Chemical cleaning of reverse osmosis and nanofiltration membranes fouled by licorice aqueous solutions

The aim of this work was finding optimum cleaning agents and conditions for cleaning reverse osmosis (RO) and nanofiltration (NF) membranes fouled by licorice aqueous solutions. The effect of various chemicals on flux recovery (FR) and resistance removal (RR) of the fouled membranes was investigated. For both membranes the results indicate that a combination of ethylene diamine tetra acetic acid (EDTA), sodium dodecyl sulphate (SDS) and sodium hydroxide may be used as cleaning agents to achieve an optimum cleaning efficiency. Zeta potential and contact angle measurements indicate the changes in charge and hydrophilicity of the surface of RO and NF membranes at various pH solutions, respectively. The effect of surface characteristics is evident in efforts to select the optimal operating conditions. The effect of cleaning condition such as concentration, temperature, pH and cleaning time was studied. The optimum temperature, cleaning time, pH and concentration were found as 35 ± 1 °C, 20 min, 12 and 0.1 wt.%, respectively. SEM pictures showed the surface morphology of RO and NF membrane.     

Simultaneous recovery of copper and surfactant by an electrolytic process from synthetic solution prepared to simulate a concentrate waste stream of a micellar-enhanced ultrafiltration process

Electroplating method was employed to recover copper and surfactant simultaneously from synthetic solutions prepared to simulate concentrated waste stream generated from micellar-enhanced ultrafiltration. Effects of surfactant and copper (II) concentrations, surfactant to copper (II) molar ratio (S/M), electroplating voltage and time, solution pH, and ionic strength on metal recovery and electrical current efficiency were investigated. Results show that at a fixed S/M ratio of 5, the first-order kinetic constant for Cu (II) removal by electroplating increases with decreasing SDS concentration. At fixed SDS concentration of 8.5 mM, increasing initial Cu (II) concentration increases both Cu (II) recovery and current efficiency. Electrolyte pH has profound effects on the metal recovery and current efficiency due to the difference in solution conductivity after pH adjustment and the extent of Cu (II) adsorption onto SDS at different pHs.     

Effect of Ionic Strength on Oil Removal from Stainless Steel in the Presence of Ionic Surfactant

Abstract

Contact angles of oil droplets on solid surfaces provide useful insight into surfactant cleaning behavior. Contact angles of hexadecane and MAR‐TEMP^® 355, an industrial quench oil, on stainless steel were measured for ionic surfactant solutions as a function of ionic strength. The ionic strength of sodium dodecyl sulfate (SDS) and cetyl trimethyl ammonium bromide (CTAB) solutions was modified by the addition of sodium chloride. Increases in the contact angle with additions of 1.0 mM and 2.5 mM NaCl were observed for the two oils in SDS and for hexadecane in CTAB. For the industrial quench oil, detachment occurred in CTAB concentrations above the critical micelle concentration; as a result, the equilibrium contact angle measurements were not measured. The critical concentration of CTAB decreased with increasing NaCl concentration. Oil‐removal studies indicate that increasing ionic strength by as little as 2.5 mM can result in improved cleaning. A theoretical insight previously used to explain contact‐angle behavior for a hexadecane‐gold system is used to describe the results obtained with the current system.     

Membrane fouling and chemical cleaning in water recycling applications

Fouling and subsequent chemical cleaning are two important issues for sustainable operation of nanofiltration (NF) membranes in water treatment and reuse applications. Fouling strongly depends on the feed water quality, especially the nature of the foulants and ionic composition of the feed water. Consequently, appropriate selection of the chemical cleaning solutions can be seen as a critical factor for effective fouling control. In this study, membrane fouling and chemical cleaning under condition typical to that in water recycling applications were investigated. Fouling conditions were achieved over approximately 18 h with foulant cocktails containing five model foulants namely humic acids, bovine serum albumin, sodium alginate, and two silica colloids in a background electrolyte solution. These model foulants were selected to represent four distinctive modes of fouling: humic acid, protein, polysaccharide, and colloidal fouling. Three chemical cleaning solutions (alkaline solution at pH 11, sodium dodecyl sulphate (SDS), and a combination of both) were evaluated for permeate flux recovery efficiency. The results indicated that with the same mass of foulant, organic fouling was considerably more severe as compared to colloidal fouling. While organic fouling caused a considerable increase in the membrane surface hydrophobicity as indicated by contact angle measurement, hydrophobicity of silica colloidal fouled membrane remained almost the same. Furthermore, a mechanistic correlation amongst cleaning efficiency, characteristics of the model foulants, and the cleaning reagents could be established. Chemical cleaning of all organically fouled membranes by a 10 mM SDS solution particularly at pH 11 resulted in good flux recovery. However, notable flux decline after SDS cleaning of organically fouled membranes was observed indicating that SDS was effective at breaking the organic foulant—Ca²⁺ complex but was not able to effectively dissolve and completely remove these organic foulants. Although a lower permeate flux recovery was obtained with a caustic solution (pH 11) in the absence of SDS, the permeate flux after cleaning was stable. In contrast, the chemical cleaning solutions used in this study showed low effectiveness against colloidal fouling. It is also interesting to note that membrane fouling and chemical cleaning could permanently alter the hydrophobicity of the membrane surface.     

Rapid pressure-less and spark plasma sintering of (Ba0.85Ca0.15Zr0.1T0.9)O3 lead-free piezoelectric ceramics

This work shows for the first time the possibility to sinter BCZT powder compacts by rapid heating rates within one hour of sintering, while achieving good piezoelectric properties. The sintering was performed by rapid (heating rates 100 and 200 °C/min) pressure-less sintering (PLS) at 1550 °C/5-60 min and by SPS sintering (100 °C/min, 1450 °C/5?60 min and 1500 °C/15?45 min). The rapid PLS samples reached a relative density up to 94 % and grain sizes of 17–36 μm acquiring d₃₃ up to 414 pC/N. Although the SPS samples reached full density at 1450 °C, their piezoelectric properties worsened due to smaller grains (10?15 μm) as well as formation of cracks at dwell times > 30 min. At elevated SPS temperature of 1500 °C/30 min, the d₃₃ increased to 360 pC/N sustaining full density. Even higher increase in d₃₃ (424 pC/N) of SPS samples was achieved by post-rapid PLS at 1550 °C/60 min resulting from further expansion in grain size.     

Slow-gelling Cr+3/polyacrylamide solutions for reservoir profile modification: Dependence of the gelation time on pH

Systematic studies of the gelation of both buffered and unbuffered aqueous Cr⁺³/polyacrylamide solutions show that the gelation time is a strong function of pH, increasing by about one order of magnitude per unit decrease in pH for polyacrylamides less than about 7.5% hydrolyzed. The gelation rate also depends strongly on the Cr⁺³ concentration, the degree of polymer hydrolysis, and temperature. At 25°C, gelation delays of more than 10 months have been obtained; the maximum delay observed at 60°C is about 1 month and at 90°C 1 d. The resistance of buffered gel solutions to change in pH results in significantly longer gelation times at 90°C and low pH than for identical unbuffered solutions; at lower temperatures, however, the differences are insignificant. Most importantly, the use of low pH to control the gelation time of Cr⁺³/polymer solutions provides an attractive, inexpensive substitute for the environmentally unacceptable Cr⁺⁶/reductant method currently employed for profile modification treatments.     

The effect of micellar lifetime on the rate of solubilization and detergency in sodium dodecyl sulfate solutions

The slow relaxation time (τ₂) of sodium dodecyl sulfate (SDS) micelles, measured by the pressure-jump technique, was maximum at 200 mM concentration at 25°C, indicating that the most stable micelles are formed at this concentration. This is presumably related to the optimum molecular packing in the micelle. The rate of solubilization of benzene and Orange OT dye into SDS solutions was also maximum at 200 mM concentration. The results are explained as follows: The distance between micelles (i.e., intermicellar distance) decreases as the surfactant concentration (or the number of micelles) increases, resulting in a stronger electric repulsion between micelles. Therefore, the micelles become more rigid, due to the compressive force of intermicellar repulsion, as the concentration increases up to 200 mM SDS. With further increase in the SDS concentration, the micellar shape changes from spherical to cylindrical to accommodate more surfactant molecules in the solution and to minimize the free energy of the system. The interior of the tightly packed micelles is more hydrophobic than that of loosely packed micelles and, therefore, the tightly packed micelles induce rapid solubilization of nonpolar molecules (e.g., benzene, Orange OT) into these micelles.     

Preparation and desalination performance of porous planar cordierite membranes using industrial solid waste as main silica source

Silica is a main component of cordierite ceramic, in the present work, industrial solid waste was used as main silica source to prepare porous planar cordierite membranes by a solid-phase sintering process with starch as pore-forming agent. It is shown that the concentration of starch plays a critical role in the pore structure and mechanical property and the cordierite membranes with a starch concentration of 40?wt% (M-40) have a desirable pore structure and flexural strength after sintering at 1300?°C for 5?h. After grafted with 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FAS, C₈), the ceramic membranes were used for desalination by vacuum membrane distillation (VMD). The results show that the membranes(M-40) possess an average flux of 11.43?kg/m² h, a high salt rejection of 99.9% under the following operation conditions: a NaCl concentration of 3.5?wt%, a feed rate of 300?ml/min and a temperature of 80?°C. After desalination for 120?h, the water contact angle decreases to 130°. The cordierite membranes exhibit poor resistance to thermal acid/alkali solution(boiling, pH?=?1 and 14, respectively, soaked for 8?h) but excellent resistance to ambient temperature acid/alkali solution (25?°C, pH?=?1 and 14, respectively, soaked for 120?h).     

Soil Clean up by in-situ Surfactant Flushing. VI. Reclamation of Surfactant for Recycle

Abstract

Solvent extraction has been studied for use in reclaiming contaminated surfactant solutions for reuse in soil surfactant flushing in the remediation of hazardous waste sites. Hexane was used as the solvent to extract p-dichlorobenzene (DCB), naphthalene, and biphenyl from 25, 50, and 100 nM sodium dodecylsulfate (SDS) solutions in a continuous countercurrent flow column. The contaminant concentration in the aqueous SDS was followed with time, and the removal was modeled using an unsteady-state model which included diffusion kinetics. The mass transfer time constant was approximately 2 hours. The percent removal of DCB increased with increasing hexane flow rate and decreased with both increasing SDS flow rate and increasing SDS concentration. The concentrations of all three contaminants were reduced by about 90% or better. Extraction of contaminated SDS solutions with hexane appears to be an effective method for cleaning up these surfactant solutions for recycle.     

Selective separation of copper (II) and cobalt (II) from wastewater by using continuous cross‐flow micellar‐enhanced ultrafiltration and surfactant recovery from metal micellar solutions

Performance of continuous cross‐flow micellar‐enhanced ultrafiltration (MEUF) method was investigated for the selective separation of copper (Cu²⁺) and cobalt (Co²⁺) from the aqueous phase using sodium dodecyl sulfate (SDS) as an anionic surfactant and iminodiacetic acid (IDA) as a chelating agent. Operating parameters such as operating time (10–120 min), cross‐flow rate (100–250 mL/min), pH of the solution (2.8–5.6), molar concentration ratio of the chelating agent to metals (the C/M ratio, 0.5–2.5), molar concentration ratio of the surfactant to metals (the S/M ratio, 5–8) and mode of operation were studied to investigate the effectiveness of the process on selective separation. At optimal parameters, above 90% selective separation (Cu²⁺ in permeate and Co²⁺ in retentate) was achieved. Two methods were studied for the separation of Co²⁺ and SDS from retentate stream; acidification followed by UF and addition of chelating agent followed by UF with surfactant recovery of 75% and 83%, respectively, and Co going into the permeate.     

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     

Improved mechanical properties of chitosan fibers

A highly deacetylated chitosan from shrimp with a degree of deacetylation of 95 ± 3% was prepared and spun into a monofilament fiber using a solution of 5% by weight chitosan in 5% by volume aqueous acetic acid. Samples of the spun fibers were immersed in separate solutions containing phosphate ions and phthalate ions, and subsequently washed and dried. The various solutions ranged in pH from 4.12 to 7.75. The highest dry mechanical properties resulted from solutions containing phthalate ions between 4.5–5.5 pH, and from solutions containing phosphate ions at pH 5.4. Immersion time was varied between 1 and 60 min at 25.8°C, and temperature was varied between 25.8 and 70.0°C, in the phosphate ion solutions at a pH of 5.8. Dry mechanical properties were highest at 25.8°C and after 1 h of treatment. Chitosan films were subjected to similar treatments in phosphate and phthalate ion solutions. Fourier transform infrared data (FTIR) on the films suggest that some interaction is occurring between the phosphate ions and the amine group on the chitosan backbone. An additional experiment was performed whereby the same chitosan was used to prepare a dope of 4% by weight chitosan in 4% by volume aqueous acetic acid with 30% by volume methanol. This solution was spun into fibers, but was subjected to a “final draw” by increasing the speed of the winder. With increasing the final draw, denier and elongation‐at‐break decreased, while the other mechanical properties showed a marked increase. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 72: 1721–1732, 1999     

Effect of deaeration processing on the behavior of an acrylonitrile–acrylamide copolymer and carbon fiber precursors

The effect of the deaeration process on the behavior of acrylonitrile–acrylamide copolymer solutions was demonstrated experimentally in detail. The corresponding mechanical properties and morphology of the resultant precursors were also been examined. It was found that the viscosity of the copolymer solutions at rest increased continuously with the deaeration time prolonged at every fixed temperature stage, but it considerably increased when the deaeration temperature decreased. The changes in the viscosity of the solutions at 80°C were less prominent than those of the solutions at 20°C in the beginning stage; beyond 60 min, the changes became remarkable. In concentrated copolymer solutions, the dimethyl sulfoxide composition weight percentage decreased with an increase in the deaeration temperature; the increasing temperature reduced the solvent power continuously at a high deaeration temperature, so more solid–elastic gels were formed in the solutions with an increase in time. At the same degree of vacuum, when the temperature varied from 20 to 80°C and, in particular, the deaeration temperature was beyond 60°C, the products from the copolymer seemed to have slightly narrower molecular weight distributions. With the deaeration temperature increasing, the tensile strength, elongation at break, and bulk density of the resultant precursors increased, but their fineness and coefficient of variation decreased. The morphology of the precursors was more compact and more round beyond 60°C than below 60°C. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

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.     

Preparation of a Chemical Polyblend Sizing Agent via Polymerization of Acrylic Acid with Polyvinyl Alcohol

A polyblend sizing agent was prepared by free radical polymerization of partially neutralized acrylic acid (AA) in the presence of polyvinyl alcohol, (PVOH) (Vinarol®DV of Clariant), using ammonium persulfate (AP) initiator. Polymerization was conducted under different conditions including AP concentration (0.025–0.125 mol/L), degree of neutralization (3–50%), time (0–60 min), temperature (50–80°C), AA/PVOH ratio (0.2:1.2), type of neutralizing agent (NaOH or NH₄OH), and PVOH concentration (50–150 g/L). At optimum polymerization conditions, 100 g/L PVOH, 75 g/L AA (3% neutralized using NH₄OH), 0.1 mol/L AP, at 70°C for 25 min, a polyblend was prepared with a percent total conversion of 94%. It was then neutralized with NaOH to a pH of 7. Rheological properties of 10% aqueous solution of the polyblend or PVOH at 80°C revealed that the first was of a non-Newtonian pseudoplastic flow and the latter is of a non-Newtonian thixotropic flow. Solubility time of the polyblend film was shorter than that of PVOH, either after thermal treatment (120°C/15 min)or without thermal treatment. Sized gauzy fabric samples using the polyblend were of higher tensile strength and extent of size removal than those sized with PVOH.     

Effect of Dipping Temperature and Dipping Time on Drying Rate and Color Change of Grapes

Thompson seedless grapes (Vitis vinifera) were pretreated in potassium carbonate and ethyl oleate solutions for 1, 2, and 3 min at 30, 40, 50, and 60°C and dried in a convective air dryer at 60°C. The effect of dipping time and solution temperature on drying rate and color kinetics were investigated. Grapes dipped into the solution at 60°C for 2 and 3 min had the fastest drying rate. Among the seven semi theoretical models compared, the Midilli equation best described the drying curves of grapes for all dipping pretreatments. Color data were obtained using a machine vision system in CIE L*a*b* color space. Regardless of the dipping time and temperature applied, all raisins had varying degrees of brown coloring. At all dipping times and temperatures the highest R ² value was obtained for a* values, which followed zero-order reaction kinetics during drying.     

Growth mechanism and photocatalytic properties for dye degradation of hydrophobic mesoporous ZnO/SDS films prepared by electrodeposition

The growth by electrodeposition of ZnO/SDS hybrid thin films from aqueous mixed solution of zinc chloride and sodium dodecylsulfate (SDS), an anionic surfactant, using molecular oxygen as a precursor, has been studied. Significant morphological changes have been observed with the deposition time. At low electrodeposition time the layer is composed of flake-shaped aggregated grains whereas for a time longer than 10–15 min an inner layer composed of aggregated particles appears below the flake-type one. The flakes have a lamellar structure oriented parallel to the substrate. Krypton adsorption experiments show that the mesoporosity of the films is due to pores larger than 8 nm and probably arises from the nanoparticulate phase. The as-deposited films are hydrophobic with contact angles ranging between 110° and 130°. The hydrophobic character of these mesoporous ZnO films is found to substantially improve the efficiency of ZnO films for methylene blue photodegradation, their performances being similar to those of thicker hydrophilic mesoporous films.     

Preferential degradation of noncholine phosphatides in soybean lecithin by thermalization

Purified soybean lecithin and the gum derived from soybean oil processing were heated separately in bulk at 125 to 200°C for 60 min, or at 175°C for 30, 60, 90 and 120 min, and the products were analyzed by thin-layer chromatography and high-performance liquid chromatography. It was found that the noncholine phosphatides are preferentially degraded relative to phosphatidylcholine, and that these phosphatides are broken down in the order phosphatidyl-ethanolamine (PE)>phosphatidylinositol (PI)>phosphatidic acid (PA) with increasing temperature. At 175°C, the heating time required to degrade the noncholine phosphatides was between 30 and 60 min. Diglycerides were the principal products of thermalization at 77% of the total material, indicating that the 3-phosphoester linkage is the most heat-labile portion of the noncholine phosphatide molecules. Cleavage of the fatty acids from positions 1 and 2 of the phosphatides was minimal, as indicated by the relatively low amount of free fatty acids (8% of the total) when the lecithin was heated at 180°C for 90 min. The appearance of brown discoloration, characteristic of heated lecithin, coincided mainly with the decomposition of PE.     

Foam separation of active carbon

An experimental investigation is presented of the foam separation of powdered active carbon, equilibriated with an aqueous, synthetic waste water containing phenol and a cationic (ethylhexadecyldimethylammonium bromide (EHDA-Br)), anionic (dodecyl sodium sulphate), or non-ionic (alkyl phenoxy polyethoxy ethanol) surfactant. The effect of surfactant, of pH, of initial carbon concentration, and of initial surfactant concentration on the flotation of carbon is investigated. At pH 3, 7, and 10, the cationic surfactant yields the best flotation of carbon, which increases with increasing pH. At pH 7, a suspension containing 800 mg/1 carbon can be reduced to 24 mg/1 in 10 min. with 0·37 mM EHDA-Br. The relative concentrations of carbon and of surfactant must be controlled carefully to yield sufficient free surfactant to obtain a foam but not excessive free surfactant to impair the foam separation process. Foam volumes are controlled by free (non-adsorbed) surfactant.     

DISPLACEMENT OF A HYDROCARBON OIL FROM A METAL SURFACE USING A SURFACTANT SOLUTION

ABSTRACT

Separation of oils from solid surfaces is important in cleaning and degreasing operations. Water and oils are immiscible requiring the use of an additive which is miscible with water yet has an affinity for oils. Surface active agents, known as surfactants, have this property, being miscible with water while having an affinity for hydrocarbons. In some cases, surfactant solutions displace oils from a solid surface (i.e., remove oil by replacing the oil/solid interfacial area with surfactant solution/solid interfacial area). The presence of alkalinity as well as surfactant concentration is known to affect the ability of a surfactant solution to wet the solid surface and displace the oil. Experiments have been performed to determine quantitatively the effects of surfactant concentration and pH on the displacement of an oil from a metal surface. The displacement is measured in terms of the contact angle formed by the oil on the solid surface in the presence of the surfactant solution, the amount of time needed for the surfactant solution to cause part of the oil to detach from the solid surface, and the volume of the detached oil. Measuring the contact angle of the oil as a function of time shows that surfactant concentration and pH affect the displacement of oil from a metal surface. Increasing the pH of a solution of Triton X-100, a non-ionic surfactant, enhances oil displacement. Increasing the surfactant concentration also enhances oil displacement. The volume of oil which detaches from the solid surface increases with increasing pH and increasing surfactant concentration.