► Various conventional treatment technologies for removal of As are critically reviewed. ► Hybrid or integrated systems may adjust the limitations of conventional processes. ► Reduction of As to ...metallic As by ZVI may prevent secondary environmental pollution. ► Directions for future research in mitigation of As are given.
Arsenic contaminations of groundwater in several parts of the world are the results of natural and/or anthropogenic sources, and have a large impact on human health. Millions of people from different countries rely on groundwater containing As for drinking purposes. This paper reviews removal technologies (oxidation, coagulation flocculation, adsorption, ion exchange and membrane processes) with attention for the drawbacks and limitations of these applied technologies. The technologies suggested and applied for treatment of As rich water have various problems, including the need for further treatment of As containing secondary waste generated from these water treatment processes. More efficient technologies, with a lower tendency to generate waste include the removal of As by membrane distillation or forward osmosis, instead of using pressure driven membrane processes and subsequently reducing soluble As to commercially valuable metallic As are surveyed. An integrated approach of two or more techniques is suggested to be more beneficial than a single process. Advanced technologies such as membrane distillation, forward osmosis as well as some hybrid integrated techniques and their potentials are also discussed in this review. Membrane processes combined with other process (especially iron based technologies) are thought to be most sustainable for the removal of arsenic and further research allowing scale up of these technologies is suggested.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In this work, Eucommia ulmoides leaf extract (EUOLstabilized silver nanoparticles (EUOL@AgNPs) incorporated sulfonated polyether sulfone (SPES)/polyethersulfone (PES) electrospun nanofiber membranes ...(SP ENMs) were prepared by electrospinning, and they were studied for the removal of lead (Pb(II)) and cadmium (Cd(II)) ions from aqueous solutions. The SP ENMs with various EUOL@AgNPs loadings were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscope, thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and contact angle (CA) measurements. The adsorption studies showed that the adsorption of Cd(II) and Pb(II) was rapid, achieved equilibrium within 40 min and 60 min, respectively and fitted with non-linear pseudo-second-order (PSO) kinetics model. For Cd(II) and Pb(II), the Freundlich model described the adsorption isotherm better than the Langmuir isotherm model. The maximum adsorption capacity for Cd(II) and Pb(II) was 625 and 370.37 mg g
respectively at neutral pH. Coexisting anions of fluoride, chloride, and nitrate had a negligible influence on Cd(II) removal than the Pb(II). On the other hand, the presence of silicate and phosphate considerably affected Cd(II) and Pb(II) adsorption. The recyclability, regeneration, and reusability of the fabricated EUOL@AgNPs-SP ENMs were studied and they retained their high adsorption capacity up to five cycles. The DFT measurements revealed that SP-5 ENMs exhibited the highest adsorption selectivity for Cd(II) and the measured binding energies for Cd(II), Pb(II), are 219.35 and 206.26 kcal mol
, respectively. The developed ENM adsorbent may find application for the removal of heavy metals from water.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The present investigation reports as it is possible to prepared polyvinylidene fluoride (PVDF) membranes for microfiltration (MF) and ultrafiltration (UF) applications, by using triethyl phosphate ...(TEP) as non⁻toxic solvent in accordance with the Green Chemistry. Casting solutions containing different concentrations of polyethylene glycol (PEG) were prepared in order to study its effect on the final membrane morphology and properties. The possibility to finely modulate membrane properties was also investigated by applying two different membrane preparation techniques, the Non-Solvent Induced Phase Separation (NIPS) and its coupling with Vapour Induced Phase Separation (VIPS). Membranes' morphology was detected by Scanning Electron Microscopy (SEM). Thickness, porosity, contact angle, pore size and water permeability were also recorded. Both the PEG content in the dope solution and the selected time intervals during which the nascent films were exposed to established relative humidity and temperature were found to play a crucial role in membrane formation. In particular, it was demonstrated as, by varying PEG content between 10 and 20 wt %, and by setting the exposure time to humidity at 0/2.5/5/7.5 min, membranes with different pore diameter and bicontinuous structure, suitable for UF and MF applications, could be easily obtained.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
The approach of the present work is based on the use of poly (methylmethacrylate) (PMMA) polymer, which is compatible with PVDF and TiO₂ nanoparticles in casting solutions, for the preparation of ...nano-composites membranes using a safer and more compatible solvent. TiO₂ embedded poly (vinylidene fluoride) (PVDF)/PMMA photocatalytic membranes were prepared by phase inversion method. A non-solvent induced phase separation (NIPS) coupled with vapor induced phase separation (VIPS) was used to fabricate flat-sheet membranes using a dope solution consisting of PMMA, PVDF, TiO₂, and triethyl phosphate (TEP) as an alternative non-toxic solvent. Membrane morphology was examined by scanning electron microscopy (SEM). Backscatter electron detector (BSD) mapping was used to monitor the inter-dispersion of TiO₂ in the membrane surface and matrix. The effects of polymer concentration, evaporation time, additives and catalyst amount on the membrane morphology and properties were investigated. Tests on photocatalytic degradation of methylene blue (MB) were also carried out using the membranes entrapped with different concentrations of TiO₂. The results of this study showed that nearly 99% MB removal can be easily achieved by photocatalysis using TiO₂ immobilized on the membrane matrix. Moreover, it was observed that the quantity of TiO₂ plays a significant role in the dye removal.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
The use of membrane-based technologies has been applied for water treatment applications; however, the limitations of conventional polymeric membranes have led to the addition of inorganic fillers to ...enhance their performance. In recent years, nanocomposite membranes have greatly attracted the attention of scientists for water treatment applications such as wastewater treatment, water purification, removal of microorganisms, chemical compounds, heavy metals, etc. The incorporation of different nanofillers, such as carbon nanotubes, zinc oxide, graphene oxide, silver and copper nanoparticles, titanium dioxide, 2D materials, and some other novel nano-scale materials into polymeric membranes have provided great advances, e.g., enhancing on hydrophilicity, suppressing the accumulation of pollutants and foulants, enhancing rejection efficiencies and improving mechanical properties and thermal stabilities. Thereby, the aim of this work is to provide up-to-date information related to those novel nanocomposite membranes and their contribution for water treatment applications.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
•Recent laboratory and pilot-scale trials for arsenic removal have been summarized.•Advantages on membrane technologies show feasibility for small-scale applications.•Treatment concept depends on ...hydrogeological conditions such as pH and Eh.•Strategies for safe disposal of arsenic waste sludge and concentrates are reviewed.
Various technologies are used for the treatment of arsenic (As) contaminated water, but only a few seem to be suitable for small-scale applications; these are mostly used in rural communities where the access to potable water is the most vulnerable. In this review paper, the salient advantages and most notable challenges of membrane-based technologies for the removal of arsenate As(V) and arsenite As(III) are evaluated and systematically compared to alternative technologies such as e.g. adsorption. A comparison of different scientific papers, case studies and pilot trials is used to discuss the most important aspects when evaluating As mitigation technologies, including the ability to comply with the stringent WHO drinking water guideline limit value of 10 µg/L As and the safe disposal of produced As-laden waste. The use of renewable energies such as solar power in small-scale (<10 m³/day) membrane applications is evaluated. Finally, a conceptual approach for holistic As mitigation is proposed as an important approach to prevent exposure to As by providing a safe water supply.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The application of membrane technology to remove pollutant dyes in industrial wastewater is a significant development today. The modification of membranes to improve their properties has been shown ...to improve the permeation flux and removal efficiency of the membrane. Therefore, in this work, graphene oxide nanoparticles (GO-NPs) were used to modify the polyethersulfone (PES) membrane and prepare mixed matrix membranes (MMMs). This research is dedicated to using two types of very toxic dyes (Acid Black and Rose Bengal) to study the effect of GO on PES performance. The performance and antifouling properties of the new modified membrane were studied using the following: FTIR, SEM, AFM, water permeation flux, dye removal and fouling, and by investigating the influence of GO-NPs on the structure. After adding 0.5 wt% of GO, the contact angle was the lowest (39.21°) and the permeable flux of the membrane was the highest. The performance of the ultrafiltration (UF) membrane displayed a rejection rate higher than 99% for both dyes. The membranes showed the highest antifouling property at a GO concentration of 0.5 wt%. The long-term operation of the membrane fabricated from 0.5 wt% GO using two dyes improved greatly over 26 d from 14 d for the control membrane, therefore higher flux can be preserved.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Membrane separation has been widely used for various applications including microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF) processes in the fields of biomedicine, food, and water ...purification. In this work, a facile synthesis of new polyamide thin-film composite nanofiltration membranes (NF-TFC) for water purification was described. The polyamide thin film was deposed over a synthetic cellulose acetate (CA) support by interfacial polymerization method. 1,3 cyclohexane bis (methylamine) (CHMA) and trimesoyl chloride (TMC) were used as monomers. The membranes were characterized using Scanning Electron Microscopy (SEM), Fourier Transform Infrared spectroscopy (FT-IR), water uptake, porosity, contact angle, water permeability and rejection towards specific salt and dye molecules. The effect of the variation of the CHMA concentration (0.2–2 wt.%) on the morphology, porosity, water permeation and rejection properties of the prepared membranes was studied. SEM results displayed the growth of the membrane thickness when the CHMA concentration increased from 0.2 to 2 wt.%. The strong adhesion between the cellulose acetate substrate and the polyamide layer explained by the formation of the polyamide film in the substrate surface and inside the pores. The water permeability varied from 36.02 to 17.09 L h
−1
m
−2
bar
−1
. The salt rejection of Na
2
SO
4
and NaCl increased from 9 to 68% and from 38.41% to 89.4%, respectively, when the CHMA concentration was changed from 0.2 to 2 wt.%. The prepared membranes were further applied successfully for the removal of malachite green and congo red. The results indicated that the maximum rejection reached 89% and 85% for malachite green and congo red, respectively.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
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•Tamisolve® was used as a non-toxic solvent for P(VDF-HFP) membranes preparation.•The prepared porous P(VDF-HFP) membranes were fully characterized.•The membranes were tested in ...membrane distillation and membrane crystallization.•Membrane crystallization allowed achieving crystals with rejection greater than 99%.
The replacement of the toxic solvents with non-toxic equivalents attracts a great attention in membrane preparation and application processes. The purpose of this work is to study the preparation of poly(vinylidene fluoride-hexafluoropropylene) P(VDF-HFP) flat sheet membranes by non-solvent induced phase separation (NIPS) using Tamisolve® as a non-toxic solvent, for membrane distillation (MD) and membrane crystallization (MCr) applications. The prepared porous P(VDF-HFP) membranes were fully characterized in terms of morphology, porosity, thickness, pore-size, contact angle and pure water permeability (PWP). The effect of additive(s) and polymer content were investigated. Moreover, preliminary DCMD and MCr tests were carried out and the achieved results indicate the good performance of the prepared flat sheet membranes in terms of permeate flux and salt rejection in comparison to a commercial PVDF membrane. The obtained results confirmed the ability of the eco-friendly Tamisolve® NxG to compete with the highly toxic diluents usually used in membrane fabrication by phase inversion method.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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