Biobased membrane

Abstract

A composition for forming a bio-compatible membrane applicable to building material, such as concrete, cement, etc., to a method of applying said composition for forming a biocompatible membrane, a biocompatible membrane, use of said membrane for various purposes, and to building material comprising said membrane.

Claims

1. Method of forming a bio-compatible impermeable membrane comprising the steps of: providing a composition consisting essentially of (i) water, (ii) a water-soluble anionic bio-degradable polymer obtained from bacteria, and (iii) platelet nanoparticles, wherein the water-soluble anionic bio-degradable polymer is in an amount of 1.5-10 wt %, wherein platelet nanoparticles are in an amount of 0.01-5 wt %, based on a total weight of the composition, wherein an amount (wt %) of water-soluble anionic bio-degradable polymer is larger than an amount of platelet nanoparticles, wherein an amount of platelet nanoparticles and water-soluble anionic bio-degradable polymer is 1.51-10 wt. %, applying the composition onto a surface under ambient conditions, the surface providing polyvalent cations, and reacting the water-soluble anionic bio-degradable polymer and polyvalent cations, thereby forming the bio-compatible impermeable membrane on the surface.

2. The method according to claim 1, wherein the surface is pre-treated and/or pre-shaped.

3. The method according to claim 1, wherein the surface is one or more of concrete, cement material, or brick.

4. The method according to claim 1, wherein the composition is applied at least once by one or more of spraying, brushing, nebulizing, or pouring, and wherein the composition is applied directly after casting cement or concrete.

5. A method of protecting a surface from degradation by performing a method according to claim 1, such as wherein the surface is protected from one or more of drying, oxidizing, corroding, wearing, fouling, or dehydrating.

6. A flexible coating comprising polyvalent cations, water, and a water soluble anionic bio-degradable polymer, obtained by a method according to claim 1.

7. One or more of concrete, cement material, or brick, comprising a water impermeable flexible polymer coating according to claim 6.

8. An aqueous composition for forming a bio-compatible impermeable membrane on a surface wherein the surface is one or more of concrete, cement material, or brick, consisting essentially of: (i) as a balance water, (ii) a water-soluble anionic bio-degradable polymer obtained from bacteria, wherein the water-soluble anionic bio-degradable polymer when in contact with polyvalent cations under ambient conditions forms a gel, the water-soluble anionic bio-degradable polymer being dissolved in the water, and (iii) platelet nanoparticles, the platelet nanoparticles being suspended in the water, wherein the water-soluble anionic bio-degradable polymer is in an amount of 1.5-10 wt %, wherein the platelet nanoparticles are present in an amount of 0.01-5 wt %, based on a total weight of the composition, wherein an amount (wt %) of water-soluble anionic bio-degradable polymer is larger than an amount of platelet nanoparticles, wherein an amount of platelet nanoparticles and water-soluble anionic bio-degradable polymer is 1.51-10 wt. %, wherein the water-soluble anionic bio-degradable polymer is selected from anionic polysaccharides or acidic biopolymers, wherein the polyvalent cation is one or more of calcium, iron, copper, strontium, cobalt, aluminium, zinc, magnesium, or nickel, and wherein the platelet nanoparticles are one or more of a natural or artificial clay, or a silicate mineral.

9. The composition according to claim 8, wherein the platelet nanoparticles are present in an amount of 0.1-5 wt %.

Description

SUMMARY OF FIGURES

(1) FIG. 1. Thermogravimetric curves of samples with different calcium content alginates.

(2) FIG. 2a. ESEM/BSE micrographs comparing near surface area of cement cured with a layer of water and FIG. 2b. sodium alginate.

DETAILED DESCRIPTION OF FIGURES

(3) The figures are further detailed in the description of the experiments below.

Examples/Experiments

(4) The invention although described in detailed explanatory context may be best understood in conjunction with the accompanying examples and figures.

(5) The present invention has led to various scientific publications and presentations further supporting the present application. Specifically worthwhile mentioning are the presentation Highly ordered biopolymer clay nanocomposites by J. Zlopasa et al, on the Dutch Polymer Days, Mar. 17-18 2014, A novel biobased curing compound for cement-based, by J. Zlopasa et al., Proceedings of International Conference APPLICATION OF SUPER ABSORBENT POLYMERS AND OTHER NEW ADMIXTURES IN CONCRETE CONSTRUCTION, Dresden 14-17 Sep. 2014, Germany, and Using biobased polymers for curing cement-based materials by J. Zlopasa et. al., Proceedings of the Intern. Conference on Ageing of Materials & Structures, Delft 26-28 May 2014, The Netherlands. These presentations and their contents are incorporated by reference into the present application.

(6) In a first experiment various combinations of polymer, nanoparticle, silicate, respectively, and clay were tested. The experiment consisted of pouring solutions of cement surface. All but one mentioned exhibited rapid pal formation when they got into contact with cement surface, the surface providing Ca.sup.2+ ions. The results are summarized in the table I below.

(7) TABLE-US-00001 TABLE 1 Sample Na Alginate Na MMT Na.sub.2SiO.sub.3 Result 1 + + 2 + + + 3 + + + + 4 + + + 5 + 0 6 + + 0 7 + 0

(8) The alginate relates to a bacterial alginate, obtained from sludge. MMT relates to montmorillonite. Therein a + indicates rapid formation of a gel, the gel having characteristics in line with the description above. 0 indicates forming of a gi but questionable if the gel has all the characteristics mentioned. For example the gels of samples 5-7 cracked upon drying. - indicates no gel being formed.

(9) The concentrations of Na-alginate in samples 1, 2, 3 and 4 is 2 wt. %, and concentrations of NaMMT and Na.sub.2SiO is about 5 wt. % with respect to the weight of Na alginate: in total composition that relates to 2 wt. % of Na Alginate and 0.107 wt. % of Na.sub.2SiO.sub.3 and/or 0.107 wt. % of NaMMT. The concentration for samples 5 and 7 was 2 wt. %, for NaMMT and Na.sub.2NaSiO.sub.3, respectively. And for sample 6, the concentration was 2 wt. % of Na.sub.2SiO.sub.3 and about 5 wt. % of NaMMT on the weight of Na.sub.2SiO.sub.3; in total composition that relates to 2 wt. % of Na.sub.2SiO.sub.3 and 0.107 wt. % of NaMMT.

(10) Mechanical Testing

(11) The measurements for the mechanical test were performed using Dynamic mechanical analysis. The results are presented in terms of storage modulus, which is considered to be similar to (the values of the Youngs modulus, due to the elastic response. For the modulus a value of 4.16 GPa was found. Typical values found are 2-10 GPa.

(12) The water-vapor transmission was determined gravimetrically by a water-vapor permeability test, which was performed using a cup method, according to ASTM E96. The water vapor permeability was found to be 1.8*10.sup.1 g/smPa. Typical values found are 1-10*10.sup.10 g/smPa.

(13) FIG. 1 presents the mass loss of alginates with different degrees of Ca-cross-linking, obtained by thermogravimetric analysis. The thermogravity (in %) is plotted against the temperature (in C.). The samples were analyzed under 10 K/min heat rate and the mass loss was monitored. Decomposition of Na-alginate and Ca-alginate result in formation of Na.sub.2CO.sub.3 and CaCO.sub.3, respectively. With this method inventors were able to characterize a degree of crosslinking of calcium in biobased membranes. The mass loss of samples corresponds to an amount of calcium added to the sodium alginate. FIG. 1 provides data determined on standard solutions, in order to obtain curves, which curves are used to recalculate results of experimental data in terms of amounts of alginate being present. It is observed that the present composition provides good barrier properties.

(14) TABLE-US-00002 TABLE 2 Mass losses of different degree of crosslinking from FIG. 1. mass loss % Degree of crosslinking 23.35 1 26.48 0.67 28.29 0.48 30.9 0.2 32.76 0

(15) Results from examining a near surface area of cement after 28 days of hydration are shown in FIGS. 2a and 2b. The volume of the liquids (water (FIG. 2a) and 2 wt. % Na-alginate solution (FIG. 2b), respectively) applied on the 24 cm.sup.2 surface of cement was 10 ml. The samples were stored at 50% RH and 20 C. In the water cured sample (FIG. 2a), most of the water evaporated in 4 days' time, while in the case of alginate solution sample a gel surface maintained for 7 days, after which a dried alginate film was formed.

(16) From the ESEM/BSE images (FIGS. 2a and 2h), inventors observe the developed microstructures of cement paste, from which inventors conclude that a more porous microstructure is developed when the cement is cured with water, evidenced by more open structures in FIG. 2a, which is considered a disadvantage. This observation corroborates with the measurements of mass loss of the cement samples over 28 days, from which inventors observed a reduced mass loss of cement paste covered with Na-alginate solution compared to water applied on the surface of cement. It should also be noted that water and Na-alginate both leach some calcium from cement, in order to form CaCO.sub.3 and Ca-alginate, respectively. By examining the micrographs, it appears that the presence of Na-alginate lowers the leaching of calcium, which also contributes to a denser microstructure.

(17) Inventors mixed 0.45 w/c cement paste, and distributed equally in four trays, one control tray without a coating, and three were covered with Na Alginate, Na Alginate/5 w. % MMT and Na Alginate/20 wt. % MMT, respectively. The time of application of the coatings was a few minutes after the cement paste was mixed and poured. The Graffiti paint was applied after: 1 h, 3 h, 4 h, 20 h, 24 h, 27 h and 45 h, respectively.

(18) After 50 h inventors removed the coating and there was no graffiti on the cement. In other words the present coating is a good anti-graffiti coating.

(19) Methods

(20) Aerobic Granular Sludge for Investigation

(21) The aerobic granular sludge from which the extracellular polymeric substances of the present example were obtained was collected from the Nereda pilot plant, operated by DHV at the wastewater treatment plant Epe, The Netherlands. The reactor was fed with municipal sewage. The influent consisted of approximately 25% of slaughterhouse wastewater, which was discharged in the sewage system. Average parameters of the influent were: CODtotal 585 mg/L, suspended solids 195 mg/L, NH.sub.4N 55 mg/L and PO4-P 6.3 mg/L. The reactor was operated in Sequencing Batch (SBR) mode for biological phosphate and nitrogen removal. Operational details were described in Lin et al. (2010). After start-up, biomass concentration in the reactor was maintained around 8 to 10 g TSS/L. Oxygen in the reactor was controlled between 2 to 3 mg/L during aeration. Temperature and pH were not controlled in this system and depended on the incoming sewage. During steady operation, aerobic granular sludge was collected and sieved to give granules with a diameter >2 mm.

(22) The granules were then dried.

(23) Isolation of Extracellular Polymeric Substances

(24) Dried granules (0.5 g) were homogenized for 5 min (Labgen tissue homogenizer, Cole-Parmer, USA) and extracted in 80 ml 0.2 M Na.sub.2CO.sub.3 at 80 C. for 1 h. After centrifuging at 15,000 rpm for 20 min, the pellet was discarded. The supernatant pH was adjusted to 2 by adding 0.1 M HCl. The precipitate was collected by centrifugation (15,000 rpm, 30 min), washed by di-deionized water until effluent pH reached 7, and dissolved in 0.1 M NaOH. Extracellular polymeric substances in the supernatant were precipitated by the addition of cold absolute ethanol to a final concentration of 80% (vol/vol). The precipitate was collected by centrifugation (15,000 rpm, 30 min), washed three times in absolute ethanol and lyophilized. The resulting mixture of extracellular polymer substances is an example of extracellular polymeric substances (EPS) obtainable from granular sludge according to the invention.

(25) Ash content of the EPS was measured according to the standard method (APHA).

(26) Characterization of EPS

(27) Before characterization, EPS (0.5 g) was dissolved in 15 mL of NaOH solution (0.05 M). The pH was then adjusted to 7.0 by 0.05 M HCl. Finally the solution was placed inside a dialysis tubing (3500 MWCO) and dialyzed against demineralized water for 48 hours to remove loosely bound ions and lyophilized.

Morphology of EPS by Atomic Force Microscopy

(28) Imaging of EPS was carried out in air at ambient temperature and humidity using freshly-cleaved mica pre-treated by 3 mM NiCl.sub.3. Aliquots (2 ul) of extracellular polymeric sub-stances (5 mg/L) were deposited onto mica surfaces for 10 s, and then quickly removed by the pipette. Those surfaces were air dried (1 h) in a dust-free enclosure. Samples were scanned with a Digital Instruments Multimode atomic force microscope (Veeco nanoscopy iva dimension 3100, Veeco Inc., Santa Barbara, USA).

(29) EPS Composition Analysis by Pyrolysis-Gas Chromatography-Mass Spectrometry

(30) Pyrolysis was carried out on a Horizon Instruments Curie-Point pyrolyser. The lyophilized extracellular polymeric sub-stances were heated for 5 s at 600 C. The pyrolysis unit was connected to a Carlo Erba GC8060 as chromatograph and the products were separated by a fused silica column (Varian, 25 m, 0.25 mm i.d.) coated with CP-Sil5 (film thickness 0.40 m). Helium was used as carrier gas. The oven was initially kept at 40 C. for 1 min, next it was heated at a rate of 7 C./min. to 320 C. and maintained at that temperature for 15 min. The column was coupled to a Fisons MD800 mass spectrometer (mass range m/z 45-650, ionization energy 70 eV, cycle time 0.7 s). Identification of the compounds was carried out by their mass spectra using a NIST library or by interpretation of the spectra, by their retention times and/or by comparison with literature data.

(31) Lipid Content of EPS

(32) For lipids analysis in the extracellular polymeric sub-stances, the methods proposed by Smolders et al. (1994) were used with modification. Pure fatty acids (Sigma-Aldrich) were used as external standard. Freeze-dried extracellular polymeric substance samples and fatty acid standards were weighed using an analytical balance and transferred into tubes with screw caps. One milligramme of C15 fatty acid in 1-propanol was used as internal standard. 1.5 mL of a mixture of concentrated. HCl and 1-propanol (1:4), and 1.5 mL of dichloroethane were added into the tubes and heated for 2 h at 100 C. After cooling, free acids were extracted from the organic phase with 3 mL water. One milliliter of the organic phase was filtered over water-free sodium sulphate into GC vials. The lipids in the organic phase were analyzed by gas chromatography (model 6890N, Agilent, USA) equipped with a FID, on an HP Innowax column.

(33) EPS Molecular Weight Analysis

(34) Size exclusion chromatography was performed with a Superdex 75 10/300 GL column (AKTA Purifier System, GE Healthcare). Elution was carried out at roach temperature using PBS at constant 0.4 mL/min flow rate and detection was monitored by following the absorbance of the eluted molecules at 210 nm.

(35) Superdex 75 10/300 GL (GE Healthcare) column separates molecules of 1 000 to 150 000 Daltons (Da) with a total exclusion volume of 7.9 mL. Measurement of the elution volume of dextran standards (1000 Da, 5000 Da, 12000 Da, 25 000 Da and 50 000 Da) led to the calibration equation:
Log(MW)=6.2120.1861 Ve

(36) MW: Molecular Weight of the molecule in Dalton (Da)

(37) Ve: elution volume in mL (assayed at the top of the peak)

(38) Chromatogram profiles were recorded with UNICORN 5.1 software (GE Healthcare). Peak retention times and peak areas were directly calculated and delivered by the program.

(39) Bleaching of EPS

(40) EPS (1 g) was put into H.sub.2O.sub.2 (30%) for 24 hours, collected by centrifuge at 4000 rpm and lyophilized.

(41) Morphology of Extracellular Polymeric Substances by the Atomic Force Microscope

(42) The yield of extracellular polymeric substances was 1604 mg/g (VSS ratio).

(43) The extracellular polymeric substances have a fiber-like structure. The width of the fiber is around 20 nm. The fibers extend along the surface and entangle with each other, forming a web-like structure that covers the whole surface of the mica. This demonstrates that the extracellular polymeric substances have a perfect film-forming property and can form a continuous film on a surface. The thickness of extracellular polymeric sub-stance film is around 4 nm. In addition to the fibers, there are a few globules distributing on the fibers and pointing to the air. The height of the globules can reach 15 nm, which is 2 times higher than the thickness of extracellular polymeric substance film. Due to the significant difference in height, the globules looked much brighter than the fibers under the atomic force microscope. As the sample was prepared by depositing extracellular polymeric substance water solution on a surface and air dried, those globules extending out of the surface and pointing to the air must have hydrophobic property.

(44) Therefore, the extracellular polymeric substances have both a hydrophilic part and hydrophobic part. When the extracellular polymeric substances stay at the surface between water and air, the hydrophilic parts spread along the surface, forming a film and the hydrophobic parts distribute on the film and pointing to the air.

(45) Extracellular Polymeric Substance Composition Analysis

(46) The composition of the extracellular polymeric sub-stances was analyzed by pyrolysis-GC-MS. In the spectrum (FIG. 4), polysaccharide-derived products such as 5-methylfuraldhyde and levoglucosenone were identified, implying a contribution from carbohydrate units to the extracellular polymeric substance sample. Lipids and wax esters composed of C.sub.16 and C.sub.18 fatty acids and alcohol moieties of the same carbon lengths were found as well. By contrast, all pyrolysis products of proteins and other combinations of amino acids were much less prominent, indicating that they were relatively minor components of the extracellular polymeric substances. In addition, there is a so-called unresolved complex mixture consisting of ma similar compounds that co-elute and which cannot be identified by their mass spectra at present. In brief, the pyrolysis-GC-MS analysis displays that, comparing to carbohydrates and lipids, proteins are a minor part of the extracellular polymeric substances.

(47) The lipid content in the extracellular polymeric sub-stances was measured as 8.20.9 mg/g extracellular polymeric substances.

(48) Since normally polysaccharides are hydrophilic and lipids are hydrophobic, it can be assumed that the fiber-like structure which forms film on the surface are mostly polysaccharides and those globules pointing towards the air are mostly lipids.

(49) Molecular Weight of Extracellular Polymeric Substances

(50) The size distribution profile of the extracellular polymeric substances by size exclusion chromatography is determined. There are 5 fractions with different elution vol-ume. The fraction with the shortest elution volume, which has the highest molecular weight, separate well with other frac-tions. The three fractions with an elution volume between 13 ml to 17 ml co-eluted. The molecular weight of these 5 fractions and their percentages are listed in Table 3. It can be clearly seen that most of isolated extracellular polymeric, substances (94%) has a molecular weight of more than 5.8 KDa, and about of the extracellular polymeric substances has a molecular weight higher than 150 KDa. As carbohydrates with higher molecular weight tend to extend on the surface, it could be an explanation for the perfect film-forming property of the isolated extracellular polymeric sub-stances.

(51) TABLE-US-00003 TABLE 3 Molecular weight of different fractions in extra- cellular polymeric substances isolated from granular sludge and their percentage. Elution volume of the Molecular weight Percentage of the fraction peak (ml) (Da) (% peak area) 7.83 7 10.sup.4 29.74 13.48 1.44 10.sup.4 18.82 15.57 5.79 10.sup.3 45.15 17.58 2.15 10.sup.3 4.42 20.13 6.56 10.sup.2 1.87

(52) It should be appreciated that for commercial application it may be preferable to use one or more variations of the present system, which would similar be to the ones disclosed in the present application and are within the spirit of the invention.