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Separation and Purification Technology (v.52, #2)
Pervaporation of benzene/cyclohexane mixtures through CMS-filled poly(vinyl alcohol) membranes by Honglei Sun; Lianyu Lu; Fubing Peng; Hong Wu; Zhongyi Jiang (pp. 203-208).
The effect of carbon molecular sieve (CMS) incorporated into poly(vinyl alcohol) (PVA) on pervaporation of benzene/cyclohexane mixtures was studied. The characterization results showed that filling of CMS decreased the hydrogen bond interaction among PVA polymer chains and made chains more flexible and relaxed, which resulted in decreasing of PVA membrane crystallinity, and thus created higher free volume in the membranes. CMS filling effectively increased DS values of membranes in almost whole feed composition range. Due to the more relaxed polymer chain packing and stronger sorption ability, the permeation flux of CMS-filled PVA membranes increased effectively, but excessive filling would decrease the permeation flux. With increase of benzene weight fraction, operating temperature and feed flow rate, the permeation flux of benzene increased, while the separation factor decreased. Compared with unfilled PVA membrane (flux of benzene 21.87g/m2h, separation factor 16.7), flux of benzene of PVA-CMS-06 membrane (mass ratio of CMS to PVA was 6%) increased remarkably to 59.25g/m2h and separation factor increased to 23.21.
Keywords: Pervaporation; Carbon molecular sieve; Poly(vinyl alcohol); Benzene; Cyclohexane
Selective absorption of H2S from gas mixtures into aqueous solutions of blended amines of methyldiethanolamine and 2-tertiarybutylamino-2-ethoxyethanol in a packed column by Jian-Gang Lu; You-Fei Zheng; Du-Liang He (pp. 209-217).
In this work, an experimental investigation for selective absorption of H2S from gas-mixed streams into an aqueous blend of methyldiethanolamine (MDEA) and 2-tertiarybutylamino-2-ethoxyethanol (TBEE) in a packed column at atmospheric pressure and a constant liquid flowrate was performed. TBEE, a severe sterically hindered amine, was added into MDEA to form the blended amines. The effect of H2S loading of lean-solution, temperature of lean solution, the mole ratio of CO2/H2S in gas mixtures, and the gas flowrate on absorption performance were investigated by means of the evaluation of removal efficiency and selectivity factor. Based on the mass balance, overall volumetric mass-transfer coefficient ( KG a) of H2S was determinated. The performance of simultaneous absorption of CO2 and H2S into the aqueous blend of MDEA and TBEE is compared with that of the single aqueous solution of MDEA. The effect of gas flowrate, H2S and CO2 concentration of gas-phase on KG a of H2S were studied also. The aqueous blend of MDEA and TBEE has been found to be an efficient mixed solvent for selective H2S removal. The experimental results also testified the advantages of severe sterically hindered amines (e.g., TBEE) over traditional amines in selective H2S absorption. This work provides the useful results for the aqueous blended amines containing sterically hindered amines to be extensively applied in the field of selective H2S removal.
Keywords: Gas absorption; Selective H; 2; S removal; Blended alkanolamines; Methyldiethanolamine; 2-Tertiarybutylamino-2-ethoxyethanol
The effects of current density and phosphate concentration on phosphate removal from wastewater by electrocoagulation using aluminum and iron plate electrodes by Şahset İrdemez; Nuhi Demircioğlu; Yalçın Şevki Yıldız; Züleyha Bingül (pp. 218-223).
In this study, effects of initial phosphate concentrations and current densities on the phosphate removal by electrocoagulation using either aluminum or iron plate as electrodes were investigated.In the experiments, the results indicate that increase of initial phosphate concentration has reduced removal rate. But energy consumption has decreased because of wastewater conductivity increase. Efficiency of 100% using aluminum electrodes has been obtained in all of initial phosphate concentration, whereas removal efficiency has decreased by increasing initial phosphate concentration in iron electrodes.Either aluminum or iron electrodes were used to investigate effect of current density. It was found that removal rate and removal efficiency have increased by increasing current density. But, system energy consumption has increased by increasing current density.It can be said that aluminum electrode is more suitable than iron electrode by taking into account either removal rate and removal efficiencies on phosphate removal by electrocoagulation.Consequently, electrocoagulation is comparatively suitable process for phosphate removal from wastewater.
Keywords: Aluminum electrode; Electrocoagulation; Electrochemical treatment; Iron electrode; Phosphate removal
Multicomponent H2/CO/CO2 adsorption on BaZSM-5 zeolite by Sang Kompiang Wirawan; Derek Creaser (pp. 224-231).
A step change response method was used to compare the adsorption behavior of CO2 with that of binary H2/CO2, CO/CO2 and ternary H2/CO/CO2 gas mixtures on BaZSM-5 zeolite. Experiments were conducted with adsorption temperatures from 323 to 473K and a total pressure of 1atm. A comparison between single-component CO and CO2 adsorption on BaZSM-5 was also made. The CO2 adsorption capacity was significantly higher than that of CO on BaZSM-5, due to the higher polarity and acidity of CO2. The CO2 adsorption capacity of BaZSM-5 for a H2/CO2 gas mixture was higher than that for single-component CO2 adsorption. TPD and FTIR results showed that the quantity of strongly adsorbed species increased significantly for CO2 adsorption in the presence of H2, compared to that for single-component CO2 adsorption. This effect appears to be due to an interaction between H2 and CO2 on the surface with the Ba cation to form stronger carbonate species. When the CO partial pressure was increased at constant CO/CO2 total pressure, a slight decrease in CO2 adsorption was observed compared to that for single-component CO2 adsorption. On the other hand, a significant decrease in CO uptake could be seen with increasing CO2 uptake. Thus, the smaller adsorption capacity for CO/CO2 gas mixtures compared to each single-component adsorption was probably due to the competitive adsorption of CO2 and CO molecules on weak physisorption sites. The CO adsorption could be described by a single-site Langmuir model and an extended Langmuir model could be applied to describe the CO/CO2 adsorption on BaZSM-5.
Keywords: Multicomponent adsorption; BaZSM-5; Step change response; Langmuir adsorption model; FTIR spectra
On nanofiltration Desal-5 DK performances with calcium chloride–water solutions by Carolina Mazzoni; Serena Bandini (pp. 232-240).
A study on the performances of nanofiltration Desal-5 DK membranes is presented in the case of CaCl2–water mixtures. Extensive experimentation at room temperature is performed to characterize the membrane separation efficiency in a wide range of electrolyte composition (1–500mol/m3) at various feed pH values (5–6.5). The applied pressure in the feed side is kept in the range from 3 to 30bar.The effect of pH and concentration is investigated both on salt rejection and on total volume flux. The results are exhaustive and useful to draw general trends. Calcium rejection increases as the concentration increases and decreases as the feed pH increases. However, as the salt concentration increases, calcium rejection goes through a maximum value; at asymptotic conditions the maximum value is located at a concentration close to 100mol/m3CaCl2. The effect occurs in the whole pressure range investigated and it is much more remarkable at the higher pH values.Volumetric membrane charge values corresponding to each operative conditions experimented are calculated through the “integral� version of the Donnan Steric Pore Model and Dielectric Exclusion. Membrane charge is obtained as an increasing function with pH, whereas it shows an unimodal behaviour in the concentration range investigated. At low concentrations the membrane charge is negative, it switches to positive values as the concentration increases and finally decreases till to negative values at higher concentrations. Amphoteric behaviour of polyamide Desal membranes is re-confirmed, although a remarkable dependence of the points of zero charge is obtained upon salt concentration.
Keywords: Nanofiltration; pH; Electrolytes; Membrane charge; Amphoteric behaviour
The effect of polyacrylamide charge density and molecular weight on the flocculation and sedimentation behaviour of kaolinite suspensions by M.S. Nasser; A.E. James (pp. 241-252).
The effects of the surface charge and molecular weight of anionic and cationic polyacrylamide (PAM) on the surface chemistry, settling rates, floc sizes and sediment bed compactness of kaolinite suspensions has been investigated at pH 7. At optimum polymer concentrations, the kaolinite floc sizes were larger and the settling rates greater in the presence of anionic PAM than cationic PAM. Optimum flocculation for these anionic flocculants was linked to a small reduction in the magnitude of the zeta potential. In the case of cationic polymer, the optimum flocculation was linked to the reduction of the magnitude of the zeta potential to zero by charge neutralization. The results show that the magnitude of the compressive yield stress Py( Ï•) is strongly dependent upon the floc structure; with greater compressive yield stress being observed for the cationic PAM than for the anionic PAM. The difference in the compression sensitivity of the flocculated slurries may be attributed to floc structure-related adsorption. Cationic polymer chains adsorb via hydrogen bonding interactions between the silanol and aluminol OH groups at the particle surface and polymer's primary amide functional groups, these electrostatic attractions between the positively charged polymer and the negatively charged kaolinite produce strong and less compressible floc structures. For anionic PAM, however, although the adsorption still occurs through hydrogen bonding between the silanol and aluminol OH groups at the particle surface and polymer's primary amide functional groups, the interactions appear to be weakened as a consequence of electrostatic repulsion between the negatively charged polymer and negatively charged kaolinite surface. These repulsive forces allow the polymer molecules to be extended and produce loops and tails, which lead to the formation of large open-structure flocs having less resistance to compression loads and, subsequently, produce compact sediments having greater gel points Ï•g following the application of some compression load. It is found that the compressive yield stress and gel point are important factors that should be considered when selecting the type of polyelectrolyte for use in a particular solid liquid separation. A strong correlation between the polymer type and flocculation, compression sensitivity of flocs and sedimentation behaviour of kaolinite is established.
Keywords: Kaolinite flocculation; Polyacrylamide; Charge density; Compressive yield stress; Gel point
Biosorption of mercury on magnetically modified yeast cells by Handan Yavuz; Adil Denizli; Hakan Güngüneş; Mirka Safarikova; Ivo Safarik (pp. 253-260).
Brewer's yeast (bottom yeast, Saccharomyces cerevisiae subsp. uvarum) cells were magnetically modified using water based magnetic fluid stabilized perchloric acid. The magnetically modified yeast cells were characterized by scanning electron microscopy (SEM) and electron spin resonance (ESR). Hg2+ biosorption-desorption properties of magnetically modified yeast cells from synthetic solutions were utilized in batch system. The biosorption process was fast; 80% of biosorption occured within 60min and equilibrium was achieved at around 90min. The maximum Hg2+ biosorption capacity was obtained to be 114.6mg/g at 35°C. The suitability of the Langmuir, Freundlich and Redlich-Peterson adsorption models to the equilibrium data was investigated for mercury-biosorbent system. The results were well fitted to the Langmuir isotherm. The applicability of two kinetic models including pseudo-first order and pseudo-second order model was estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium capacity and correlation coefficients. Results suggest that chemisorption processes could be the rate-limiting step in the biosorption process. The yeast biomass can be easily regenerated by 0.1M HNO3 with higher effectiveness. Biosorption of heavy metal ions from artificial wastewater was also studied. The biosorption capacities are 29.9mg/g for Cu2+, 76.2mg/g for Hg2+, 14.1mg/g for Ni2+ and 11.8mg/g for Zn2+.
Keywords: Mercury removal; Magnetic biosorbents; Yeast; Heavy metal removal
Effect of carbon molecular sieve on phenol formaldehyde novolac resin based carbon membranes by Xiaoyong Zhang; Haoquan Hu; Yudong Zhu; Shengwei Zhu (pp. 261-265).
Carbon molecular sieve membrane (CMSM) was prepared by dip coating a phenol formaldehyde novolac resin (PFNR) based green membrane support with an ethanol solution containing PFNR and carbon molecular sieve (CMS). X-ray diffraction and nitrogen adsorption isotherms were employed to characterize the carbon structures. The results indicated that the CMSM shows high selectivity for separation of gases like O2/N2 and H2/CH4 system from pure gas permeation experiments. The permeation rate of H2, O2, and CO2 increases with the addition of CMS to the coating agent, while that of N2 and CH4 decreases. Correspondingly, the ideal separation factor of H2/CH4 enhances from 316 with a 50wt.% PFNR ethanol solution as coating agent to 468 with a 50wt.% PFNR ethanol solution involving CMS as coating agent, representing an increase of 48%. The addition of CMS redounds to the permeation of O2 and reduction of defect in the carbon membrane.
Keywords: Carbon membrane; Gas separation; Carbon molecular sieve; Phenol formaldehyde novolac resin
Investigation of nanofiltration as a purification step for lactic acid production processes based on conventional and bipolar electrodialysis operations by Antoine Bouchoux; Hélène Roux-de Balmann; Florence Lutin (pp. 266-273).
Nanofiltration was investigated for usability in a specific lactic acid production process based on conventional and bipolar electrodialysis operations. Industrial fluids, corresponding to two potential integration levels and coming from an existing installation, were investigated. The commercially available DK nanofiltration membrane was used and performances in terms of lactate/lactic acid recovery rate and purification efficiency are reported. Nanofiltration was able to efficiently remove magnesium and calcium ions from a sodium lactate fermentation broth before its concentration and conversion by electrodialysis (first potential integration level). Maximum impurities rejections and lactate recovery were obtained at maximum transmembrane pressures. Mg2+ and Ca2+ rejections were 64±7 and 72±7%, respectively and lactate recovery rate reached 25±2molm−2h−1 for Δ P=20bar. Sulfate and phosphate ions were also partially removed from the broth (40% rejection). At the invert, chloride ions were negatively retained by the membrane and were consequently more concentrated in the permeate. Nanofiltration also led to a nearly total decolouration of the fermentation broth. On the other hand, sulfate and phosphate rejections obtained from the filtration of a converted broth containing the lactic acid under its neutral form (second potential integration level) were also satisfactory, i.e. 47±5 and 51±5%, respectively. High recovery rates were observed in that case, i.e. 48±2molm−2h−1 at 20bar. It indicated that NF could also be used as final purification step in the process.
Keywords: Downstream processing; Lactic acid; Nanofiltration; Fermentation broth; Electrodialysis
Performance of a pilot-scale cross-flow rotating packed bed in removing VOCs from waste gas streams by Chia-Chang Lin; Tzu-Ying Wei; Shu-Kang Hsu; Wen-Tzong Liu (pp. 274-279).
This study investigates the feasibility of applying a pilot-scale cross-flow rotating packed bed (RPB) to absorb volatile organics compounds (VOCs) from waste gas streams. Isopropyl alcohol (IPA) was used as a model VOC herein. The overall volumetric gas-side mass transfer coefficient ( KG a) was determined at various values of operating parameters including rotor speed, gas flow rate and liquid flow rate. The results demonstrated that a cross-flow RPB can yield the KG a values of about 81–1651/s, corresponding to a removal efficiency of 95% at a gas flow rate ranged from 150 to 300m3/h, indicating that the mass transfer efficiency of a cross-flow RPB is greater than that of a countercurrent-flow RPB. Consequently, a cross-flow RPB is an effective absorber for removing VOCs from waste gas streams.
Keywords: Rotating packed bed; Cross-flow; Absorption; Mass transfer; Isopropyl alcohol; Volatile organics compounds
The adsorption behaviors of Methylene Blue and Methyl Orange in a diaminoethane sporopollenin-mediated column system by Muhittin Küçükosmanoğlu; Orhan Gezici; Ahmet Ayar (pp. 280-287).
The adsorption behaviors of Methylene Blue and Methyl Orange on a diaminoethane sporopollenin (DAE-S) solid phase were investigated in a column arrangement, and breakthrough profiles were used in evaluations and quantifications. The adsorption behaviors were evaluated using some common adsorption isotherm models and Scatchard plot analysis. The results showed that the DAE-S was useful for abstracting anionic dyes from cationic dyes. Thus, the usability of a biopolymer derived material (DAE-S) as a cheap, environmentally friendly and effective solid/stationary phase is discussed through the present study, and the adaptability of the DAE-S to common processes performed under column conditions is also drawn in detail.
Keywords: Solid-phase extraction; Liquid chromatography; Stationary phase; Breakthrough curve; Adsorption; Adsorption isotherm; Scatchard plot analysis
A novel in-situ technique of ultra purification of cadmium for electronic applications by S.T. Ali; R.C. Reddy; N.R. Munirathnam; C. Sudheer; G. Anil; T.L. Prakash (pp. 288-294).
A novel in-situ ultra purification technique incorporating both ‘distillation’ and ‘zone refining’ was devised using simple see-through quartz wares. The purification experiments, e.g. distillation followed by zone refining were carried out on 3N7 purity raw cadmium in a clean room environment of class 10,000. After a single run of purification employing one distillation and subsequent 25 passes of zone refining, cadmium of purity m6N (99.9999%) achieved w.r.t. metallic impurities (viz. Si, Ca, Fe, Ni, Cu, Zn, As, Se, Ag, Sb, Tl, Pb, Bi, etc.) as analyzed by inductively coupled plasma optical emission spectroscopy (ICP-OES). The trace oxygen as analyzed by O-N analyzer reduced from 230–350ppm for raw Cd to 20–27ppm for distilled and zone refined Cd. Carbon analyzed by glow discharge optical emission spectroscopy (GD-OES) reduced from 60–70 to 4–7ppm on purification. The different process parameters such as soaking temperature for distillation, zoning temperature, speed of zone, etc., were optimized and the analysis results were discussed w.r.t. vapor pressures and segregation coefficients.
Keywords: In-situ purification of cadmium; Distillation and zone refining; Impurity analysis using ICP-OES, GD-OES and O-N analyzer
Study of oil sorption by expanded perlite at 298.15K by D. Bastani; A.A. Safekordi; A. Alihosseini; V. Taghikhani (pp. 295-300).
Sorption capacity as well as sorption kinetics of oil onto four different expanded perlites with different physical and surface properties were studied. In order to meticulously measure the amount of oil to be sorbed onto the adsorbents used in this study both static and dynamic methods were employed. It would be worth noting that the adsorbent, i.e., perlite can spread on the oil and float on the surface thanks to its low density. The variation of the amount of oil sorbed onto the adsorbents with time was recorded and the weight of adsorbent was monitored at each specified time. The experimental results showed that grain sizes with high surface area can sorb oil to be spread on water surface. It should be also stressed that the experiments conducted were replicated three times and the results reported are the average of replicas. The results obtained were correlated with the first order, second order sorption kinetics as well as the intra-particle diffusion models. The results showed that the second order kinetic model studied can more accurately correlate the experimental data generated than the first order sorption kinetic and the intra-particle diffusion models.
Keywords: Perlite; Oil spill; Sorption capacity; Sorption kinetics
Removal of 1,1,1-trichloroethane from water using a polyvinylidene fluoride hollow fiber membrane module: Vacuum membrane distillation operation by Bing Wu; Xiaoyao Tan; K. Li; W.K. Teo (pp. 301-309).
Polyvinylidene fluoride (PVDF) hollow fiber membranes with an asymmetric structure have been prepared by the phase inversion method using dimethylacetamide (DMAc) as solvent and LiCl–H2O as additives and applied for volatile organic compounds (VOCs) removal from water. The membrane was characterized using scanning electron microscopy (SEM) for observing its microstructures and a gas permeation method for measuring its porosity, pore size and pore size distribution. The results have provided the conditions for tailor-made hollow fiber membranes with the desired morphology suitable for vacuum membrane distillation (VMD). Moreover, the structural parameters such as mean pore size and effective porosity determined are being used as parameters in the mathematical modeling of the VMD process. A hollow fiber membrane module was then fabricated using a selected PVDF hollow fiber membranes and applied for removal of 1,1,1-trichloroethane (TCA) from water. The effects of various operating parameters including downstream vacuum level, feed temperature, feed flow rate and TCA feed concentration on the performance of the module were investigated both theoretically and experimentally. A high feed temperature and/or a low downstream pressure favored the enhancement of TCA removal, but also yielded dramatically a high water permeation flux, resulting in an excessive dilution of the permeated VOC. Under optimal operating conditions, particularly the downstream vacuum level, feed temperature and feed flow rate, TCA removal efficiency up to 97% was achievable. A mathematical model, which takes into consideration of mass transfer resistances in both liquid and membrane phases, predicts well the TCA removal data in comparison with the experimentally observed results under the favorable operation ranges employed in vacuum membrane distillation.
Keywords: VOCs; Hollow fiber membrane; PVDF; Vacuum membrane distillation
Beta-lactoglobulin removal from whey protein concentrates by M. Eugenia Lucena; Silvia Alvarez; Carlos Menéndez; Francisco A. Riera; Ricardo Alvarez (pp. 310-316).
A commercial whey protein concentrate (WPC65, supplied by ILAS S.A., Spain) was used as raw material to obtain an alpha-lactalbumin (α-La) enriched solution. Firstly, α-La was simultaneously precipitated with bovine serum albumin (BSA) and immunoglobulins (Igs) by adding lactic acid as Ca2+ ion sequestrant at a pH value around 4.0. The α-La precipitation process was observed to be reversible. Therefore, when the original pH was recovered the protein became soluble again. The proposed process consists of the following steps: (1) precipitation, (2) centrifugation (I), (3) precipitate washing (twice), (4) centrifugation (II) and finally (5) solubilization of the precipitate. Steps 1 and 2 were studied in a previous work by the same authors. Steps 3–5 were investigated in this work. These steps were performed and optimized at laboratory scale. The final α-La enriched solution obtained had a purity of about 74%, while the recovery of this protein was about 86%. More than 99% of the β-lactoglobulin (β-Lg) present in the WPC was removed in the process. This α-La enriched solution can be considered as a good base to prepare infant formulas. This product is very interesting because of its high water solubility and the very low β-Lg concentration. The concentration of β-Lg in the supernatant fractions was higher than 85% (on a dry basis); therefore these fractions could be further concentrated by membrane technology (ultrafiltration) to obtain a β-Lg enriched concentrated product.
Keywords: Alpha-lactalbumin; Beta-lactoglobulin; Whey protein concentrate; Infant formulas
Decomposition rates of methyl tert-butyl ether and its by-products by the Fenton system in saline wastewaters by E.M. Siedlecka; P. Stepnowski (pp. 317-324).
The primary aim of this study was to gain an understanding of how different concentrations of chloride ions affect the oxidation of methyl t-butyl ether (MTBE) in the Fenton system. Oxidation of MTBE in a chloride-free reaction mixture was rapid and very effective, but was inhibited even by the lowest chloride concentrations employed. After 90min of reaction in the presence of 0.05–1M of chloride ions, the effectiveness of MTBE degradation dropped to 97–68%, respectively. It was found that the inhibition of Fenton's reaction by chloride ions depends on two factors, thus, complexation and radical scavenging. Under the experimental conditions of the current study, comparison of rate constants for possible degradation reactions showed that most of theOH radicals formed by the reaction of H2O2 with Fe2+ were consumed by Cl−. The influence of chloride ions on the degradation of four intermediate products in identical system was also studied: in chloride-free solution under the same experimental conditions, t-butyl alcohol (TBA) was the major by-product, followed by t-butyl formate (TBF) and acetone. In the process of degradation, the distribution of MTBE intermediates varied with the different chloride concentrations. Furthermore, by varying the concentrations of Fe2+ and H2O2, it was possible to track the behavior of MTBE degradation products in the Fenton system in order to find optimal conditions for saline wastewater treatment.
Keywords: Abbreviations; AOPs; advanced oxidation processes; DO; dissolved oxygen; FID; flame ionization detector; MA; methyl acetate; MTBE; methyl; tert; -butyl ether; TBA; tert; -butyl alcohol; TBF; tert; -butyl formateAdvanced oxidation processes (AOPs); Hydrogen peroxide; Fenton reaction; MTBE; Oxidation; Salinity
pH, Ionic strength and flow velocity effects on the NOM filtration with TiO2/ZrO2 membranes by Ã?ngeles de la Rubia; Manuel RodrÃguez; Daniel Prats (pp. 325-331).
The effects of pH, ionic strength and flow velocity on the volumetric permeate flux and the rejection of dissolved organic carbon (DOC) in a 15kDa ceramic ultrafiltration membrane are evaluated. The decrease of pH produces a drop in the elimination of DOC, despite humic acid accumulation in the surface of membrane. Membrane has a lower humic acid flux resistance when pH decreases due to molecular compression of humic acid. Ionic strength has a relevant influence in humic substances processed with ceramic ultrafiltration membranes. A significant permeate flux reduction is approached when ionic strength increases as well as DOC removal reduction. Regarding the ionic strength rise, it can be observed that the resistance of the cake layer falls as in the case of falling pH. On the other hand, permeate flux rises due to the reduction of the effective size of the molecule. Concerning flow velocity, permeate flux reduction plays a significant role in contrast to DOC removal. Low flow velocity allows cake layer formation that considerably reduces flux permeate. Experiments carried out at neutral pH and low ionic strength, to analyse flow velocity, show no electro kinetic effects that influence the cake layer formation and flux permeate.
Keywords: Ceramic membrane; Humic substances; Ultrafiltration; Zeta potential
Modified cellulose fibres for adsorption of organic compound in aqueous solution by Fadhel Aloulou; Sami Boufi; Jalel Labidi (pp. 332-342).
This paper presents the results of an experimental study of removal of organic contaminant from wastewater using chemically modified cellulose fibres. The adsorption capacities of the modified fibres towards various organic molecules were investigated. The ensuing modified fibres appeared to be efficient absorbent for different dissolved organic molecules in water. The recycling tests revealed that the exhausted substrates could be regenerated without loosing their capacity. The adsorption isotherm related to different solutes follows the Langmuir model in entire range of concentration. To confirm the possibility of using the modified cellulose fibres as a sorbent for the removal of dissolved organic pollutant, adsorption breakthrough curves were established under different operating condition such as concentration, flow rate and the column length. The main advantage of this substrate lies in its relative facile regeneration without a significant loss of its adsorption capacity.
Keywords: Cellulose fibres; Adsorption; Organic solute; Regeneration
New extractive configuration separating azeotropic mixture in semi-batch way by Csaba Stéger; Endre Rév; László Horváth; Zsolt Fonyó; Michel Meyer; Zoltán Lelkes (pp. 343-356).
A new variant of batch extractive distillation, the so-called inverse-fed batch extractive distillation is presented. The total amount of the entrainer is pre-loaded to the boiler, and the mixture charge to be separated is continuously fed to the column in this novel configuration.The feasibility study of conventional extractive distillation was extended and a thorough study was performed to separate a maximum boiling azeotrope with intermediate boiling entrainer. The new configuration was found more efficient than the conventional one. The results of the feasibility study was validated and completed with a sensitivity analysis performed with commercial simulator software.
Keywords: Batch extractive distillation; Feasibility study; Batch rectifier
Novel operational method of continuous foam separation of gold – Injection of metal and/or surfactant solutions into rising foam bed by T. Kinoshita; Y. Ishigaki; K. Yamaguchi; S. Akita; Y. Yamada; S. Nii; K. Takahashi; F. Kawaizumi (pp. 357-362).
A novel operational method of continuous foam separation, in which metal and/or surfactant solutions were injected into the rising foam bed, has been applied to the Au(III) recovery from binary metal solutions with Cu(II). The effects of experimental parameters, such as an air flow rate, metal concentration and solution acidity, were discussed in terms of the percent recovery and the separation factor of Au(III). A nonionic surfactant, polyoxyethylene nonyl phenyl ether, used in this study showed a strong affinity to Au(III) in HCl media and played a double role of foam-producing and metal collecting reagent. By injecting a metal solution to the foam bed, the recovery of Au(III) was improved due to the efficient contact between the metal and the foam surface counter-currently. On the other hand, injection of a surfactant solution facilitated the washing-out of the metals in the interstitial water between the adjacent foam, enhancing the separation of Au(III) from Cu(II). Furthermore, simultaneous injection of metal and surfactant solutions to the foam bed was also examined, and satisfactory results were obtained both in the yield and purity of Au(III).
Keywords: Foam separation; Gold; Counter current contact; Injection of solution
Preparation of polymer blend hollow fiber membrane via thermally induced phase separation by Xunyao Fu; Hideto Matsuyama; Masaaki Teramoto; Hideki Nagai (pp. 363-371).
Polymer blend hollow fiber membranes were prepared via thermally induced phase separation (TIPS). Poly(vinyl butyral) (PVB) and poly(ethylene- co-vinyl alcohol) (EVOH) were used as polymers and diluent was polyethylene glycols (PEG) with the molecular weight of 200. The phase diagrams obtained in the polymer blends system indicated both UCST (upper critical solution temperature) and LCST (lower critical solution temperature) behaviors. For LCST behavior, there were two kinds of phase separations. It was considered that the phase separation occurred at higher temperature was between PVB and EVOH, and that occurred at lower temperature was between polymer and diluent. The addition of EVOH had an eminent effect on the hollow fiber membrane structure and membrane performance. With the increase of EVOH content in the polymer blend system, the membrane became more hydrophilic, and the water permeability became higher due to the enlargement of the pores. The addition of EVOH was also effective to improve the mechanical property of hollow fiber membrane.
Keywords: Thermally induced phase separation; Polymer blend hollow fiber membrane; Poly(vinyl butyral); Poly(ethylene-; co; -vinyl alcohol); Hydrophilic membrane
Optical quantification of fouling during nanofiltration of dyes by Srimanta Pal; Avijit Ghosh; Timir Baran Ghosh; Sirshendu De; Sunando DasGupta (pp. 372-379).
Attenuated total internal reflection Fourier transform infra-red (ATR-FT-IR) spectrum analysis is done to characterize a thin film composite (TFC) nanofiltration (NF) membrane. The chemical compositions of the skin layer (composite polyamide) and the support substrate (polysulfone) are evaluated. Using a high-resolution optical microscope, the thickness of the different layers of the composite membrane is measured. The deposition and penetration of crystal violet molecules on and inside the composite membrane during nanofiltration at different operating conditions are optically measured. The deposition and penetration as a function of location on the membrane are also measured. The experimental results are found to be consistent with the basic physics of the process.
Keywords: Nanofiltration membrane; FT-IR; Characterization; Optical microscope; Deposition; Penetration
Effect of draw ratio and coagulant composition on polyacrylonitrile hollow fiber membranes by Da-Guang Yu; Wen-Li Chou; Ming-Chien Yang (pp. 380-387).
Asymmetric polyacrylonitrile (PAN) hollow fiber membranes were fabricated via the dry-jet wet spinning process. The effects of the draw ratio and the DMF content in the coagulation bath on the mechanical properties, permeation, and morphology were investigated. The external surface and cross-section of the resulting hollow fibers were examined using a scanning electron microscope (SEM) and the thermal properties were measured. Additional characterization using X-ray and porosity measurement suggested the improvement in molecular orientation. The results show that the maximum draw ratio increased with the DMF content in the coagulant. The pure water permeability increased while the retention decreased with the increase of the draw ratio. On the other hand, both the permeability and the retention increased with the DMF content.
Keywords: Polyacrylonitrile; Dry-jet wet spinning; Hollow fiber; Drawn ratio; Coagulant bath
Application of a novel strategy—Coordination polymerization precipitation to the treatment of Cu2+-containing wastewaters by Fenglian Fu; Runming Chen; Ya Xiong (pp. 388-393).
A process of coordination polymerization precipitation was proposed as a new alternative to the conventional treatment method for removing heavy metals wastewater. A chelating reagent with two chelating groups, N, N-bis-(dithiocarboxy)piperazine, was employed as the first coordination polymerization precipitant to remove copper(II) from wastewaters containing free and complex copper(II). It was observed that BDP could effectively reduce 50.00mg/L free and complex Cu2+ in wastewater to much lower than 0.5mg/L by bridging Cu2+ to yield highly insoluble linear chelating polymer and the polymer precipitates were easier to settle and less susceptible to leaching than copper diethyldithiocarbamate.
Keywords: Heavy metal; Copper wastewater; Coordination polymerization precipitation (CPP)
Optimization of phosphate removal from wastewater by electrocoagulation with aluminum plate electrodes by Şahset İrdemez; Yalçın Şevki Yildiz; Vahdettin Tosunoğlu (pp. 394-401).
The Taguchi method was used to determine the optimum conditions for the phosphate removal from wastewater by electrocoagulation with aluminum plate electrodes. The experimental parameters investigated were initial phosphate concentration, initial pH of the wastewater, supporting electrolyte concentration, supporting electrolyte type and current density. The ranges of experimental parameters were between 50 and 500mg/L (as PO4–P), 4–7 for initial pH, 0–10mM, NaCl, NaNO3, Na2SO4 and CaCl2 and 0.25–1.00mA/cm2mm for initial phosphate concentration, initial pH of the wastewater, supporting electrolyte concentration, supporting electrolyte type and current density, respectively. Reaction period was kept constant in 25min for statistical analysis. The optimum conditions for these parameters were found to be 50mg/L, 4, 5mM, NaCl and 1.00mA/cm2, respectively. Under these conditions, the predicted and experimental removal efficiency of phosphate from wastewater by electrocoagulation with aluminum plate electrodes were 99.9 and 100.0%, respectively. A statistical analysis of variance (ANOVA) was performed to see whether the process parameters were statistically significant or not. According to the F-test results, it can be concluded that the degrees of the influences of parameters on the removal efficiency is initial phosphate concentration, current density and initial pH of the solution.
Keywords: Taguchi method; Optimization; Phosphate removal; Electrocoagulation; Aluminum electrode