Ultrafiltration Membrane Separation Research Articles

High-strength, super-hydrophilic alginate electrospun nanofibrous membranes for rapid oil-water emulsion separation

Ultrafiltration membrane separation technology is considered an effective method for separating oil-water emulsions. However, oil droplets can easily deposit on the surface of the membranes, leading to severe fouling and a decrease in flux. In this study, poly (ethylene oxide)/acrylamide/sodium alginate (PEO/AM/NaAlg) hydrogel nanofibers were deposited on a poly (hydroxybutyric acid) (PHB) electrospun nanofibrous membrane. Subsequently, superhydrophilic (ethylene oxide)-poly(acrylamide)/calcium alginate hydrogel nanofiber composite filtration membranes (PEO/PAM/CaAlg-PHB) were prepared by polymerization and Ca2+ cross-linking using a PHB electrospun nanofibrous membrane as the matrix. The morphology, tensile strength, water contact angle, and oil–water emulsion separation properties of the PEO/PAM/CaAlg-PHB hydrogel filtration membrane were investigated. The results showed that the PEO/PAM/CaAlg-PHB membrane had good anti-fouling performance, with a tensile strength of 1.95 MPa. After 3 h of the filtration operation, the stable flux and oil–water emulsion rejection of the membrane reached 2925.2 L m−2 h−1 bar−1 and 98.66 %, respectively. The preparation method was simple, cost effective, and environmentally friendly, without introducing any organic pollutants. The PEO/PAM/CaAlg-PHB hydrogel filtration membrane shows promise for separating oil–water emulsions.

Development of a hybrid bio-purification process of lactic acid solutions employing an engineered E. coli strain in a membrane bioreactor

BackgroundA potential alternative to lactic acid production through sugar fermentation is its recovery from grass silage leachate. The separation and purification of lactic acid from fermentation broths remain a key issue, as it amounts to up to 80% of its industrial production cost. In this study, a genetically engineered E. coli strain (A1:ldhA), that cannot catabolize lactic acid, has been used to selectively remove impurities from a synthetic medium comprising typical components (i.e., glucose and acetic acid) of green grass silage leachate. A systematic approach has been followed to provide a proof-of-concept for a bio-purification process of lactic acid solutions in a membrane bioreactor operating in semi-continuous mode.ResultsThe synthetic medium composition was initially optimized in shake-flasks experiments, followed by scale-up in bench-scale bioreactor. Complete (i.e., 100%) and 60.4% removal for glucose and acetic acid, respectively, has been achieved in batch bioreactor experiments with a synthetic medium comprising 0.5 g/L glucose and 0.5 g/L acetic acid as carbon sources, and 10 g/L lactic acid; no lactic acid catabolism was observed in all batch fermentation tests. Afterwards, a hybrid biotechnological process combining semi-continuous bioreactor fermentation and ultrafiltration membrane separation (membrane bioreactor) was applied to in-situ separate purified medium from the active cells. The process was assessed under different semi-continuous operating conditions, resulting in a bacteria-free effluent and 100% glucose and acetic acid depletion, with no lactic acid catabolism, thus increasing the purity of the synthetic lactic acid solution.ConclusionsThe study clearly demonstrated that a bio-purification process for lactic acid employing the engineered E. coli strain cultivated in a membrane bioreactor is a technically feasible concept, paving the way for further technological advancement.

Anti-fouling tight ultrafiltration membrane for gastrodin purification

The issues of flux decline and irreversible membrane fouling must be considered in membrane separation. In this paper, the culture medium, bacterial cells, and proteins were removed using a one-step tight ultrafiltration (UF) membrane separation process. Although the membrane resistance of the tight UF membranes increased owing to their smaller pore size, the stable flux of the 6 nm membrane during fermentation broth filtration of gastrodin was 28.0% higher than that of loose UF membranes, and the flux recovery ratio reached 97.3%. During purification, a higher filtration flux was obtained by retaining the operating pressure within the range of 2–3 bar and the operating temperature range of 50–60 °C. The average flux of a 6 nm 19-channel membrane reached 56 L·m−2·h−1, and the total yield of gastrodin reached 96.2%. This study provides a basis for the large-scale application of tight UF membrane in food industry.

PAN/TiO2 Ultrafiltration Membrane for Enhanced BSA Removal and Antifouling Performance

Membrane separation has been widely utilized to eliminate pollutants from wastewater. Among them, a polyacrylonitrile (PAN) ultrafiltration (UF) membrane has presented outstanding stability, and distinguished chemical and thermal properties. However, UF membranes inevitably incur fouling issues during their operation procedure caused by contaminant adhesion on the membrane surface, which would restrict the operational efficiency and increase the maintenance cost. The conventional physical and chemical cleaning is not an effective technique to reduce the fouling due to the additional chemical addition and inevitable structure damage. Recently, UF membranes combined with photocatalytic materials are suggested to be a useful approach to conquer the membrane fouling issues. Herein, TiO2 nanoparticles were utilized to blend with a PAN casting solution for fabricating a composite UF membrane via a phase inversion method. With a certain TiO2 addition, the obtained membranes presented an enhancement of hydrophilicity, which could promote the water permeability and antifouling performance. The optimized M3 membrane prepared with 15.0 wt% PAN and 0.6 wt% TiO2 exhibited an excellent water permeability up to 207.0 L m−2 h−1 bar−1 with an outstanding 99.0% BSA rejection and superior antifouling property. In addition, the photocatalytic TiO2 nanoparticles endowed the M3 membrane with a remarkable self-cleaning ability under the UV irradiation. This facile construction method offered new insight to enhance the UF membrane separation performance with an enhanced antifouling ability.

Evaluation of vibratory shear-enhanced processing module-integrated three-dimensional printed spacers for enhanced wastewater ultrafiltration.

The article evaluates the effectiveness of two new designed module-integrated three-dimensional (3D) printed spacers in enhancing wastewater ultrafiltration efficiencies using vibratory shear-enhanced processing (VSEP). The study investigates the star-shaped spacer filled module channel (star spacer) and the column-shaped herringbone spacer filled module channel with the same position as the flow direction (column spacer) and with the opposite position as the flow direction (rev column spacer). It compares the VSEP module-integrated spacers with membrane module vibration (module vibration) and empty membrane module channel (control) configurations. The results show that the module integration of the 3D printed spacers can greatly improve the specific, average, and constant permeate fluxes and can contribute to reducing the total, reversible and irreversible resistance values, and specific energy consumption of the ultrafiltration membrane separation experiments. Overall, this study provides valuable insights into improving the performance of wastewater ultrafiltration systems and fouling mitigation through the module integration of 3D printed spacers and membrane module vibration. PRACTITIONER POINTS: Vibratory shear-enhanced processing (VSEP) ultrafiltration module-integrated 3D printed spacers were successfully fabricated and evaluated for improved wastewater treatment. Two spacer designs, a star-shaped and a column-shaped herringbone, were compared with an empty membrane module channel with and without vibration. Two configurations of the column-shaped spacer, in the same and reversed flow direction, were tested. Specific energy consumption was calculated and compared for all configurations. Significant improvements in ultrafiltration performance were observed with the use of spacers compared with an empty module channel, including enhanced permeate fluxes and reductions in both total and reversible, as well as irreversible, resistance.

Treatment of flue gas desulfurization wastewater by a coupled precipitation-ultrafiltration process

Flue gas desulfurization (FGD) wastewater is characterized by low pH, high content of hardness ions and COD. In this work, chemical precipitation and ultrafiltration (UF) membrane separation were corporately coupled to treat the FGD wastewater on a lab scale to remove the hardness as well as some organic compounds for further advanced treatment. Firstly, influential factors for precipitation to deal with the simulated wastewater, including reaction time, stirring speed, and dosage, were investigated by batch tests, while CaO and Na2CO3 were used as the first and second precipitants. The batch results showed that the removal rates of Mg2+ and Ca2+ could be both higher than 98% under the optimal reaction condition. Then a polyvinylidene fluoride tubular UF membrane was used to remove the precipitates without adding flocculants. Thirdly, the coupled process with the optimal operation parameters was adopted to treat real FGD wastewater. Almost all the hardness ions and most COD could be removed, while rapid permeability decline was observed in the UF process due to the high COD, which could be recovered by a simple cleaning. In summary, when the mass ratios of [CaO]/[Mg2+] and [Na2CO3]/[Ca2+] were 2.5 and 2.7, the flow velocity was around 5 m/s, the removal rates of the hardness ions can be above 98% and the membrane flux can be recovered by 98% with a backwash with pure water and an HCl solution of pH = 2. This work proved that the coupled process is a technically feasible technology for treating FGD wastewater to realize the ZLD.

Comparative Study on the Structural Properties and Bioactivities of Three Different Molecular Weights of Lycium barbarum Polysaccharides.

The molecular weight, the triple-helix conformation, the monosaccharide content, the manner of glycosidic linkages, and the polysaccharide conjugates of polysaccharides all affect bioactivity. The purpose of this study was to determine how different molecular weights affected the bioactivity of the Lycium barbarum polysaccharides (LBPs). By ethanol-graded precipitation and ultrafiltration membrane separation, one oligosaccharide (LBPs-1, 1.912 kDa) and two polysaccharides (LBPs-2, 7.481 kDa; LBPs-3, 46.239 kDa) were obtained from Lycium barbarum. While the major component of LBPs-1 and LBPs-2 was glucose, the main constituents of LBPs-3 were arabinose, galactose, and glucose. LBPs-2 and LBPs-3 exhibited triple-helix conformations, as evidenced by the Congo red experiment and AFM data. Sugar residues of LBPs-2 and LBPs-3 were elucidated by NMR spectra. The polysaccharides (LBPs-2 and LBPs-3) exhibited much higher antioxidant capacities than oligosaccharide (LBPs-1). LBPs-3 showed higher oxygen radical absorbance capacity (ORAC) and superoxide dismutase (SOD) activity than LBPs-2, but a lower capability for scavenging ABTS+ radicals. In zebrafish, LBPs-2 and LBPs-3 boosted the growth of T-lymphocytes and macrophages, enhanced the immunological response, and mitigated the immune damage generated by VTI. In addition to the molecular weight, the results indicated that the biological activities would be the consequence of various aspects, such as the monosaccharide composition ratio, the chemical composition, and the chemical reaction mechanism.

Reduction of Ultrafiltration Membrane Fouling by the Pretreatment Removal of Emerging Pollutants: A Review.

Ultrafiltration (UF) processes exhibit high removal efficiencies for suspended solids and organic macromolecules, while UF membrane fouling is the biggest obstacle affecting the wide application of UF technology. To solve this problem, various pretreatment measures, including coagulation, adsorption, and advanced oxidation, for application prior to UF processes have been proposed and applied in actual water treatment processes. Previously, researchers mainly focused on the contribution of natural macromolecular pollutants to UF membrane fouling, while the mechanisms of the influence of emerging pollutants (EPs) in UF processes (such as antibiotics, microplastics, antibiotic resistance genes, etc.) on membrane fouling still need to be determined. This review introduces the removal efficiency and separation mechanism for EPs for pretreatments combined with UF membrane separation technology and evaluates the degree of membrane fouling based on the UF membrane's materials/pores and the structural characteristics of the cake layer. This paper shows that the current membrane separation process should be actively developed with the aim of overcoming specific problems in order to meet the technical requirements for the efficient separation of EPs.

Membrane bioreactor (MBR) performance in fish canning industrial wastewater treatment

Abstract The fish canning industries produce a large amount of wastewater. The high-strength wastewater from fish processing industry is of great concern worldwide. This type of wastewater is rich in organic matter and has high total dissolved solids (TDS). The elimination of salts is usually expensive and, on the other hand, the high salinity and the seasonal variation of the effluent characteristics make the removal of organic matter difficult using only a biological process. For this purpose, the use of a membrane bioreactor (MBR) process combining both a biological treatment and ultrafiltration membrane separation could be a perfect option for fish canning wastewater treatment. In this work, the performance of a MBR process is investigated to treat the fish canning industry wastewater. The removal efficiency of important parameters such as chemical oxygen demand (COD), five day-biological oxygen demand in (BOD5), total suspended solids (TSS), nitrate (NO3−), total Kjeldahl nitrogen (TKN), orthophosphate (PO43−) and TDS are followed. Experimental results show that the overall removal efficiencies obtained are: 96.6% for COD, 98% for BOD, 99.5% for TSS, 90% for nitrate, 96% for TDS and greater than 97% for TKN and PO43−. These results confirm that combination of both biological treatment and membrane process is regarded as an effective approach to reduce the contaminants in fish canning wastewater. Membrane bioreactor presents several advantages in terms of water resource protection because of the great quality of the treated water that can be reused.

Ultrafiltration Process Yield Study on Aqueous Solution of Total Ginsenosides

Ultrafiltration membrane separation is a technology used to separate large and small molecules in solution by using the principle of membrane screening. This technology can retain the effective components of traditional Chinese medicine extract, remove macromolecular impurities and endotoxin, and meet the requirements of high quality, high efficiency, and low pollution in the modern production of traditional Chinese medicine. The study investigated the impact of 100 KDa molecular weight prepared from different ultrafiltration membrane on the ginsenosides ingredient composition of ginsenosides Rg1, ginsenoside Re, ginsenoside Rf, ginsenoside Rb1, ginsenoside Rg2, ginsenoside Rc, ginsenoside Rb2, ginsenoside Rb3, ginsenoside Rd and ginsenoside Rg3. Changes in retention rates were compared by the component changes in high-performance liquid chromatography in the volume concentrates, par volume of water constant volume diafiltration and 50% ethanol constant volume diafiltration ultrafiltration process. The results demonstrate that the 100 K cellulose ultrafiltration membrane was used for ginsenosides ultrafiltration. The yield and retention were superior to those of the polyethersulfone ultrafiltration membrane with the same molecular weight cutoffs.

Production of succinic acid through the fermentation of Actinobacillus succinogenes on the hydrolysate of Napier grass

BackgroundNapier grass biomass can be hydrolyzed mainly containing glucose and xylose after alkaline pretreatment and enzymatic hydrolysis. This biomass can be fermented using Actinobacillus succinogenes to produce succinic acid. The yield of succinic acid was 0.58 g/g. Because metabolizing xylose could produce more acetic acid, this yield of succinic acid was lower than that achieved using glucose as the sole carbon source.ResultsThe addition of glycerol as a fermentation substrate to Napier grass hydrolysate increased the reducing power of the hydrolysate, which not only increased the production of succinic acid but also reduced the formation of undesirable acetic acid in bacterial cells. At a hydrolysate:glycerol ratio of 10:1, the succinic acid yield reached 0.65 g/g. The succinic acid yield increased to 0.88 g/g when a 1:1 ratio of hydrolysate:glycerol was used. For the recovery of succinic acid from the fermentation broth, an outside-in module of an ultrafiltration membrane was used to remove bacterial cells. Air sparging at the feed side with a flow rate of 3 L/min increased the filtration rate. When the air flow rate was increased from 0 to 3 L/min, the average filtration rate increased from 25.0 to 45.7 mL/min, which corresponds to an increase of 82.8%. The clarified fermentation broth was then electrodialized to separate succinate from other contaminated ions. After electrodialysis, the acid products were concentrated through water removal, decolorized through treatment with activated carbon, and precipitated to obtain a purified product.ConclusionsThe yield of succinic acid was increased by adding glycerol to the hydrolysate of Napier grass. The downstream processing consisting of ultrafiltration membrane separation and single-stage electrodialysis was effective for product separation and purification. An overall recovery yield of 74.7% ± 4.5% and a purity of 99.4% ± 0.1% were achieved for succinic acid.

Optimization of Ultrafiltration Membrane Separation Technology and Characterization of Peptides from Bovine Bone Marrow

Salt extraction and Ultrafiltration membrane (UFM) separation technology of bovine bone marrow protein (BBMP) were optimized, and the structures of proteins and peptides, as well as biological activities were evaluated. The maximum protein content and yield obtained were 57.40 mg/mL, 56.80% respectively by salt extraction under the following conditions: concentration 0.5 mol/L, extraction of 2 times per 3 h; temperature, 45 °C. Maximum membrane flux and protein content reached to 25.29 L/(m2 h), 76.9 mg/mL using UFMs method optimized by the response surface methodology (RSM) at 10 kDa membrane, operation pressure 0.20 MPa; concentration rate 5, and temperature 40 °C. Among them, the 3 kDa permeate part has the highest radical scavenging capacity against DPPH and hydroxyl free radicals (41 ± 0.20%, 53 ± 0.35%, respectively). These isolated parts were characterized by Fourier transform infrared spectrometry (FT-IR), scanning electron microscopy (SEM), atomic force microscope (AFM), sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE), and Liquid chromatography-Mass spectrometer-Mass spectrometer (LC–MS/MS). The key functional groups, molecular weight, and mass data accordance with the UFM separation results. Therefore, the separation of protein and peptides with different molecular weights can be achieved by UFM. This study can provide technical support for the full utilization and scientific application of BBM resources, as well as the technical and theoretical foundation for the development of peptides for potential health foods or drugs supplementary materials.

Ultrafiltration membrane separation technique for drinking water

This study was conducted to examine the suitability of dam water, which constitutes as a source for drinking water, with the ultrafiltration (UF) system, which is a membrane treatment technique. For this purpose, after floating water samples were taken from the dam water approximately once a week in a period of about 3 months, physical, chemical and microbiological analyses of the inlet and outlet waters were carried out, and the results were evaluated. According to the results of the analyses, after the raw water was passed through the UF pilot system, the average inlet turbidity value was 10 nephelometric turbidity units (NTU), while the turbidity dropped to 0.14 NTU when the particles were removed almost completely. The average value of suspended solids in the raw water was 9.5 mg/l, while it was completely removed in the leaving water. It is seen that Escherichia coli, coliform and Enterococcus, which are the most abundant bacteria in water, are completely removed from the raw water. There was not much change in the amount of ions, pH and electrical conductivity in the structure of raw water. According to this research, it is understood that reservoir dam waters are suitable for treatment using the UF membrane technique.

Hydrothermal SiO2 Nanopowders: Obtaining Them and Their Characteristics.

The technological mode of obtaining amorphous SiO2 nanopowders based on hydrothermal solutions is proposed in this study. Polycondensation of orthosilicic acid as well as ultrafiltration membrane separation, and cryochemical vacuum sublimation were used. The characteristics of nanopowders were determined by tunneling electron microscopy, low-temperature nitrogen adsorption, X-ray diffraction, and small-angle X-ray scattering. The scheme allows to adjust density, particle diameters of nanopowders, specific surface area, as well as diameters, area and volume of the pore. Thus, the structure of nanopowders is regulated—the volume fraction of the packing of spherical particles in aggregates and agglomerates, the size of agglomerates, and the number of particles in agglomerates. The pour densities of the nanopowders depend on the SiO2 content in sols, which were 0.02 to 0.3 g/cm3. Nanoparticles specific surface area was brought to 500 m2/g by low temperature polycondensation. Nanoparticle aggregates specific pore volume (0.2–0.3 g/cm3) weakly depend on powders density. The volume fraction of the packing of SiO2 nanoparticles in aggregates was 0.6–0.7. Solid samples of compacted nanopowders had a compressive strength of up to 337 MPa. Possible applications of hydrothermal SiO2 nanopowders are considered.

Investigation of Naphthalene Removal from Aqueous Solutions in an Integrated Slurry Photocatalytic Membrane Reactor: Effect of Operating Parameters, Identification of Intermediates, and Response Surface Approach

A laboratory scale indigenous integrated slurry photocatalytic membrane reactor (PMR), coupling TiO2/UV-C photocatalysis and ultrafiltration (UF) membrane process was evaluated for the removal of naphthalene (NAP)—one of the low molecular weight polycyclic aromatic hydrocarbons (PAHs), frequently detected in municipal and industrial wastewaters. The different operational parameters such as initial NAP concentration (5–25 mg/L), catalyst dosage (0.1–0.9 g/L), and feed solution pH (3–9) were investigated for NAP and total organic carbon (TOC) removal. The experimental results obtained from the batch study of the integrated process showed 92.8% and 90.2% of NAP and TOC removals while the individual processes; UV-TiO2 (76.8% NAP and 56.4% TOC removals) and UF membrane separation process (49.1% NAP removal) exhibited low removal rates for the same experimental conditions. The NAP and TOC removals obtained during continuous flow studies were 93.1% and 91.4% at 180 min and thereafter remained constant up to 560 min of reactor running time. This study also includes the identification of intermediates that are formed after 30 min of operation of PMR. The photocatalytic degradation of NAP followed pseudo-first-order kinetics and the obtained experimental data were analyzed with response surface methodology (RSM) using design expert software.

Metal–organic framework-based ultrafiltration membrane separation with capacitive-type for enhanced phosphate removal

The great potential of ultrafiltration (UF) membranes for phosphate rejection has been challenged by the selectivity-permeability trade-off. Here, we propose a filtration system based on a novel dual-layer UF mixed matrix membrane (MMM) with a capacity for capacitive deionization (CDI), which was fabricated by incorporating NH2-MIL-101 into a polyethersulfone (PES) polymer matrix and the in-situ combination of carbon cloth (CC). The MMM exhibited an improved porosity of 85.52%, a declined water contact angle of 53.25°, and a 5.7% increase in water permeability in comparison to those of the PES membrane due to the hydrophilic and mesoporous NH2-MIL-101 particles. While incorporating the CC provided the non-conductive PES polymer with high electroconductivity. As an electrode, the CC/MMM exhibited a relatively high permeance of 424.63 L/h MPa m2, good antifouling performance, and remarkable phosphate rejection that reached 100% during the 2-h filtration period in the electrically-enhanced dead-end filtration cell. The removal capacity of the cell exceeded 22.51% and 74.0% for the energized CC/PES membrane and uncharged CC/MMM, respectively, due to the superior phosphate adsorption ability of NH2-MIL-101 and enhanced deionization capacity due to the electric field. UF MMM separation coupled with the electrochemical technique exhibited great potential to enhance the selective rejection of phosphate ions at low levels, while maintaining high membrane permeability and shortening the treatment time required by the CDI technique.

Determination of the relative molecular mass distribution of the ultrafiltration fractionation product of lignosulfonate by advanced polymer chromatography

The effects of testing conditions, such as pH and ionic strength of the mobile phase, on the relative molecular mass obtained by advanced polymer chromatography (APC) were investigated systematically. The non-size exclusion effects were discussed for lignosulfonate and its ultrafiltration fractionation product. The relative molecular mass distribution of lignosulfo-nate was well-characterized by an APC system using three columns in series, with a 10 μ L injection volume and 0.1 mol/L NaNO3 as the aqueous mobile phase, at a flow rate of 0.5 mL/min. The relative molecular mass distribution is in the eight molecular mass ranges. Optimized test conditions were used to characterize the ultrafiltration fractionation product of lignosulfonate. The obtained number average relative molecular masses (Mn) of the three components were 40410, 12208, and 1516 Da, indicating that lignosulfonate was well separated into three fractions by ultrafiltration membrane separation. The APC technique presented herein provides the basis for further application of the fractional separation products of lignosulfonate.

Combination of Coagulation-flocculation and Ultrafiltration Processes using Cellulose Acetate Membrane for Wastewater Treatment of Tofu Industry

The tofu industry is generally a household-scale industry so that the efficiency of water used and wastewater treatment are mistreated. Wastewater from tofu industry is very hazardous when discharged directly into the aquatic environment as it contains high organic pollutants which is indicated by high concentrations of BOD (biological oxygen demand), COD (chemical oxygen demand), TSS (total suspended solid), TDS (total dissolved solid) and turbidity. The optimization of wastewater treatment process is needed to meet the quality standards set by the government and also needed to obtain more effective and efficient effluent treatment. The aim of this study is to evaluate the performance of combination coagulation-flocculation and ultrafiltration processes for tofu industry wastewater treatment. The process of pretreatment coagulation and flocculation using poly aluminum chloride (PAC) was conducted to extend the life of the ultrafiltration membrane and improve the performance of ultrafiltration membrane separation. The experimental results showed that TSS and turbidity decreased with precipitation time whereas COD did not significantly change. TDS after coagulation-flocculation has increased due to the addition of PAC. The TSS, TDS, COD and turbidity of wastewater were drastically reduced after experiencing ultrafiltration process. After the ultrafiltration process, the TSS, Turbidity, COD and TDS rejection were 98.8%, 98.1%, 71.0% and 50.6%, respectively.

Production of egg white protein hydrolysates with improved antioxidant capacity in a continuous enzymatic membrane reactor: optimization of operating parameters by statistical design.

This study focuses on the influence of operating conditions on Alcalase-catalyzed egg white protein hydrolysis performed in a continuously stirred tank reactor coupled with ultrafiltration module (10kDa). The permeate flow rate did not significantly affect the degree of hydrolysis (DH), but a significant increase in process productivity was apparent above flow rate of 1.9cm3 min-1. By contrast, an increase in enzyme/substrate (E/S) ratio provided an increase in DH, but a negative correlation was observed between E/S ratio and productivity. The relationship between operating conditions and antioxidant properties of the hydrolysates, measured by three methods, was studied using Box-Behnken experimental design and response surface methodology. The statistical analysis showed that each variable (impeller speed, E/S ratio, and permeate flow rate) had a significant effect on the antioxidant capacity of all tested systems. Nevertheless, obtained response functions revealed that antioxidative activity measured by DPPH, ABTS and FRAP methods were affected differently by the same operating conditions. High impeller speeds and low permeate flow rates favor ABTS while high impeller speeds and high permeate flow rates had a positive effect on the DPPH scavenging activity. On the other hand, the best results obtained with FRAP method were achieved under moderate operating conditions. The integration of the reaction and ultrafiltration membrane separation in a continuous manner appears to be a right approach to improve and intensify the enzymatic process, enabling the production of peptides with desired antioxidant activity.

Classification and Analysis of Dissolved Organic Matter in 2-Buternal Manufacture Wastewater

The dissolved organic matters from 2-buternal manufacture wastewater were fractionated into seven fractions by ultra-filtration membrane separation. The amounts and structural compositions of organic compounds in different molecular weight ranges were characterized by dissolved organic carbon (DOC), ultraviolet spectrum (UV), Fourier transform infrared spectrometer (FT-IR) and gas chromatography with mass spectrometry (GC-MS). The results showed that the fraction of molecular weight less than 1×103 had the largest proportion in the wastewater, and occupied 88.57% of the DOC. There were 27 kinds of compounds qualitatively analyzed by GC-MS, mainly including aldehyde, ketone, ester, alcohol, phenol, organic acid, alkane and other heterocyclic compounds. The proportions of compounds of peak area accounting for total peak area of organic matters were 6.9%, 5.3%, 35.4%, 13.2%, 4.6%, 0.4%, 1.7% and 16.8% respectively, adding up to 84%. The analysis of UV and FT-IR demonstrated that the spectral absorptive characteristics of organic compounds from different fractions were not significantly different. The fractions contained carbonyls, hydroxys and aromatic compounds, which was consistent with the qualitative analysis of GC-MS. The results of this study provide an important guidance for the development and optimization of 2-buternal manufacture wastewater treatment process.