FI127777B

FI127777B - Extracted lignocellulosic material as an adsorbent

Info

Publication number: FI127777B
Application number: FI20175292A
Authority: FI
Inventors: Mika Mänttäri; Mari Kallioinen
Original assignee: Lappeenrannan Teknillinen Yliopisto
Priority date: 2017-03-29
Filing date: 2017-03-29
Publication date: 2019-02-15
Also published as: FI20175292L

Abstract

According to an example aspect of the present invention, there is provided a method of removing dissolved contaminants from an aqueous liquid. The aqueous liquid is contacted with an adsorbent which comprises a finely divided lignocellulosic material, which has been subjected to extraction to remove hemicellulose and/or other components therefrom, to bind at least a portion of the organic compounds to the adsorbent.

Description

20175292 prh 23 -01- 2019

FIELD

The present invention relates to removal and separation of contaminants from aqueous liquids. In particular the invention concerns the use of an adsorbent 5 lignocellulosic material for removing dissolved contaminants from an aqueous liquid.

BACKGROUND

Water pollution occurs when pollutants, such as chemical contaminants, are directly or indirectly discharged into bodies of water such as lakes, rivers, oceans, aquifers and groundwater.

Chemical contaminants include both organic and inorganic substances.

Examples of organic contaminants include detergents, disinfection by-products found in chemically disinfected drinking water, such as chloroform, food processing waste, which can include oxygen-demanding substances, such as fats and grease, insecticides and herbicides, comprised of for example, a huge range of organohalides 15 and other chemical compounds, petroleum hydrocarbons, including fuels (gasoline, diesel fuel, jet fuels, and fuel oil) and lubricants (motor oil), and fuel combustion byproducts, from storm water runoff, volatile organic compounds, such as industrial solvents, from improper storage, chlorinated solvents, for example polychlorinated biphenyl (PCBs), and trichloroethylene, perchlorate, various chemical compounds 20 found in personal hygiene and cosmetic products, and pharmaceutical drugs and their metabolites as well as compounds dissolved from wood in different treatments such as lignin and its derivatives and wood lipophilic and phenolic extractives.

Inorganic contaminants include sulfur dioxide from industrial discharges, ammonia from food processing waste, industrial by-products, nitrates and phosphates from 25 fertilizers, and heavy metals from e.g. acid mine drainage.

The pulp and paper industry is one of the heaviest users of water in the industrial economy using even tens of cubic meters of water for every ton of product depending on the product and process. Pulp and paper mills produce wastewater in volume which must be treated before water can either be recycled for use in the mills or safely 30 discharged. Improving the recovery of contaminants stemming from pulp and paper mill process and waste water is therefore imperative.

20175292 prh 23 -01- 2019

The production of new biobased products such as hemicelluloses from lignocellulosic materials needs also large volumes of water and purification of final products from impurities is needed.

In the art, there are a number of solutions for removing, for example pollutants in municipal waste water treatment plants (WWTP). Suitable methods include the use of active sludge, filtration and the addition of chemical components. For removing micropollutants it has recently been suggested to use of powder activated carbon (PAC) as a complement to municipal WWTP in order to achieve a significant reduction of micropollutants and ecotoxicity in receiving waters.

The conventional technologies are hampered by the costs of providing suitable absorbents. In case of mechanical technologies, such as filtering, clogging is a conventional problem which is encountered in particular when the aqueous streams contain colloidal impurities. In membrane filtration fouling of the filtration material is also caused by adsorption of organic compounds on the membrane structure.

SUMMARY OF THE INVENTION

It is an aim of the invention to overcome at least some of the above mentioned disadvantages and to provide a method of separating contaminants from aqueous flows and effluents using materials.

It is another aim of the invention to provide a method of separating contaminants, 20 which method can be used as a preliminary purification step before conventional separation technologies.

The present invention is based on the concept of using extracted lignocellulosic material as an adsorbent for the removal of contaminants from aqueous liquids.

According to a first aspect of the present invention, there is provided an adsorbent 25 which comprises a finely divided lignocellulosic material, which has been subjected to extraction to remove hemicellulose components therefrom. In some embodiments, the lignocellulosic material is extracted with an aqueous solution, which may contain acidic or buffering components, to remove a significant portion of the hemicelluloses and optionally other compounds contained therein. The material thus obtained has 30 surprisingly been found to efficiently remove contaminants, such as dispersed or dissolved contaminants, from aqueous liquids.

The invention is defined by the features of the independent claims. Specific embodiments are defined in the dependent claims.

20175292 prh 23 -01- 2019

Considerable advantages are obtained by the invention. Thus, the novel adsorbents have excellent absorption and adsorption properties. They can be used for removing by sorption a number of pollutants, both organic and inorganic substances as well as microbial components, from aqueous streams and effluents. The novel materials can 5 be combined with other separation processes to achieve a pre-purification step. In a particularly preferred embodiment, the method is combined with conventional mechanical separation operations, such as membrane filtration.

The present adsorbent materials can be produced by a straightforward method using inexpensive starting materials. In particular, the material is produced from 10 lignocellulosic raw-materials obtained as a by-product in other processes.

Further features and advantages of specific embodiments will be discussed in more detail in the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a graph showing UV absorbance values of various aqueous liquids having 15 various contaminants;

Figure 2 is a graph illustrating the effect of ratio of extracted sawdust and extraction liquor on the removal of UV absorbing material; and

Figure 3 is a graph illustrating filtration capacity when extraction liquor (108) and extraction liquor pretreated with extracted wood (109) is ultrafiltered to concentrate 20 and purify hemicelluloses.

DEFINITIONS

In the present context, the term “lignocellulosic material” comprises plant dry matter composed of carbohydrate polymers including cellulose and hemicellulose, and lignin. “Lignocellulosic material” includes virgin lignocellulosic material such as wood 25 chips from, for example, softwood, for example spruce, pine or larch, or from hardwood, such as birch, poplar, aspen, alder, eucalyptus or mixed tropical hardwood, or mixtures thereof. “Lignocellulosic material” also includes recycled lignocellulosic materials as well as waste lignocellulosic material, such as by-products from industry and agriculture such as com stover, sugarcane, bagasse, cotton, straw 30 etc. and saw mill, pulp mill and paper mill discards.

The term “aqueous liquids” means liquids in which there is at least some water present including for example, industrial effluents such as hot water extraction liquors,

20175292 prh 23 -01- 2019 extraction liquors from wood pulping mills, waste waters from pharmaceutical plants, waste waters from oil refineries, as well as agricultural run-offs and waterways such as canals and rivers, other bodies of water such as reservoirs, and natural or manmade ponds or lakes.

The term “contaminants” comprises inorganic and organic compounds, typically dissolved in aqueous liquids. Similarly, “impurity” can be defined in the same way.

“Organic compounds” includes compounds and substances comprising mixtures of compounds such as those found in industrial effluents including for example phenolic compounds, resinous and fatty acids, nitrogenous compounds, such as drug or 10 pesticide residues or proteins, polymeric compounds and oils.

“Inorganic compounds” includes sulfur dioxide from industrial discharges, ammonia from food processing waste, industrial by-products, nitrates and phosphates from fertilizers, and heavy metals from e.g. acid mine drainage.

“Extraction Liquor” is a solution into which organic substances have been extracted 15 from lignocellulosic material.

“Chips” includes wood chips, bark chips and nutshells. In particular, “chips” refers to slate-like or plate-like particles.

“Saw dust” stands for finely divided wood material obtained from mechanical processing of wood and bark for example by sawing and typically comprising 20 irregularly shaped particles or spherical or cubical particles. Commonly, the particles of saw dust are smaller in size than “chips” and pass through sieves of Tyler Mesh 10 or greater, in particular up to at least Tyler Mesh 80.

EMBODIMENTS

As mentioned above, the present invention relates to a method of removing 25 contaminants from a liquid, typically an aqueous liquid. The liquid is contacted with an adsorbent. By means of the invention, it has surprisingly been found that lignocellulosic material that has been subjected to extraction to remove hemicellulose components is an excellent adsorbent. The extracted lignocellulosic material, which is finely divided, removes at least a portion of contaminants from liquids by binding 30 the contaminants to the adsorbent.

The liquids are typically aqueous although the present technology is suitable also for treating non-aqueous liquids or anhydrous liquids. Thus, the “liquid” can be for

20175292 prh 23 -01- 2019 example formed by an organic liquid, such as a polar or non-polar organic liquid. Such liquids are typically selected from the group of aliphatic and aromatic alcohols, ketones, aldehydes, ethers, esters as well as various hydrocarbon liquids, which may be halogenated.

Many industrial effluents are aqueous, and the present technology is particularly suitable for processing of such flows.

One embodiment of the present invention provides a method of removing contaminants from an aqueous liquid, wherein the aqueous liquid is contacted with an adsorbent which comprises a finely divided lignocellulosic material, which has 10 been subjected to extraction to remove hemicellulose components therefrom, to bind at least a portion of the contaminants to the adsorbent, for example in the case of extraction liquor the adsorbent binds and removes lignin from the liquor, thus providing a means to recover target compounds such as further hemicelluloses, which are useful as raw materials in the production of e.g. biopolymers, from the liquor.

In an embodiment the contaminants are selected from dissolved inorganic and organic compound and mixtures thereof.

In one embodiment the adsorbent is obtained by extracting lignocellulosic material with an aqueous solution, optionally containing an alkaline, acidic or buffering component, to remove a significant portion of the hemicelluloses and/or other 20 components contained therein. The pH of the aqueous solution is typically less than or equal to 5.0, preferably less than or equal to 4.6, suitably in the range of 2.8 to 4.2, most preferably in the range of 3.0 to 4.0. High molar mass hemicelluloses are easier to separate from extraction liquor by ultrafiltration than hemicelluloses of lower molar mass. Removal of a significant portion of the hemicellulose and/or other components 25 contained therein from the lignocelluosic material provides an extracted lignocelluosic material.

In an embodiment the lignocellulosic material used as an adsorbent has a hemicellulose content which is at least 10 wt-%, preferably at least 20 wt- %, in particular 30 to 95 wt-%, smaller than that of the lignocellulosic material before 30 extraction. Removal of greater amounts of hemicellulose from the lignocellulosic material increases the adsorbent properties of the adsorbent.

In a further embodiment the finely divided lignocellulosic material used as adsorbent has a lignin content which is at least 60 wt %, preferably 70 wt-%, suitably 80 wt-% of the lignin content of the lignocellulosic material before extraction. A high lignin content

20175292 prh 23 -01- 2019 is desirable as lignin has a great affinity for adsorbing both inorganic contaminants, such as heavy metals, and organic contaminants, such as polymeric compounds and oils.

The adsorbent can be obtained by various means and methods. In one embodiment the adsorbent is obtained by subjecting the lignocellulosic material to hot water extraction, said hot water extraction preferably being carried out at temperature in excess of 100 °C, for example about 110 to 250 °C, in particular 120 to 200 °C, such as 145 to 200 °C. The treatment time depends on temperature. Typically the duration is 5 min to 7 days, for example 10 min to 2 days for example 15 min to 720 min. Higher 10 temperatures and longer extraction times lead to higher extraction yields, i.e. a greater amount of the hemicelluloses is extracted as temperature and time of extraction increase.

In one embodiment the lignocellulosic material is recovered after extraction and used as an adsorbent for binding dissolved compounds from the aqueous liquid essentially 15 without any intermittent washing of the lignocellulosic material. This provides an economically and environmentally sound way of binding the crudest compounds from the aqueous liquids.

In a further embodiment the lignocellulosic material is recovered after extraction and washed, and is used as an adsorbent for binding dissolved compounds from the 20 aqueous liquid. After washing, the adsorbent has a greater available surface and a larger number of functional groups available for the binding of dissolved compounds from the aqueous liquid.

In a still further embodiment the lignocellulosic material recovered after extraction is dried before use as an adsorbent for binding dissolved compounds from the aqueous 25 liquid. Drying the adsorbent increases the adsorption of dissolved compounds from the aqueous liquid.

In an embodiment, the lignocellulosic material is used as an adsorbent at conditions which are different from those employed during the extraction of the hemicelluloses.

It is in some cases desirable that the extracted lignocellulosic material is 30 functionalised. Such functionality is useful to vary the adsorbability of the material. In one embodiment the extracted lignocellulosic material is treated with a chemical agent selected from the group of alkaline compounds, acidic compounds and solvents and combinations thereof to modify its adsorption properties, before use. Treatment of the

20175292 prh 23 -01- 2019 extracted lignocellulosic material with a chemical agent allows diverse functionalities to be introduced to the lignocellulosic material by chemical reaction.

The lignocellulosic material to be extracted comes from various sources of biomass ranging from annual and perennial plants, for example grasses such as bamboo, to 5 wood or nutshells. In an embodiment the lignocellulosic material comprises wood, such as softwood, for example spruce, pine or larch, hardwood, such as birch, poplar, aspen, alder, eucalyptus, oak or mixed tropical hardwood, or mixtures thereof. In one embodiment the lignocellulosic material to be extracted comprises bark of the said wood(s). In another embodiment the lignocellulosic material to be extracted 10 comprises nutshells.

The lignocellulosic material is finely divided. In an embodiment the lignocellulosic material comprises sawdust. The sawdust can comprise wood sawdust or bark sawdust or a combination thereof. In a still further embodiment the lignocellulosic material to be extracted comprises chips. The chips can be either chips of wood, chips 15 of bark or nutshells, or a combination thereof. The diversity of sources of lignocellulosic materials allows embodiments of the invention to be carried out anywhere where there is a source of lignocellulosic material without incurring heavy transportation costs.

The particle sizes of the lignocellulosic material can vary. In an embodiment the 20 adsorbent comprises lignocellulosic material having a d50 particle size of 0.05 mm to

6.0 mm, preferably 0.1 to 5.0 mm, suitably 0.2 to 3 mm.

In another embodiment, the adsorbent comprises finely divided lignocellulosic material having particles which pass sieves of Tyler Mesh 10 to 80.

The adsorbability of the adsorbent is directly proportional to the dso particle size of the 25 lignocellulosic material.

The liquid is contacted with the adsorbent to remove dissolved inorganic or organic compounds from the liquid. In an embodiment the liquid is contacted with the adsorbent at a ratio between the lignocellulosic material and the liquid amounting to from 0.01:1 to 0.25:1 by mass, preferably at least 0.04:1 by mass, suitably about 0.2:1 30 by mass. The ratio is adjusted dependent on the amount of contaminants in the liquid.

In further embodiments the liquid can be contacted with a synthetic adsorbent material, simultaneous with the lignocellulosic adsorbent material, or before contacting the liquid with the lignocellulosic material, or after contacting the liquid with

20175292 prh 23 -01- 2019 the lignocellulosic material. In an embodiment, the adsorbent material is a mixture of both lignocellulosic material and a synthetic adsorbent material. In one embodiment the adsorbent further comprises a synthetic adsorbent material, preferably selected from the group consisting of aromatic type adsorbents, modified aromatic type 5 adsorbents, methacrylic adsorbents and mixtures thereof. The synthetic adsorbent can be selected to be specific for a particular type of contaminant removing it from the aqueous liquid. This allows for the removal of contaminants that are, e.g. particularly difficult to wash from the lignocellulosic adsorbent.

The adsorbent material is suitable to be used several times. In an embodiment 10 adsorbent material onto which at least a portion of the contaminants from the liquid have been adsorbed is recovered and reused as an adsorbent material. The recycling and reuse of the adsorbent material is both environmentally and economically advantageous.

In a further embodiment the recovered adsorbent material is dried, washed, and dried, 15 before reuse as an adsorbent material. In one embodiment the adsorbent material is washed with a washing agent selected from the acids and bases. Thus, the washing agent may contain for example a weak or strong inorganic or organic acid, such as a mineral acid or a carboxylic acid, or a base, for example as a weak or strong inorganic base, such as an alkali metal hydroxide or carbonate, ammonium hydroxide or an 20 organic amine. Washing with an acid washing agent allows for the selective removal of contaminants that are soluble in acid from the adsorbent material. Washing with a basic washing agent then provides the removal of contaminants that are soluble in basic washing agents from the adsorbent, to provide a washed adsorbent material that is essentially free from adsorbed contaminants. Washing with an acid can be 25 carried out before or after washing with a base.

As described above, the adsorbent is useful for removal of contaminants from liquids. In some embodiments the contaminants are organic compounds. In one embodiment the liquid contains organic compounds selected from the group of phenolic compounds, such as lignin, resinous and fatty acids, nitrogenous compounds, such 30 as drug or pesticide residues or proteins, polymeric compounds and oils and combinations thereof.

The adsorbent can be arranged for contact with the liquid in various ways. In an embodiment the adsorbent is arranged in an adsorption zone, and the liquid is conducted through that zone and intimately contacted with the adsorbent in the zone. 35 This provides a constant flow of a modified liquid.

20175292 prh 23 -01- 2019

In a further embodiment the adsorption zone comprises a filtration bed formed by the adsorbent.

In one embodiment the adsorbent is mixed with the aqueous liquid to form a slurry in which the contaminants of the aqueous liquid are contacted with the adsorbent and 5 bonded to the adsorbent.

The method results in the provision of a modified liquid. In an embodiment a modified liquid which has a reduced content of contaminants is recovered as an effluent of the adsorption zone.

In one embodiment the aqueous phase of the slurry is separated from the dispersed 10 material and recovered as a modified liquid with a reduced content of contaminants.

In a further embodiment the portion of contaminants adsorbed onto the adsorbent material is at least 20 %, in particular at least 30 %, preferably at least 50 %, by weight of the amount of contaminants present in the liquid.

In a still further embodiment the modified liquid is re-contacted with an adsorbent 15 material, for example by recycling.

As described above the liquid is typically aqueous. Such an aqueous liquid can be obtained from a number of sources. In an embodiment the aqueous liquid is selected from the group consisting of hot water extraction extracts, process liquors from wood pulping mills, waste waters from pharmaceutical plants, waste waters from oil 20 refineries, and agricultural run-offs. The aqueous liquid can even be drinking water from a water main.

In one embodiment the liquid, in particular aqueous liquid, contains dissolved hemicelluloses. Hemicelluloses are very desirable and useful as raw materials in the production of e.g. biopolymers. In a further embodiment the aqueous liquid contains 25 dissolved hemicelluloses and lignin compounds or fragments, and at least a part, preferably at least a majority of the lignin compounds or fragments are adsorbed to the adsorbent to provide a modified aqueous liquid. In an embodiment the modified aqueous liquid obtained by adsorption of the lignin compounds or fragments is conducted to a molecular filtration step for recovering hemicelluloses.

As mentioned above hemicelluloses are very desirable and useful as raw materials. In an embodiment at least a portion of the recovered hemicelluloses is directed to further processing for use in industry, e.g. as a substrate in the production of speciality chemicals such as sugars and alcohols. In a further embodiment at least a portion of

20175292 prh 23 -01- 2019 the recovered hemicelluloses is refined for use e.g. as packing and packaging material.

The following non-limiting example illustrates the invention:

Example

Saw dust of soft wood was extracted in batch mode cooking vessel for 90 minutes at 160 °C. The extraction liquor contained hemicelluloses and impurities such as lignin. The residual saw dust was separated from extraction liquor and used to purify the extraction liquor from impurities.

Wood materials after extraction of dissolving compounds (mainly hemicelluloses and 10 smaller molar mass carbohydrates) have proved to have excellent absorption properties.

Figure 1 illustrates the effect of extracted sawdust on the UV absorbances of aqueous liquids having various contaminants. The UV absorbance of the extraction liquor (104), of water after treatment with extracted sawdust (101), and of extraction liquor 15 after treatment with extracted sawdust (103) is shown. The UV absorbance due to dissolution of contaminants from sawdust is subtracted from the UV absorbances of the extraction liquor after treatment with extracted sawdust (102).

The wood material after extraction purifies extraction liquor by removing lignin compounds as will appear from Figure 1. More than 50% of lignin (UV absorbing 20 material) was removed from the extraction liquor without significant change in the hemicellulose content when dried material was used.

Figure 2 illustrates the effect of ratio of extracted sawdust and extraction liquor on the removal of UV absorbing material. Data was measured at five different ratios: 0 g extracted sawdust to 1 g of extraction liquor, 0.01:1, 0.04:1, 0.1:1 and 0.2:1. The 25 substantial differences in UV absorbance values measured at 278 (106), 208 (107) and 228 nm (105) can be observed.

As will appear, the efficiency was somewhat lower than above in Figure 1, but clearly seen also for wet materials. Approximately 30 % of UV absorbing materials was removed with wet wood material. Original saw dust had only a minor effect on the UV 30 absorbing compounds. Adsorption experiments followed by filtration to remove saw dust from extraction liquor lead to about 15% decrease in UV absorbance.

Table 1 shows the effect of saw dust on the reduction of UV absorbance.

Table 1. Effect of used saw dust, and used and washed saw dust on the reduction of UV-absorbances of the extraction liquor

Ratio 0.1	UV 278 nm	UV208 nm	UV 228 nm
Dried saw dust	35.7 %	52.2 %	48.2 %
Used and dried	22.4 %	33.0 %	30.0 %
Used, washed and dried, 20 °C	38.1 %	45.3 %	43.8 %
Used, washed and dried, 60 °C	33.2 %	43.2 %	41.1 %

20175292 prh 23 -01- 2019

As Table 1 indicates, the sawdust can be used again to purify the extraction liquor.

The removal efficiency decreased slightly but was still about 30 %. If the saw dust was washed with water between the treatment steps, the removal efficiency was similar to when original dried saw dust was used.

The removal of UV-absorbing compounds improves the further fractionation and concentration of hemicelluloses by membrane filtration. More than five times increase 10 in filtration capacity was achieved, as can be seen from Figure 3.

Based on the retention in the membrane filtration the residual saw dust removes preferably high molar mass impurities such as lignin. These compounds are concentrated with hemicelluloses and therefore the pretreatment before membrane filtration did not only increase the capacity in membrane filtration but also improves 15 the purity of final product i.e. concentrate after membrane filtration.

It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is 20 used for the purpose of describing particular embodiments only and is not intended to be limiting.

Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus,

20175292 prh 23 -01- 2019 appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely 10 based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and 15 autonomous representations of the present invention.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One 20 skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

While the forgoing examples are illustrative of the principles of the present invention 25 in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of a or an, that is, a singular form, throughout this document does not exclude a plurality.

INDUSTRIAL APPLICABILITY

At least some embodiments of the present invention find industrial application in the paper and pulp industries. Lignocellulosic materials after extraction of dissolving compounds (mainly hemicelluloses and smaller molar mass carbohydrates) are found to have excellent absorption properties. The wood material after extraction purifies 5 extraction liquor by removing lignin and wood extractive compounds. This increases the purity of target compounds such as hemicelluloses. In addition, the treatment improved the efficiency of membrane filtration which was used to purify and concentrate hemicelluloses. Both the filtration capacity and purity of final product was improved. The material can also be used in a method to purify waters, e.g. to remove 10 organic micropollutants (drug residues, pesticides) or oil from water.

Claims

CLAIMS:

A method for removing dissolved impurities from a liquid, comprising contacting the liquid with an adsorbent comprising

5 finely divided lignocellulosic material subjected to extraction to remove hemicellulose and / or other constituents to bind at least a portion of the organic compounds to the adsorbent.

The process according to claim 1, wherein the impurities are selected from dissolved inorganic and organic compounds and mixtures thereof.

10

The process according to claim 1 or 2, wherein the adsorbent is produced by extraction of the lignocellulosic material with an aqueous solution optionally containing an alkaline, acid or buffer component to remove a significant portion of the hemicellulose and / or other compounds therein.

A method according to any one of the preceding claims, wherein

The hemicellulose content of the lignocellulosic material used as the adsorbent is at least 10% by weight, preferably at least 20% by weight, in particular 30-95% by weight, less than the corresponding content of the lignocellulosic material before extraction.

A process according to any one of the preceding claims, wherein the fine lignocellulosic material used as the adsorbent

The lignin content is at least 60% by weight, preferably 70% by weight, suitably 80% by weight of the lignin content of the lignocellulosic material before extraction.

The process according to any one of the preceding claims, wherein the adsorbent is produced by subjecting the lignocellulosic material to hot water extraction, wherein the hot water extraction is preferably carried out at a temperature above 100 ° C to 250 ° C,

110 to 200 ° C, preferably for a period of 10 minutes to 7 days.

The method according to any one of the preceding claims, wherein the lignocellulosic material is recovered after extraction and used as an adsorbent to bind dissolved compounds from the aqueous solution substantially without any intermittent washing of the lignocellulosic material.

30

The process of any one of claims 1 to 6, wherein the lignocellulosic material is recovered after extraction, washed and used as an adsorbent to bind dissolved compounds from the aqueous liquid.

20175292 prh 23 -01-20199

The process of any one of the preceding claims, wherein the lignocellulosic material recovered after extraction is dried before being used as an adsorbent to bind dissolved compounds from the aqueous liquid.

A method according to any one of the preceding claims, wherein before

5, the extracted lignocellulosic material is treated with a chemical selected from the group consisting of alkali compounds, acid compounds and solvents, or combinations thereof, to modify the adsorption properties.

The method according to any one of the preceding claims, wherein the lignocellulosic material contains wood, such as softwood, e.g.

10 pines or hardwoods, hardwoods such as birch, poplar, aspen, alder, eucalyptus or a mixture of tropical hardwoods or a mixture thereof.

The process according to any one of the preceding claims, wherein the adsorbent comprises a lignocellulosic material having a d 50 particle size of 0.05 to 6.0 mm, preferably 0.1 to 5.0 mm, suitably 0.2 to 3 mm.

15

The method according to any one of the preceding claims, wherein the liquid is contacted with the adsorbent in a lignocellulosic material to liquid mass ratio of 0.01: 1 to 0.25: 1, preferably at least 0.04: 1, suitably about 0.2: 1.

A method according to any one of the preceding claims, wherein the adsorbent further comprises a synthetic adsorbent material, preferably selected

20 groups consisting of aromatic-type adsorbents, modified aromatic-type adsorbents, methacrylic adsorbents and mixtures thereof.

The method of any one of the preceding claims, wherein the adsorbent material, wherein at least some of the impurities in the aqueous liquid are

25 adsorbed, recovered and used as adsorbent material.

The method of claim 15, wherein the recovered adsorbent material is dried, washed and dried before being used again as an adsorbent material.

The method of any one of the preceding claims, wherein the liquid 30 contains organic compounds selected from the group consisting of phenolic compounds such as lignin, resin and fatty acids, nitrogen compounds such as drug or pesticide residues or proteins, polymeric compounds and oils and mixtures thereof.

20175292 prh 23 -01-20199

A method according to any one of the preceding claims, wherein the liquid is aqueous.

A process according to any one of the preceding claims, wherein the adsorbent is disposed within the adsorption region and the aqueous liquid is

5 through the region and contacting the adsorbent in the region.

The method of claim 19, wherein the adsorption region includes a filter bed formed by an adsorbent.

The method of claim 19 or 20, wherein the modified aqueous liquid having a lower impurity content is recovered

10 adsorption regions as effluent.

A process according to any one of claims 1 to 19, wherein the adsorbent is mixed with a liquid, in particular an aqueous liquid, to form a slurry, wherein impurities of the liquid are contacted with the adsorbent and bound to the adsorbent.

15

The method of claim 22, wherein the liquid phase of the slurry is separated from the dispersed material and recovered as a modified liquid with a lower impurity content.

The method of any one of the preceding claims, wherein the proportion of impurities adsorbed to the adsorbent material is at least 20% by weight.

20%, in particular at least 30% by weight, preferably at least 50% by weight, of the impurities in the liquid.

The method of any one of claims 17 to 22, wherein the modified fluid is contacted with the adsorbent material, for example, by recycling.

25

The method of any one of the preceding claims, wherein the liquid is aqueous and is selected from the group consisting of hot water extraction extracts, wood processing plant process fluids, pharmaceutical effluent, oil refinery effluent, and agricultural effluents.

The method of any one of the preceding claims, wherein the liquid 30 contains dissolved hemicellulose.

The method of claim 26, wherein the liquid contains dissolved hemicellulose and lignin compounds or fragments and at least a portion, preferably at least most of the lignin compounds or fragments is adsorbed onto the adsorbent and forms a modified liquid.

5

The method of claim 28, wherein the modified fluid produced by adsorption of lignin compounds or fragments is subjected to a molecular filtration step to recover hemicelluloses.

The method of claim 29, wherein at least a portion of the recovered hemicellulose is sent for further processing for use in industry, e.g.

10 as a substrate for the production of secretory chemicals such as sugars and alcohols.

The method of claim 29, wherein at least a portion of the recovered hemicellulose is processed for use, e.g., in packaging and packaging material.