physics: Conference Series, 2019
This paper accords the likelihood of applying Donnan and Steric Partitioning Pore Model (DSPM) together with extended Nernst-Planck model to elucidate the capacity of charge and Donnan exclusion mechanisms in removing ions from simulated wastewater in Nano-Pro-3012 membrane filtration process. The extended Nernst-Planck model reports the transportation of cations across Nano-Pro-3012 with respect to electrical potential gradient, movement of solutes and pressure difference through the membrane. The working principle of these two equations is dependent on the adsorption of the charged surface, diffusion and convective transport. This principle was established with a software called Comsol multi-physic 4.3b to explain the capacity of charge and Donnan exclusion mechanism of Nano-Pro-3012. The extended Nernst-Planck model and the Darcy law model were applied to evaluate the physical interrelationship amidst Nano-Pro-3012 and ionic solutions with the aim of having a good understanding of the transport and rejection working operation of the ions. The principle of these equations was first used to envisage the capability of Nano-Pro-3012. The data obtained were validated with the laboratory data. There was an establishment that movement of solutes across the membrane bring about diffusion transport. The total flux in solution increases due to the working operation of the diffusion which in turns reduces the electrical potential, as a result, reduces the flux in the membrane. Ions smaller than pore sizes are rejected and the theoretical data is in conformity with the experimental data.
DESALINATION AND WATER TREATMENT, 2018
In the present work, three types of hollow fiber nanofiltration membranes (NF1, NF2 and NF3) were employed for the rejection and permeation flux of cobalt ions from aqueous wastewater. The operating variables-initial ion concentration (10−250 ppm), feed solution pH (5.5−6.5), pressure applied (1 bar) and feed flow rate (0.6 L/min)-were studied. It is observed that the obtained cobalt ion rejection values increase with the decrease in initial concentration and increase in pH at constant feed flow rate. The maximum observed rejection of the metal is found to be 77%, 50.2% and 46.8% and 38%, 30% and 29% for NF1, NF2 and NF3 for the initial feed concentration in the 10−250 ppm range, respectively. In addition, the flux decreases with the increase in both pH and initial concentration. Combined film theory−solution diffusion (CFSD), combined film theory−Spiegler-Kedem (CFSK) and combined film theory−finely porous (CFFP) membrane transport models were employed to estimate membrane transport parameters and mass transfer coefficient (k). Moreover, enrichment factor, concentration polarization modulus and Péclet number were estimated using various parameters. Analysis of the experimental data using CFSD, CFSK and CFFP models showed good agreement between theoretical and experimental results. Effective membrane thickness and active skin layer thickness were evaluated using CFFP model, indicating that the Péclet number is important for determining the mechanism of separation by diffusion.
Journal of Engineering
The present work reports on the performance of three types of nanofiltration membranes in the removal of highly polluting and toxic lead (Pb2+) and cadmium (Cd2+) from single and binary salt aqueous solutions simulating real wastewaters. The effect of the operating variables (pH (5.5-6.5), types of NF membrane and initial ions concentration (10-250 ppm)) on the separation process and water flux was investigated. It was observed that the rejection efficiency increased with increasing pH of solution and decreasing the initial metal ions concentrations. While the flux decreased with increasing pH of solution and increasing initial metal ions concentrations. The maximum rejection of lead and cadmium ions in single salt solution was 99%, 97.5 % and 98 % at pH 6, 6.5 and 6.2 and 78%, 49.2% and 44% at pH 6.5, 6.2 and 6.5 for NF1, NF2 and NF3 respectively. On the other hand, maximum permeate flux for single NF2 (32.2)> NF3 (16.1)>NF1 (14.2) (l/m2.h) for 100 ppm, higher than binary sal...
Characterization and performance of nanofiltration membranes
Environmental Chemistry Letters, 2014
Mechanisms of ionic transport in nanofiltration are poorly known. Modelling can be used to predict membrane performance, to reveal separation mechanisms, to select appropriate membranes, and to design processes. Several models have been proposed to describe nanofiltration membranes. Some models rely on simple concepts, while other models are more complex and require sophisticated solution techniques. Here, we review predictive models used for characterizing nanofiltration membranes for the separation of wastewater. The most popular model uses the extended Nernst-Planck equation, which describes the ionic transport mechanisms in details. Results obtained by using the extended Nernst-Planck equation show that the performance of nanofiltration membranes is strongly dependent on charge, steric, and dielectric effects.
ChemistrySelect, 2023
Heavy metals present in wastewater and water scarcity are a global challenge worldwide. The elimination of heavy metals in wastewater is necessary to protect the ecosystem and human health. Heavy metals such as lead, cadmium, and mercury are among many other toxic heavy metals present in wastewater. There are several conventional methods that have been implemented to mitigate heavy metal pollution in wastewater and according to literature, it has been evident that the nanofiltration (NF) separation technique requires minimal pressure to obtain high rejections of multivalent inorganic salts compared to conventional methods. NF separation process is highly competitive in terms of selectivity and cost-benefit. The growing research trend of NF fabrication and modification collates that the technology has been applied in various industrial and municipality wastewater treatment facilities. The review paper aims to illustrate the health impacts of heavy metal exposure, the cons of conventional methods and the utilization of NF membranes in wastewater treatment, the overall factors affecting membrane performance, and future aspects of the separation techniques.
Removal of heavy metal ions by nanofiltration
Desalination, 2013
This study describes the rejection of heavy metal ions using a commercial nanofiltration membrane (NF270). The effect of feed pH, pressure and metal concentration on the metal rejections and permeate flux and in some cases permeate pH was explored. The results showed that with all metals examined (except As (III)), when the feed pH is below the isoelectric point, the rejection increased. NF270 rejected almost 100% of copper ions at low concentrations, but decreased to 58% at the highest concentration examined. Using 1000 mg/L concentration level, pH = 1.5 ± 0.2 and 4 bar the rejection was 99%, 89% and 74% for cadmium, manganese and lead respectively. However at pH above the isoelectric point the average rejections decreased. NF270 was unable to retain As(III). The metals caused a flux decline due to membrane fouling in the order of severity: Cu 2+ > Cd 2+ ≈ Mn 2+ > Pb 2+ ≈ As 3+. The correlation between adsorbed amounts of the metals onto NF270 with the normalised flux shows that as the amount increased the normalised flux decreased, except for arsenic that had a higher deposited amount and higher flux. The RMS roughness as obtained by AFM showed that roughness was decreased by membrane fouling.