Removal of contaminants from essential oils

Abstract

NOT VISIBLE DUE TO STATUS OF PATENT

Description

[0001] REMOVAL OF CONTAMINANTS FROM ESSENTIAL OILS

[0002] HELD OF THE INVENTION

[0003] The invention generally relates to the removal of contaminants such as agricultural residues from essential oils.

[0004] BACKGROUND OF THE INVENTION

[0005] Essential oils are commonly used to flavor food and drink, and enhance aroma in incense, perfumes, and household cleaning products. Many essential oils, such as citrus, lavender, and mint, are produced by extracting the oils from the surface of the plant or the peel of the fruit. Chemicals, such as pesticides, herbicides, insecticides, and fungicides, are used in the plant growing process. Agricultural residues (ARs) are chemicals remaining on the exterior surfaces of the plant and fruit after washing during harvest. As a result, ARs contaminate the extracted essential oil. Many ARs are toxic, and regulatory bodies globally have restricted or banned their use in farming and their presence in food additives, especially flavorings.

[0006] ARs are difficult to remove from essential oils due to their molecular structure and low concentration requirements. Several removal methods have been investigated. A distillation method has been investigated to separate ARs from essential oils by removing a high-pesticide distillate from the remaining mixture. Contacting contaminated essential oil with a strong ion exchange resin has been explored. Passing the contaminated essential oil over a selectively permeable membrane has also been tested. These methods have broadly failed to isolate ARs from the essential oil’s significant flavor molecules and negatively impacts the sensory (i.e., taste or smell) acceptability, which affects the quality of the essential oil product being produced.

[0007] Therefore, it is desirable to devise alternative, commercially feasible processes to remove ARs and other contaminants from essential oils to meet regulatory requirements without affecting the sensory acceptability. Such alternative processes would allow essential oil derived from plants and fruit grown in countries where harmful chemicals have not been phased out to be effectively processed. BRIEF SUMMARY OF THE INVENTION

[0008] A process has been developed for removing contaminants such as agricultural residues (ARs) from essential oils, such as citrus peel oils, including orange, mandarin, lemon, lime, and grapefruit.

[0009] In accordance with one embodiment, the process comprises contacting an ion exchange resin in silver form with the contaminated essential oil such that at least a portion of the contaminant is retained by the ion exchange resin and producing a treated effluent comprising the essential oil having a reduced concentration of the contaminant. Once the resin is exhausted as indicated by an increase in the concentration of contaminant in the treated effluent, as determined by gas chromatography tandem mass spectrometry (GC-MS-MS), the exhausted ion exchange resin is contacted with a silver salt solution to recharge the ion exchange resin with silver and produce a recharging effluent. The silver ions from the silver salt solution replace silver ions bound to the contaminant on the ion exchange resin, releasing the contaminant from the resin in the form of a silver salt-contaminant complex in the recharging effluent.

[0010] In accordance with another embodiment, the process comprises contacting an ion exchange resin with a solution of a silver salt such that silver ions are bound to the ion exchange resin to produce an ion exchange resin in silver form. The ion exchange resin in silver form is contacted with a rinse solvent to remove unbound silver ions and produce a rinsed ion exchange resin in silver form. The rinsed ion exchange resin in silver form is contacted with the contaminated essential oil such that at least a portion of the contaminant is retained by the ion exchange resin to produce a treated effluent comprising the essential oil having a reduced concentration of the contaminant. Once the ion exchange resin is exhausted as indicated by an increase in the concentration of contaminant in the treated effluent, the resin is contacted with a wash solvent to remove residual essential oil. The washed exhausted ion exchange resin is then contacted with a silver salt solution to recharge the ion exchange resin with silver and produce a recharging effluent. Silver ions replace silver ions bound to the contaminant on the ion exchange resin, releasing the contaminant from the resin in the form of a silver salt-contaminant complex in the recharging effluent. The process further comprises producing an aqueous solution of a silver salt from the recharging effluent and contacting the ion exchange resin with the silver salt solution produced from the recharging effluent.

[0011] Other objects and features will be in part apparent and in part pointed out hereinafter.

[0012] BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0013] Figure 1 is a schematic illustration of a fixed bed ion exchange system in a down flow arrangement for the removal of contaminants from an essential oil in accordance with one embodiment of the invention.

[0014] Figure 2 is a schematic illustration of an electro-dialysis cell for recovery of a silver salt solution from an effluent feed comprising a silver-containment complex and / or other silver ion-containing process effluent in accordance with one embodiment of the invention.

[0015] Figure 3 is a schematic illustration of the electro-dialysis cell for recovery of a silver salt solution used in Example 3.

[0016] DETAILED DESCRIPTION OF THE INVENTION

[0017] The present invention relates to a process of removing contaminants such as agricultural residues from an essential oil without affecting the essential oil’s significant flavor molecules. Various aspects of the invention relate to an adaptation of argentation chromatography in which an ion exchange resin in silver form is contacted with contaminated essential oil to produce essential oil with a lower concentration of contaminant. The ion exchange resin in silver form is prepared by contacting an ion exchange resin with a solution comprising a silver salt prior to contact with the essential oil and recharging the ion exchange resin with silver ions as needed during the process. Further, aspects of the invention relate to recovering the silver used in the process to produce the silver salt solution for reuse in the process.

[0018] In one embodiment, the process for removing a contaminant from an essential oil comprises contacting an ion exchange resin in silver form with the contaminated essential oil such that at least a portion of the contaminant is retained by the ion exchange resin to produce a treated effluent comprising the essential oil having a reduced concentration of the contaminant. Treatment of the contaminated essential oil continues until the resin is exhausted as indicated, for example, by an increase in the concentration of contaminant in the treated effluent. An example contaminant concentration detection method may include, but is not limited to, GC-MS-MS. The exhausted ion exchange resin is then contacted with a silver salt solution to recharge the ion exchange resin with silver and produce a recharging effluent. During recharging, silver ions from the silver salt solution replace silver ions bound to the contaminant on the ion exchange resin, releasing the contaminant from the resin in the form of a silver salt-contaminant complex. The recharging effluent comprises the silver salt-contaminant complex.

[0019] As detailed herein, the ion exchange resin in silver form is suitably produced by contacting the ion exchange resin with a solution of a silver salt to charge the ion exchange resin with silver ions bound to the resin.

[0020] In certain embodiments, the process further comprises recovering silver from the recharging effluent to produce a silver salt solution for use in charging and recharging the ion exchange resin.

[0021] The ion exchange resin used in the process suitably comprises a matrix in the form of small microbeads that are insoluble in the process liquids with which it is contacted. For example, the resin may be fabricated from an organic polymer substrate having a highly porous structure. Typically, the polymer substrate from which the ion exchange resin is formed has a degree of cross-linking density of less than about 30% or less than about 20%, based on the total weight % of an added cross-linking monomer. In one embodiment, a suitable cross-linking monomer comprises divinylbenzene.

[0022] In one embodiment, the ion exchange resin is a strongly acidic cation exchange resin with positively charged ions (e.g., H+or Na+). In one embodiment, the ion exchange resin has a sulfonic acid active functional group.

[0023] The ion exchange resin is selected to exhibit a binding capacity sufficient to effectively bind silver and contaminants under given flow conditions before a significant breakthrough occurs. Silver binding capacity is determined by the amount of a silver salt solution that passes over the resin before breakthrough of Ag-i- is observed in the eluent. Generally, a resin exhibiting a relatively high silver binding capacity will provide a higher contaminant removal efficacy. For example, in one embodiment, the resin exhibits a binding capacity of at least about 0.8 meq / mL and a silver (Ag+) binding capacity of at least about 1.4 mmol Ag+ / g. Resins exhibiting silver (Ag+) binding capacities as low as 0.1 mmol Ag+ / g may be employed, but contaminant removal efficacy will be lowered.

[0024] A resin with a higher silver binding capacity will typically have an increased number of functional groups attached to the resin, which correlates with the efficacy of the resin's contaminant removal. A higher number of functional groups tends to reduce the pore volume and surface area of the resin. Accordingly, in accordance with some embodiments, increasing the binding capacity of the resin tends to proportionally reduce the pore volume and the surface area.

[0025] In certain embodiments, the highly porous structure of the ion exchange resin may be characterized by one or more properties, including an average pore diameter of from about 15 nanometers to about 30 nanometers and in one embodiment from about 20 nanometers to about 25 nanometers, as determined using the BJH method with a sharp monomodal distribution with standard deviation from about 1.5 to about 3 nanometers; and / or a specific pore volume of from about 0.2 ml / g to about 0.9 ml / g or from about 0.2 ml / g to about 0.4 ml / g as determined using the BJH method; and / or total surface area of from about 25 m2 / g to about 400 m2 / g, for example, from about 25 m2 / g to about 50 m2 / g or from about 25 m2 / g to about 40 m2 / g or from about 250 m2 / g to about 350 m2 / g as determined by BET analysis.

[0026] Examples of suitable commercially available ion exchange resins useful in the practice of the present invention include the ion exchange resin sold under the tradename RELITE RAD / F, commercially available from Mitsubishi Chemical Corporation (Tokyo, Japan). This resin is a highly porous copolymer of styrene- divinylbenzene (DVB), classified as a strongly acidic cationic ion exchange resin and having a sulfonic acid active functional group. A further example of a suitable ion exchange resin for use in the practice of the present invention is that sold under the tradename DIAION RCP200, also commercially available from Mitsubishi Chemical Company. This resin is classified as a highly porous type, strongly acidic cation exchange resin with a copolymer / matrix of styrene-DVB and a sulfonic acid active functional group. Other strongly acidic ion exchange resins suitable for use in the present invention can be readily identified by those skilled in the art.

[0027] The ion exchange resin is disposed in a suitable vessel having one or more inlets for introducing the contaminated essential oil and other reagents as described herein and one or more outlets for removing the treated effluent. The ion exchange vessel may be constructed out of various materials such as glass, fiberglass, or metal. The dimensions of the vessel and quantity of ion exchange resin disposed therein is dependent on the volume of contaminated essential oil that needs to be treated and can be readily determined by those skilled in the art.

[0028] The ion exchange resin may be disposed within the vessel in the form of a fixed bed or may be gently mixed with the contaminated essential oil and other process liquids contacted with the resin. Typically, the contaminated essential oil to be treated enters the vessel through one or more inlets and the treated effluent exits the vessel through one or more outlets opposite the one or more inlets. Liquid flow from the one or more inlets, through the ion exchange vessel and to the one or more outlets can be downward or upward. In a fixed bed down flow embodiment, contaminated essential oil may be distributed over the top of the ion exchange resin to enhance contact with the resin as it flows downwardly through the fixed bed.

[0029] Turning to Fig. 1, an essential oil treatment system 1 in a fixed bed, down flow embodiment is illustrated schematically. Ion exchange vessel or column 3 has a fixed bed 5 comprising ion exchange resin disposed therein. Column 3 comprises a head 7 at the top of the column having an inlet 9 through which process liquids, such as contaminated essential oil and silver salt solution, are introduced into the column and distributed over fixed bed 5. Process liquids introduced into column 3 contact the ion exchange resin and flow downwardly through fixed bed 5 and are discharged as effluents from a bottom 11 of the column through an outlet 13.

[0030] In a mixed ion exchange vessel embodiment, the contaminated oil and other process liquids in contact with the ion exchange resin may be mixed using impellers and / or the motive force of the process liquids introduced to the vessel through the one or more inlets.

[0031] In one embodiment, the process for removing contaminants from an essential oil is operated as a cycle that may include four distinct steps: charging; treatment; recharging; and silver recovery and salt regeneration.

[0032] Charging

[0033] In order to prepare the ion exchange resin in silver form ready for removal of contaminants from the essential oil to be treated, a silver salt solution in an appropriate solvent is contacted with the ion exchange resin to transfer silver ions (Ag+) present in the silver salt solution to the resin. Charging the ion exchange resin with silver ions suitably takes place in the ion exchange vessel in which the resin is disposed. The ion exchange resin comprises a strongly acidic cationic ion exchange resin with positively charged ions bound to the resin. During the charging step, the silver ions (Ag+) from the salt solution preferentially displace cations on the resin into a charging effluent comprising a salt of the displaced cations, which is removed from the vessel. In one embodiment, the cation bound to the ion exchange resin is hydrogen ions (H+) and the silver salt solution is an aqueous solution of silver nitrate ( AgNC ) such that the charging effluent comprises nitric acid (HNO3). In another embodiment, the cation bound to the ion exchange resin is sodium ions (Na+) and the silver salt solution is silver nitrate such that the charging effluent comprises sodium nitrate (NaNC ). Although an aqueous solution of silver nitrate can be suitably used as the salt solution to prepare the resin in silver form, other silver salts such as silver chloride (AgCl) and silver sulfate (Ag2SC>4) can be employed so long as the solvent used to form the salt solution is selected to ensure sufficient solubility of the silver salt. For example, a silver salt solution can be prepared from silver chloride using ammonia, hydrochloric acid, or sulfuric acid as the solvent.

[0034] The concentration of the silver salt in the charging solution is not narrowly critical. Generally, higher concentrations of the silver salt will speed the formation of the ion exchange resin in silver form. Typically, the concentration of the silver salt is from about 0.1 N to about 2 N. Similarly, the volume and flowrate of the silver salt charging solution will vary depending on the quantity and type of ion exchange resin and can be adjusted as needed by monitoring the charging endpoint as described herein.

[0035] In order to determine the progress and endpoint of the charging step, the pH of the charging effluent exiting the ion exchange resin can be monitored at intervals or continuously using a pH meter and compared to the pH of the silver salt solution. For example, in an embodiment where the ion exchange resin is in H+form and the silver salt solution is an aqueous solution of silver nitrate, the charging effluent exiting the ion exchange resin at the start of the charging step will initially have a pH of from about 1 to about 2 due to the high concentration of nitric acid in the effluent. As the charging step progresses, the pH of the charging effluent exiting the ion exchange resin will become less acidic as fewer H+ions are being displaced. In accordance with one such embodiment, the charging step is considered sufficiently complete, for example, when the monitored pH of the charging effluent has increased to from about 1 to about 6.

[0036] Following the charging step and prior to the subsequent treatment of the contaminated essential oil, the ion exchange resin in silver form may optionally be rinsed with a rinse solvent to remove any unbound silver ions from the resin. For example, in one embodiment, the ion exchange resin in silver form is first contacted and rinsed with water followed by an approximately equal volume of an organic solvent miscible with water (e.g., ethanol). The water suitably removes the silver ions and the organic solvent rinse removes the water from the resin that could cause an undesirable biphasic response during subsequent treatment. The water used to rinse the ion exchange resin in silver form containing silver ions may be collected as a rinse effluent and forwarded to the silver recovery and salt regeneration step described below.

[0037] Treatment

[0038] The treatment step comprises removing contaminant from the essential oil by contacting the contaminated essential oil with the rinsed ion exchange resin in silver form disposed within the ion exchange vessel. The contaminant in the essential oil bonds to silver ions bound to the ion exchange resin, thereby removing the contaminant from the essential oil. The treated essential oil is discharged from the ion exchange vessel as a treated effluent comprising the essential oil having a reduced concentration of contaminant. The concentration of contaminants in the treated effluent can be reduced by about 90%, about 95% or about 99% or greater as compared to the original concentration, depending on the chemical structure of the contaminants considered.

[0039] The volume and flowrate of the contaminated essential oil contacted with the ion exchange resin will vary depending on the capacity of the treatment system including the quantity and type ion exchange resin, the concentration and type of contaminant to be removed and the desired purity of the treated essential oil and can be adjusted as needed by monitoring concentration of the contaminant in the treated effluent as described herein. The progress of the treatment step may be monitored by determining the concentration of contaminant in a sample or fraction of the treated effluent exiting the ion exchange vessel at intervals or continuously. For example, in one embodiment, the contaminant concentration in a sample of treated effluent is measured offline using gas chromatography-mass spectrometry (GC-MS). The specific GC-MS analysis methodology is dependent on the target contaminant that is being measured and is well-known in the art.

[0040] The ion exchange resin in silver form continues to remove contaminant from essential oil until the available silver ions bound to the ion exchange resin are depleted resulting in significant breakthrough of contaminant in the treated effluent as determined by the concentration of contaminant in the treated effluent increasing above a specified limit. For example, in one embodiment the treatment step is continued until the concentration of contaminant in the treated effluent is reduced to a level of no greater than about 10 ppm, no greater than about 5 ppm, no greater than about 3 ppm, no greater than about 1 ppm or less as desired.

[0041] Once the concentration of contaminant in the treated effluent exceeds the desired specification, the ion exchange resin is exhausted (i.e., the ion exchange resin no longer has enough bound silver ions available to effectively remove the contaminant from the essential oil) and the exhausted resin is recharged as disclosed below. Typically, the ion exchange vessel and quantity of ion exchange resin are sized such that multiple bed volumes (volume of oil / volume of resin) of the contaminated essential oil can be treated before the ion exchange resin is exhausted.

[0042] Recharging

[0043] The exhausted ion exchange resin is optionally washed with a wash solvent to remove essential oil residue from the resin prior to recharging the resin with silver ions. In one embodiment, the exhausted ion exchange resin is suitably washed with a solution comprising approximately equal volumes of water and an organic solvent (e.g., ethanol).

[0044] The washed exhausted ion exchange resin is subsequently recharged by contacting the washed resin with a silver salt solution, for example, the same silver salt solution used in the initial charging of the ion exchange resin, to thereby regenerate the resin in silver form and produce a recharging effluent. During recharging, silver ions from the silver salt solution replace silver ions bound to the contaminant on the ion exchange resin, releasing the contaminant from the resin in the form of a silver salt-contaminant complex (e.g., AgNOs-AR complex). As the ion exchange resin is recharged with silver ions, the silver salt-contaminant complex is discharged from the ion exchange vessel as part of the recharging effluent.

[0045] The recharged ion exchange resin in silver form is used to treat additional contaminated essential oil by repeating the treatment and recharging steps until the efficacy of the ion exchange resin in contaminant removal is sufficiently depleted (e.g., as determined by a significant decrease in the contaminant breakthrough time), at which time a portion or all of the ion exchange resin may be replaced with fresh resin and charged with silver ions.

[0046] Silver Recovery and Salt Regeneration

[0047] A further aspect of the invention is recovering silver from the recharging effluent and other silver ion-containing process effluents. The recovered silver may be used to produce a silver salt solution that can be used to produce and recharge the ion exchange resin in silver form. In addition to the recharging effluent, the rinse effluent generated when rinsing unbound silver ions from the ion exchange resin with water following the charging step may be processed for silver recovery.

[0048] In accordance with one embodiment, elemental silver is recovered by electroplating. In such an embodiment, an electroplating bath comprising the recharging effluent comprising the silver salt-contaminant complex and / or other silver ion-containing process effluent is introduced into the container of an electroplating cell into contact with an anode and a cathode. An electric current is then applied and passed through the cell such that silver ions in the bath deposit as elemental silver onto the anode until the electroplating capacity of the anode is depleted. The construction of such a cell and its operation are well-known in the electroplating art. In one embodiment, the cathode comprises graphite and the anode comprises platinum.

[0049] After recovery of the silver, the electroplating bath comprising low levels of contaminant may be disposed of appropriately, for example, as process wastewater.

[0050] The recovered elemental silver can be used to regenerate a silver salt solution used in the charging and recharging steps. For example, in one such embodiment, the anode with elemental silver deposited thereon and the cathode are subsequently contacted with an aqueous acidic electrolyte solution comprising a mineral acid and the polarity of electrical current applied to the anode and cathode of the cell is reversed. Silver ions are transferred into the electrolyte solution to form a silver salt solution with the anion of the mineral acid. The mineral acid is selected such that the regenerated silver salt is the same salt desired for use in charging and recharging the ion exchange resin. For example, nitric acid is used to form a silver nitrate solution, hydrochloric acid is used to form silver chloride solution or sulfuric acid is used to form silver sulfate solution.

[0051] Example 2 provides a detailed description of an electroplating process used to recover elemental silver from the recharging effluent and regenerating a silver nitrate salt solution from the recovered silver.

[0052] In accordance with another embodiment, silver ions are isolated from the recharging effluent comprising the silver salt-contaminant complex and / or other silver ion-containing process effluent by electro-dialysis to regenerate a silver salt solution used in the charging and recharging steps. In such embodiment, an electro-dialysis cell comprising multiple compartments separated by alternating anionic and cationic permeable membranes disposed between a cathode and an anode is used to regenerate a silver salt solution. The construction and operation of suitable electro-dialysis cells for use in the present invention are well-known in the electro-dialysis art.

[0053] In accordance with such embodiment, an effluent feed and a receiving feed are introduced into adjacent compartments of the electro-dialysis cell. The effluent feed comprises the recharging effluent and / or other silver ion-containing process effluent and the receiving feed comprises a mineral acid solution. The mineral acid is selected such that the regenerated silver salt is the same salt desired for use in charging and recharging the ion exchange resin. For example, nitric acid is used to form a silver nitrate solution, hydrochloric acid is used to form silver chloride solution or sulfuric acid is used to form silver sulfate solution.

[0054] An electrical current is applied to the cell such that ions are transported through either the cationic or the anionic permeable membranes (i.e., the silver cations (Ag+) in the effluent feed are transferred through the cationic permeable membranes towards the cathode and anions in the effluent feed are transferred through the anionic permeable membrane towards the anode). The configuration of the electro-dialysis cell causes the cations and anions to be concentrated in the compartments comprising the receiving feed solution thereby generating a concentrated silver salt solution and depleted feed comprising the silver saltcontaminant complex that are discharged from the cell.

[0055] The depleted feed comprising low levels of the silver salt-contaminant complex may be disposed of appropriately, for example, as process wastewater.

[0056] Turning to Fig. 2, one embodiment of an electro-dialysis cell for recovery of a silver salt solution from an effluent feed comprising the recharging effluent comprising an AgNCh-AR complex and / or other silver ion-containing process effluent and utilizing a receiving feed comprising a nitric acid solution (HNO3) is illustrated schematically. Application of an electric current causes nitrate ions (NO3 ) to transfer through the anionic permeable membranes towards the anode and the silver ions (Ag+) to transfer through the cationic permeable membranes towards the cathode.

[0057] Examples of commercially available cationic ion exchange membranes useful in the practice of the present invention include the cationic ion exchange membranes sold under the tradename CMX commercially available from ASTOM Corporation. Examples of commercially available anionic ion exchange membranes useful in the practice of the present invention include the cationic ion exchange membranes sold under the tradename Neosepta AMX, and commercially available from ASTOM Corporation.

[0058] Example 3 provides a detailed description of an electro-dialysis process used to regenerate silver nitrate salt solution from the recharging effluent.

[0059] Essential Oils and Contaminants

[0060] The present invention can be used to remove contaminants found in a variety of essential oils. In one embodiment, the essential oil to be treated in accordance with the present invention is derived from citrus fruit peel oils (e.g., cold-pressed citrus fruit peel oils). Citrus fruits include orange, lemon, lime, tangerine, grapefruit, etc.

[0061] The present invention can be used to remove a variety of contaminants from essential oils, including without limitation, agricultural residue (AR) contaminants such as pesticides, herbicides, insecticides, and fungicides used in growing plants and fruits from which the essential oil is derived. In the case of citrus fruit peel oils, these AR contaminants remain on the fruit’s peel even after washing during harvest and contaminate the essential oil derived from the peel.

[0062] In one embodiment of the present invention, the contaminant includes a sulfurphosphorous bond, for example, organothiophosphate ARs.

[0063] Non-limiting examples of AR contaminants include methamidophos, parathion, malathion, ethion, chlorpyrifos, propiconazole, fenbuconazole, difenoconazole, tebuconazole, prochloraz, pyrimethanil, trifloxystrobin, propargite, bifenthrin, triphenyl thiophosphate, phosmet, and any combination thereof. The process of the present invention is particularly effective in removing chlorpyrifos, tebuconazole, and phosmet from essential oils such that the concentration of these contaminants is reduced to very low levels (e.g., 100 ppb or less).

[0064] Having described the invention in detail, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.

[0065] EXAMPLES

[0066] The following non-limiting examples are provided to further illustrate the present invention.

[0067] Example 1. Agricultural Residue removal from orange essential oil

[0068] Charging: 30 mL of a strongly acidic ion exchange resin comprising hydrogen ions sold under the tradename RELITE RAD / F, commercially available from Mistsubishi Chemical Corporation, was loaded into a 15 mm diameter glass column. An ion exchange resin in silver form was produced by feeding 90 mL of a 0.25N silver nitrate solution into the glass column at 1-2 mL / min such that the silver nitrate solution contacted the ion exchange resin. The silver ions preferentially displaced the hydrogen ions on the resin into a charging effluent which was removed from the vessel. The pH of the charging effluent at the end of silver nitrate feed was between about 5 to about 6. The ion exchange resin in silver form was then successively rinsed with 50 mL of water at 1-2 mL / min followed by 50 mL of ethanol at 1-2 mL / min.

[0069] Treatment: An essential oil derived from orange, concentrated by a factor of 10 and comprising 4 ppm chlorpyrifos, 12 ppm malathion, 6 ppm pyrimethanil, and 6.2 ppm phosmet was fed into the glass column at 1-2 mL / min such that the essential oil contacted the ion exchange resin in silver form to remove ARs. A total of 3 to 4 bed volumes (volume oil / volume of resin) may be treated before the resin is exhausted. The concentrations of ARs in the treated effluent were reduced to <0.01 ppm chlorpyrifos, <0.1 ppm malathion, <0.2ppm pyrimethanil, and <0.1 ppm phosmet.

[0070] Recharging-. The exhausted resin was washed with a solution comprising 100 mL of ethanol and 50 mL of water to remove residual oil from the resin. 90 mL of a 0.25N silver nitrate solution was passed through the ion exchange resin for recharging and generating a recharging effluent comprising silver nitrate- AR complex ( AgNCh- AR). The recharged resin underwent treatment and recharging steps for 5 regeneration cycles with no significant decrease in the volume of orange essential treated before breakthrough was observed.

[0071] Example 2: Recovering silver from recharging effluent by electroplating.

[0072] A 0.095N silver nitrate-AR complex (AgNCh-AR) solution from the recharging effluent produced in Example 1 was introduced into a beaker of an electroplating cell into contact with a graphite cathode and a platinum anode. An electric current was applied at 0.4 amps for 32 minutes at 2-3 volts such that silver ions in the silver nitrate-AR complex deposit as elemental silver on the anode. The anode with elemental silver thereon and the cathode were introduced to a 0.1M nitric acid solution. The polarity of the electrical current applied to the anode and cathode of the cell was reversed. The deposited elemental silver transfers to the nitric acid solution such that a silver nitrate (AgNOs) solution was formed without bound ARs. The silver nitrate solution was used in charging and recharging the ion exchange resin.

[0073] Example 3: Recovering silver from recharging effluent by electro-dialysis As illustrated in Fig. 3, four solutions were introduced into a four- compartment glass electro-dialysis cell comprising a cathode and an anode at either end. A IM sodium nitrate (NaNCL) was introduced into the catholyte cell. A IM sodium sulphate (Na2SO4) solution was introduced into the anolyte cell (opposite the catholyte cell). A IM nitric acid (HNO3) solution was introduced in the compartment adjacent the catholyte cell. A 0.095N silver nitrate - AR complex (AgNCL-AR) solution from the recharging effluent produced in Example 1 , was introduced in the compartment adjacent the anolyte cell, such that the silver nitrate-AR solution and the nitric acid solution were adjacent. The compartments comprising the nitric acid solution and silver nitratecomplex were separated by a cationic ion exchange membrane sold under the tradename Neosepta CMX, commercially available from ASTOM Corporation. The anolyte cell and catholyte cell compartments were separated from adjacent compartments by an anionic ion exchange membranes sold under the tradename Neosepta AMX, commercially available from ASTOM Corporation.

[0074] An electric current was applied to the electro-dialysis cell at 0.20- 0.09 amps for 40 minutes. Silver ions (Ag+) from the silver nitrate- AR complex solution were pulled through the cationic permeable membrane to the nitric acid solution. Nitrate ions (NO3 ) from the sodium nitrate solution were pulled through the anionic permeable membrane to the nitric acid solution. Nitrate ions (NO3 ) in the silver nitrate- AR complex solution were pulled through the anionic permeable membrane to the sodium sulfate solution. The additional ions in the nitric acid solution formed a concentrated silver nitrate ( AgNCh) solution which was used for charging and recharging the ion exchange resin. The silver nitrate-AR complex solution was discharged from the cell as a depleted feed with a silver concentration reduced by 76%.

[0075] When introducing elements of the present invention or the various embodiments(s) thereof, the articles "a", "an", "the" and "said" are intended to mean that there are one or more of the elements. The terms "comprising", "including" and "having" are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0076] In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

[0077] As various changes could be made in the above processes without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawing[s] shall be interpreted as illustrative and not in a limiting sense.

Claims

CLAIMS:

1. A process for removing a contaminant from an essential oil comprising: contacting an ion exchange resin in silver form with the contaminated essential oil such that at least a portion of the contaminant is retained by the ion exchange resin to produce a treated effluent comprising the essential oil having a reduced concentration of the contaminant until the resin is exhausted as indicated by an increase in the concentration of contaminant in the treated effluent; and contacting the exhausted ion exchange resin with a silver salt solution to recharge the ion exchange resin with silver and produce a recharging effluent, wherein during recharging, silver ions from the silver salt solution replace silver ions bound to the contaminant on the ion exchange resin, releasing the contaminant from the resin in the form of a silver salt-contaminant complex, the recharging effluent comprising the silver salt-contaminant complex.

2. The process of claim 1 , wherein the ion exchange resin in silver form is produced by contacting the ion exchange resin with a solution of a silver salt such that silver ions are bound to the ion exchange resin and producing a charging effluent comprising the silver salt solution having a reduced concentration of silver ions.

3. The process of claim 2, wherein the pH of the charging effluent is monitored and compared to the pH of the silver salt solution to determine when the ion exchange resin in silver form is sufficiently charged with silver ions.

4. The process of claim 2 or 3, wherein the ion exchange resin is in acid form prior to contacting the silver salt solution and is contacted with the silver salt solution until the pH of the charging effluent pH is from about 5 to about 6.

5. The process of any one of the preceding claims, wherein the ion exchange resin in silver form is rinsed to remove unbound silver ions prior to contacting the contaminated essential oil.

6. The process of any one of the preceding claims, wherein the ion exchange resin in silver form is rinsed to remove unbound silver ions by contacting the ion exchange resin successively with water and then an organic solvent prior to contacting the contaminated essential oil.

7. The process of any one of the preceding claims, wherein the exhausted ion exchange resin is washed with an aqueous solution to remove residual essential oil before contacting with the silver salt solution.

8. The process of any one of the preceding claims, wherein the exhausted ion exchange resin is washed with a solution comprising ethanol and water to remove residual essential oil before contacting the silver salt solution.

9. The process of any one of the preceding claims, wherein the ion exchange resin is a strongly acidic ion exchange resin.

10. The process of any one of the preceding claims, wherein the ion exchange resin has a sulfonic acid active group.

11. The process of any one of the preceding claims, wherein the ion exchange resin comprises an organic polymer substrate having a cross-linking density of less than about 30% or less than about 20% based on the total weight % of added cross-linking monomer.

12. The process of any one of the preceding claims, wherein the ion exchange resin has a binding capacity of at least about 1 meq / mL.

13. The process of any one of the preceding claims, wherein the ion exchange resin has a silver ion (Ag+) binding capacity of at least about 1.4 mmol / g.

14. The process of any one of the preceding claims, wherein the ion exchange resin is of the highly porous type.

15. The process of any one of the preceding claims, wherein the ion exchange resin has an average pore diameter of from about 15 to about 30 nanometers as determined using the BJH method.

16. The process of any one of the preceding claims, wherein the ion exchange resin has a specific pore volume of from about 0.2 ml / g to about 0.8 ml / g or from about 0.2 ml / g to about 0.4 ml / g as determined using the BJH method.

17. The process of any one of the preceding claims, wherein the ion exchange resin has a specific surface area of from about 25 m2 / g to about 50 m2 / g or from about 25 m2 / g to about 40 m2 / g or from about 250 m2 / g to about 300 m2 / g as determined by BET analysis.

18. The process of any one of the preceding claims, wherein the silver salt solution comprises an aqueous solution of silver nitrate.

19. The process of any one of the preceding claims, wherein the ion exchange resin in silver form is disposed in a fixed bed when contacted with the contaminated essential oil.

20. The process of any one of the preceding claims, wherein silver is recovered from the recharging effluent and used to produce a silver salt solution for use in charging and recharging the ion exchange resin.

21. The process of claim 20, wherein silver is recovered by electroplating comprising contacting an electroplating bath comprising the recharging effluent with an anode and a cathode of an electroplating cell and passing electrical current through the cell to deposit elemental silver onto the anode.

22. The process of claim 21, wherein the cathode comprises graphite.

23. The process of claim 21 or 22, wherein the anode comprises platinum.

24. The process of any one of claims 21 to 23, further comprising contacting the anode having elemental silver deposited thereon and a cathode with an aqueous acidic solution and reversing the polarity of electrical current applied to the anode and cathode to form a silver salt solution.

25. The process of claim 20, wherein the silver is recovered from the recharging effluent by electro-dialysis comprising introducing the recharging effluent and a mineral acid solution into adjacent compartments of an electro-dialysis cell andpassing electric current through the cell, wherein silver ions from the recharging effluent are transferred through a cationic permeable membrane to the mineral acid solution to form a silver salt solution.

26. The process of any one of the proceeding claims, where the contaminant is an agricultural residue.

27. The process of claim 26, wherein the agricultural residue is an organothiophosphate.

28. The process of claims 26 or 27, wherein the agricultural residue is selected from the group consisting of methamidophos, parathion, malathion, ethion, chlorpyrifos, propi conazole, fenbuconazole, dif enoconazole, tebuconazole, prochloraz, pyrimethanil, trifloxystrobin, propargite, bifenthrin, triphenyl thiophosphate, phosmet, and any combination thereof.

29. The process of any one of the proceeding claims, wherein the essential oil is derived from citrus.

30. The process of any one of the proceeding claims, wherein the essential oil is derived from the group consisting of orange, lemon, lime, tangerine, grapefruit, and any combination thereof.

31. A process for removing contaminant from an essential oil comprising: contacting an ion exchange resin with a solution of a silver salt such that silver ions are bound to the ion exchange resin to produce an ion exchange resin in silver form; contacting the ion exchange resin in silver form with a rinse solvent to remove unbound silver ions and produce a rinsed ion exchange resin in silver form; contacting the rinsed ion exchange resin in silver form with the contaminated essential oil such that at least a portion of the contaminant is retained by the ion exchange resin to produce a treated effluent comprising the essential oil having a reduced concentration of the contaminant until the resin is exhausted as indicated by an increase in the concentration of contaminant in the treated effluent;contacting the exhausted ion exchange resin with a wash solvent to remove residual essential oil from the exhausted ion exchange resin; contacting the washed exhausted ion exchange resin with a silver salt solution to recharge the ion exchange resin with silver and produce a recharging effluent, wherein during recharging, silver ions from the silver salt solution replace silver ions bound to the contaminant on the ion exchange resin, releasing the contaminant from the resin in the form of a silver salt-contaminant complex, the recharging effluent comprising the silver salt-contaminant complex; producing an aqueous solution of a silver salt from the recharging effluent; and contacting the ion exchange resin with the silver salt solution produced from the recharging effluent.