Separation of Water and Nitric Acid with Porous Hydrophobic Membrane by Air Gap Membrane Distillation (AGMD)

Abstract

This study investigates the effect of operation parameters on the separation of nitric acid‐water mixture using air gap membrane distillation (AGMD). Porous hydrophobic PTFE membrane was used. The performance was evaluated based on the permeate flux and the nitric acid selectivity. Operating parameters such as feed solution temperature, feed concentration, flow rate, and air gap width were varied. Nitric acid selectivity was found to increase with the increase in feed solution temperature, feed concentration, flow rate, and air gap width. Permeate flux increased, when the feed temperature and the flow rate were increased. The effect of recirculation of the feed solution was also studied. With the recirculation mode, at different initial solution volumes, it was observed that the nitric acid concentration in the feed and the permeate, increased. The rate of flux decline was greater, when the initial feed solution volume was lower.     

Investigation of Selectivity and Kinetic Behavior of Strong‐Base Ion Exchange Resin Purolite A 520E for Nitrate Removal from Aqueous Solution

Abstract

The aim of this work is to present experimental results on the removal of nitrate by nitrate selective ion exchange resin, Purolite A 520E. The resin particle size, nitrate concentration, temperature, and stirring speed were investigated as experimental parameters and the optimum conditions for nitrate removal were determined. Nitrate removal by strong base anion exchange resin Purolite A 520E was carried out with the batch method in the presence of chloride and sulfate ions. The existence of a high concentration of competing ions in a solution resulted in a reduction of nitrate removal. Nitrate removal ratios decreased from 98% to 85% and 88%, respectively, in the presence of chloride and sulfate ions when the chloride and sulfate ratios were increased in solution. The process kinetics were predicted by using Homogenous Diffusion Models. It was seen that about 98% of nitrate in the aqueous solution could be removed using optimum conditions.     

A Double Liquid Membrane System for the Removal of Actinides and Lanthanides from Acidic Nuclear Wastes

Abstract

Supported liquid membranes (SLM), consisting of an organic solution of n-octyl(phenyl)-N, N-diisobutylcar-bamoylmethylphosphine oxide (CMPO) and tributyl-phos-phate (TBP) in decalin are able to perform selective separation and concentration of actinide and lantha-nide ions from aqueous nitrate feed solutions and synthetic nuclear wastes.

In the membrane process a possible strip solution is a mixture of formic acid and hydroxylammonium formate (HAF). The effectiveness of this strip solution is reduced and eventually nullified by the simultaneous transfer through the SLM of HNOs which accumulates in the strip solution. A possible way to overcome this drawback is to make use of a second SLM consisting of a primary amine which is able to extract only HNO₃ from the strip solution.

In this work the results obtained by experimentally studying the membrane system: synthetic nuclear waste/CMPO-TBP membrane/HCOOH-HAF strip solution/ primary amine membrane/NaOH solution, are reported. They show that the use of a second liquid membrane is effective in controlling the HN0₃ concentration in the strip solution, thus allowing the actinide and lanthanide ions removal from the feed solution to proceed to completion.     

Microemulsion Liquid Membranes. I. Application to Acetic Acid Removal from Water

Abstract

A separation technique utilizing nonionic microemulsions as emulsion liquid membranes has been successfully applied to the removal of acetic acid from an aqueous feed phase. The surfactant systems were carefully characterized in order to assure that they were truly microemulsions. The effects of mixing intensity, feed concentration, treat ratio, and microemulsion viscosity on the separation kinetics were investigated. The microemulsions did not typically display leakage and had negligible swell over 5-minute duration. The reversible phase behavior of the microemulsion was utilized to demulsify the liquid membrane phase and recover the acetate ion via a temperature change of approximately 40°C. Material balances closed to within 10% and rates of separation were faster than the sampling rates when the microemulsion was fully dispersed in the aqueous feed phase.     

Affinity Dialysis–A Method of Continuous,Rapid Metal Ion Separation Using Dialysis Membranes and Selective,Water-Soluble Polymers as Extractants

Abstract

A membrane process utilizing dialysis and selective complexation by water-soluble polymers has been developed. This process, termed affinity dialysis, has been shown to selectively extract and concentrate both cations and anions in a manner similar to ion exchange or solvent extraction. The selective removal of calcium from sodium with selectivity of about 30, removal of chromate ion from dilute streams, and separation of transition metal ions such as Cu/Fe and Cu/Zn have all been successfully demonstrated. Effects of different polymers, polymer concentration, temperature, and flow rates have been studied. The effect of increased polymer concentration is to increase product concentration if appropriate changes in feed, polymer solution, and strip flow rates are made. A continuous polymer solution recycle and regeneration system has been constructed and operated with Cu/Zn and chromate/chloride feed streams. Removal of over 95% of the desired ion in one pass and concentration factors of product over effluent in excess of 100 have been achieved at feed flow rates of 24 gal/d. Product concentrations of greater than 3% from as little as 400 ppm feed have been demonstrated in a continuous process. In addition, the degree of polymer loss to the effluent stream has been shown to be less than 0.01%/d for a typical system. Metal removal from typical feeds is about 0.9 g/m² per 1000 ppm metal in the feed. It is expected that this technique may be useful in the separation of organic and biological materials, as well as for ionic species     

Microemulsion Liquid Membranes. II. Copper Ion Removal from Buffered and Unbuffered Aqueous Feed

Abstract

A separation technique utilizing nonionic microemulsions as emulsion liquid membranes has been successfully applied to the removal of copper ion from both buffered and unbuffered aqueous feed. The reversible phase behavior of the microemulsion was utilized to demulsify the liquid membrane phase and recover the copper ion via a temperature change of approximately 40°C. Material balances closed to within 15%. Benzoylacetone posed no special problems when employed as a complexing reagent in buffered media but was not effective for copper removal from unbuffered solution. LIX 860 was found to be effective in unbuffered media if it was present in concentrations equal to or greater than the stabilizing surfactant.     

Effect of Color and Surfactants on Nanofiltration for the Recovery of Carpet Printing Wastewaters

Abstract

Carpet printing wastewater (CPW) was spiked with metal‐complex dyes at concentrations of 10 and 30 mg/L to investigate the effect of feed color on separation performance of nanofiltration (NF). The rejection was excellent; 98–100% for color and COD under all spiking conditions. Although the flux decline increased with increasing dye concentration, the concentration polarization was the main cause of the flux decline. The effect of surfactants on NF separation performance was also investigated by preparing synthetic wastewaters with dyes and auxiliary chemicals. The presence of a non‐ionic penetrant did not adversely affect the color rejection whereas the COD rejection was reduced from 100% to 91%. Furthermore, fouling became dominant when surfactants were used.     

Selective Removal of Uranium from High‐Level Waste Solution Employing Tri‐n‐Butyl Phosphate as the Extractant

Abstract

Conditions for the selective removal of uranium from high‐level waste solution have been optimized using tri‐n‐butyl phosphate (TBP) as the extractant. Various aqueous soluble reducing agents viz. hydroxylamine nitrate (HAN), hydrazine nitrate (HN), and diethyl hydroxylamine nitrate (DEHAN) as well as n‐dodecane soluble reductant viz. tert‐butyl hydroquinone (TBH) have been evaluated for the separation of U with respect to Pu and Np. The combination of DEHAN and TBH has been found to be most promising for the selective extraction of U from HLW. Extraction data of a few other metal ions expected to be present in high‐level waste solutions viz. Am(III), Eu(III), Zr(IV), Sr(II), and Cs(I) are also obtained.     

Development of Cellulose Acetate Propionate Membrane for Separation of Ethanol and Ethyl tert-Butyl Ether Mixtures

Abstract

For pervaporation separation of ethanol and ethyl tert-butyl ether mixtures, a cellulose acetate propionate membrane was chosen as the experimental membrane because of its high selectivity and good mass fluxes. The properties of the membranes were evaluated by the pervaporation separation of mixtures of ethyl tert-butyl ether/ethanol and the sorption experiments. The experimental results showed that the selectivity and the permeates depend on the ethanol concentration in the feed and the experimental temperature. With increases of the ethanol weight fraction in the feed and the temperature, the total and partial mass fluxes increased. With respect to the temperature, ethanol mass flux obeys the Arrhenius equation. The selectivity of this membrane decreases as the temperature and the ethanol concentration in the feed increase. This membrane shows special characteristics at the azeotropic composition. In the vicinity of the azeotropic point, minimum values of ethanol concentration in the permeate and in sorption solution are obtained. The swelling ratios increase when temperature and the ethanol concentration in the feed are increasing. The ethanol concentration in the sorption solution is also influenced by the temperature and the mixture's composition. When the temperature increases, the sorption selectivity of the membrane decreases.     

Separation of Metals by Rotating Film Pertraction

Separation of zinc (II) and iron (III), present in acidic HCl solutions, with tri‐n‐octylamine was studied applying a rotating film pertraction (RFP) technique. The effect of the main process parameters, disc rotation velocity and hydrochloric acid concentration in the feed, was investigated. It was found that tri‐n‐octylamine is a suitable extractant for zinc recovery or Zn/Fe separation from chloride media. High feed acidity favors more complete zinc recovery, while moderate HCl concentration ([HCl] = 0.25 mol/L) provides much better separation of the metals. The lower acidity (less than 0.10 mol/L) is recommended when pure zinc strip solution is aimed at.     

Electroextraction Separation of Dyestuffs

ABSTRACT

Electroseparation technologies have prospects for significant growth well into the next century. Electroextraction, a coupled separation technique of solvent extraction with electrophoresis, was used to remove dyestuffs from their aqueous stream. A study on the characteristics of the separation technique was carried out with n-butanol/acid-chrom blue K/water and n-butanol/methyl blue/water as working systems. A continuous separation equipment was designed and used in this work. The influences of two-phase flow, field strength, and concentration of the feed on the recovery of solute were studied. The results showed that much higher recovery of solute with less solvent consumption could be achieved by using this technique to remove dyes from their aqueous streams, especially for the separation of the dilute solution. When the field strength is increased, the recovery and mass flux increase. When the feed flow rate and the initial solute concentration are increased, the recovery decreases and the mass flux increases.     

Selective Separation of Toluene/n‐Heptane by Supported Ionic Liquid Membranes with [Bmim][BF4]

Room‐temperature ionic liquids serve as alternative solvents for volatile organic compounds in liquid‐liquid extraction and liquid membrane separation. 1‐Butyl‐3‐methylimidazolium tetrafluoroborate ([Bmim][BF₄]) was applied for extraction and supported ionic liquid membranes (SILMs) to separate toluene and n‐heptane. A high separation factor of toluene was achieved due to the strong interaction between ionic liquid cations and toluene. The mass transfer performance of the SILM process was enhanced by higher operating temperature. With the increase of initial toluene concentration in the feed phase, the mass transfer flux and removal efficiency of the SILM process were improved, while the separation factor decreased. The mass transfer flux was growing with the increase of flow rate at both sides. The SILM process was stable over a long time period due to the high viscosity and low volatility of [Bmim][BF₄].     

Mutual Separation of (W,As, Mo,V, Ge,B) Oxoanions from Bi‐metallic Solution by Resin having Methyl‐Amino‐Glucitol Moiety

Abstract

The mutual separation of (W, As, Mo, V, Ge, B)‐oxoanions using resin having methyl‐amino‐glucitol polymeric moiety from bimetallic solution was investigated by means of dynamic column experiments. The effect of solution pH on the separation efficiency and on the co‐removal level of metallic impurities was followed in this study. The conditions for efficient desorption of metals were determined in order to get the highly concentrated, impurities free solution suitable for recovery and reuse of separated metal. Effective separation of molybdenum and vanadium from boron or germanium and tungsten from arsenic was achieved.     

Partitioning of Actinides from High Level Waste of PUREX Origin Using Octylphenyl-N,N'-diisobutylcarbamoylmethyl Phosphine Oxide (CMPO)-Based Supported Liquid Membrane

Abstract

The present studies deal with the application of the supported liquid membrane (SLM) technique for partitioning of actinides from high level waste of PUREX origin. The process uses a solution of octylphenyl-N,N'-diisobutylcarbamoylmethyl phosphine oxide (CMPO) in n-dodecane as a carrier with a polytetrafluoroethylene support and a mixture of citric acid, formic acid, and hydrazine hydrate as the receiving phase. The studies involve the investigation of such parameters as carrier concentration in SLM, acidity of the feed, and the feed composition. The studies indicated good transport of actinides like neptunium, americium, and plutonium across the membrane from nitric acid medium. A high concentration of uranium in the feed retards the transport of americium, suggesting the need for prior removal of uranium from the waste. The separation of actinides from uranium-lean simulated samples as well as actual high level waste has been found to be feasible using the above technique.     

Sorption,diffusion, and pervaporation separation of water–acetic acid mixtures through the blend membranes of sodium alginate and guar gum‐grafted‐polyacrylamide

Nonporous homogeneous dense membranes were prepared from the blends of sodium alginate (Na–Alg) with guar gum‐grafted polyacrylamide (GG‐g‐PAAm) in the ratios of 3 : 1 and 1 : 1 and these were tested for the pervaporation separation of water–acetic acid mixtures at 30°C. Blend compatibility was studied in solution by measuring the viscosity and the speed of sound. Membranes were crosslinked by glutaraldehyde. The GG‐g‐PAAm polymer and the crosslinked blend membranes were characterized by Fourier transform infrared spectra. High separation selectivity was exhibited by the pure Na–Alg membrane for water–acetic acid (HAc) mixtures containing 20 mass % of water. The permeation flux increased with increasing mass percent of water in the feed as well as with an increase in the amount of GG‐g‐PAAm in the blend, but separation selectivity decreased. Sorption selectivity was higher for the Na–Alg membrane than for the blend membranes, but it decreased with increasing mass percent of GG‐g‐PAAm in the blends. Diffusion selectivity values vary systematically with the blend composition, but not with the amount of water in the feed. Diffusion coefficients of the water–HAc mixtures were calculated from Fick's equation using sorption data and compared with those calculated from flux values obtained in pervaporation experiments. The Arrhenius activation parameters were calculated for the 20 mass % of water in the feed using flux and diffusion data obtained at 30, 40, and 50°C. The diffusion and pervaporation results are explained in terms of solution–diffusion concepts. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 259–272, 2002     

Denitrifying phosphorus removal with nitrite by a real‐time step feed sequencing batch reactor

BACKGROUND: Nitrite is toxic to anoxic phosphorus uptake when it exceeds a threshold concentration. In this study, denitrifying phosphorus removal with nitrite as electron acceptor was investigated in a sequencing batch reactor (SBR) operated using a real‐time step feed strategy. RESULTS: The nitrite pulse concentration was initially determined by batch experiments. pH increased with use of nitrite for phosphate uptake, and decreased when the nitrite was used up. Nitrite was added promptly after the pH reached the peak value, and phosphate uptake continued, driven by the nitrite addition. The pH was adjusted to 7.50 using HCl with each pulse of nitrite addition. ORP could be used to determine the endpoint of denitrifiying phosphorus removal. However, the variation of second derivative of ORP with time was much more sensitive and should be a more suitable control parameter than ORP itself to determine the endpoint of denitrifying phosphorus removal. CONCLUSION: Compared with denitrifying phosphorus removal with nitrate as electron acceptor, denitrifying phosphorus removal with nitrite using real‐time step feed can save 22.3% of polyhydroxyalkanoate (PHA) for phosphorus removal and 49.4% of PHA for nitrogen removal. In addition, the reaction time could be shortened. Copyright © 2010 Society of Chemical Industry     

Permeation and Separation Characteristics of Acetic Acid‐Water Mixtures by Pervaporation through Acrylonitrile and Hydroxy Ethyl Methacrylate Grafted Poly(vinyl alcohol) Membrane

Abstract

In this study, acrylonitrile (AN) and hydroxyl ethyl methacrylate (HEMA) were grafted onto poly(vinyl alcohol) (PVA) using cerium (IV) ammonium nitrate as initiator at 30°C. The graft copolymer was characterized using the Fourier transform infrared spectroscopy (FTIR) and elemental analysis. The grafted PVA membranes (PVA‐g‐AN/HEMA) were prepared by a casting method, and used in the separation of acetic acid‐water mixtures by pervaporation. The effects of the membrane thickness, operating temperature, and feed composition on the permeation rate and separation factor for acetic acid‐water mixtures were studied. Depending on the membrane thickness, the temperature and feed composition PVA‐g‐AN/HEMA membranes gave separation factors 2.26–14.60 and permeation rates of 0.18–2.07 kg/m²h. It was also determined that grafted membranes gave lower permeation rates and greater separation factors than PVA membranes. Diffusion coefficients of acetic acid‐water mixtures were calculated from permeation rate values. The Arrhenius activation parameters were calculated for the 20 wt.% acetic acid content in the feed using the permeation rate and the diffusion data obtained at between 25–50°C.     

A low pressure SWCNT-ENM sandwich membrane system for the removal of PPCPs from water

While carbon nanotubes are known as efficient adsorbents for removal of a number of contaminants from water, the possibility of their leaching into drinking water has prevented their application in water treatment. In this study, single walled carbon nanotubes (SWCNT) were sandwiched between two electrospun nanofibre membranes (ENM). The relatively small pore size of the ENM prevented the mechanically entangled nanotubes from passing through and contaminating the water. The performance of the SWCNT-ENM was evaluated in a lab-scale setup for the removal of PPCPs. For this purpose, a feed solution spiked with known concentrations of six PPCPs was passed through the membrane system. The target substances included acetaminophen (ACT), bezafibrate (BZF), iopromide (IOP), diclofenac (DCF), carbamazepine (CBZ), and sulphamethoxazole (SMX). The same test was also conducted using a single contaminant (ACT). Results demonstrated a decrease in the overall percent removal of PPCPs as feed flow rate and PPCP concentration increased. For multi-component feeds containing equal amounts of the aforementioned PPCPs, the overall percent removal decreased from 90.8% to 71.0% when increasing the feed concentration from 30 to 600 μg/L. Experiments using sandwiched powdered activated carbon (PAC) showed that the dynamic adsorption capacity of PPCPs by SWCNT-ENM was higher than that of PAC-ENM, and remained unaffected by the feed composition. In addition, the high porosity of this novel membrane allowed for flow of water with low resistance such that the trans-membrane pressure was found to be as low as 4 kPa at a pure water flux of 330 L/m²h.     

Removal of Perchlorate from Contaminated Water Using a Regenerable Polymeric Ligand Exchanger

Abstract

A polymeric ligand exchanger (PLE), DOW 3 N‐Cu, has been investigated for perchlorate (ClO₄ ^?) removal from contaminated water. Batch kinetic tests revealed that the perchlorate sorption equilibrium for DOW 3 N‐Cu can be reached within 20 hours and perchlorate removal by DOW 3 N‐Cu follows standard ion exchange stoichiometry. Fixed‐bed column runs showed that 12,388 bed volumes of perchlorate‐free water can be obtained when DOW 3 N‐Cu was used to treat a simulated contaminated water with an influent perchlorate concentration of 200 µg/L. It was found that the regeneration of spent DOW 3 N‐Cu is pH dependent. It was shown that addition of ethanol and a surfactant Tween 80 to a 4% NaCl/2% NaOH regenerant solution increased the regeneration efficiency of spent DOW 3 N‐Cu by 11 and 5 percent, respectively. Nearly 90% of perchlorate capacity of saturated DOW 3 N‐Cu was recovered using 35 bed volumes of a regenerant containing 4% (w/w) NaCl, 2% NaOH, 5% Tween 80, and 5% ethanol.     

Selective Flotation‐Separation and Inductively Coupled Plasma‐Atomic Emission Spectrometric Determination of Ultra Trace Amounts of Silver Ion Using Bis(2‐mercaptoanil)acetylacetone

Abstract

A rapid, selective and highly sensitive flotation method is developed for separation and enrichment of ultra trace amounts of Ag⁺ ion from water samples. At pH 6.0 and using sodium dodecylsulfate as a foaming agent, Ag⁺ was separated with bis(2‐mercaptoanil)acetylacetone (BMAA) added to 1000 mL of aqueous solution. The proposed procedure of pre‐concentration is applied prior to the determination of silver ion using inductively coupled plasma‐atomic emission spectrometry (ICP‐AES). The influences of pH, concentration of BMAA, applicability of different surfactants and foreign ions on the separation efficiency were investigated. The pre‐concentration factor of the method is 1000 and the detection limit is 0.045 µg mL^?1.