Organic Ultrafiltration Membranes Research Articles

A heterogeneous double chamber electro-Fenton with high production of H2O2 using La–CeO2 modified graphite felt as cathode

Hydrogen peroxide synthesis by electro-reduction of O 2 to substitute the current anthraquinone process has attracted a great deal of attention. Low oxygen utilization rate and low hydrogen peroxide production remain obstacles to electro-Fenton application. In situ H 2 O 2 generated by electrochemical reaction depends on the electrochemical performance of the cathode and the structure of the reactor. Here, novel graphite felt (GF) modified by La-doped CeO 2 (La–CeO 2 ) was developed as a cathode. A new double chamber electro-Fenton reactor was proposed, where an organic ultrafiltration membrane was used to prevent H 2 O 2 from spreading to the anode. The effects of hydrothermal temperature, time and urea concentration on the electrochemical properties of graphite felt were investigated. The accumulated concentration of H 2 O 2 on the modified cathode reached 218.4 mg·L –1 in 1 h when the optimal conditions of hydrothermal temperature 120 °C and urea concentration 0.55% (mass) in 24 h. The degradation rate of methyl orange reached 98.29%. The new electro-Fenton reactor can efficiently produce hydrogen peroxide to degrade various organic substances and has a high potential for treating wastewater in the chemical industry.

Comparison of different ultrafiltration membranes as first step for the recovery of phenolic compounds from olive-oil washing wastewater

The production of olive oil generates wastewater with a high organic load and toxicity due to the high concentration of phenolic compounds. In recent years, the study on the treatments of these waters has been intensified together with the search for a process to recover these phenolic compounds due to their great antioxidant potential. All this with the aim of implementing the concept of circular economy. In this study, four different organic ultrafiltration membranes were evaluated in order to recover the phenolic compounds present in olive oil washing wastewater (OOWW) from an oil mill in the Valencian Community (Spain). The tested membranes differ in materials and molecular weight cut-off (MWCO): two permanently hydrophilic polyethersulfone (PESH) membranes with MWCO of 4 and 50 kDa, respectively, one polyethersulfone (PES) membrane with a MWCO of 5 kDa and a regenerated cellulose acetate (RCA) membrane with a MWCO of 10 kDa. Transmembrane pressure (TMP) and crossflow velocity (CFV) were varied from 1 to 3 bar and from 1.5 to 3.4 m·s−1, respectively. The effectiveness of the different membranes and operating conditions were evaluated comparing the permeate flux and the rejection of chemical oxygen demand (COD) and total phenolic compounds (TPhs). The membranes with lower MWCO showed stable permeate fluxes without significant changes over time, while the 50 kDa membrane showed a gradual decrease, without achieving a stable flux. Low rejection of phenolic compounds was observed in all cases, while the rejection of COD varied between 19.5 % and 62.9 % depending on the membrane and operating conditions tested. Except for the 50 kDa PESH membrane, initial permeability recovery greater than 95 % was achieved with a 35 °C water rinse, indicating that membrane fouling was not severe. Since the aim was to recover the TPhs in the permeate stream and separate them from the organic matter, the 5 kDa PES membrane at 2 bar and 2.5 m·s−1 was considered to be the best option. At those conditions a stable permeate flux of 40 L·h−1·m−2 was obtained, while the lowest TPhs rejection was observed (8.01 %) with a high COD rejection (61.18 %).

Synthesis of new low-cost organic ultrafiltration membrane made from Polysulfone/Polyetherimide blends and its application for soluble azoic dyes removal

This study concerns the synthesis and characterization of a new organic ultrafiltration membrane by phase inversion process based on the physical blends of Polysulfone/Polyetherimide (PS/PEI). The organic membranes we have synthesized are innovative; their first performance is to process soluble azoic dyes. They also have a low preparation cost and easy handling. We varied from 5 to 20 wt.% of PEI compared to the wt.% of PS. The microstructural membrane structure obtained was characterized by Fourier Transform Infrared spectroscopy (FTIR) and by nuclear magnetic resonance spectroscopy (NMR). The measurement of the contact angle characterized the surface properties of the membrane and the morphology was evaluated using the scanning electron microscope (SEM). The prepared membrane was evaluated by ultrafiltration of solutions of acid orange 74 (AO-74) and methyl orange (MO). The effect of adding polyetherimide in addition to the polysulfone increases the retention rate of the two dyes at a pressure of 4 bar. The results of the experimental filtration of the optimized membrane (prepared with 20 wt.% of PEI) have a water permeability of 22.66 L/hm2 bar, a maximum rejection rate of RM20 (AO-74) = 68.5% and RM20 (OM) = 64.7% respectively and a good high dye flow of around 10,08 L/h m2 for orange-74 acid AO-74 and 16,30 L/h m2 for methyl orange (OM).

Enhancement of pilot scale production of l(+)-lactic acid by fermentation coupled with separation using membrane bioreactor

Traditional batch fermentation leads to a higher energy consumption and lower production capability because of longer culture time. In this work, a pilot scale bioreactor composed of a 3000L fermentor and external ceramic microfiltration equipment was used to perform cell-recycle fermentation. Repeat feeding medium was also used to relieve the substrate inhibition. In such pilot system, the maximum yield and productivity of l(+)-lactic acid production reached 157.22±3.42g/L and 8.77±0.15g/L/h which were 4.23% and 315.64% higher than those of batch fermentation, respectively, when equal amount of sugar was consumed. The cost of l(+)-lactic acid production was successfully reduced about two-thirds by the increase of yield and productivity. 12 rounds of cell-recycle fermentations were successfully achieved in the pilot system. The membrane filtration productivity reached to 61.27±2.74L/m2/h which increased 172.80%, while the cell damaging rate dropped to 3.88±0.18% which decreased 85.77%, compared with those of the ultrafiltration. Furthermore, the ceramic microfiltration membrane showed advantages in tolerance for the temperature, pressure and acid, compared with the organic ultrafiltration membrane. The experimental results indicated that the method could give a reference for low cost production of l(+)-lactic acid in an industrial scale.

An experimental and theoretical analysis of turbulence promoter assisted ultrafiltration of synthetic fruit juice

Ultrafiltration of synthetic fruit juice (mixture of pectin and sucrose) is performed in continuous cross flow mode with an organic ultrafiltration membrane (PPE 30, poly phenylene ethersulfone) of 30 K molecular weight cut off. The permeate fluxes are measured under various operating conditions, namely, transmembrane pressure and cross flow velocity. Significant enhancement of permeate flux is achieved by incorporation of cylindrical promoters placed perpendicular to the flow. Image analyzing video microscopy is used to quantify the deposition profile of pectin on the membrane surface. The consistency of these measurements in relation to enhancement of permeate flux are examined. The coupled fluid flow and mass transfer processes including the effects of the promoters are modeled and solved using FLUENT. The geometry of the system is constructed using GAMBIT and special attentions are given to mesh sizes in the different zones of flow, e.g., finer mesh is used near the membrane surface. The calculated values of permeate flux under various operating conditions agree well with the experimental data.

Optical evaluation of deposition thickness and measurement of permeate flux enhancement of simulated fruit juice in presence of turbulence promoters

Ultrafiltration of simulated fruit juice (pectin and sucrose) is performed in continuous cross-flow mode with an organic ultrafiltration membrane (poly phenylene ethersulfone, PPE 30) of 30 K molecular weight cut off. The permeate fluxes are measured under different operating conditions of pressure, cross-flow velocity and pectin concentration. Significant enhancement of permeate flux is achieved by incorporation of straight cylindrical promoters placed across the flow. The optimum number of such promoters and their sizes are evaluated. Image analyzing video microscopy is successfully used to accurately quantify the deposition of pectin molecules on the membrane surface. The deposition thickness decreases with increase in cross-flow velocity, increases with pectin concentration but is less susceptible to increases in pressure. The effects of the shape of the promoters on flux enhancement and deposition thickness are also investigated in detail and approximately parabolic shaped promoters are chosen with further increases in flux enhancement (keeping the number of promoters same as in the case of straight promoters). The deposition thickness profiles around a promoter and the average deposition thickness on the whole membrane are optically measured and the consistency of the results in relation to enhancement of permeate flux are examined.

Experimental study of metal ions removal from aqueous solutions by complexation–ultrafiltration

An organic ultrafiltration membrane in polyethersulfone is employed in the present study for the removal of cupric ions, complexed beforehand on poly (vinyl alcohol), from aqueous solutions. The rejection of the complexed metal ions is highlighted by means of viscometric and UV–vis spectroscopic analysis of the feed solutions and the ultrafiltrates. The considered parameters are, in particular: (a) the pressure: the results obtained show that the variation of the pressure acts on the flow without affecting the rejection rate. Indeed, whatever the value of the applied pressure, the macrocomplex is completely rejected when the formation conditions of the macrocomplex are met. (b) The pH: the rejection rate becomes more significant as the formation pH of the complex is approached and reaches a maximum in the pH range above 7.0 and the UV–vis spectra of feed solutions for several pH show clearly that it is well in this field of pH that the macrocomplex is formed. (c) The relative concentration of the reacting species: the maximum of rejection is reached, at the pH formation of the macrocomplex, for a concentration of poly(vinyl alcohol) of 1.5 g/L when the metal solution to treat is at the concentration of 5 × 10 −4 M.

Membrane characterization using microscopic image analysis

Five organic ultrafiltration membranes, made of different materials (PES, PVDF and PAN), have been visualized by a field emission scanning electron microscope (FESEM). Obtained images have been treated by the processing and analysis program NIH image and parameters such as, porosity ( A k), pore density ( N), mean pore radius ( r p) and pore size distribution have been quantified for each membrane. The mean pore size obtained from image analysis agrees well with rejection data of fluorescein isothiocyanate dextrans, using the Ferry’s law approximation. The membrane thickness Δ x has been also measured on images. Results allowed the comparison between the A k/Δ x values obtained from image analysis and the A k/Δ x values obtained by diffusion experiments. Results, combined with porosity and water permeability values, gave information on the material hydrophilicity.

Ultrafiltration of a waste emulsified cutting oil using organic membranes

The influence of operating conditions on permeate flux was investigated using organic ultrafiltration membranes to treat a synthetic cutting-oil emulsion containing 0.05 to 0.8 wt. % oil. A commercial cutting oil, Alba-Kool, and four organic ultrafiltration membranes, two made of polysulfone (PM10 and PM30) and the other two of regenerated cellulose (YM10 andYM30), with cut-off sizes of 10 000 or 30 000 Dalton, were used.All experiments were performed in a commercially available stirred ultrafiltration cell. Within the range of operating conditions studied, it was found that the highest fluxes wereobtained at the following conditions: crossflow velocity (rotation speed) of 375 rpm, temperature of 40 °C andtransmembrane pressure of 0.1–0.15 MPa. Oil rejections between99 and 99.9% were obtained. Complete membrane regeneration wasachieved with a 2 vol. % aqueous solution of a commercial cleaning agent (Derquim+, Panreac).

A model for calculating the steady state flux of organic ultrafiltration membranes for the case of cutting oil emulsions

The present study provides a model based on a dimensionless analysis that gives the basis for design of cross-flow ultrafiltration processes in the case of treatment of cutting oil emulsions. The model gives the resistance of the polarization layer in terms of the pressure drop across the membrane, the velocity of the feed fluid in the membrane module, the viscosity and the density of the emulsion. It is compared with a great number of experimental results obtained with SARELF A cutting oil emulsions. The model can be used for unit optimization.

Preparation of proteolytic enzyme extracts from Ananas comosus L., Merr. fruit juice using semipermeable membrane, ammonium sulfate extraction, centrifugation and freeze-drying processes

Crude purified bromelain extracts were obtained from 0.26% protein pineapple juice using sequential batch membrane processing systems which included microfiltration (MF) and ultrafiltration (UF) followed by ammonium sulfate extraction, ultracentrifugation and freeze drying. The membrane treatments (with an 8 μm mineral MF and a 10000 molecular weight cut-off (MWCO) organic UF membranes), combined with 60% ammonium sulfate extraction resulted in 0.75–0.8% protein concentration, with 99% protein rejection. A 70% ammonium saturation and ultracentrifugation process (27 000 × g at 2–3 ° C), prior to freeze drying, were used in the last step to remove the residual non-protein constituents. These processes achieved low-moisture freeze-dried, and light-colored extracts, free of non-protein constituents and which accounted for about 50% yielded extracts containing 98% protein. The extracts assayed for bromelain and proteolytic activity resulted in almost 100% potential recovered, at completion. However, bromelain and proteolytic activity decay during the processes described above is essentially caused by losses through adsorption on the UF membrane relative to the level of concentration reached.