Filtration Mode Research Articles

A novel antifouling technique for the crossflow filtration using porous membranes: Experimental and CFD investigations of the periodic feed pressure technique

Oily water production is one of the many drawbacks of petroleum and several other industries. Finding effective ways for the treatment of produced water remain one of the main areas of interest in membrane sciences. Albeit the many advantages of membrane technology, they suffer from the unavoidable problem of fouling, which results from the accumulation of dispersed materials at the surface of membranes. Membrane modification and operational optimization have been approached as a potential cure of the problem of fouling. In this work we introduce a new and novel method that minimizes the development of fouling and in the same time utilizes no chemicals (i.e., environmentally friendly). The core of this method is based on alternating the pressure in the feed channel in a periodic manner and is therefore named the periodic feed pressure technique, PFPT. The idea is to make pinned droplets at the surface of the membrane lose essential forces that keep them sticking to the surface. The drag force due to permeation flux and the capillary force due to interfacial tension represents the two forces that largely contribute to the pinning of oil droplets at the surface of the membrane. Other forces including buoyancy and lift forces are generally small to be of significant influence. The idea of the PFPT is, therefore, to eliminate the force due to permeation drag. This is done by setting the transmembrane pressure (TMP) to zero at fixed intervals allowing pinned oil droplets to dislodge the surface. When the TMP is set to zero, permeation flux stops and the force due to permeation drag vanishes. This significantly reduces the overall residence time of pinned oil droplets, minimizing the chance for other oil droplets to cluster and coalesce with pinned ones. The PFPT does not cause any damage to the support layer of the polymeric membrane, which is a drawback of back-flushing methodology. The novel PFPT displays minimal membrane fouling and very similar permeation recovery despite only half the cycle time is in filtration mode. In this work, we show how the permeation flux is recovered and provide comparisons between the PFPT and regular filtration methodology. Furthermore, we compare the overall amount of filtrate at the end of the experiments using both methods. It is interesting to note that, the amount of filtrate using the PFPT is very much comparable to that obtained using regular filtration methodology and even higher. By optimizing the frequency of the cycle and the amplitude of the pressure change, it is possible to customize the PFPT to various membrane technologies and to achieve the highest recovery of the flux. Visual inspections of the membranes post operation and post rinsing indicate that membranes undergoing filtration using the PFPT achieves a very clean surface compared with those undergoing regular filtration processes. This method is a promising solution to membrane fouling that is easy to implement without any additional use of chemicals or equipment. Computational fluid dynamics (CFD) investigation is also conducted on microfiltration processes to show why this technique works.

Fouling behaviours of two stages microalgae/membrane filtration system applied to palm oil mill effluent treatment

Fouling by solids and microorganisms is the major obstacle limiting the efficient use of membrane wastewater treatment. In our previous study, two stages microalgae/membrane filtration system was proposed to treat anaerobic digested palm oil mill effluent (AnPOME). This two stages microalgae/membrane filtration system had showed great potential for the treatment of AnPOME with high removal of COD, NH3-N, PO43-, TSS, turbidity, and colour. However, fouling behavior of the membrane in this two stages microalgae/membrane filtration system was still unknown. In this study, empirical models that describe permeate flux decline for dead-end filtration (pore blocking - complete, intermediate, and standard; and cake layer formation) presented by Hermia were used to fit the experimental results in identifying the fouling mechanism under different experimental conditions. Both centrifuged and non-centrifuged samples were taken from the medium with 3 days RT intervals, from day 0 to day 12 to study their influence on fouling mechanisms described by Hermia for ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) filtration mode. Besides, a more detailed study on the use of resistance-in-series model for dead-end filtration was done to investigate the fouling mechanisms involved in membrane filtration of AnPOME collected after microalgae treatment. The results showed that fouling of UF and NF membrane was mainly caused by cake layer formation and it was also supported by the analysis for resistance-in-series model. Whereas, fouling of RO membrane was dominated by concentration polarization.

Factors Affecting Mass Transport Properties of Poly(ε-caprolactone) Membranes for Tissue Engineering Bioreactors.

High porosity and mass transport properties of microfiltration polymeric membranes benefit nutrients supply to cells when used as scaffolds in interstitial perfusion bioreactors for tissue engineering. High nutrients transport is assumed when pore size and porosity of the membrane are in the micrometric range. The present work demonstrates that the study of membrane fouling by proteins present in the culture medium, though not done usually, should be included in the routine testing of new polymer membranes for this intended application. Two poly(ε-caprolactone) microfiltration membranes presenting similar average pore size (approximately 0.7 µm) and porosity (>80%) but different external surface porosity and pore size have been selected as case studies. The present work demonstrates that a membrane with lower surface pore abundance and smaller external pore size (approximately 0.67 µm), combined with adequate hydrodynamics and tangential flow filtration mode is usually more convenient to guarantee high flux of nutrients. On the contrary, having large external pore size (approximately 1.70 µm) and surface porosity would incur important internal protein fouling that could not be prevented with the operation mode and hydrodynamics of the perfusion system. Additionally, the use of glycerol in the drying protocols of the membranes might cause plasticization and a consequent reduction of mass transport properties due to membrane compaction by the pressure exerted to force perfusion. Therefore, preferentially, drying protocols that omit the use of plasticizing agents are recommended.

Sustaining membrane permeability during unsteady-state operation of anaerobic membrane bioreactors for municipal wastewater treatment following peak-flow

In this study, the impact of peak flow on anaerobic membrane bioreactor operation is investigated to establish how system perturbation induced by diurnal peaks and storm water flows will influence membrane permeability. Good permeability recovery was attained through increasing gas sparging during peak flow, which was explained by the transition in critical flux of the suspension at higher shear rates. However, supra-critical fluxes could also be sustained, provided peak flow was for a short duration. We suggest longer durations of supra-critical operation could be sustained through introduction of reactive fouling control strategies (e.g. TMP set-point control). An initial flux below the critical flux, prior to the introduction of peak flow, was advantageous to permeability recovery, suggesting membrane ‘conditioning’ is important in governing recoverability following peak flow. The importance of conditioning was confirmed through analysis of multiple peak flow events in which the loss of permeability following each peak-flow event was increasingly negligible, and can be ascribed to the arrival of a steady-state in membrane surface deposition. Whilst responding to peak flow with increased gas sparging has been shown effective, the energy demand is considerable, and as such a pseudo dead-end filtration strategy was also evaluated, which required only 0.04 kWh m−3 of energy for gas sparging. Comparison of both filtration modes identified comparable fouling rates, and the feasibility of a low energy gas sparging method for peak flow management that has successfully enabled supra-critical fluxes to be achieved over long-periods in other MBR applications. Importantly, membrane area provides the highest contribution toward capital cost of AnMBR. The potential to turn-up flux in response to peak-flow has been identified in this study, which suggests membrane area can be specified based on average flow rather than peak flow, providing substantial reduction in the capital cost of AnMBR for municipal wastewater treatment.

On the rejection and reversibility of fouling in ultrafiltration as assessed by hydraulic impedance spectroscopy

The manifestation of critical fluxes in membrane filtration has typically served to set an upper value above which detrimental fouling events and a substantial increase of membrane resistance occurs. Despite the usefulness of critical flux concepts for conducting sustainable membrane processes, the specific phenomena causing them cannot be easily identified via conventional membrane filtration modes. Usually arbitrary fouling rates are selected to delimit the boundary between under- and over-critical flux operation. Timescales respective for colloidal matter accumulation are overlooked.Frequency response analysis of transmembrane pressures has been recently presented as a highly-sensitive method to track fouling in ultrafiltration. This hydraulic impedance spectroscopy method allows not only measuring membrane resistances but also corresponding time constants related to colloidal matter accumulation. In this work, hydraulic impedance spectra are gained for the ultrafiltration of different model foulants to assess the origin of critical fluxes for two different membranes. A correlation among characteristic impedance features and the type of fouling could be established: the evolution of phase shift between flux and pressure at increasing fluxes allows identifying the formation of external fouling layers, while registering of hysteresis loops at reversed frequency sequences signals the development of irreversible internal fouling. The hydraulic impedance method emerges as a precise and more sensitive monitoring tool to diagnose the beginning and nature of critical fouling.

Zeolite Integrated Nanocellulose Films for Removal of Loose Anionic Reactive Dye by Adsorption vs. Filtration Mode during Textile Laundering

Water stable, flexible and ecological acceptance composite films were prepared by the solvent casting process using native, dealuminated (treated with HCl to affect the surface chemistry and pore structure) and/or surface modified (coated with a cationic surfactant PDADM of different molecular weights) H-ZSM-5 type zeolite of different shapes (spherical vs. rod) and Si/Al ratios (P26 vs. P371) as adsorbents and cellulose nanofibrils (CNFs) as a networking matrix (in a weight ratio of 4:1). The films were tested for removal of the black anionic reactive dye with the highest bleeding effect at the first rinsing cycle of textile laundering. The effects of zeolite structure and surface chemistry on films dye’ removal kinetics from a standardised rinsing bath were investigated for up to 140 min at room temperature and using 0.1 g/l of dye concentration, depending on the film-to-bath weight-to-volume ratios (from 1:10 to 1:1000), thus simulating different rinsing conditions. The results show that up to 80 % of the dye was removed in the first 20 min in the lowest weight-to-volume ratio (1:10), fitting the Langmuir isotherm, and the process followed the pseudo-second order kinetic, yielding a multi-layer adsorption mechanism with a monolayer capacity of ~11 mg/g and ~21 vs. ~30 mg/g by films prepared from native or HCltreated and PDADMA100 vs. PDADMA400 coated P371 zeolites, respectively. Such efficacy was due to the more densely and fully surface-covered longitudinal P371 with PDADM400, given the huge electrostatic attraction sites for dye molecules, compared to the partly interpenetrated PDADM into relatively larger pore-sized (~450 nm vs. 220 nm) of P26. The filtration performance of the films was also examined, be used for the removal of the dye from the rinsing bath, released from the washing drum. An ultra-high flux rate (11.000 kL/m2 h MPa) with 45 % of dye removal efficacy and capacity of ~24 mg/g was provided by films prepared from spherical and aggregated P26PDADMA-400, showing its high potential also as a filter membrane.

Model of grout filtration in a porous soil

To strengthen the foundations and protect them from ground water, liquid grout is pumped under pressure into a loose porous soil. Modern construction techniques use colloids or suspensions which form a waterproof layer upon solidification. Calculation of grout distribution in a porous soil is an important part of designing buildings and structures. The distribution of suspended particulates in unconsolidated soil is described by mathematical equations of particles filtration in the porous media. The aim of this work is modelling of suspended particles transport and deposit formation in a porous soil for different filtration modes. The distributions of solid particles of different sizes transported by the carrier fluid and retained on the frame of the porous medium at different kinetic rates of deposit growth are examined. Model of one-dimensional filtration with size-exclusion particle retention mechanism includes a hyperbolic system of the first order differential equations with inconsistent initial and boundary conditions that leads to discontinuous solutions. A modified mathematical model for polydisperse media with the competition between particles of different sizes for small pores is considered. The computational scheme for numerical solutions is constructed by finite difference method. Optimization methods to improve convergence and reduce computation time are used. A multi-particle model of grout filtration in a porous soil is constructed, considering the variety of sizes of suspended particles. A numerical calculation of the problem is performed for various blocking filtration coefficient. Solutions are obtained with a discontinuity on the concentration front. Approbation of the obtained numerical solutions is carried out. Plots of the suspended and retained particles concentrations depending on time and coordinates are constructed. A new model of multi-particle transport in a porous medium widely extends the design capabilities of waterproof underground walls. The solution of the filtration problem for solid particles of different sizes makes it possible to calculate the optimal composition of grout for constructing a waterproof layer in a porous soil. The developed computing finite-difference methods allow to obtain the numerical solution of complex systems of equations with good accuracy and a moderate amount of computation.

SHS TECHNOLOGY OF COMPOSITION FERROALLOYS PART I. METALLURGICAL SHS PROCESS. SYNTHESIS OF FERROVANADIUM AND FERROCHROMIUM NITRIDES

The article presents research findings in the development of a specialized SHS technology for composite ferrous alloys for steel melting and blast furnace iron-making. To resolve the principle goal of creating metallurgical production lines it was developed a new approach to practical implementation of the SHS method – a metallurgical SHS process. The metallurgical version of SHS is based on using different metallurgical alloys as the main raw stock; those include dust-type wastes of ferrite alloys production. In this case, the process of synthesis by combustion is implemented via exothermic exchange reactions. Here, composite materials form; they are based on inorganic compositions bound with iron and/or an alloy based on iron. It has been shown that depending on the aggregate state of source reagents, metallurgical SHS processes can be gasless, gasabsorbing or gas-yielding. Combustion modes for these processes largely differ. To arrange for metallurgical SHS process in weakly exothermic systems, one can use different versions of the thermal bonding principle. The authors have investigated self-propagating high-temperature synthesis of nitrided ferrovanadium and ferrochrome. It has been shown that the phase composition of the source alloy has strong impact on the consistent behaviors of the combustion flow and the combustion mechanism of ferrovanadium (if combustion is taking place in nitrogen atmosphere). In the course of nitriding σ-(Fe – V), process activation takes place; the activation is related to the transformation of the intermetallide into α-solid solution when the phase transition temperature is reached (~1200 °C). The composition structure of ferrovanadium nitride products is formed by the confluence of solid-liquid droplet-particles that consist of molten Fe and solid vanadium nitride. A 3-phase mechanism of ferrochrome interaction with nitrogen facilitates the achievement of a high degree of nitriding. It was shown that the combustion rates of ferrochrome (and chrome) during nitriding in coflow filtration mode increase as the nitrogen flow rate is increased. Here, the degree of ferrochrome nitriding during forced filtration (4.7 – 7.5 % N) is much less than that during non-forced filtration (8.8 – 14.2 % N).

Effect of the membrane/protein interaction nature on adsorptive properties of ultrafiltration membranes based on aromatic poly- and copolyamides

Membranes are a science intensive product of interindustry use, without which a breakthrough development of basic and high-technology sectors of economy, development of science as well as effective solution of important goals of the social sphere and problems of environment protections are impossible. Active development of medicine, pharmaceutical industry and biotechnology in the recent years contributed to the growth of scientific and commercial interest in ultrafiltration. The most important characteristic of ultrafiltration membranes is selectivity. According to existing views the basis of the separation mechanism implemented in ultrafiltration is size selectivity. However, such phenomena as concentration polarization and adsorption play a very important role in separation. Investigation of these phenomena is of significant practical interest, because its results in many ways determine the choice of the membrane media, conditions of its recovery, the mode and conditions of filtration. Adsorption of proteins on the surface of porous membranes is a rather complicated process due to the individual mechanism implemented in each specific case. Therefore, the issue of the contribution of various types of interactions into the process of adsorption still remains controversial. To determine the nature of membrane/protein interaction and clarify the factors of its control, the present work involved investigation of sorption of several proteins on a number of synthesized porous membranes based on aromatic polyamides noted for the presence, nature and concentration of ionogenic groups. The investigations were carried out using bovine serum albumin, lysozyme of hen's eggs, myoglobin and bacitracin. Adsorption of proteins by the membranes was investigated in the static mode. The protein concentration was determined using the SF-2000 spectrophotometer (experimental-design bureau Spektr) by optical density at the wave length λ=278 nm. To mathematically process the experimental data, the two-parameter models by Langmuir, Freundlich, Temkin and the three-parameter model by Langmuir-Freundlich were used. To assess the compliance degree of the experimental data to the selected mathematical models, the values of the coefficient of determination (R2) and sum squares errors (SSE) were used. It has been shown that in the case of the presence of charge in protein macromolecules and the membrane surface the role of electrostatic forces is dominant in the protein adsorption mechanism, however, the contribution of non-electrostatic interactions in the investigated membrane/protein systems is significant.

Albumin Apheresis for Artificial Liver Support: In Vitro Testing of a Novel Filter.

Currently there is no direct therapy for liver failure. We have previously described selective plasma exchange therapy using a hemofilter permeable to substances that have a molecular mass of up to 100 kDa. The proof-of-concept studies and a Phase I study in patients with decompensated cirrhosis demonstrated that hemofiltration using an albumin-leaking membrane is safe and effective in removing target molecules, alleviating severe encephalopathy and improving blood chemistry. In this study a novel large-pore filter for similar clinical application is described. The performance of the filter was studied in vitro; it was found to effectively remove a wide spectrum of pathogenic factors implicated in the pathophysiology of hepatic failure, including protein bound toxins and defective forms of circulating albumin. Data on mass transport characteristics and functionality using various modes of filtration and dialysis provide rationale for clinical evaluation of the filter for artificial liver support using albumin apheresis.

Submerged low-cost pyrophyllite ceramic membrane filtration combined with GAC as fluidized particles for industrial wastewater treatment

Submerged ceramic membrane reactor treating industrial wastewater was combined with granular activated carbon (GAC) particles to control membrane fouling and organic removal efficiency. The GAC particles were suspended along the membrane surface under bulk recirculation only through the reactor without any gas sparging. Membrane support coated with Al2O3 layer (CPM) and uncoated one (UPM) was compared at constant flux mode of filtration. The membrane support consisted of 80% of pyrophyllite and 20% of alumina. Under up-flow velocity of 0.031 m s−1 through bulk recirculation only without GAC particles, the fouling rates were observed as 0.011 and 0.013 bar h−1 for the CPM and UPM, respectively. With suspension of GAC particles, fouling mitigation was enhanced considerably and this effect was more pronounced with CPM than UPM under the same upflow velocity (90 vs. 57%). In addition, the GAC suspension increased critical flux by 46% higher with CPM than that observed without the carbon particles. The organic removal efficiency of the UPM was lower than that of CPM while the fouling rate was much greater probably due to pore blocking caused by organic dye compounds. For the both membranes, suspension of GAC particles along the membrane surface increased organic removal efficiency higher than 90%. The organic removal efficiency was enhanced by increasing permeate flux, but it became lower as upflow velocity was higher.

Bacteriophage-based strategies for biofouling control in ultrafiltration: In situ biofouling mitigation, biocidal additives and biofilm cleanser

The ability of bacteriophages to infect and destroy specific bacteria makes them promising antimicrobial agents in industrial processes. In this study, potential strategies of bacteriophage-facilitated biofouling control during membrane ultrafiltration (UF) were investigated through use of the model T4 bacteriophage and the model host bacterium, Escherichia coli. In the dead-end filtration mode, phages were immobilized on the membrane surface to serve as biocidal agents and inhibit the propagation of bacteria in situ. After 6 h of filtration, a 36% flux reduction was observed for the T4-functionalized membrane in comparison to 71% for the non-functionalized membrane. Surface modification of the membrane using O2 plasma treatment resulted in increased numbers of bound phage and enhanced biofouling resistance of the membrane. Introducing the phage into the feed of a cross-flow filtration system effectively mitigated the water flux reduction of the membrane caused by bacterial growth. By modifying the concentration of phage additives, the growth of bacteria was delayed, inhibited, or eliminated. Phage treatment changed the structure of biofilms on the membrane surface and facilitated in situ biofilm cleaning. A 20% greater recovery in water flux was observed for the biofilm-contaminated membrane following phage-assisted cleaning when compared to the membrane cleaned via a physical washing process. Taken together, these results show that bacteriophage assisted anti-biofouling strategies have the potential to mitigate biofouling in membrane processes in an environmentally friendly manner.

Dynamic cross-flow electro-Fenton process coupled to anodic oxidation for wastewater treatment: Application to the degradation of acetaminophen

In this work, we present an integrated dynamic cross-flow electro-Fenton (DCF-EF) system for the treatment of the pharmaceutical, acetaminophen (paracetamol), in aqueous medium. A carbonaceous electrocatalytic membrane was used as cathode, allowing the continuous production of H2O2 during EF in dynamic filtration mode. The transmembrane pressure (TMP) and current were the two driving forces of the system, whose influence strongly affected the global efficiency. It was found that H2O2 production from the electrochemical reduction of dissolved O2 was favoured at higher TMP values as a consequence of an increase of the O2 partial pressure, and higher H2O2 amounts entailed an increase in the efficiency of the process. Current also had a positive effect on H2O2 production and acetaminophen degradation and mineralization efficiencies up to an optimal value. Complete degradation of the drug and 44% mineralization were achieved under optimal conditions (2.0 bar and 100 mA). On the other hand, the results pointed out that the use of a Ti4O7 rod as counter electrode (anode) had an important contribution to the mineralization of the acetaminophen’s solutions owing to the formation of hydroxyl radicals (OH) on its surface, which highlighted the oxidative power of this anode material. The oxidation mechanisms involved during the process were assessed by electrochemical measurements with both electrodes (carbon membrane and Ti4O7 rod), and a degradation pathway for paracetamol oxidation was proposed based on the identification of the main aromatic and aliphatic degradation by-products. This DCF-EF process is presented as a potential alternative for water treatment and reuse in which the integration of membrane and electrochemical technologies brings together separation science and advanced oxidation.

Solvent-free production of nano-FeS anchored graphene from Ulva fasciata: A scalable synthesis of super-adsorbent for lead, chromium and dyes

Here we demonstrate, a simple and solvent-free synthetic route for the production of FeS/Fe(0) functionalized graphene nanocomposite (G-Fe) via a one-step pyrolysis of seaweed biomass (Ulva fasciata). It is proposed that the natural abundance of both inorganic and organic sulfur in the seaweed induces the reduction of exfoliated graphitic sheets at elevated temperatures. FeCl3 was employed both as the iron precursor as well as the templating agent. Iron doping played a dual-faceted role of exfoliating as well as activating agent, producing composite with high adsorption capacity for Pb2+ (645 ± 10 mg/g), CR (970 mg/g), CV(909 mg/g), MO (664 mg/g), MB (402 mg/g) dyes and good recyclability (8 cycles). Pb2+ adsorption was irreversible even at low pH values and the spent composite (G-Fe-Pb) was utilized for efficient Cr(IV) removal (̴100 mg/g). The adsorption data followed the pseudo second order kinetics while the equilibrium data fitted perfectly into the Langmuir adsorption equation. Further, a thin layer of composite was deposited on a filter paper by vacuum filtration which was tested under continuous filtration mode for RB5 dye removal. Preliminary results highlight the potential of this composite to be used in pretreatment steps in hybrid membrane processes for filtration of complex wastewater feeds.

Urea-assisted one-step synthesis of cobalt ferrite impregnated ceramic membrane for sulfamethoxazole degradation via peroxymonosulfate activation

In this study, a novel CoFe2O4 nanocatalyst impregnated Al2O3 ceramic membrane was prepared via a urea-assisted one-step combustion method. The catalytic membrane was characterized by field emission scanning electron microscopy (FESEM) with energy dispersive X-Ray analysis (EDX) and applied for the catalytic degradation of sulfamethoxazole (SMX) via peroxymonosulfate (PMS) activation under a dead-end membrane filtration mode for the first time. Results indicate that CoFe2O4 could be impregnated into the macropores throughout the whole Al2O3 ceramic membrane via this method and the CoFe2O4 loading amount could be controlled by the multiple impregnation cycles. The membrane filtration operation mode significantly enhances the accessibility of the catalytic active sites to PMS and SMX in microreactor environment and thus the CoFe2O4 impregnated membrane displays excellent catalytic activity for the SMX degradation. The pure water permeability flux can maintain at ∼3000 L m−2 h−1 bar−1 (LMHB) with the catalyst loading amount of 0.015 g/g Al2O3. In the membrane filtration system, the removal rate of SMX with the initial concentration of 10 mg L−1 can achieve to ∼98%, 70% and 40% with the residence time of 90, 36 and 18 s. The catalytic membrane shows a great tolerance at wide pH range (3–11), the existence of humic acid and anions. Meanwhile, the membrane shows self-cleaning property by retaining >90% of initial flux after 3 treatment cycles. Electron paramagnetic resonance (EPR) and radical quenching experiments indicate that both sulfate radical and hydroxyl radical are generated and sulfate radical is the dominant active species in the process.

Stability of Calcium Chloride in the Air–Steam Gasification of Solid Fuel in Filtration Mode

The emission of HCl from calcium chloride during the air–steam gasification of solid fuel in the filtration combustion mode was studied. The limiting amounts of HCl released into the gas phase under real conditions of a shaft kiln gasifier were estimated. It was shown that the most important factors responsible for the stability of CaCl2 are the humidity of an oxidant gas and the process temperature.

Single Step Preparation of Zirconia Ultrafiltration Membrane over Clay-Alumina Based Multichannel Ceramic Support for Wastewater Treatment

Zirconia ultrafiltration membranes are widely developed and used for past several years. But the conventional sol-gel methods of zirconia membrane preparation involve many steps. In the present study an attempt was made to develop defect free zirconia ultrafiltration (UF) membrane in single step coating of zirconia nanopowder suspension by slip casting method over multichannel ceramic support. The porous support was made from a novel composition of clay and α-alumina having 19-channels circular configuration. Zirconia UF membrane was developed at the inner surface of the support up to 0.2 m length. Membrane had a mean pore diameter of 40 nm. Clean water permeability of 48 lm-2h-1bar-1 was obtained for the membrane under cross-flow filtration mode. Membrane was utilized for treatment of industrial and domestic wastewater. Membrane treated water was characterized to evaluate the reduction of organic and inorganic contaminants. About 82% and 92% removal of COD were obtained for tannery wastewater and kitchen sink wastewater respectively and turbidity being reduced below 1 NTU for both the effluents. Complete removal of pathogenic organisms was achieved. Membrane treated wastewater may be reused for agricultural purposes.

Mineralization of organic pollutants by anodic oxidation using reactive electrochemical membrane synthesized from carbothermal reduction of TiO2.

Reactive Electrochemical Membrane (REM) prepared from carbothermal reduction of TiO2 is used for the mineralization of biorefractory pollutants during filtration operation. The mixture of Ti4O7 and Ti5O9 Magnéli phases ensures the high reactivity of the membrane for organic compound oxidation through •OH mediated oxidation and direct electron transfer. In cross-flow filtration mode, convection-enhanced mass transport of pollutants can be achieved from the high membrane permeability (3300 LMH bar-1). Mineralization efficiency of oxalic acid, paracetamol and phenol was assessed as regards to current density, transmembrane pressure and feed concentration. Unprecedented high removal rates of total organic carbon and mineralization current efficiency were achieved after a single passage through the REM, e.g. 47 g m-2 h-1 - 72% and 6.7 g m-2 h-1 - 47% for oxalic acid and paracetamol, respectively, at 15 mA cm-2. However, two mechanisms have to be considered for optimization of the process. When the TOC flux is too high with respect to the current density, aromatic compounds polymerize in the REM layer where only direct electron transfer occurs. This phenomenon decreases the oxidation efficiency and/or increases REM fouling. Besides, O2 bubbles sweeping at high permeate flux promotes O2 gas generation, with adverse effect on oxidation efficiency.

Sulfur-Doped Laser-Induced Porous Graphene Derived from Polysulfone-Class Polymers and Membranes.

Graphene based materials have profoundly impacted research in nanotechnology, and this has significantly advanced biomedical, electronics, energy, and environmental applications. Laser-induced graphene (LIG) is made photothermally and has enabled a rapid route for graphene layers on polyimide surfaces. However, polysulfone (PSU), poly(ether sulfone) (PES), and polyphenylsulfone (PPSU) are highly used in numerous applications including medical, energy, and water treatment and they are critical components of polymer membranes. Here we show LIG fabrication on PSU, PES, and PPSU resulting in conformal sulfur-doped porous graphene embedded in polymer dense films or porous substrates using reagent- and solvent-free methods in a single step. We demonstrate the applicability as flexible electrodes with enhanced electrocatalytic hydrogen peroxide generation, as antifouling surfaces and as antimicrobial hybrid membrane-LIG porous filters. The properties and surface morphology of the conductive PSU-, PES-, and PPSU-LIG could be modulated using variable laser duty cycles. The LIG electrodes showed enhanced hydrogen peroxide generation compared to LIG made on polyimide, and showed exceptional biofilm resistance and potent antimicrobial killing effects when treated with Pseudomonas aeruginosa and mixed bacterial culture. The hybrid PES-LIG membrane-electrode ensured complete elimination of bacterial viability in the permeate (6 log reduction), in a flow-through filtration mode at a water flux of ∼500 L m-2 h-1 (2.5 V) and at ∼22 000 L m-2 h-1 (20 V). Due to the widespread use of PSU, PES, and PPSU in modern society, these functional PSU-, PES-, and PPSU-LIG surfaces have great potential to be incorporated into biomedical, electronic, energy and environmental devices and technologies.

Hybrid Processes for Extraction–separation of Tocopherols from Crude Palm Oil

The aim of this study was to evaluate the hybrid processes for extraction and separation of tocopherols from crude palm oil. The saponification method was used to extract crude palm oil under various concentrations of alcoholic KOH in the range of 10–60% w/v in a lab scale unit. The experiments were conducted at a temperature and saponification time in the range of 60–80°C and 20–40 min respectively. The performance and efficiency of ultrafiltration were investigated by filtering a fraction of unsponifiables. The results showed that the optimum condition of saponification was 10% alcoholic KOH with the minimum loss of α–tocopherol of around 19%. A lab scale filtration unit with a hydrophobic sheet membrane was operated under a frontal filtration mode at room temperature. The results pointed out that ultrafiltration could remove most of the residual triglycerides and phospholipids contained in unsponifiables at a TMP of 0.25–1.0 bars. The removal of up to 70% of triglycerides and phospholipids was reached when the mixture was ultrafiltered. In addition, these hydride processes present a one of the great option for α–tocopherol purification losing about 5% of yield.