WO2016081992A1

WO2016081992A1 - Absorbent material

Info

Publication number: WO2016081992A1
Application number: PCT/AU2015/050736
Authority: WO
Inventors: Qipeng Guo; Tao Zhang
Original assignee: Deakin University
Priority date: 2014-11-25
Filing date: 2015-11-23
Publication date: 2016-06-02

Abstract

The present invention relates to an open cell thermoplastic sulfonated polystyrene porous xerogel for absorbing hydrophobic liquid, wherein at least some of the sulfonated groups are neutralised.

Description

ABSORBENT MATERIAL

Field of the Invention The present invention relates generally to absorbent materials, and in particular it relates to materials for absorbing hydrophobic liquid such as oil.

Background of the Invention Hydrophobic liquids such as oil are known for their low or negligible miscibility with water. This poor miscibility with water gives rise to unique problems in the day to day application of such liquids. For example, in modern society the wide spread use of hydrophobic liquids all too frequently results in large scale spills (e.g. the oil spill in the Gulf of Mexico in 2010) or increasing amounts of domestic and industrial waste water contaminated with hydrophobic liquid being discharged into the environment.

The increased presence of hydrophobic liquids in the environment can not only cause irrevocable damage to the ecosystem but it also represents loss of a valuable resource. Considerable research has therefore been directed toward technology for addressing such hydrophobic liquid pollution.

To date, several techniques for dealing with hydrophobic liquid pollution have been developed, including the use of dispersants, solidifiers and absorbent materials. Dispersants function to emulsify hydrophobic liquid within water, thereby facilitating the break up and dispersal of the hydrophobic liquid. However, this inherently makes it particularly difficult to separate and isolate the hydrophobic liquid, with the net result being the hydrophobic liquid and dispersant remain persistent in the environment, albeit in a more disperse form.

On the other hand, solidifiers function to promote gellation of the hydrophobic liquid, thereby facilitating separation and isolation of the resulting gel from, for example a solid surface or water. However, solidifiers are typically impractical for large scale hydrophobic liquid clean up applications and it can be problematic to separate and recover the hydrophobic liquid from the so formed gel. Absorbent materials function by in effect acting as a sponge that preferentially absorbs hydrophobic liquid. The use of such materials is particularly promising in that they can be effective in small or large scale applications, enable the absorbed hydrophobic liquid to be recovered relatively easily (e.g. by simple compression of the material), and can often be reused after the hydrophobic liquid has been recovered.

A variety of absorbent materials for absorbing hydrophobic liquids are known. Many of these materials are polymer structures and include porous polymer materials.

Porous polymer materials for absorbing hydrophobic liquids are, for example, disclosed in US 3,494,862 and WO 1998/056430. However, the polymer system disclosed in US 3,494,862 is prone to dissolving in a variety of hydrophobic liquids, thereby limiting its application. The polymer system disclosed in WO 1998/056430 makes use of hydrophobic polymer that requires surfactant to promote acceptable absorbance properties which can leech into and pollute the environment. The polymer system disclosed in WO 1998/056430 is also prone to dissolving in certain hydrophobic liquids.

While absorbent materials known in the art have been used to successfully separate and isolate hydrophobic liquid from the environment, in practice such materials can be expensive to manufacture, are prone to being degraded/dissolved by the hydrophobic liquids, and/or require the use of adjuvants, such as surfactants, to promote acceptable absorption.

Accordingly, there remains an opportunity to develop new absorbent material that overcomes one or more disadvantages of the prior art absorbent materials and/or provides a useful alternative. Summary of the Invention

The present invention therefore provides an open cell thermoplastic sulfonated polystyrene porous xerogel for absorbing hydrophobic liquid, wherein at least some of the sulfonated groups are neutralised.

It has now been surprisingly found the porous xerogel in accordance with the invention is highly efficient and effective at absorbing hydrophobic liquids such as oil. The porous xerogel presents a polymer surface which advantageously promotes rapid absorption of a high volume of hydrophobic liquid thereby effectively and efficiently isolating the hydrophobic liquid within its porous polymer structure. In other words, the porous xerogel has surprisingly been found to function as a highly effective and efficient sponge for hydrophobic liquid.

In addition to being highly effective and efficient at absorbing hydrophobic liquid, the porous xerogel can be produced (i) in a very cost effective manner, which may include using waste polystyrene, and (ii) such that it is insoluble in most hydrophobic liquids.

The present invention also provides a method of preparing an open cell thermoplastic sulfonated polystyrene porous xerogel for absorbing hydrophobic liquid, the method comprising:

(i) providing a composition comprising sulfonated polystyrene dissolved in solvent, wherein at least some of the sulfonated groups are neutralised;

(ii) combining the composition provided in (i) with (a) aqueous solution comprising one or more dissolved salts, and (b) hydrophobic solvent, to produce a high internal phase emulsion organogel; and

(iii) removing liquid from the so formed organogel to afford the porous xerogel.

The present invention further provides a method of isolating hydrophobic liquid, the method comprising contacting the hydrophobic liquid with an open cell thermoplastic sulfonated polystyrene porous xerogel according to the invention which absorbs and isolates the hydrophobic liquid therein. The porous xerogel in accordance with the invention has been found to be particularly effective at isolating hydrophobic liquid from aqueous liquid. In one embodiment, the method of isolating a hydrophobic liquid therefore relates to isolating the hydrophobic liquid from aqueous liquid.

In one embodiment, the hydrophobic liquid is an oil such as petroleum, animal or plant oil.

Further aspects and embodiments of the invention are discussed in more detail below. Brief Description of the Drawings

The invention will herein be described with reference to the following non-limiting drawings in which: Figure 1 shows a scanning electron microscope (SEM) image of a sulfonated polystyrene porous xerogel in accordance with the invention showing the porous structure of the xerogel;

Figure 2 shows the absorption rate of the sulfonated polystyrene porous xerogel in accordance with the invention to toluene;

Figure 3 shows oil absorption capacity of the sulfonated polystyrene porous xerogel in accordance with the invention to various hydrophobic liquids; and

Figure 4 illustrates absorption capacities of the sulfonated polystyrene porous xerogel in accordance with the invention and toluene recovery with toluene absorption/squeezing-out cycle numbers.

Some Figures contain colour representation or entities. Coloured versions of the Figures are available upon request. Detailed Description of the Invention

The present invention provides an open cell thermoplastic sulfonated polystyrene porous xerogel.

Those skilled in the art will appreciate the xerogel in accordance with the invention can broadly and more simplistically be described as a type of polymer foam. For convenience, the xerogel in accordance with the invention may therefore also be referred to herein as the "polymer foam" in accordance with the invention.

The polymer foam in accordance with the invention is "porous" and has an "open cell structure". By being "porous" is meant that the polymer foam has a structure made up of holes or voids that present as a collection of interconnected cells. By having an "open cell" structure is meant that the cells that provide for the porous nature of the foam are interconnected through so called "ruptured" cell walls such that liquid may pass through cell structures that make up the interconnected cell network of the foam. The "open cell" structure of the foam may also be referred to as providing for a "reticulated" foam structure in that the faces (or windows) of the cells are removed leaving primarily cell struts (or edges) to provide for the structural features of the foam.

There is no particular limitation on the size of the pores that make up the foam structure. Generally, the largest dimension of pores within the foam will range from about 1 micron to about 100 microns. The open cell structure of the polymer foam in accordance with the invention provides for a high surface area, which in turn enables the foam to exhibit a high absorption capacity for the hydrophobic liquid. For example, the polymer foam may have a surface area ranging from about 5 to about 100 m /g. Polymer foam in accordance with the invention will generally exhibit a density ranging from about 0.02 g/cm³ to about 0.2 g/cm³.

The polymer foam advantageously exhibits a high absorption capacity for hydrophilic liquid. Generally, the polymer foam will exhibit an absorption capacity for hydrophobic liquid ranging from about 15 to about 30 times the starting mass of the polymer foam (i.e. the mass of the polymer foam prior to absorbing the hydrophobic liquid). The polymer foam in accordance with the invention is thermoplastic. By being "thermoplastic" is meant that upon being subjected to heat the polymer composition of the foam will soften and flow and subsequently harden upon cooling. In other words, polymer foam in accordance with the invention is not intended to embrace "thermoset" polymer foam. Thermoset polymer foam would typically have a highly crosslinked polymer structure that would not soften and flow upon application of heat.

The polymer foam in accordance with the invention will therefore generally not have a crosslinked polymer structure.

Accordingly, the polymer foam may also be described as an open cell thermoplastic non- crosslinked sulfonated polystyrene porous xerogel.

Surprisingly, despite having a thermoplastic polymer matrix the polymer foam in accordance with the invention remains relatively insoluble in most hydrophobic liquids. To promote a desirable degree of insolubility in hydrophobic liquids conventional polymer foams are often provided with a crosslinked polymer structure. While crosslinking the polymer structure can impart insolubility in hydrophobic liquids, additional manufacturing steps are required and the resulting crosslinked polymer foam structure can be brittle and difficult to recycle.

The unique composition of the polymer foam in accordance with the invention advantageously provides for an excellent balance between hydrophobic liquid absorbing capacity, insolubility in hydrophobic liquids, mechanical properties and aqueous wettability (i.e. for when the polymer foam in used to absorb hydrophobic liquid from a hydrophobic liquid/aqueous liquid mixture).

By the polymer foam according to the present invention being "sulfonated polystyrene" is intended to mean the polymeric matrix of the foam is made up of sulfonated polystyrene polymer. In other words, the foam is a sulfonated polystyrene foam.

The sulfonated polystyrene may be derived from preformed polystyrene that is subsequently sulfonated. Techniques for sulfonating polystyrene are well known to those skilled in the art and involve functionalising the pendant aromatic rings of polystyrene with sulfonic acid groups. Suitable sulfonation reagents that may be used for preparing sulfonated polystyrene include acryl sulfate and acetyl sulfate. Techniques for preparing a sulfonated polystyrene using sulfonation reagents are described in US 3,870,841, US 3,836,511 and US 5,239,091, the contents of which are incorporated herein by cross reference.

Sulfonated polystyrene may also be prepared by polymerising styrene sulfonic acid monomer (or salt thereof) alone or in combination with styrene monomer.

If desired, sulfonated polystyrene prepared by polymerising styrene sulfonic acid monomer (or salt thereof) in combination with styrene monomer may be subsequently sulfonated as herein described.

Accordingly, reference herein to "sulfonated polystyrene" polymer is intended to mean polymer made up of styrene repeat units where at least some of the pendant aromatic rings of the styrene repeat units are sulfonated with sulfonic acid (or salt thereof) groups. The sulfonic acid (or salt thereof) groups may be derived from substituted styrene monomer (i.e. styrene sulfonic acid monomer (or salt thereof)) that is polymerised to form the polymer, or the sulfonic acid (or salt thereof) groups may be introduced after the polymer has been prepared via a sulfonation reaction as described herein.

In one embodiment, the sulfonated polystyrene comprises polymerised residues of styrene monomer.

In another embodiment, the sulfonated polystyrene comprises polymerised residues of styrene sulfonic acid monomer (or salt thereof).

Reference herein to a "salt" of sulfonic acid monomer is intended to mean the sulfonic acid functional group of that monomer is neutralised with an ionic compound as described herein.

Provided the polymer foam in accordance with the invention is functional in the sense that it is capable of absorbing hydrophobic liquid, there is no particular limitation on the molecular weight of the sulfonated polystyrene. Generally, the number average molecular weight (Mn) of the sulfonated polystyrene will range from about 10,000 to about 10,000,000, or from about 100,000 to about 10,000,000.

Reference herein to Mn is intended to be that determined by gel permeation chromatography (GPC) relative to that calculated using polystyrene standards. The polymer foam in accordance with the invention is a porous xerogel. Reference herein to "xerogel" is intended to mean an open polymer network that is formed by the removal of liquid from a polymer organogel. In other words, the term "xerogel" is intended to define the unique open polymer network structure that is formed upon removal of liquid from a polymer organogel system. Those skilled in the art will appreciate that the morphology of a xerogel mirrors or is templated from the organogel from which it is derived.

Reference herein to the xerogel being "porous" is intended to further reinforce that the morphology of the polymer structure has an open cell network of interconnected cells. Importantly, the polymer foam in accordance with the invention must be suitable for absorbing hydrophobic liquid. By "hydrophobic liquid" is intended to mean liquid that is substantially immiscible with water. Examples of hydrophobic liquids include liquid hydrocarbons, liquid heterohydrocarbons, including hydrophobic solvents, oils such as petroleum, animal and plant oil, and combinations thereof.

Specific examples of hydrophobic liquids include toluene, xylene, dichloroethane, chloroform, pentane, hexane, heptane, octane, diesel, petrol, vegetable oil, engine oil, crude oil and combinations thereof.

By the polymer foam in accordance with the invention being suitable "for absorbing hydrophilic liquid" is intended to mean that the bulk structure of the foam is provided in a form that can absorb hydrophobic liquid.

Provided that the foam can absorb hydrophobic liquid, there is no particular limitation on the physical form in which it can present. For example, the foam may be provided in the form of pellets, blocks and sheets.

The foam may be used in its as manufactured form for absorbing hydrophobic liquids. Alternatively, the foam may be contained in a material, such as a mesh, which allows the hydrophobic liquid to pass through and come into contact with the foam. The foam may be provided in the form of a boom or buoy that can, for example, float on aqueous liquid.

There is no particular limitation regarding the degree of sulfonation of the sulfonated polystyrene. Generally, the average degree of sulfonation will range from about 0.1 % to about 60% , or about 0.1 % to about 50% , or about 0.1 % to about 40% , relative to the average number of polymerised monomer units that make up the polymer chains of the polymer.

The degree of sulfonation of the sulfonated polystyrene can be calculated as follows: moles of sulfonic acid

sulfonation degree = X 100%

moles of monomer units in charged block

The content of sulfonic acid groups in the sulfonated polystyrene may be determined by titration using techniques well known to those skilled in the art. Without wishing to be limited by theory, it is believed the presence of the sulfonated groups in the sulfonated polystyrene play a role in influencing formation of the morphology of the porous xerogel.

At least some of the sulfonated groups of the sulfonated polystyrene are neutralised. By the sulfonated groups being "neutralised" is meant that the sulfonic acid groups have reacted with an ionic compound to form a salt. For example, a sulfonate group (i.e. -SO₃H) may react with an ionic compound such as sodium hydroxide (NaOH) so as to form a corresponding sulfonate sodium salt. The sulfonate groups may be neutralised with counterions derived from inorganic or organic ionic compounds.

The ionic compound selected for neutralisation should afford a counterion that does not adversely affect the hydrophobic liquid absorption properties of the foam.

The ionic compound selected for neutralisation should also of course be sufficiently soluble within the reaction medium so as to be capable of undergoing the neutralisation reaction.

Examples of suitable inorganic ionic compounds include an alkali salt, an alkaline earth salt, a transition metal salt, a rare earth metal salt, or mixtures thereof. Specific examples of inorganic ionic compounds include sodium and magnesium salts.

Examples of suitable organic ionic compounds include organic amine salts. The organic amine salts may be provided in the form of a mono-amine or polyamine and have a primary, secondary or tertiary amine structure. The organic moiety or the organic amine salt may be selected from alkyl, aryl, alkylaryl, and arylalkyl.

Without wishing to be limited by theory, it is believed the presence of neutralised sulfonate groups in the polymer foam facilitates manufacture of the unique polymer foam structure. In particular, the presence of at least some neutralised sulfonate groups is believed to promote formation of a high internal phase emulsion organogel that gives rise to the advantageous porous structure of the foam. Without wishing to be limited by theory, it is also believed the presence of free sulfonate groups can promote non-covalent bonding interactions between polymer chains in the manufactured polymer foam, which in turn is believed to enhance the ability of the polymer foam to remain insoluble in most hydrophobic liquids.

In one embodiment, at least 10%, or at least 20%, or at least 30%, or at least 40%, or at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90%, or at least 95%, of the sulfonate groups present are neutralised.

In another embodiment, 90% or less, or 80% or less, or 70% or less, or 60% or less, or 50% or less, or 40% or less, or 30% of less, or 20% or less, or 10% or less, or 5% or less, of the sulfonate groups present are not neutralised (i.e. they present as -SO₃H). In a further embodiment, the amount of sulfonate groups present that are neutralised ranges from about 10% to about 95%, or about 15% to about 90%, or about 20% to about 85%.

The polymer foam according to the present invention can be prepared by providing a composition comprising sulfonated polystyrene dissolved in solvent, wherein at least some of the sulfonated groups are neutralised.

The sulfonated polystyrene used may be in a form or derived as herein described.

For example, the sulfonated polystyrene used may be derived from preformed polystyrene that is subsequently sulfonated using techniques known in the art. This approach may be desirable in that polystyrene is a relatively cheap polymer and sulfonation of it is straight forward. Furthermore, the polystyrene used may be virgin polystyrene or waste (recycled) polystyrene.

In one embodiment, the method for preparing the polymer foam further comprises a step of preparing the sulfonated polystyrene by sulfonating polystyrene using a sulfonating reagent. In a further embodiment, the polystyrene that is sulfonated comprises recycled polystyrene.

The sulfonated polystyrene used in accordance with the method of the invention may also be prepared by polymerising suitable monomers as herein described.

Accordingly, in one embodiment the method of preparing the polymer foam in according with the invention further comprises a step of preparing the sulfonated polystyrene by polymerising styrene sulfonic acid monomer (or salt thereof) optionally in combination with styrene monomer.

Techniques, reagents and equipment for preparing sulfonated polystyrene are known to those skilled in the art and can be readily applied in performing the present invention.

In the method of the invention, the composition comprises sulfonated polystyrene dissolved in solvent, where at least some of the sulfonated groups are neutralised. In this context, the term

"solvent" is intended to mean any liquid capable of dissolving the sulfonated polystyrene.

Those skilled in the art will be aware suitable solvents for dissolving the sulfonated polystyrene. For example, suitable solvents may be selected from tetrahydroforan (THF), toluene, xylene, combinations of two or more thereof, and a mixture of one or more thereof with an alcohol, for example, methanol and/or ethanol. When used, an alcohol will typically be present in an amount ranging from about 2 to about 5 vol %, relative the total volume of all solvent present.

In one embodiment, the solvent comprises a mixture of toluene and/or xylene with methanol.

The composition provided in step (i) of the method of the invention will generally comprise about 5 (w/v)% to about 20 (w/v)% of the sulfonated polystyrene.

At least some of the sulfonated groups of the sulfonated polystyrene used in accordance with the invention are neutralised. Techniques, reagents and equipment for neutralising sulfonic acid groups of sulfonated polystyrene are described herein and also known to those skilled in the art. In one embodiment, in the method of preparing the polymer foam according to the invention the composition provided in step (i) is prepared by dissolving sulfonated polystyrene in solvent and neutralising at least some of the sulfonated groups using an ionic compound. Examples of ionic compounds suitable for neutralising sulfonic acid groups are described herein.

The composition provided in step (i) of the method of the present invention is in step (ii) of that method combined with (a) aqueous solution comprising one or more dissolved salts, and (b) hydrophobic solvent, to produce the high internal phase emulsion organogel.

The composition provided in step (i) is generally combined with the aqueous solution comprising one or more dissolved salts and the hydrophobic solvent along with some form of agitation, such as stirring.

By one or more "dissolved salts" is intended to mean an ionic compound solubilised in an aqueous liquid. The salt may be an inorganic salt.

Examples of suitable salts that may be used to provide the aqueous salt solution of step (ii) include water soluble metal salts such as sodium chloride, potassium chloride, sodium sulphate and combinations thereof.

The amount of salt in the aqueous solution will generally range from about 0.05 mol L^"1 to about 1 mol L^"1.

The "hydrophobic solvent" that is combined with the composition provided in step (i) is intended to be liquid that is (a) substantially immiscible with water, and (b) at least partially or fully miscible with the composition provided in step (i). Examples of suitable hydrophobic solvents that may be used in step (ii) of the method of the invention include toluene, xylene, chloroform, anisole, dichloroethane, dichloromethane, and combinations of two or more thereof. The hydrophobic solvent will generally be used in amount such that it represents about 0.05 to about 0.25 the total volume of the resulting organogel formed. Provided the high internal phase emulsion (HIPE) organogel forms, there is no particular sequence order in which the composition provided in step (i) is to be combined with the aqueous salt solution and the hydrophobic solvent.

Combining the aqueous salt solution and the hydrophobic solvent with the composition provided in step (i) affords a high internal phase emulsion (HIPE) organogel.

Those skilled in the art will appreciate techniques, reagents and equipment suitable for forming HIPE organogels that can be applied in the present invention. Without wishing to be limited by theory, it is believed the HIPE organogel produced in accordance with the method of the invention comprises a morphology made up of (i) the sulfonated polystyrene and the hydrophobic solvent presenting in the continuous phase, and (ii) the aqueous liquid presenting in the dispersed or discontinuous phase. The neutralised sulfonic acid groups of the sulfonated polystyrene, the hydrophobic solvent and the dissolved salt in the aqueous liquid are believed to promote formation of the HIPE and its gelation to afford the HIPE organogel.

After the HIPE organogel is produced, liquid is removed from the organogel to afford the porous xerogel. Removing liquid from the organogel in effect isolates the porous xerogel from the HIPE organogel composition. In this context, "liquid" is intended to be any liquid substance present in the HIPE organogel, such as water and organic solvent.

Liquid can be removed from the HIPE organogel by any suitable means. For example, the liquid can be removed by evaporation.

Generally, substantially all liquid is removed from the HIPE organogel to afford the porous xerogel. The HIPE organogel produced in step (ii) according to the method of the invention may be washed in an aqueous solution before liquid is removed from the organogel. Accordingly, in one embodiment, the HIPE organogel produced in step (ii) is washed in an aqueous liquid before liquid is removed from the organogel to afford the porous xerogel.

The polymer foam in accordance with the invention is particularly well suited for use in isolating hydrophobic liquid. By "isolating" hydrophobic liquid is meant that the polymer foam functions as a tool or vehicle to cause hydrophobic liquid to be set apart from other features of a given environment. Isolation of the hydrophobic liquid is effected by the hydrophobic liquid becoming absorbed within the polymer structure of the porous foam.

For example, hydrophobic liquid may be located on a solid surface and bringing the polymer foam into contact with the hydrophobic liquid will promote absorption of the liquid into the polymer foam thereby isolating the hydrophobic liquid from the solid surface.

Alternatively, the hydrophobic liquid may present as a liquid mixture with an aqueous liquid. Bringing the polymer foam into contact with that liquid mixture will promote the preferential absorption of the hydrophobic liquid within the polymer foam to thereby isolate the hydrophobic liquid from the aqueous liquid.

The method of isolating hydrophobic liquid in accordance with the invention may involve initially bringing the polymer foam into direct or indirect contact with the hydrophobic liquid.

For example, the polymer foam per se may be directly placed into contact with the hydrophobic liquid.

Alternatively, the polymer foam may be contained within a suitable material, such as a mesh, that allows the hydrophobic liquid to pass through it and subsequently make contact with the polymer foam contained therein. In that case, the material containing the polymer foam will of course make initial contact with the hydrophobic liquid which will then pass through the material to make contact with the polymer foam.

Accordingly, in one embodiment the method of isolating hydrophobic liquid comprises contacting the hydrophobic liquid with the polymer foam contained within a material that enables the hydrophobic liquid to pass through it and make contact with the polymer foam.

After making contact with the hydrophobic liquid, the polymer foam in accordance with the invention absorbs and thereby contains within its polymer structure the hydrophobic liquid. The now hydrophobic liquid laden polymer foam can be readily transported to remove the hydrophobic liquid a distance away from the application site. The polymer foam advantageously preferentially absorbs hydrophobic liquid over hydrophilic liquid.

The hydrophobic liquid laden polymer foam can also advantageously be compressed so as to squeeze out and recover from the foam structure the absorbed hydrophobic liquid. Recovering the hydrophobic liquid from the polymer foam in this way enables the hydrophobic liquid to be recycled and/or disposed of in an effective and efficient manner.

The polymer foam in accordance with the invention therefore can advantageously be used repetitively to absorb an isolate hydrophobic liquid. Specifically, the foam advantageously has resilient properties that enable it to absorb hydrophobic liquid, be compressed to expel the absorbed hydrophobic liquid from the foam, and then be used to again absorb additional hydrophobic liquid, with this sequence capable of being repeated multiple times.

Accordingly, in one embodiment the method of isolating hydrophobic liquid in accordance with the invention further comprises a step of compressing the porous xerogel with hydrophobic liquid isolated therein so as to (a) expel hydrophobic liquid from the porous xerogel, and (b) enable re-use of the porous xerogel to absorb additional hydrophobic liquid.

As used herein, the term "alkyl", used either alone or in compound words denotes straight chain, branched or cyclic alkyl (or "cycloalkyl"), for example C_1-4o alkyl, or Ci-20 or CMO- Examples of straight chain and branched alkyl include methyl, ethyl, n-propyl, isopropyl, n- butyl, sec-butyl, i-butyl, n-pentyl, 1 ,2-dimethylpropyl, 1,1 -dimethyl -propyl, hexyl, 4- methylpentyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 1,1-dimethylbutyl, 2,2- dimethylbutyl, 3,3-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 1,2,2- trimethylpropyl, 1,1,2-trimethylpropyl, heptyl, 5-methylhexyl, 1-methylhexyl, 2,2- dimethylpentyl, 3,3-dimethylpentyl, 4,4-dimethylpentyl, 1,2-dimethylpentyl, 1,3- dimethylpentyl, 1,4-dimethyl-pentyl, 1,2,3-trimethylbutyl, 1,1,2-trimethylbutyl, 1,1,3- trimethylbutyl, octyl, 6-methylheptyl, 1-methylheptyl, 1,1,3,3-tetramethylbutyl, nonyl, 1-, 2-, 3-, 4-, 5-, 6- or 7-methyloctyl, 1-, 2-, 3-, 4- or 5-ethylheptyl, 1-, 2- or 3-propylhexyl, decyl, 1-, 2-, 3-, 4-, 5-, 6-, 7- and 8-methylnonyl, 1-, 2-, 3-, 4-, 5- or 6-ethyloctyl, 1-, 2-, 3- or 4- propylheptyl, undecyl, 1-, 2-, 3-, 4-, 5-, 6-, 7-, 8- or 9-methyldecyl, 1-, 2-, 3-, 4-, 5-, 6- or 7- ethylnonyl, 1-, 2-, 3-, 4- or 5-propyloctyl, 1-, 2- or 3-butylheptyl, 1-pentylhexyl, dodecyl, 1-,

2- , 3-, 4-, 5-, 6-, 7-, 8-, 9- or 10-methylundecyl, 1-, 2-, 3-, 4-, 5-, 6-, 7- or 8-ethyldecyl, 1-, 2-,

3- , 4-, 5- or 6-propylnonyl, 1-, 2-, 3- or 4-butyloctyl, 1-2-pentylheptyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonoadecyl, eicosyl and the like. Examples of cyclic alkyl include mono- or polycyclic alkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, cyclodecyl and the like. Where an alkyl group is referred to generally as "propyl", butyl" etc., it will be understood that this can refer to any of straight, branched and cyclic isomers where appropriate. An alkyl group may be optionally substituted by one or more optional substituents as herein defined. The term "aryl" (or "carboaryl") denotes any of single, polynuclear, conjugated and fused residues of aromatic hydrocarbon ring systems(e.g. C₆-24 or C₆-i8)- · Examples of aryl include phenyl, biphenyl, terphenyl, quaterphenyl and naphthyl. An aryl group may or may not be optionally substituted by one or more optional substituents as herein defined. As used herein, the term "arylalkyl" refers to groups formed from straight or branched chain alkanes substituted with an aromatic (aryl) ring. Examples of arylalkyl include phenylmethyl (benzyl), phenylethyl and phenylpropyl.

As used herein, the term "alkylaryl" refers to groups formed from aryl groups substituted with a straight chain or branched alkane (alkyl). Examples of alkylaryl include methylphenyl and isopropylphenyl. In this specification "optionally substituted" is taken to mean that a group may or may not be substituted or fused (so as to form a condensed polycyclic group) with one, two, three or more of organic and inorganic groups, including those selected from: alkyl, alkenyl, alkynyl, carbocyclyl, aryl, heterocyclyl, heteroaryl, acyl, aralkyl, alkaryl, alkheterocyclyl, alkheteroaryl, alkcarbocyclyl, halo, haloalkyl, haloalkenyl, haloalkynyl, haloaryl, halocarbocyclyl, haloheterocyclyl, haloheteroaryl, haloacyl, haloaryalkyl, hydroxy, hydroxyalkyl, hydroxyalkenyl, hydroxyalkynyl, hydroxycarbocyclyl, hydroxyaryl, hydroxyheterocyclyl, hydroxyheteroaryl, hydroxyacyl, hydroxyaralkyl, alkoxyalkyl, alkoxyalkenyl, alkoxyalkynyl, alkoxycarbocyclyl, alkoxyaryl, alkoxyheterocyclyl, alkoxyheteroaryl, alkoxyacyl, alkoxyaralkyl, alkoxy, alkenyloxy, alkynyloxy, aryloxy, carbocyclyloxy, aralkyloxy, heteroaryloxy, heterocyclyloxy, acyloxy, haloalkoxy, haloalkenyloxy, haloalkynyloxy, haloaryloxy, halocarbocyclyloxy, haloaralkyloxy, haloheteroaryloxy, haloheterocyclyloxy, haloacyloxy, nitro, nitroalkyl, nitroalkenyl, nitroalkynyl, nitroaryl, nitroheterocyclyl, nitroheteroayl, nitrocarbocyclyl, nitroacyl, nitroaralkyl, amino (NH₂), alkylamino, dialkylamino, alkenylamino, alkynylamino, arylamino, diarylamino, aralkylamino, diaralkylamino, acylamino, diacylamino, heterocyclamino, heteroarylamino, carboxy, carboxyester, amido, alkylsulphonyloxy, arylsulphenyloxy, alkylsulphenyl, arylsulphenyl, thio, alkylthio, alkenylthio, alkynylthio, arylthio, aralkylthio, carbocyclylthio, heterocyclylthio, heteroarylthio, acylthio, sulfoxide, sulfonyl, sulfonamide, aminoalkyl, aminoalkenyl, aminoalkynyl, aminocarbocyclyl, aminoaryl, aminoheterocyclyl, aminoheteroaryl, aminoacyl, aminoaralkyl, thioalkyl, thioalkenyl, thioalkynyl, thiocarbocyclyl, thioaryl, thioheterocyclyl, thioheteroaryl, thioacyl, thioaralkyl, carboxyalkyl, carboxyalkenyl, carboxyalkynyl, carboxycarbocyclyl, carboxyaryl, carboxyheterocyclyl, carboxyheteroaryl, carboxyacyl, carboxyaralkyl, carboxyesteralkyl, carboxyesteralkenyl, carboxyesteralkynyl, carboxyestercarbocyclyl, carboxyesteraryl, carboxyesterheterocyclyl, carboxyesterheteroaryl, carboxyesteracyl, carboxyesteraralkyl, amidoalkyl, amidoalkenyl, amidoalkynyl, amidocarbocyclyl, amidoaryl, amidoheterocyclyl, amidoheteroaryl, amidoacyl, amidoaralkyl, formylalkyl, formylalkenyl, formylalkynyl, formylcarbocyclyl, formylaryl, formylheterocyclyl, formylheteroaryl, formylacyl, formylaralkyl, acylalkyl, acylalkenyl, acylalkynyl, acylcarbocyclyl, acylaryl, acylheterocyclyl, acylheteroaryl, acylacyl, acylaralkyl, sulfoxidealkyl, sulfoxidealkenyl, sulfoxidealkynyl, sulfoxidecarbocyclyl, sulfoxidearyl, sulfoxideheterocyclyl, sulfoxideheteroaryl, sulfoxideacyl, sulfoxidearalkyl, sulfonylalkyl, sulfonylalkenyl, sulfonylalkynyl, sulfonylcarbocyclyl, sulfonylaryl, sulfonylheterocyclyl, sulfonylheteroaryl, sulfonylacyl, sulfonylaralkyl, sulfonamidoalkyl, sulfonamidoalkenyl, sulfonamidoalkynyl, sulfonamidocarbocyclyl, sulfonamidoaryl, sulfonamidoheterocyclyl, sulfonamidoheteroaryl, sulfonamidoacyl, sulfonamidoaralkyl, nitroalkyl, nitroalkenyl, nitroalkynyl, nitrocarbocyclyl, nitroaryl, nitroheterocyclyl, nitroheteroaryl, nitroacyl, nitroaralkyl, cyano, sulfate, phosphate, triarylmethyl, triarylamino, oxadiazole, and carbazole groups. Optional substitution may also be taken to refer to where a -CH₂- group in a chain or ring is replaced by a group selected from -0-, -S-, -NR^a-, -C(O)- (i.e. carbonyl), -C(0)0- (i.e. ester), and -C(0)NR^a- (i.e. amide), where R^a is as defined herein.

The term "alkenyl" as used herein denotes groups formed from straight chain, branched or cyclic hydrocarbon residues containing at least one carbon to carbon double bond including ethylenically mono-, di- or polyunsaturated alkyl or cycloalkyl groups as previously defined, preferably C2-20 alkenyl (e.g. C2-10 or C₂-6)- Examples of alkenyl include vinyl, allyl, 1- methylvinyl, and butenyl. An alkenyl group may be optionally substituted by one or more optional substituents as herein defined.

As used herein the term "alkynyl" denotes groups formed from straight chain, branched or cyclic hydrocarbon residues containing at least one carbon-carbon triple bond including ethylenically mono-, di- or polyunsaturated alkyl or cycloalkyl groups as previously defined. Unless the number of carbon atoms is specified the term preferably refers to C2-20 alkynyl (e.g. C2-10 or C₂-₆)- Examples include ethynyl, 1-propynyl, 2-propynyl, and butynyl isomers, and pentynyl isomers. An alkynyl group may be optionally substituted by one or more optional substituents as herein defined.

The term "halogen" ("halo") denotes fluorine, chlorine, bromine or iodine (fluoro, chloro, bromo or iodo).

The term "carbocyclyl" includes any of non-aromatic monocyclic, polycyclic, fused or conjugated hydrocarbon residues, preferably C₃-20 (e.g. C₃-10 or C₃-8). The rings may be saturated, e.g. cycloalkyl, or may possess one or more double bonds (cycloalkenyl) and/or one or more triple bonds (cycloalkynyl). A carbocyclyl group may be optionally substituted by one or more optional substituents as herein defined. The term "carbocyclylene" is intended to denote the divalent form of carbocyclyl.

The term "heteroatom" or "hetero" as used herein in its broadest sense refers to any atom other than a carbon atom which may be a member of a cyclic organic group. Particular examples of heteroatoms include nitrogen, oxygen, sulfur, phosphorous, boron, silicon, selenium and tellurium, more particularly nitrogen, oxygen and sulfur.

The term "heterocyclyl" when used alone or in compound words includes any of monocyclic, polycyclic, fused or conjugated hydrocarbon residues, preferably C₃-20 (e.g. C₃-10 or C₃-8) wherein one or more carbon atoms are replaced by a heteroatom so as to provide a non- aromatic residue. Suitable heteroatoms include O, N, S, P and Se, particularly O, N and S. Where two or more carbon atoms are replaced, this may be by two or more of the same heteroatom or by different heteroatoms. The heterocyclyl group may be saturated or partially unsaturated, i.e. possess one or more double bonds. A heterocyclyl group may be optionally substituted by one or more optional substituents as herein defined. The term "heterocyclylene" is intended to denote the divalent form of heterocyclyl.

The term "heteroaryl" includes any of monocyclic, polycyclic, fused or conjugated hydrocarbon residues, wherein one or more carbon atoms are replaced by a heteroatom so as to provide an aromatic residue. Preferred heteroaryl have 3-20 ring atoms, e.g. 3-10.

Particularly preferred heteroaryl are 5-6 and 9-10 membered bicyclic ring systems. Suitable heteroatoms include, O, N, S, P and Se, particularly O, N and S. Where two or more carbon atoms are replaced, this may be by two or more of the same heteroatom or by different heteroatoms. A heteroaryl group may be optionally substituted by one or more optional substituents as herein defined. The term "heteroarylene" is intended to denote the divalent form of heteroaryl.

The term "acyl" either alone or in compound words denotes a group containing the moiety C=0 (and not being a carboxylic acid, ester or amide) Preferred acyl includes C(0)-R^e, wherein R^e is hydrogen or an alkyl, alkenyl, alkynyl, aryl, heteroaryl, carbocyclyl, or heterocyclyl residue. The term "sulfoxide", either alone or in a compound word, refers to a group -S(0)R wherein R is selected from hydrogen, alkyl, alkenyl, alkynyl, aryl, heteroaryl, heterocyclyl, carbocyclyl, and aralkyl. Examples of preferred R include Ci_₂oalkyl, phenyl and benzyl.

The term "sulfonyl", either alone or in a compound word, refers to a group S(0)₂-R , wherein R is selected from hydrogen, alkyl, alkenyl, alkynyl, aryl, heteroaryl, heterocyclyl, carbocyclyl and aralkyl.

The term "sulfonamide", either alone or in a compound word, refers to a group S(0)NR f R f wherein each R is independently selected from hydrogen, alkyl, alkenyl, alkynyl, aryl, heteroaryl, heterocyclyl, carbocyclyl, and aralkyl.

The term, "amino" is used here in its broadest sense as understood in the art and includes groups of the formula NR^aR^b wherein R^a and R^b may be any independently selected from hydrogen, alkyl, alkenyl, alkynyl, aryl, carbocyclyl, heteroaryl, heterocyclyl, arylalkyl, and acyl. R^a and R^b, together with the nitrogen to which they are attached, may also form a monocyclic, or polycyclic ring system e.g. a 3-10 membered ring, particularly, 5-6 and 9-10 membered systems.

The term "amido" is used here in its broadest sense as understood in the art and includes groups having the formula C(0)NR^aR^b, wherein R^a and R^b are as defined as above.

The term "carboxy ester" is used here in its broadest sense as understood in the art and includes groups having the formula C0₂R^g, wherein R^g may be selected from groups including alkyl, alkenyl, alkynyl, aryl, carbocyclyl, heteroaryl, heterocyclyl, aralkyl, and acyl.

As used herein, the term "aryloxy" refers to an "aryl" group attached through an oxygen bridge. Examples of aryloxy substituents include phenoxy, biphenyloxy, naphthyloxy and the like.

As used herein, the term "acyloxy" refers to an "acyl" group wherein the "acyl" group is in turn attached through an oxygen atom. As used herein, the term "alkyloxycarbonyl" refers to an "alkyloxy" group attached through a carbonyl group. Examples of "alkyloxycarbonyl" groups include butylformate, sec- butylformate, hexylformate, octylformate, decylformate, cyclopentylformate and the like.

The invention will now be described with reference to the following non-limiting examples. EXAMPLES

The following examples illustrate the present invention in further detail however the examples should by no means be construed as limiting the scope of the invention as described herein.

Example 1. Preparation of sulfonated polystyrene

The sulfonated polystyrene (SPS) was prepared by sulfonation of commercially available polystyrene (PS) from Sigma-Aldrich. The PS has the average molecular weight _w of 192,000 with melt index of 6.0-9.0 g/10 min (200°C).

Sulfonation of PS was carried out according to the procedure of U.S. Pat. No 3,836,511. Specifically, the sulfonation was conducted in 1,2-dichloroethane (DCE) at 50-55 °C by reacting with acetyl sulphate in a nitrogen atmosphere. The acetyl sulfate was freshly prepared from acetic anhydride and concentrated sulfuric acid. Sulfonation degree of PS, i.e., the molar percentage of sulfonic acid grafted onto styrene was determined by titration with standard sodium hydroxide solution (0.1 N) using phenolphthalein as the indicator. Sulfonation degree of the present Example was found to be 4.2 mol%, i.e., 4.2 molar per 100 molar styrene were grafted with sulfonic acid.

The SPS prepared was used in the preparation of high internal phase emulsion (HIPE) organogel according to the method described below. Preparation of HIPE organogel from sulfonated polystyrene

Salts (amine and benzoxazine) of SPS were prepared through neutralization of SPS in tetrahydrofuran (THF) solution. SPS solution (5%, w/v) in THF was neutralized by alkaline solution, and then toluene (lmL) and aqueous NaCl solution (4mL) were added to the neutralized SPS solution (lmL). After stirring, HIPE organogel was formed.

The HIPE organogel prepared was used in the preparation of the sulfonated polystyrene porous xerogel according to the method described below.

Method for preparing sulfonated polystyrene porous xerogel

The as-prepared HIPE organogel was washed by adding water to it under stirring for 2 hours. The organogel was then isolated by filtration. The sulfonated polystyrene porous xerogel was obtained by drying the washed organogel for 24 hours.

The resulting sulfonated polystyrene porous xerogel was characterized using the following methods: The sulfonated polystyrene porous xerogel was characterized by its hydrophobic liquid absorption capacity, absorption rate and reusability. The mass absorption capacity is defined as (m_s-mo)/mo, where mo and m_s represent the weights of the porous materials before and after liquid-absorption, respectively. A known amount of the porous materials (mo) was placed into a beaker containing the hydrophilic liquid and left quiescent for 2 hours. The porous material was then lifted and dried to remove residual surface liquid before recording the weight of m_s. The absorption capacity was calculated via the above equation.

The absorption rate of the porous material was determined by placing a known weight of the porous material (mo) into the hydrophobic liquid, then monitoring the weight of material (m_t) at different times. The weight gain of porous material at time t was defined as (m_t-mo).

The reusability of the porous material was determined by simple mechanical squeeze, and the absorbed hydrophobic liquid was released from the porous material. The recovery rate was calculated as m_re/(m_s-mo), where m_re is the weight of the recovered hydrophobic liquid, m_s is the swollen porous material at the saturated absorption state and mo is the initial weight of the porous material.

Figure 1 shows a scanning electron microscope (SEM) image of a sulfonated polystyrene porous xerogel in accordance with the invention showing the porous structure of the xerogel;

Figure 3 shows oil absorption capacity of the sulfonated polystyrene porous xerogel in accordance with the invention to various hydrophobic liquids; and Figure 4 illustrates absorption capacities of the sulfonated polystyrene porous xerogel in accordance with the invention and toluene recovery with toluene absorption/squeezing-out cycle numbers.

Example 2: Absorption of engine oil with sulfonated polystyrene porous xerogels

1.5 g (about 25mL) of sulfonated polystyrene porous xerogel prepared above was added to a beaker containing 300 mL of water and 20 mL of engine oil (dyed with oil red O for observation). The xerogel floated on the oil layer which is red on the water surface. After about two minutes, oil was absorbed completely by the xerogel and the resultant oil-absorbed xerogel remained floating on the water surface. The oil-absorbed xerogel was collected with a tweezer and the absorbed oil in the xerogel squeezed out. The xerogel was then ready for use again. The saturated oil absorption capacity of the xerogel was not reached in this example.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps. The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Claims

1. An open cell thermoplastic sulfonated polystyrene porous xerogel for absorbing hydrophobic liquid, wherein at least some of the sulfonated groups are neutralised.

2. The open cell thermoplastic sulfonated polystyrene porous xerogel according to claim

1 having a surface area ranging form about 5 m 2 /g to about 100 m 2 /g.

3. The open cell thermoplastic sulfonated polystyrene porous xerogel according to claim

1 or 2 having a density ranging from about 0.02 g/cm 3 to about 0.2 g/cm 3.

4. The open cell thermoplastic sulfonated polystyrene porous xerogel according to any one of claims 1 to 3, wherein the sulfonated polystyrene comprises polymerised residues of styrene monomer.

5. The open cell thermoplastic sulfonated polystyrene porous xerogel according to any one of claims 1 to 4, wherein the sulfonated polystyrene comprises polymerised residues of styrene sulfonic acid monomer or salt thereof.

6. The open cell thermoplastic sulfonated polystyrene porous xerogel according to any one of claims 1 to 5, wherein the sulfonated polystyrene has a number average molecular weight (Mn) ranging from about 100, 000 to about 10,000,000.

7. The open cell thermoplastic sulfonated polystyrene porous xerogel according to any one of claims 1 to 6, wherein the sulfonated polystyrene has a degree of sulfonation ranging from about 0.1% to about 50%.

8. The open cell thermoplastic sulfonated polystyrene porous xerogel according to any one of claims 1 to 7, wherein at least 30% of the sulfonated groups present are neutralised

9. A method of preparing an open cell thermoplastic sulfonated polystyrene porous xerogel for absorbing hydrophobic liquid, the method comprising:

10. The method according to claim 9, wherein the sulfonated polystyrene provided in (i) is prepared by sulfonating polystyrene using a sulfonating reagent.

11. The method according to claim 9, wherein the sulfonated polystyrene provided in (i) is prepared by polymerising styrene sulfonic acid monomer or salt hereof.

13. The method according to claim 11, wherein the styrene sulfonic acid monomer or salt thereof is copolymerised with styrene monomer.

14. The method according to any one of claims 9 to 13, wherein the sulfonated polystyrene provided in (i) is dissolved in a solvent selected from tetrahydrofuran (THF), toluene, xylene, a combination of two or more thereof, and a mixture of one or more thereof with an alcohol.

15. The method according to any one of claims 9 to 14, wherein the composition provided in (i) comprises from about 5 w/v% to about 20 w/v% of the sulfonated polystyrene.

16. The method according to any one of claims 9 to 15, wherein in (ii) the aqueous solution comprising one or more dissolved salts are selected from sodium chloride, potassium chloride, sodium sulphate and combinations of two or more thereof.

17. The method according to any one of claims 9 to 16, wherein in (ii) the hydrophobic solvent is selected from toluene, xylene, chloroform, anisole, dichloroethane, dichloromethane, and combinations of two or more thereof.

18. A method of isolating hydrophobic liquid, the method comprising contacting the hydrophobic liquid with the open cell thermoplastic sulfonated polystyrene porous xerogel according to any one of claims 1 to 9, wherein the open cell thermoplastic sulfonated polystyrene porous xerogel absorbs and isolates the hydrophobic liquid therein.

19. The method according to claim 18, wherein the open cell thermoplastic sulfonated polystyrene porous xerogel is contained within a material that enables the hydrophobic liquid that is to be isolated to pass through it and make contact with the open cell thermoplastic sulfonated polystyrene porous xerogel.

20. The method according to claim 18 or 19 which further comprises a step of compressing the open cell thermoplastic sulfonated polystyrene porous xerogel with hydrophobic liquid isolated therein so as to (a) expel hydrophobic liquid from the porous xerogel, and (b) enable re-use of the porous xerogel to absorb additional hydrophobic liquid.