Journal of Water and Environmental Nanotechnology
Volume:2 Issue: 4, Autumn 2017

A novel Graphene oxide-polyethylene glycol and polyvinyl alcohol (GO-PEG-PVA) triple network hydrogel were prepared to remove Copper(II) ion from its aqueous solution. The structures, morphologies, and properties of graphene oxide (GO), the composite GO-PEG-PVA and PEG-PVA were characterized using FTIR, X-ray diffraction, Scanning Electronic Microscope and Thermal Gravimetric analysis. A series of systematic batch adsorption experiments were conducted to study the adsorption property of GO, GO-PEG-PVA hydrogel and PEG-PVA hydrogel under different conditions (e.g. pH, contact time and Cu2+ ions concentration). The high adsorption capacity, easy regeneration, and effective adsorption–desorption results proved that the prepared GO-PEG-PVA composite hydrogel could be an effective adsorbent in removing Cu2+ ion from its aqueous solution. The maximum adsorption capacities were found to be 917, 900 and 423 mg g–1 for GO-PEG-PVA hydrogel, GO and PEG-PVA hydrogel, respectively at pH 5, 25 °C and Cu2+ ions’ concentration 500 mg l–1. The removal efficiency of the recycled GO-PEG-PVA hydrogel were 83, 81, 80 and 79% for the first four times, which proved efficient reusability.

The objective of this work is to investigate the effect of dip-coating parameters on the performance of Alumina-PDMS hybrid nanofiltration membranes for water desalination. Ceramic supports used in this work were prepared with a 340 nm average pore size and 34% total porosity. The aim is to determine optimum conditions of dipping time, PDMS concentration, and withdrawal speed in order to achieve high rejection and flux values. Dip-coating parameters were considered as dipping time (60 - 120 s), withdrawal speed (5 - 15 mm/s) and PDMS concentration (10 - 20 wt. %). Hybrid membranes were characterized using FE-SEM and FTIR analysis techniques. Pure water flux and salt rejection were also measured to evaluate the rejection performance. Alumina-PDMS hybrid nanofiltration membranes fabricated with dipping time = 120 s, withdrawal speed = 15 mm/s and 10 wt. % PDMS exhibited the best performance giving 30.5% rejection for NaCl and 53.8% for Na2SO4.

Large quantities of oily wastewaters can be generated from the activities and processes in the petroleum industry which draining of these effluents not only pollutes the environment but also reduces the yield of oil and water. Therefore, development of treatment processes for petroleum industry wastewaters is vital in order to prevent serious environmental damage and provide a source of water for beneficial use. Reverse osmosis (RO) can be the most common membrane process used for desalination from oily wastewater and can produce water suitable for reuse at the petroleum industry. In this study, the application of RO technology for the petroleum industry wastewater treatment in different laboratory, pilot, field, and industrial scales have been reviewed. In addition, membrane fouling control, performance efficiency, treatment system configurations, pretreatment methods, quality of treated water, and economic issues have been investigated. With mixtures as complex as petroleum industry wastewaters, membrane fouling becomes a significant hurdle to implement the RO-based purification system. Operating the system within the critical flux range or adding chemicals, and/or pretreatment can usually control membrane fouling. Salt rejection of RO membranes can be 99% or higher.

The present work seeks to investigate the ability of polypyrrole/titanium dioxide nanocomposite to adsorb cadmium ions from aqueous solution. The impact of various experimental conditions, including solution pH, adsorbent dosage, adsorption time and initial concentration on the uptake of cadmium were studied. The adsorption kinetic was studied with the first-order, second-order, pseudo-first-order, pseudo-second-order and Morris–Weber models. The results revealed that adsorption process is controlled by pseudo-second-order model which illustrated that the adsorption process of cadmium is chemisorption-controlled. The adsorption capacity obtained from this model is 20.49 mg/g which close to the experimental value. The study yielded the result that when the initial concentration of the solution changed from 20 mg/l to 120 mg/l, the adsorption capacity increased from 0.99 to 24.52 mg/g. Further, Langmuir, Freundlich and Temkin isotherm models were applied to investigate the adsorption isotherm. Based on the results of the adsorption isotherm, Freundlich isotherm proved to be the best fit with the experimental data. Also, the morphology, chemical structure and thermal stability of adsorbent were studied by using SEM, EDX, FTIR, and TGA.

Zero-valent iron particles at the nanoscale are proposed to be one of the important reductants of Cr(VI), transforming the same into nontoxic Cr(III). In this study zero valent iron nanoparticles(ZVINs) were synthesized and characterized for hexavalent chromium removal from aqueous solutions. Five different zero-valent iron nanoparticle types comprising of bare and stabilized ZVINs with poly acrylamide(PAM), polyvinyl pyrrolidone(PVP), polystyrene sulfonate(PSS) and guar gum(GG) were synthesized and employed in this study. The sizes of zero-valent iron nanoparticles were found to be 40, 14, 17, 29 and 34nm, using transmission electron microscopy (TEM), corresponding to bare zero valent iron nanoparticles(ZVINs), poly acrylamide(PAM), guar gum(GG), poly styrene solfunate(PSS) and polyvinyl pyrrolidone(PVP) stabilized zero valent iron nanoparticles (ZVINs) respectively. The trend in the sizes of ZVINs with various stabilizers in the decreasing order was found to be bare ZVIN > PVP-ZVIN >PSS-ZVIN> GG-ZVIN> PAM-ZVIN respectively. Results showed that by increasing hexavalent chromium concentrations from 20 to 100 mg/L, the Cr(VI) efficiency removal decreased significantly. When the ZVINs concentrations increased from 2 to 10 gr/L(0.1 to 0.5g per 50 mL), the Cr(VI) removal efficiency enhanced. The most effective treatments of ZVINs and Cr(VI) for hexavalent chromium removal from solutions were 10 gr/lit (0.5g per 50 mL) and 20 mg/L respectively, so the efficiency of bare and polymer stabilized-ZVINs on Cr(VI) removal from solutions was found to be in the following order:  bare ZVINs < PVP-ZVINs <PSS-ZVINs< GG-ZVINs< PAM-ZVINs.

In this work, multi-walled carbon nanotubes (MWCNTs)/Co-TiO2 nanocomposites were synthesized and investigated for photocatalytic degradation of 2,4-dichlorophenol (2,4-DCP) under visible light. Characterization of photocatalysts was done by means of XRD, FT-IR and SEM/EDX techniques. Obtained results showed cobalt doping can inhibit phase transformation from anatase to rutile and eliminate the recombination of electron-hole pairs. The presence of MWCNTs can both increase the photoactivity and change surface properties to achieve sensitivity to visible light. The optimum mass ratio of MWCNTs and cobalt (Co) dopant in TiO2 was the prominent factor to harvest MWCNTs/Co-TiO2 photocatalyst. The sample containing 3.13 wt% cobalt exhibited the highest activity under visible light for 2,4-DCP degradation, which was completed within 180 min using a 0.1 g/L dose of this photocatalyst in a 40 mg/L solution of the 2,4-DCP. The reactions follow the first-order kinetics. The reaction intermediates were identified by GC–MS technique. GC–MS analysis showed the major intermediates of 2,4-DCP degradation are simple acids like oxalic acid, acetic acid, etc. as the final products.

In this study graphene quantum dots/eggshell membrane nanocomposite (GQDS/ESM) is prepared and used as an efficient solid-phase extraction (SPE) sorbent for preconcentration of organophosphorus pesticides (OPPs) from aqueous solutions. The retained analytes on the sorbent are stripped by acetonitrile and subsequently are determined by high-performance liquid chromatography. Various parameters affecting the extraction efficiency of OPPs on the GQDS/ESM, such as solution pH, amount of nano-sorbent, sample loading flow rate, elution conditions and sample volume are investigated. The results demonstrated that the proposed method has a wide dynamic linear range (0.05–100 ng mL-1), good linearity (R2>0.997) and low detection limits (0.006-0.32 ng mL-1). High enrichment factors are achieved ranging from 110 to 140. In the optimum experimental conditions, the established method is successfully applied for the determination of OPPs in spiked water samples (well, tap, shaft and canal) and apple juice. Satisfactory recovery results show that the sample matrices under consideration do not significantly affect the extraction process.

Membrane ultrafiltration (UF) is widely used in dairy industries like milk concentration and dehydration processes. The limiting factor of UF systems is fouling which is defined as the precipitation of solutes in the form of a cake layer on the surface of the membrane. In this study, the combined cake filtration-complete blocking model was compared to cake filtration mechanism for flux data through ultrafiltration of skim milk at constant flow rate. The resistance data also was modeled using cake filtration model and standard blocking model. The effect of different trans-membrane pressures and temperatures on flux decline was then investigated. Based on the results obtained here, the combined complete blocking-cake formation model was in excellent agreement with experimental data. The cake filtration model also provided good data fits and can be applied to solutions whose solutes tend to accumulate on the surface of the membrane in the form of a cake layer. With increasing pressure, the differences between the model and experimental data increased.