Solvent Sublation Research Articles

Transport extraction for trace element separation and preconcentration

A new method of sorbent supported transport extraction based on the use of open-cell polyurethane foam sorbents in solvent sublation separation has been developed. The method has been shown to be effective for the separation and preconcentration of radioiodine and/or stable iodine from 41 of deionized, drinking (tap) and surface (river) waters using N-cetylpyridinium chloride as the cationic surfactant and N 2 carrier gas as the bubbling medium. A transport extraction efficiency of about 94% was obtained in 60 to 90 min; a 300-fold preconcentration was found for radioiodine as measured by direct radioactivity counting. Both radioiodine and stable iodine can be back-extracted from the polyurethane foam support (e.g. into acetone with an efficiency of almost 95%)

Gold recovery with solvent sublation from chloride solutions

Solvent sublation (SS) has been investigated for separating gold from dilute chloride solutions using hexadecyltrimethylammonium bromide (HTMAB) both as collector and surfactant. The composition of organic and aqueous phases, and operating conditions such as gas flowrate and aeration time were studied. As a result, 10% 2-octanol in kerosene with 0.05 M Aliquat 336 was chosen as the organic phase. It is shown that gold can be separated quantitatively from a solution with only 10 ppm Au, with enrichment of 20. Comparisons to ion flotation (IF) and solvent extraction (SX) were also made. SS was found to be more effective than IF. SX is a little more effective than SS, but it takes as long as 24 h for phase disengagement, compared to <3 min for SS.

Removal of organic dye (direct blue) from synthetic wastewater by adsorptive bubble separation techniques

C.I. Direct Blue 1, an anionic dye, was removed from synthetic wastewater by ion flotation of Direct Blue-hexadecyltrimethylammonium complex. Over 98% of Direct Blue was removed from the solution in 5 min. A stoichiometric amount of surfactant was found to be most effective for Direct Blue removal. The separation efficiency increased with increasing rate of air flow and decreased with increasing concentration of NaNO 3 . The efficiency of separation of Direct Blue by solvent sublation is similar to that by ion Dotation. Direct Blue was also removed by adsorbing colloid flotation with Fe(OH) 3 floc.

Non-foaming, adsorptive bubble process for wastewater treatment

Solvent sublation, the separation process for the removal of two hydrophobic compounds (penta- and trichlorophenols) from the aqueous phase, is discussed, as is a steady-state mathematical model for the process. Solvent sublation was conducted in a continuous counter current mode. The underlying mechanisms, theory and experimental details on the effects of process variables on removal efficiency are reported.

Transport extraction for trace element separation and preconcentration

Transport extraction based on solvent sublation has been used for a 400-fold preconcentration of iodide from aqueous samples into an immiscible organic solvent. Separation efficiencies amounting up to 95% were obtained for iodide concentrations of 1-10 mg/l, independent of the volume of the aqueous samples in the range of 1-41. Iodide was oxidized to iodine, which was subsequently transport-extracted as an ionic associate with the cationic surface-active agent N-cetylpyridinium chloride into 10 ml of benzene. The effect of various parameters (concentration of iodide, bubbling time, N 2 -gas flow-rate, volume of the aqueous phase) on transport extraction was investigated

Transport extraction for trace element separation and preconcentration

A new method of sorbent supported transport extraction based on the use of open-cell polyurethane foam sorbents in solvent sublation separation has been developed. The method has been shown to be effective for the separation and preconcentration of radioiodine and/or stable iodine from 41 of deionized, drinking (tap) and surface (river) waters using N-cetylpyridinium chloride as the cationic surfactant and N2 carrier gas as the bubbling medium. A transport extraction efficiency of about 94% was obtained in 60 to 90 min; a 300-fold preconcentration was found for radioiodine as measured by direct radioactivity counting. Both radioiodine and stable iodine can be back-extracted from the polyurethane foam support (e.g. into acetone with an efficiency of almost 95%).

Ion Flotation for Chemical Analysis

Ion flotation method for the preparative sample treatment before chemical measurements was reviewed.Ion flotation is an adsorptive bubble separation technique. It is based on the fact that surface active materials have the property of adsorption on the surface, in this case, gas-liquid interface.The method could be applied when 1) the solute to be measured become easily surface active after reacted with a complexing agent or else, 2) the formation of ion pair between the solute and a surface active agent is possible.In this paper, typical examples were shown to understand the variety of the methods. They are collective separations of metal ions using complexing agents and surfactants, those of anions through derivatizing them to be hydrophobic, and the solvent sublation method, in which the solvent put on the sample solution extracts the ion pairs coming up with the bubbles.Further, a new method for the selective collection of solutes using surface active cyclodextrin which has the capability of molecular recognition was proposed with preliminary results.

Removal of Organophosphorus Pesticides from Aqueous Solution by Using Adsorptive Bubble Separation Techniques

Abstract Two organophosphorus pesticides, ddvp (phosphoric acid 2,2-dichlorovinyl dimethyl ester) and phorate (phosphorodithioic acid o,o-diethyl s-[(ethylthio)methyl] ester) were removed from aqueous solution by three adsorptive bubble separation techniques: air stripping, solvent sublation, and adsorbing colloid flotation. The effects of pH, flow rate, surfactant, ethanol, ionic strength, and coprecipitant concentration on the efficiency of pesticide removal were studied. Over 97% of phorate was removed in 30 min by solvent sublation, and 90% of phorate was removed in 10 min by adsorbing colloid flotation with Fe(OH)3, floc. The separations of ddvp by these techniques were not effective.

Continuous countercurrent solvent sublation for the removal of hydrophobic organics from water

Solvent sublation in a continuous countercurrent mode for the removal of three hydrophobic organic compounds (viz. pentachlorophenol, 2,4,6-trichlorophenol and naphthalene) from water into mineral oil was investigated. Mathematical simulations of experimental results were achieved using a steady state “stagewise” model along with the determination of key hydrodynamic parameters for the bubble column such as bubble radius and number of equilibrium stages. The importance of using bubbles of small radii even at high air flow rates was apparent.

Studies in Batch and Continuous Solvent Sublation. IV. Continuous Countercurrent Solvent Sublation and Bubble Fractionation of Hydrophobic Organics from Aqueous Solutions

Abstract Experimental results on the solvent sublation of four hydrophobic compounds [pentachlorophenol (PCP), 1,2,4-trichlorobenzene (TCB), 2,3,6-trichloroanisole (TCA), and 2,4,6-trichlorophenol (TCP)] from the aqueous phase tc organic solvents are reported. The experiments were conducted with the aqueous and air phases in continuous countercurrent modes and the organic solvent as a stagnant layer. TCB, TCA, and TCP were sublated into mineral oil. PCP at pH 2.9 as neutral molecules were sublated into mineral oil and decyl alcohol while ionic PCP at pH 8.9 were sublated as a complex with hexadecyltrimethyl ammonium bromide into decyl alcohol. The effect of the two organic solvents were compared for neutral PCP sublation from the aqueous phase. The effects of air flow rates, influent feed rates, and the volume of organic solvent were studied. Comparisons were made between the bubble fractionation and solvent sublation of neutral PCP and TCP into mineral oil. The efficiency of sublation was largest for TCB...

Studies in Batch and Continuous Solvent Sublation. III. Solubility of Pentachlorophenol in Alcohol–Water Mixtures and its Effects on Solvent Sublation

Abstract The solubility of pentachlorophenol (PCP) in pure water and alcohol–water mixtures at pH = 2.5 and 5.0 at 25°C are reported. The use of the two-suffix Margules equation and UNIFAC to predict these effects is ascertained. The implications of these observations with respect to the solvent sublation of PCP in the presence of alcohol resulting from the redissolution of the organic solvent is also described.

Studies in Batch and Continuous Solvent Sublation. II. Continuous Countercurrent Solvent Sublation of Neutral and lonic Species from Aqueous Solutions

Abstract A complete mathematical model is proposed for the continuous countercurrent operation of a solvent sublation column. It takes into account all possible transport mechanisms in sublation. This is an extension of a previously published model for a lab-scale batch process. Experimental results on the continuous countercurrent removal of pentachlorophenol as a pentachlorophenolate + hexadecyltrimethyl ammonium bromide complex into decyl alcohol is also reported and checked against the model.

Solvent Sublation and Adsorbing Colloid Flotation of Acid Red

Abstract Acid Red 114. an anionic dye, was removed from aqueous solution by solvent sublation of Acid Red–hexadecyltrimethylammonium complex into paraffin oil. 95% of Acid Red was removed from the solution in 5 min by solvent sublation. A stoichiometric amount of surfactant (1 mol surfactant to 1 mol dye) was found to be most effective for Acid Red removal. The effect of neutral salts and ethanol on solvent sublation was studied. Adsorbing colloid flotation of Acid Red with Fe(OH)3 floc and sodium lauryl sulfate was very effective, with 99% of Acid Red removal in 5 min. Adsorbing colloid flotation of Acid Red with Al(OH)3 floc was also effective, with 99% of Acid Red removal in 3 min. The effect of neutral salts on adsorbing colloid flotation was studied.

Studies in Batch and Continuous Solvent Sublation. I. A Complete Model and Mechanisms of Sublation of Neutral and Ionic Species from Aqueous Solution

Abstract A complete model incorporating all known transport mechanisms for solutes between aqueous and organic solvent phases in solvent sublation is proposed. The predictions from the model with respect to the different transport mechanisms were substantiated with experiments on the solvent sublation of neutral pentachloro-phenol (PCP) molecules (pH = 3.0) and ionic PCP molecules as PCP + hexadecyl trimethyl ammonium bromide complex (pH = 8.9) into different solvents—mineral oil (a nonionic solvent) and decyl alcohol (a partly ionic solvent). Effects of inorganic salts on the sublation of both types of PCP molecules were investigated.

Adsorptive Bubble Separation of Heptachlor and Hydroxychlordene

Abstract Heptachlor (HTC) and its hydrolytic product, 1-hydroxychlordene (HDCD), were removed from aqueous solutions by air stripping, solvent sublation, and foam fractionation. The effects of air flow rate, added salt, ethanol, and surfactants were studied. Foam fractionation was found to be most effective, with 99% of HTC and 97% of HDCD being removed from the aqueous solution in 5 min. This study shows that foam fractionation may find applicability for nonionic organic pollutants removal from aqueous solution. Those nonionic organic pollutants which can be removed by solvent sublation may also be removed by foam fractionation with much better separation efficiency and no organic phase (such as paraffin oil) being required.

Removal of organic compounds from water by solvent sublation

Under some circumstances the removal of organic hydrocarbons from water by stripping with air bubbles can be enhanced significantly using solvent sublation. In solvent sublation, part of the solute concentrated in nongaseous form within the Gibbs layer of the rising bubbles is intercepted and removed by an immiscible solvent floating on the surface of the water undergoing purification. In the present investigation of air stripping conducted with and without solvent sublation, concentration profiles along a column were measured as a function of time. The effects of solute volatility and solvent properties on the removal of hydrocarbons were investigated quantitatively. The solutes studied in this work were toluene and o-dichlorobenzene and the sublation solvents used were mineral oil, 1-octanol, and 2-octanol. In the removal of toluene from water, sublation with 1- and 2-octanol as solvents gave better results than sublation with mineral oil as solvent. Sublation with mineral oil as solvent produced results about equivalent to those of air stripping without solvent sublation. For o-dichlorobenzene removal from water, sublation with 1-octanol as solvent gave the highest removal rate, followed by sublation with 2-octanol, sublation with mineral oil, and, finally, air stripping without solvent sublation. The differences in the removal of hydrocarbons by solventless air stripping and that by solvent sublations with different solvents can be rationalized in terms of the differing volatilities of the hydrocarbon solutes and the differing physical properties of the sublation solvents.

Adsorptive Bubble Separation of Dinitrophenol

AbstractDinitrophenol was removed from aqueous solution by various adsorptive bubble separation techniques. Foam fractionation of dinitrophenol with hexadecyltrimethylammonium bromide(HTA) was most effective with over 99% removal in 15 min. The addition of a surfactant in greater than stoichiometric amounts was required for effective separation. Solvent sublation of the dinitrophenol‐HTA complex was also effective. The separation efficiency of solvent sublation of dinitrophenol‐HTA was similar to that of foam fractionation. The separation by solvent sublation of dinitrophenol without adding any surfactant was very poor. Adsorbing colloid flotation with Fe(OH)3 was not effective in removing dinitrophenol from aqueous solution.

Solvent Sublation of Hexachlorobutadiene and 2,4,6-Trichlorophenol

Abstract Hexachlorobutadiene and 2,4,6-trichlorophenol were removed from aqueous solutions into paraffin oil by solvent sublation. Over 99% of hexachlorobutadiene was removed from a solution containing 100 ppb hexachlorobutadiene initially in 10 min. The rate of removal of hexachlorobutadiene by air stripping is somewhat slower than that by solvent sublation. The effects of added salt and ethanol on solvent sublation and air stripping of hexachlorobutadiene were studied. About 64% of 2,4,6-trichlorophenol were removed by solvent sublation from a solution containing 50 ppm 2,4,6-trichlorophenol initially at pH 1.84 for a 1-h run. The rate of removal of 2,4,6-trichlorophenol can be improved by adding the cationic surfactant, hexadecyltrimethylammonium bromide (HTA). As high as 95% of 2,4,6-trichlorophenol was removed in 1 h if 10 ppm HTA was added to the solution before solvent sublation runs.

Selective Flotation of Metal Ions by Using Chelating SurfactantS

Chelating surfactants have been prepared and applied as ion-flotation collectors. Metal ions are floated by scum flotation using the surfactants in a HLB range of 4-14, which are regulated by varying the alkyl group. The selective flotation from the metal ions mixture has been attributable to the smaller HLB of the metal complexes. The HLB values of 16-24 are suitable for foam fractionation and those of 1-6 are for solvent sublation.

Solvent Sublation-Spectrophotometric Determination of Trace Nickel(II) in Drinking Water

A solvent sublation-spectrophotometrc method for the determination of nickel(II) is proposed. Solvent sublation is used here to concentrate trace nickel(II) using 1-(2-pyridylazo)-2-naphthol (PAN) as a collector. At pH 3 to 11 a red complex of nickel(II) formed with PAN can be floated with the aid of small nitrogen bubbles, then dissolved in benzene. The main factors affecting the solvent sublation of nickel(II) were determined by an orthogonal experimental method. This method permits the determination of nickel(II) in the range 0-1μg/ml and can be applied to samples of drinking water with good results.