Effect of Low Temperatures on the Performance of an Anaerobic Baffled Reactor (ABR)

The effect of a decrease in operating temperature on the performance of two 10 dm³ anaerobic baffled reactors (ABR) was examined in terms of steady state chemical oxygen demand (COD) removal efficiency. To minimise variations, and have a totally biodegradable feed, a synthetic carbohydrate (sucrose)–protein (meat extract) substrate was used. The reactors were operated at 20 h hydraulic retention time (HRT), 4 g dm⁻³ COD, and 35°C as a base-line condition. Because of their different histories, the reactors responded differently to a decrease in operating temperature to 25°C. Reactor 1 remained stable at 97% COD removal, whereas Reactor 2 decreased to 93% removal, but rose to 97% after adding an effluent recycle of 0·25. At 15°C, the efficiency of Reactor 1 dropped to 75%, while the removal of Reactor 2 declined to 83%, and no improvement in efficiency occurred with an effluent recycle at 0·25. At 25°C, the decreased rate of catabolism of the slow-growing syntrophs and methanogens resulted in a shift of the volatile fatty acids (VFA) peak to the second compartment. However, the biomass present in the reactor prevented VFAs breaking through in the effluent. Nevertheless, at 15°C VFAs were present in the effluent, perhaps due to the lower rates of metabolism and an increase in the K_s for VFAs. Finally, at 15°C part of the increase in the effluent COD was due to the enhanced production of soluble microbial products (SMP), or a decrease in their metabolism, with these compounds constituting some 10% of the inlet COD. © 1997 SCI.     

Purification and Concentration of Caustic Mercerization Wastewater by Membrane Processes and Evaporation for Reuse

A membrane-based treatment strategy was developed for purifying the highly alkaline textile mercerization wastewater. 0.2-μm MF and 100 kDa UF membranes were evaluated as pretreatment alternatives before 10 kDa UF and 200 Da NF membranes. Turbidity was almost totally removed by both pretreatment options, while UF (100 kDa) showed higher COD retention than MF. In total recycle mode of filtration, fouling of both UF and MF membranes were 80% reversible by physical and almost totally reversible (≥ 97%) by chemical cleaning. In the second stage filtrations applied to the pretreated wastewater samples, NF could yield high (97-98%) COD retentions and low permeate COD concentrations (≤ 22 mg/L), while 10 kDa UF could only reduce the COD concentration to 150 mg/L. While no NaOH was lost in the MF+UF process, the use of NF as second stage resulted in 12-17% NaOH retention. The permeate flux in all second stage processes were stable, implying that the majority of the feed components that would cause fouling had been removed in the pretreatment stages. Permeate of the MF+NF sequence was concentrated by evaporation with no foaming problems, showing that the hybrid process can be applied to recycle a purified and concentrated caustic stream to the mercerization process.     

Separation of Tea Saponin by Two-Stage Continuous Foam Fractionation

A technology of two-stage continuous foam fractionation for tea saponin recovery was studied for increasing both the enrichment ratio and the recovery percentage. In the first stage, the effect of air flow rate, the initial pH, the feed flow rate, and the feed position were studied at a temperature of 60°C. The results showed that when the conditions of the first stage were at a temperature of 60°C, air flow rate 150 mL/min, pH 5.3, feed flow rate 1.92 mL/min, and feed position at the interface between the liquid phase and the foam phase, the enrichment ratio, and the recovery percentage of tea saponin were 4.02 and 56.4%, respectively, and the effluent solution was added to the second stage as the initial solution. When the conditions of the second stage were at a temperature of 30°C and an air flow rate of 300 mL/min, the recovery percentage of tea saponin reached 47.6%, and the foamate was added to the first stage as feed solution. The total recovery percentage of tea saponin reached 86.3% by the two-stage continuous foam fractionation.     

NMR study of the stabilities of urea–formaldehyde resin components toward hydrolytic treatments

The solid residues of nine urea–formaldehyde (UF) resins after hydrolytic treatment at pH4 and 86°C for 20 h and the solid residues of one UF resin after eight different hydrolytic treatments were examined by ¹³C-CP–MAS NMR. The relative stability toward hydrolysis of each structural component in each UF resin was established for various hydrolytic conditions. In general, UF resins prepared from starting mixtures with a formal F/U molar ratio of 1.00 show a high degree of stability toward hydrolysis. Cross-linking methylene linkages in the UF resins show a higher susceptibility to hydrolytic treatments at pH 4 and 86°C than do linear methylene linkages. UF resins prepared with an F/U molar ratio of 2.00 are susceptible to hydrolysis at pH 4 and 86°C. Dimethylene ether linkages, methylols attached to tertiary amides, and poly(oxymethylene glycol) moieties are probably the main formaldehyde emitters in UF resin products. © 1994 John Wiley & Sons, Inc.     

Separation of Liquiritin from Glycyrrhizic Acid in Licorice Root Extract by Nanofiltration Membrane

The aim of this work was to study the separation of liquiritin (LQ) from glycyrrhizic acid (GA), in licorice aqueous solutions using nanofiltration (NRT-7450) membrane. The LQ and GA components are the main active ingredients of licorice root extract with various pharmacological effects, The effects of transmembrane pressure, feed temperature, feed pH, and cross-flow velocity on permeate flux and recovery were determined. A lab scale cross-flow set up using flat-sheet configuration membrane was employed for all experiments. SEM micrographs showed the changes in the fouled surface during operating time. The applied transmembrane pressure, feed temperature, feed pH, and cross-flow velocity were varied from 4 to 10 bars, 30 to 40°C, 3 to 9, and 0.8 to 3.1 m s^?1 respectively. The obtained recoveries for GA and LQ varied between 0.65 to 1.86% and 16.89 to 41.65%, respectively. The optimum operating conditions for separation LQ from GA in licorice aqueous solutions using NRT-7450 nanofiltration membrane were 1.8 m s^?1cross-flow velocity, 8 bars transmembrane pressure, 40°C of feed temperature and pH 7.     

Nanofiltration of Bleaching Pulp and Paper Effluents in Tubular Polymeric Membranes

Abstract

A systematic investigation of the nanofiltration (NF) of alkaline bleaching effluent (E₁) from the pulp and paper industry is carried out through a first assessment of NF of model systems, namely, solutions of salts—NaCl and Na₂SO₄—and organic solutes—glucose, saccharose, and raffinose—which develop membrane–solute(s) interactions similar to those developed by the bleaching effluent. The ampholytic polymer of the membrane active layer, under controlled feed conditions, develops a surface charge distribution which determines the membrane performance. The verification of the effects of the anion valence and the feed concentration on the salts rejections, in accordance with the Donnan exclusion principle, is an important feature of this work. For the bleaching effluent, the NF performance is strongly dependent on the pH due to the influence of this parameter on the membrane surface charge. The contribution of this work toward the optimization of the NF operating conditions would allow for future scale-up of this separation process for E₁ effluent purification and water recovery in the pulp and paper industry.     

Hydrolytic degradation of cured urea–formaldehyde resin

The degradation of cured urea–formaldehyde (UF) resin in aqueous suspension was investigated by gravimetric analysis of the changes in the content of nonextractable low-molecular components. In acid conditions (pH 4.0) at 47°C the consecutive processes of post-curing and of polymer break-down (activation energy 90 kJ/mol) are detectable whereas at 80°C and 97°C only the formation of the extractable hydrolysates is observed. The degraded polymer contains less carbonyl groups than does the original resin substrate as shown by means of infrared (IR) analysis. In contrast to the results of the tests carried out in acid conditions, in neutral and basic aqueous media the hydrolytic decomposition of UF macromolecular network is less significant. During the hydrolysis of UF polymer at 30°C–45°C the concentration of formaldehyde released from the resin to the aqueous phase increases initially (2 days) at a relatively high rate both at acid and alkaline pH. Then its growth slows down but is still detectable in acid conditions, whereas in basic medium no further liberation of HCHO is observed.     

Ultrafiltration and nanofiltration membranes applied to the removal of the pharmaceuticals amoxicillin,naproxen, metoprolol and phenacetin from water

BACKGROUND: In the removal of pharmaceuticals present in aquatic systems by membrane processes, some important issues must be explored in order to obtain a better knowledge of the global process. Among these issues, a better understanding of the influences of the operating parameters on the membrane flux, an analysis of membrane resistances and fouling, and determination of the removal of specific substances, must be studied. RESULTS: Four selected pharmaceuticals (amoxicillin, naproxen, metoprolol and phenacetin) were subjected to ultrafiltration (UF) and nanofiltration (NF) processes for their removal from several water matrices. The determined permeate fluxes at the steady state were affected by the main operating conditions: molecular weight cut‐off (MWCO) of the membrane, transmembrane pressure TMP, cross‐flow velocity and temperature. The retention coefficients with the UF membranes followed the sequence naproxen > metoprolol > amoxicillin > phenacetin, and with the NF membranes, followed the trend: amoxicillin > naproxen > metoprolol > phenacetin, due to the role of other mechanisms such as size exclusion and electrostatic repulsion. In the case of the selected water matrices, the retention coefficient was referred to some quality parameters (total organic carbon, chemical oxygen demand and absorbance at 254 nm), leading to moderate (UF) or high (NF) removals of the organic matter content. CONCLUSIONS: The NF CK membrane achieved the highest retention of these pharmaceuticals (excepting phenacetin), and provided retentions for quality parameters around 80% in the four water systems tested. Copyright © 2011 Society of Chemical Industry     

Effect of Processing Parameters on Gossypol Levels in Protein Isolates from Cottonseed by Alkali Extraction/Ultrafiltration/Diafiltration

Abstract

Three different varieties of cottonseed (S1, S2, and S3) were dehulled, separated, and defatted by hexane extraction under controlled conditions (moisture < 3%, temperature < 50°C). The defatted flours, designated as CS1 and CS2 (glandless) and CS3 (glanded), which had free-gossypol levels of 0.15, 0.28, and 0.68%, respectively, and protein levels of 61.4, 61.7, and 58.5%, respectively, were taken for aqueous extraction using NaOH as the alkali in the presence of Na₂S₂O₄, a reducing agent. The extract, after centrifugation, was immediately taken for ultrafiltration (UF) using polysulfone membranes, followed by diafiltration (DF). Experiments at 40 and 60°C, to examine the UF performance and gossypol binding effect, were carried out with strict control of the feed pH. The intensely yellow-colored permetes, probably due to alkali-soluble sodium gossypolate and gossypol-like pigments, were checked for color intensity as a qualitative measure in ultrafiltration concentrate. The intensity was found to be on the decline, less during UF and more during diafiltration. The final UF/DF dried products were analyzed for free gossypol (FG), bound gossypol (BG), total gossypol (TG), and protein. Protein isolates (PI) from Samples CS1 and CS2 were found to have very low FG, with little effect of the processing conditions on binding of gossypol with the protein. PI from Sample CS3 was found to have slightly high FG with relatively high BG. The effect of temperature was found to result in high permeation rates without much effect on the rejection of the components and the binding of gossypol. The gossypol and protein contents of three UF/DF dried proteins were 0.006, 0.012, and 0.041% FG, and 89.4, 90.1, and 86.4% protein. The colors of PI from Samples CS1 and CS2 were lighter while PI from Sample CS3 was relatively darker.     

Preparation,morphologies, and properties of positively charged quaternized poly(phthalazinone ether sulfone ketone) nanofiltration membranes

Positively charged quaternized poly(phthalazinone ether sulfone ketone) (QAPPESK) nanofiltration (NF) membranes were prepared from chloromethylated poly(phthalazinone ether sulfone ketone) by the dye/wet phase inversion method with N‐methyl‐2‐pyrrolidone (NMP) and N,N‐dimethylacetamide (DMAc) as solvents. The effects of the ratio of NMP to DMAc, the evaporation time, the evaporation temperature, and the coagulation temperature on membrane performance were evaluated by the orthogonal design method. The results showed that the optimal preparation conditions were an NMP/DMAc ratio of 2/8, an evaporation time of 5 min at 70°C, and a coagulation temperature lower than 5°C. The effects of the additive type and concentration on the QAPPESK NF membrane cross‐section morphology and performance were investigated in detail. Furthermore, QAPPESK NF membranes exhibited good thermal stability with stable membrane performance for 120 h at 60°C. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of hydrolysis degree of soy protein isolate on the structure and performance of hydrolyzed soy protein isolate/urea/formaldehyde copolymer resin

The hydrolyzed soy protein isolate (HSPI) with different hydrolysis degree was applied to modify urea‐formaldehyde resins (UF) via copolymerization process. The properties of HSPI were characterized by attenuated total reflection Fourier transform infrared spectroscopy (ATR‐FTIR) and TGA. The results show that HSPI with different hydrolysis degree is obtained. ¹H NMR and ATR‐FTIR spectra indicate that HSPI with different hydrolysis degree can incorporate into the structure of cured and uncured UF. The UF modified with higher hydrolysis degree of HSPI possess more stable units and contribute to the lower exothermic peak temperature in DSC curves. The bonding strength of HSPI modified UF increases as the hydrolysis degree of HSPI increases at the hot‐press temperature of 120°C and decreases at the hot‐press temperature of 150°C. The best bonding strength is 1.53 MPa at the hot‐press temperature of 135°C and improved 56.12% compared with UF. In addition, the formaldehyde emission is dramatically reduced. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41469.     

Anaerobic filters for municipal wastewater treatment

Four laboratory reactors (two downflow rock, one downflow wood, and one horizontal flow rock) were operated at 35–38°C for an initial period of six months and later at 23-27°C, with primary clarifier effluent (PCE) from a municipal wastewater treatment plant as the feed to the reactors. A pilot-scale rock medium reactor located at a municipal wastewater treatment plant was operated at 24–28°C initially in the downflow mode and later at 18-20°C in the upflow mode with PCE as feed. The laboratory study showed that PCE can be successfully treated using both downflow and horizontal flow anaerobic filters, with similar performance under both flow modes. Bench-scale filters obtained better BOD and SS removals compared to the pilot-scale filter.     

Study of hybrid isocyanate and high-mono-hydroxymethyl urea content urea-formaldehyde resins

Based on the difference in the reaction rate of different groups of urea-formaldehyde resins and isocyanate resins, this study designed two different urea-formaldehyde resins: a normal urea-formaldehyde resin (UF) and one with high mono-hydroxymethylurea content (UF*) to react with polymeric methylene diphenyl diisocyanate (pMDI) resin. The difference in mono- and di-hydroxymethyl urea content between UF and UF* resins was analyzed by nuclear magnetic resonance (NMR) spectroscopy, and results showed that the mono-hydroxymethyl urea content of the UF* resin was much higher than that of the conventional UF resin. The fourier transform infrared spectrometer (FTIR) analysis of differences between UF* and UF resin showed that the UF* process did not change the main structure of the conventional urea formaldehyde resin. Differential scanning calorimeter (DSC) analysis showed that the curing temperature of the hybrid UF*-pMDI resin was reduced 27.3°C compared to that of the UF-pMDI resin. When these hybrid resins were used to bond plywood respectively, test results showed that the UF*-pMDI resin improved the dry and wet bonding strength by 2.6% and 3.9%, respectively, compared with the UF-pMDI resin under the condition of hot pressing time (3 min) and temperature (140°C), meeting the requirement of Chinese standard of GB/T 9846–2015 for Class III board. This study provides a new path for further improving the performance and design of hybrid resins based on isocyanate and urea-formaldehyde resin.     

Spray Drying of Yogurt: Optimization of Process Conditions for Improving Viability and Other Quality Attributes

Plain yogurt was subjected to spray drying to determine the optimum processing conditions that yield maximum survival ratio of lactic acid bacteria, maximum overall sensory attributes, minimum color change, and acceptable moisture content. The inlet (150–180°C) and outlet air temperatures (60–90°C) and the feed temperature (4–30°C) were the independent factors. A pilot-scale spray dryer was used to conduct a set of drying experiments where the process conditions were selected according to central composite rotatable design (CCRD). The resulting yogurt powder at each condition was also subjected to the measurement of some physical properties (water activity, titratable acidity [lactic acid, %] and pH) to determine the effects of spray-drying conditions. The morphological structure of the powder was inspected by scanning electron microscopy (SEM) analysis. Optimization by the application of the desirability function method resulted in air inlet temperature of 171°C, air outlet temperature of 60.5°C, and feed temperature of 15°C as the optimum processing condition. The mathematical optimum condition was experimentally verified.     

N, O-羧甲基壳聚糖复合纳滤膜的制备及其对酒厂发酵废水的截留效果

N, O-carboxymethyl chitosan （NOCC） composite nanofiltration （NF） membranes were prepared by coating and cross-linking. The fermentation effluent from a wine factory was treated with the resulting NOCC/polysulfone （PSF） composite NF membranes. The permeate flux and the removal efficiencies of the resulting NF membranes for the color, chemical oxygen demand （CODcr）, total organic carbon （TOC）, and conductivity of the fermentation effluent were investigated in relation to the driving pressure, the feed flow, and the operation time. The permeate flux and the removal efficiencies were found to increase with the increase of the driving pressure or the feed flow. At 0.40 MPa and ambient temperature the removal efficiencies were 95.5%, 70.7%, 72.6%, and 31.6% for color, CODcr, TOC, and conductivity, respectively. The membrane was found to be stable over a 10-h ooeration for the fermentation effluent treatment.     

The influence of degreasing agents used at car washes on the performance of ultrafiltration membranes

The influence of washing chemicals used at car washes on the flux and retention of three ultrafiltration (UF) membranes has been studied. Eleven commercial degreasing agents, two shampoo agents and a wax were included in the investigation. The membrane performance when treating waste water collected at a car wash at different times of the year was also studied. The retention of the different chemicals varied greatly, but there was no significant difference in COD retention among the three UF membranes. The highest flux was observed when treating the alkaline degreasing agents and the shampoo solutions. The flux and COD retention when treating the waste water from the car wash were 30–50 l/m ² h and 60%, respectively. One of the low-retention degreasing agents was treated by nanofiltration (NF). The retention was significantly higher when using NF, but the COD concentration in the permeate was still too high to allow the permeate to be discharged without further treatment.     

多孔陶瓷膜用于碳量子点的分离与纯化

尺寸分布均一的碳量子点由于其良好的光学特性,在光电设备、离子检测、纳米传感器、生物成像和催化剂等领域具有广阔的应用前景。采用陶瓷膜“超滤-纳滤”双膜法,对微波合成的碳量子点进行分离和纯化。研究了pH对碳量子点料液荧光强度和粒径分布的影响。在pH=3时,碳量子点分散较好,荧光强度较高。陶瓷超滤膜可以有效截留碳量子点料液中的大颗粒杂质,渗透侧的碳量子点平均粒径约为2 nm,分散良好,无团聚现象。陶瓷纳滤膜对碳量子点具有良好的截留性能,在浓缩和水洗过程中可以进一步去除料液中的小分子杂质。经双膜法处理后,发射光谱由多峰分布变为单峰分布,且峰宽变窄,碳量子点的发光纯度得到了明显提高。     

Performance evaluation of polyamide nanofiltration membranes for phosphorus removal process and their stability against strong acid/alkali solution

In this study,a quantitative performance of three commercial polyamide nanofiltration(NF) membranes(i.e.,NF,NF90,and NF270) for phosphorus removal under different feed conditions was investigated.The experiments were conducted at different feed phosphorus concentrations(2.5,5,10,and 15 mg·L~(-1)) and elevated pHs(pH 1.5,5,10,and 13.5) at a constant feed pressure of 1 MPa using a dead-end filtration cell.Membrane rejection against total phosphorus generally increased with increasing phosphorus concentration regardless of membrane type.In contrast,the permeate flux for all the membranes only decreased slightly with increasing phosphorus concentration.The results also showed that the phosphorus rejections improved while water flux remained almost unchanged with increasing feed solution pH.When the three membranes were exposed to strong pHs(pH 1.5 and 13.5) for a longer duration(up to 6 weeks)it was found that the rejection capability and water flux of the membranes remained very similar throughout the duration,except for NF membrane with marginal decrement in phosphorus rejection.Adsorption study also revealed that more phosphorus was adsorbed onto the membrane structure at alkaline conditions(pH 10 and 13.5) compared to the same membranes tested at lower pHs(pH 1.5 and 5).In eonelusion,NF270 membrane outperformed Nf and NF90 membranes owing to its desirable performance of water flux and phosphorus rejection particularly under strong alkali solution.The NF270 membrane achieved 14.0 L·m~(-2)·h~(-1) and 96.5% rejection against 10 mg·L~(-1) phosphorus solution with a pH value of 13.5 at the applied pressure of 1 MPa.     

Hemicelluloses separation from caustic-containing process stream by ultrafiltration

The present work aimed to study the performance of ultrafiltration (UF) membranes for hemicelluloses separation, from a caustic-containing highly alkaline, cellulose purification solvent stream of viscose rayon production process, and to understand the membrane behaviour, effect of multiple use cycle, identify potential performance drawbacks and propose possible solutions. Screening experiments showed that an UF membrane with a nominal molecular weight cut-off value of 3 kDa can be used to separate hemicelluloses from alkaline process stream. UF membrane was found to be prone to performance deterioration with time due to fouling. Higher feed temperature helped in improving the membrane flux values while maintaining hemicelluloses retention.     

Silicate and zirconium phosphate modified Nafion/PTFE composite membranes for high temperature PEMFC

The PEMFC performance of MEAs prepared from Nafion-212 (thickness 50 μm, Du Pont Co), porous poly(tetrafluoro ethylene) (PTFE, thickness 15 ~ 18 μm) film reinforced Nafion (NF, thickness 20 ± 2 μm), silicate hybridized NF (NF-Si, thickness 21 ± 2 μm), and zirconium phosphate hybridized NF (NF-Zr, thickness 21 ± 2 μm) membranes were investigated at 110 °C/ 51.7% RH, 120 °C/ 38.2% RH, and 130 °C/ 28.6% RH. We show PEMFC performances of these MEAs decrease in the sequence of: NF-Zr> NF-Si> NF> Nafion-212. The NF, NF-Si, and NF-Zr membranes have lower membrane thickness and lower Nafion content and require less water for proton transport than Nafion-212 at temperatures above 110 °C, and thus have higher conductivity and better PEMFC performance than Nafion-212. Incorporating silicate and zirconium phosphate into NF membranes enhances water retention of membranes at temperatures above 110 °C and improves PEMFC performances. Besides enhancing water retention, incorporating zirconium phosphate into membranes also provides more routes for proton transport via H⁺ exchange between H₃ ⁺O and HPO₄-Zr- and between H₂ ⁺PO₄-Zr- and HPO₄-Zr-. Thus NF-Zr has a higher conductivity and better PEMFC performance than NF and NF-Si.