Surface Treatment of Polymer Membranes for Effective Biofouling Control

Membrane biofouling is the consequence of the deposition of microorganisms on polymer membrane surfaces. Polymeric membranes have garnered more attention for filtering and purifying water because of their ease of handling, low cost, effortless surface modification, and mechanical, chemical, and thermal properties. The sizes of the pores in the membranes enable micro- and nanofiltration, ultrafiltration, and reverse osmosis. Commonly used polymers for water filter membranes are polyvinyl chloride (PVA), polyvinylidene fluoride (PVDF), polyamide (PA), polyethylene glycol (PEG), polyethersulfone (PES), polyimide (PI), polyacrylonitrile (PAN), polyvinyl alcohol (PA), poly (methacrylic acid) (PMAA), polyaniline nanoparticles (PANI), poly (arylene ether ketone) (PAEK), polyvinylidene fluoride polysulfone (PSF), poly (ether imide) (PEI), etc. However, these polymer membranes are often susceptible to biofouling because of inorganic, organic, and microbial fouling, which deteriorates the membranes and minimizes their lives, and increases operating costs. Biofouling infection on polymer membranes is responsible for many chronic diseases in humans. This contamination cannot be eliminated by periodic pre- or post-treatment processes using biocides and other chemicals. For this reason, it is imperative to modify polymer membranes by surface treatments to enhance their efficiency and longevity. The main objective of this manuscript is to discuss application-oriented approaches to control biofouling on polymer membranes using various surface treatment methods, including nanomaterials and fouling characterizations utilizing advanced microscopy and spectroscopy techniques

Measurement of trace metals in powder activated carbon (PAC) using proton induced x-ray emission (PIXE)

We have used proton-induced x-ray emission (PIXE) to quantify ppm level of arsenic adsorbed in powder activated carbon (PAC), during the exposure of PAC to arsenic solutions. To evaluate different aspects of adsorption mechanisms in PAC, we have carried out equilibrium and kinetic adsorption experiments. After the exposure, arsenic concentration in adsorbent was quantified by means of PIXE (with 1.0 mm diameter ion beam). The As concentrations determined using PIXE compared favourably to those determined from inductively coupled plasma (ICP) measurements. 1. Introduction: Quantification of trace metals in any adsorbent directly with high accuracy and sensitivity is a challenging task. A rapid, high-sensitivity, non-destructive, quantitative, multi-elemental analytical method is best suited to investigate the issues associated with detecting trace elements. Proton induced x-ray emission (PIXE) is such an analytical tool and it is suitable for simultaneously quantifying trace elements with sensitivity of at least parts per million (ppm) [1]. In this study, trace arsenic concentrations in drinking water were investigated by PIXE. Since activated carbon (AC) can effectively remove hazardous trace elements from the drinking or wastewater, it is commonly being used to treat wastewater [2, 3]. As such, activated carbon is an excellent adsorbent for the investigation of the analysis of trace arsenic concentrations in water by characterisation techniques such as PIXE. In this work, PAC has been used as an adsorbent to remove arsenic from drinking water. The amount of arsenic adsorbed was measured by PIXE. Various adsorption experiments were conducted to evaluate both the different aspects of adsorption mechanisms in PAC; and the detection limit and accuracy of PIXE measurements. The results are compared with those from inductively-coupled-plasma (ICP) measurements

Coaxial Electrospun Nanofibrous Membranes for Enhanced Water Recovery by Direct Contact Membrane Distillation

Membrane distillation (MD) is an emerging technology for water recovery from hypersaline wastewater. Membrane scaling and wetting are the drawbacks that prevent the widespread implementation of the MD process. In this study, coaxially electrospun polyvinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP) nanofibrous membranes were fabricated with re-entrant architecture and enhanced hydrophobicity/omniphobicity. The multiscale roughness was constructed by incorporating Al2O3 nanoparticles and 1H, 1H, 2H, 2H Perfluorodecyltriethoxysilane in the sheath solution. High resolution transmission electron microscopy (HR-TEM) could confirm the formation of the core-sheath nanofibrous membranes, which exhibited a water contact angle of ~142.5° and enhanced surface roughness. The membrane displayed a stable vapor flux of 12 L.m−2.h−1 (LMH) for a 7.0 wt.% NaCl feed solution and no loss in permeate quality or quantity. Long-term water recovery from 10.5 wt.% NaCl feed solution was determined to be 8–10 LMH with >99.9% NaCl rejection for up to 5 cycles of operation (60 h). The membranes exhibited excellent resistance to wetting even above the critical micelle concentration (CMC) for surfactants in the order sodium dodecyl sulphate (SDS) (16 mM) > cetyltrimethylammonium bromide (CTAB) (1.5 mM) > Tween 80 (0.10 mM). The presence of salts further deteriorated membrane performance for SDS (12 mM) and Tween-80 (0.05 mM). These coaxial electrospun nanofibrous membranes are robust and can be explored for long-term applications

Quantification of arsenic in activated carbon using particle induced X-ray emission

To date, the trace elemental analysis of solids with inhomogeneous internal structure has been limited, particularly in the case of adsorbents. High-energy ion beam based particle induced X-ray emission (PIXE) is an ideal analytical tool suitable for simultaneous quantification of trace elements with high accuracy. In this study, PIXE was used to quantify arsenic in the adsorbents, granular activated carbon (GAC) and powder activated carbon (PAC). Pelletized and unmodified GAC and PAC samples were analyzed along with powder samples deposited on thin teflon filters. These sample preparation methods resulted in samples of various thicknesses and densities. PIXE measurements taken from these samples were compared to results from neutron activation analysis (NAA) and atomic absorption spectroscopy (AAS). There is a good agreement between the values from the NAA and pelletized PIXE measurements and some AAS measurements

By-product recovery from cottage cheese production by nanofiltration

Cottage cheese whey has been a problem waste as it is dilute, salty and acidic. The use of nanofiltration has been applied to cottage cheese whey to concentrate its solids content four fold, while removing about three-quarters of the sodium and potassium salts and some acid. This desalted nanoconcentrated whey was found to be quite stable under refrigeration for up to 6 weeks. It could then be considered as a recovered by-product for use as an ingredient in dairy and other food products. A preliminary process economics case study was carried out for a plant producing 30,000 l/day of cottage cheese whey. The capital cost required was estimated as $700,000. The payback period was calculated to be less than 10 months

Can we quantify trace metals in an adsorbent using proton induced x-ray emission (PIXE)?

Granular activated carbon (GAC) has been extensively used to remove trace metals from drinking water. We have used PIXE to quantify trace metals, in particular, arsenic in GAC. The results were compared with atomic absorption spectrophotometry (AAS). Some differences have been observed between these two measurements mainly due to the inhomogeneous structure of GAC. 1. Introduction: Granular activated carbon (GAC) has been extensively used to remove trace metals from drinking water for a number of years because it is a highly cost effective treatment on a small scale. To date, there has been no published literature on non-destructive methods to quantify the actual amount of trace metals adsorbed by the GAC directly. Proton induced X-ray emission (PIXE) is an ideal analytical tool, which is suitable for simultaneously quantifying trace elements with sensitivity of at least parts per million (ppm)

Application of air flow for mitigation of particle deposition in submerged membrane microfiltration

This study investigates the effect of microfiltration operating conditions on membrane fouling of colloidal particles of kaolin clay. Experiments were conducted with a flat sheet membrane submerged in a suspension prepared from kaolin clay powder of size varying from 0.1 to 4 mm (Sigma) with a mean particle size 2.10 mm. The particle size distribution of clay was unimodal and the concentration of kaolin clay was similar to the biomass concentration in a membrane bioreactor (10 g/L). The effects of scouring and permeate flux rates were studied in terms of the membrane fouling rate. A linear relationship between the transmembrane pressure (TMP) and particle deposition was established for different air flow rates and permeate flow rates. Air scouring was more effective at a low permeate flux. There was only a minor change in the mean particle size of deposited colloidal particles on the membrane at a given flux under varying air flows and at the beginning all had a similar rise in TMP. However, at the later stages as particles accumulated on the membrane surface there was a significant rise in TMP. 15 LMH flux was observed as critical flux beyond which a rise in the permeate flux showed a sharp rise in the TMP which varied with air flow rates and particle deposition. The sharp TMP rise that occurred during the initial few hours of operation indicated that air flow for fouling mitigation strategies should target this period to optimise the membrane process. The study showed that air flow and flux rates are the two major governing factors for particle deposition on the membrane surface

Seasonal influence on urban dust PAH profile and toxicity in Sydney, Australia

Road dust is one of the major threats to the urban environment due to wash-off of dust to the surrounding catchments during wet weather period. The dust contains wide range of toxic contaminants such as heavy metals, polycyclic aromatic hydrocarbons (PAHs) and endocrine disrupting chemicals. Among the toxic contaminants, PAHs are of environmental concern due to their potential carcinogenic and mutagenic effect besides endocrine disruptive behaviour. Eighteen road dust samples from Sydney were collected in different time periods for a year and analysed for 16 US EPA PAHs. Total PAHs content range in the dust was 9-105 μg/g. Total and individual PAH contents were highest in the finest size fraction

Fabrication of r-GO/GO/α-Fe₂O₃/Fe₂TiO₅ Nanocomposite Using Natural Ilmenite and Graphite for Efficient Photocatalysis in Visible Light

Hematite (α-Fe2O3) and pseudobrookite (Fe2TiO5) suffer from poor charge transport and a high recombination effect under visible light irradiation. This study investigates the design and production of a 2D graphene-like r-GO/GO coupled α-Fe2O3/Fe2TiO5 heterojunction composite with better charge separation. It uses a simple sonochemical and hydrothermal approach followed by L-ascorbic acid chemical reduction pathway. The advantageous band offset of the α-Fe2O3/Fe2TiO5 (TF) nanocomposite between α-Fe2O3 and Fe2TiO5 forms a Type-II heterojunction at the Fe2O3/Fe2TiO5 interface, which efficiently promotes electron-hole separation. Importantly, very corrosive acid leachate resulting from the hydrochloric acid leaching of ilmenite sand, was successfully exploited to fabricate α-Fe2O3/Fe2TiO5 heterojunction. In this paper, a straightforward synthesis strategy was employed to create 2D graphene-like reduced graphene oxide (r-GO) from Ceylon graphite. The two-step process comprises oxidation of graphite to graphene oxide (GO) using the improved Hummer’s method, followed by controlled reduction of GO to r-GO using L-ascorbic acid. Before the reduction of GO to the r-GO, the surface of TF heterojunction was coupled with GO and was allowed for the controlled L-ascorbic acid reduction to yield r-GO/GO/α-Fe2O3/Fe2TiO5 nanocomposite. Under visible light illumination, the photocatalytic performance of the 30% GO/TF loaded composite material greatly improved (1240 Wcm−2). Field emission scanning electron microscopy (FE-SEM) and high-resolution transmission electron microscopy (HR-TEM) examined the morphological characteristics of fabricated composites. X-ray photoelectron spectroscopy (XPS), Raman, X-ray diffraction (XRD), X-ray fluorescence (XRF), and diffuse reflectance spectroscopy (DRS) served to analyze the structural features of the produced composites

Procédés hybrides associant la filtration membranaire et l'adsorption/échange ionique pour le traitement des eaux usées en vue de leur réutilisation

L'objectif de cette étude est de développer un procédé hybride combinant la séparation membranaire et l'adsorption/ échange ionique pour traiter les effluents secondaires en vue leur réutilisation. L'application de ce type de procédé aux eaux usées nécessite une recherche des coûts les plus faibles en tenant compte de la spécifité des matières organiques contenues dans ces effluents. Par ailleurs il parait souhaitable de développer un procédé durable c'est-à-dire de minimiser la consommation énergétique et de faire en sorte que les additifs utilisés soient régénérables. Ceci nous a conduit à privilégier un procédé ou membranes immergées et adsorbant régénérable sont associés dans le même réacteur. Nous nous sommes intéressés principalement au traitement des composés organiques des effluents secondaires, soit en étudiant la fraction hydrophobe composée de substances humiques (majoritairement acides fulviques dans notre étude), soit en en travaillant avec une solution synthétique de composition proche de celle d'un effluent secondaire. Pour ce faire, cette étude à comporté les étapes suivantes : 1 Recherche d'un matériau alternatif au charbon actif en poudre CAP avec une étude comparative des cinétiques et des isothermes d adsorption; 2. Etude de la réponse du procédé hybride à deux échelles en utilisant le CAP et la résine substitut ; 3. Amélioration d un protocole qui permette de prédire le potentiel de colmatage des eaux vis à vis des étapes de nanofiltration ou d'osmose inverses qui pourraient compléter le procédé étudiéThis study deals with the development of a hybrid process combining membrane filtration and adsorption or ion exchange for the treatment of secondary effluent for their reuse. The application of this process to the treatment of wastewaters needs to look for the lowest cost by taking into account the specificity of the organic matter of the effluents and by developing a durable process by lowering its energetic consummation and using regenerable adsorbents. This led us to privilege the combination in the same reactor, an immersed membrane and a regenerable adsorbent. We were interested mainly in the treatment of the organic compounds of the secondary effluents, either by studying the hydrophobic fraction humic substances (mainly fulvic acid in our study), or a synthetic secondary effluent.For these purposes, our study followed these steps:1. Research of an alternate material to the Powdered Activated Carbon PAC; a comparative study of the kinetics and isotherms of adsorption was then investigated. 2. Study of the response of the hybrid process at two scales by using PAC and the Ion Exchange Resin. 3. Improvement of a protocol of the determination of the fouling potential of the treated water that could be treated by either nanofiltration or reverse osmosisTOULOUSE-INSA (315552106) / SudocSudocFranceF