FI91770B - Cationic tannin useful as flocculant and composition useful as flocculant in wastewater purification - Google Patents

Description

91770

This invention relates to cationic tannins useful as a flocculant in conifer bark extracts and to compositions useful as a flocculant in wastewater treatment.

The bark of conifers growing in Finland, spruce (Picea abies) 10 and pine (Pinus sylvestris), can be extracted with various aqueous and organic solvents and the obtained extract can be used for recovery. Under favorable conditions, 14 to 16% of spruce bark is extracted with hot water and about 6% of pine bark, based on the weight of the dry bark.

15 The hot water extract of spruce bark is very heterogeneous and often contains only about 50% water-soluble tannin (Stiasny number 50). If the extraction of spruce bark with water contains alkali and sulphite, significantly higher extraction yields are obtained than if only 20 had been extracted with hot water (spruce about 25%, pine about 8%). Ethanol-water (60:10% by volume) and acetone-water (50:50 by volume) dissolve about 28% and 30% of the spruce bark at 140 ° C, respectively. The extract yields corresponding to pine bark are lower (18 - 20%). The tannins of spruce and pine bark extracts have a potential use in wood glues, especially if the extracts are fractionated by ultrafiltration, for example. In this case, however, non-tannin-containing fractions are obtained, for which non-adhesive use should be found.

30 It has previously been shown that extracts of spruce and pine bark, regardless of their tannin content, can be used to produce cationic products which flocculate colloidal silica and dredging sludge well (Pulkkinen E. and Seppänen R., "Preparation and testing 35 of cationic flocculants from agueous extracts of conifer tree barks ", Forest Products Research Society, 40th Annual Meeting, June 22-26, 1986, Washinton, USA, Abstract 8; 2 91770 and Seppänen R., Mäkelä A. and Pulkkinen E., "Use of cationic derivatives of tree bark extracts and lignins as a flocculant for wastewater treatment", Chemistry Days 5 - 6 November 1986, Helsinki, abstract 6.26, Kemia-Kerni 11, 5 1986). However, in the past, cationic tannins have not been used to flocculate colloidal substances in wastewater and to precipitate organic chlorine fractions in bleaching wastewater.

. The present invention shows that the cationization method and flocculation efficiency of the shell extracts 10 can be further substantially improved. Surprisingly, it has also been possible to prepare effective flocculants from fractions rich in non-tannins.

The invention thus relates to a cationic tannin useful as a flocculant, characterized in that the tannin-containing softwood bark extract is cross-linked before cationization with glycidyltrimethylammonium chloride or N- (3-chloro-2-hydroxypropyl) trimethylammonium. Thanks to cross-linking, the tannin flocculation ability of the 20 cationic ones is clearly improved.

The cationic tannins of the invention provide spruce and pine bark extracts by modifying inexpensive polycations that neutralize the negative charges of contaminants and flocculate inorganic and organic compounds, such as organic chlorine compounds from bleach effluents, and further nitrogen and phosphorus.

Even small differences in flocculation power become clear in laboratory tests (dish test or photometer-30 dispersion analyzer (PDA) test with, for example, microcrystalline silica or cellulose as a colloidal reference). In large-scale wastewater treatment processes, the efficiency of cationic shell extracts in the removal of colloidal solids and bleach effluents from organic chlorine-containing compounds 3,91770 can be seen e.g. landing, flotation and sludge concentration (water removal).

In the present invention, spruce and pine bark extracts have been cationized with the following epoxyammonium and chlorohydrin-5 ammonium salt reagents:

NaOH

theanine-OH i CH 2 CHCH 2 CH 2 Cl 9 -V

10 glycidyltrimethylammonium chloride GTAK reagent tannin OCf ^ CHCH ^ tCHy ^ Cl0

OH

15 f

N * OM

nopex Γ NSCI * H2 °

CH 2 CHCH 3 N 2 CH 2 CH 2 NaOH

Cl OH N- (3-chloro-2-hydroxypropyl) trimethylenium chloride 20 GTAK-HCl reagent (chlorohydrin reagent)

Aminomethylation of tannins with formaldehyde and dime-25 amine is also possible (Tappi Vol.

61, No. 5, May 1978). It is further apparent from the invention that GTAK reagent and GTAK-HCl reagent adhere to the shell extract in high yield (about 90%). This reduces the amount of by-products generated from the reagents and substantially improves the raw material cost per active product.

If the tannin content of the shell extract is high, it can be crosslinked with a small amount of formaldehyde before etherification (cationization) and a highly efficient cationic tannin can be obtained. If, on the other hand, the shell extract is crosslinked with epichlorohydrin before cationization, an effective flocculant can also be prepared from the shell extract containing a high amount of non-tannins or a fraction thereof (Stiasny number e.g. 40).

The cationic tannins produced belong to a group of cationic polymers which, alone or with inorganic coagulants, are known to adhere to the surface of negatively charged particles in waste water, neutralize the negative charge of the surface and thus precipitate a colloidal solid in the waste water. If it is desired to increase the floc size of the particles neutralized with cationic tannin, a high molecular weight cationic, anionic or neutral linear polymer is added to the fine floc, whereby its long flexible molecular chains connect the contaminant particles into highly descending bundles.

It is an object of the invention to find a combination dose in a specific application in which the neutralizing agent is a cationic tannin and the crosslinking agent is a high molecular weight linear polymer, and to study the relative amount and method of feeding such a two-component dose to obtain the best flocculation result.

The flocculation efficiencies of cationic polyelectrolytes and cationic tannins can be compared by pre-25 tests. In the vessel test, the colloidal dispersion (silica, cellulose) is mixed with different maximum flocculant dosages, whereby, after settling of the precipitate, the lowest residual turbidity of the series clarifier indicates the optimum flocculation dose for the dispersion used. When applying the vessel test 30 to wastewater, it is often impossible to measure turbidity. Instead, the chemical oxygen demand (COD), phosphorus, or amount of organic chlorine in the series of brighteners, as estimated, gives the optimal dose. Tests performed on the PDA indicate the relative size of the flock and also the durability, 35 if the test is performed at different speeds. PDAs.

The 5,91770 test becomes especially valuable when applied to wastewater. The effluent is circulated in the vessel of the device with a flocculant or coagulant solution of a certain concentration, it is determined at which dose the formation of the floc begins, what is the optimum dose and how the strength of the floc can be influenced by the crosslinking polymer.

Not only the colloidal fraction of the wastewater, but also the salts of organic acids it contains can be precipitated with sufficiently high doses of cationic tannin. In this case, the consumption of flocculant or coagulant is often too high to be economical, so recovery of the precipitant from the slurry becomes considered.

The following examples illustrate the invention.

Example 1 This example details how to obtain a cationic ether from the tannin of a hot water extract of spruce bark (Stias-ny Chapter 84) with GTAK reagent, the preparation and flocculation efficiency of which are optimized.

Table 1 shows the initial state of cationization.

20

table 1

Preparation of cationic tannin with GTAK reagent _Grams_ 25 _Wet Dry Moles Mole ratio

Spruce bark hot water extract Stiasny Chapter 84, ka. 47.5% 653 310 30 GTAK reagent, M 151.64

Activity 70%

Dry matter 79% 454 317.8 2.10 1 100% epoxy 35 40.9 (non-epoxy)

NaOH, M 40.01 15 0.37 0.18 6 91770

Significant in the initial situation is the high dry matter content (61.8%) and the molar excess of NaOH relative to the GTAK reagent. The reagent had been obtained from Raisio Oy.

Aqueous tannin for etherification (ca.

47.5%) was homogenized in a Baker-Perkins screw mixer (volume about 1 liter), after which solid NaOH was added to the reactor and stirred at room temperature for 2 hours. The reagent was then added and stirring was continued at room temperature. Samples taken from the reaction mixture were flocculated in a vessel test in a silica dispersion (270 mg / 600 ml) after 14, 17, 40 and 52 hours. The reaction was quenched by neutralizing the reaction mixture with 2 M hydrochloric acid. The results are shown in Figure 1. Results are expressed as percent turbidity units (% FTU) and the dose of flocculant is expressed as a percentage by weight of silica.

It can be seen from Figure 1 that the cationization has taken place completely at room temperature in 40 hours.

A sample of the crude product thus obtained was diluted and ultrafiltered through a Diaflo YM2 membrane (Amicon Corp., exclusion limit 1000). The purified and dried product contained 4.4% nitrogen (determined by the Kjeldahl method).

Calculation of Reagent Yield From 100 g of ultrafiltered cationic shell extract 25 was found: = 0.3143 x 151.64 = 47.66 g of GTAK reagent and 14 52.34 g of tannin.

GTAK reagent is bound to tannin as follows: 30 0.3143 X 310.0 = 88 6% 52.34

Flokkauskokeet

Vessel tests were performed on (6-well) equipment (Phipps & Bird) and the colloidal dispersion was microcrystalline silica (Min-U-Sil 5, Pennsylvania Glass and h 7 91770

Sand Corp.) / which was slurried in 1,800 g of 4 liters of water at pH 4.0 to 4.1 hours. The precipitators were added to 800 ml beakers containing 600 ml of silica dispersion (270 mg of silica) with rapid stirring and stirred successively as follows: 20 min at 65 rpm, 20 min at 30 rpm, followed by clarification for 30 min. Residual turbidity was measured with a Hach turbidometer from 25 ml samples taken 2 cm below the liquid surface. The results are shown in Figure 2.

It can be seen from Figure 2 that the cationic tannin purified by ultrafiltration precipitates colloidal silica much more efficiently than the commercial cationic polymer Fennopol 194 K, Kemira Oy (highly cationic polyacrylamide; M is about 4 million). In tests with a photo-15 meter dispersion analyzer (PDA 2000, Rank Brothers Ltd), the cuvette was connected by a 3 mm hose to a 1.5 liter reaction vessel equipped with an engine stirrer (paddle stirrer) equipped with a tachometer. Sampling into the cuvette took place from the bottom of the reaction vessel at a distance of 15 cm. The flow rate was controlled by an LKB 12000 Variopres peristaltic pump. Printing took place on a plotter. Sensitivity was adjusted with a PDA-2000 analyzer (Gatin RMS, DC), so no front resistor was required. The flow rate under all conditions was 1.22 25 ml / min.

Test conditions:

Silica: 450 mg / 1,000 ml

Microcrystalline cellulose: 450 mg / 1000 ml pH: 4.0 - 4.1 30 Initial mixing: 65 rpm

Stir during test: 65 rpm Flow: 1.22 ml / min

Analyzer Sensitivity: RMS 1.07 Filter on DS 5.4 Limit on 8,91770

Determining the Optimal Dose with a Dispersion Analyzer (PDA) The PDA prints on the horizontal axis of the plotter the time that has elapsed since the flocculant dose was injected.

5 The vertical axis shows the relative floc size (in volts). The optimum dose at the relative flock size and the rate at which it is reached is the maximum. Based on Table 2, the optimum dose of cationic tannin, i.e. 0.058% silica, is achieved when the relative floc size is 10 3.95 V and the floc growth rate is 9.22 volts / min.

Table 2

PDA determination of the optimal dose of cationic tannin for colloidal silica 15 _

Dosage Relative Floc growth rate% of silica flock size (volts) volts / min_ 0.023 1.35 0.75 0.029 2.65 3.55 20 0.035 3.10 6.15 0.046 3.55 8.55 0.058 3.95 9.22 0.070 3.95 5.56 0.081 2.95 3.70 25 _

It is noted that the optimum dose obtained with PDA (0.058% silica) is higher than the corresponding dose obtained in the vessel test (0.035% silica).

Example 2 This example describes experiments in which tannin obtained from spruce bark by hot water extraction has been cross-linked with formaldehyde before cationization. The results show that, due to cross-linking, the optimum blocking dose of the corresponding potassium 9 91770 thionic tannin with respect to colloidal silica is reduced and the durability of the joy is increased.

The example starts from a bark extract with a lower soluble tannin content than the bark extract used in Example 5 (Stiasny number 70 vs. 84). The shell extract is first crosslinked with formaldehyde and then cationized with GTAK reagent.

a) To determine the gelation sensitivity of the shell extract, a gelation time determination was first performed.

Gel Time Assay 30 g of hot water extract of spruce bark (Stiasny number 70) was dissolved in 100 ml of water containing 3.36 g of NaOH. 45.1 g of this solution (containing 10.4 g of extract) was cross-linked with 1.5 ml of 37% formaldehyde at 50 ° C on a Tecan gel time meter (GT 3 disc diameter 14 mm). The gel time was 138 min. Prior to gelation, the solution contained 22.3% dry extract. The amount of NaOH calculated from the dry extract was 11.5% and the CH 2 O content per dry extract was 0.178 mol / 100 g.

20

Table 3

Cross-linking and cationization of hot water extract of spruce bark 25 _Grams_ __Wet Dry Moles

Crosslinking 50 ° C / 30 h Alkaline solution of spruce bark hot water extract (Stiasny number 70) 30 16.7

Organic part 15.0

NaOH 1.67 0.042 CH 2 O 37% 1.24 0.46 10 91770

The solution contained 11.1% NaOH from the dry extract and 0.103 moles of CH 2 O / 100 g of shell extract.

_Grams_ 5 Wet Dry_Moles

Etherification 50 ° C / 20 h

Reagent GTAK (M 151.64)

Reagent dry matter 10 was 79% and contained epoxide 66.2% 19.1 15.1 12.6 0.083 (100% epoxide) A sample of the crude product was filtered through Diaflo YM2 (Ami-con Corp., exclusion limit M 1000) , in which case 3.9% of nitrogen was found in the purified product.

Calculation of Reagent Yield 100 g of ultrafiltered cationic shell extract was found = 0.2786 x 151.64 = 42.25 g of GTAK reagent and 14 57.75 g of shell extract.

25 GTAK reagents are bound to tannin as follows: 0.279 moles N_ 15 g bark extract_ 57.75 g bark extract 0.083 moles reagent °> 279_x 15-% = 87 3% 30 57.75 x 0.083 b) In the second experiment, the bark extract was cross-linked with 0.154 moles of formaldehyde per 100 g per tannin and then reacted with GTAK reagent at 50 ° C for 3 hours in a Berghoff autoclave to give a purified product nitrogen content of 3.5%. In a comparative experiment without I; 11,91770 crosslinks were cationized under the same conditions, giving a purified product nitrogen content of 3.6%.

Table 4

Effect of crosslinking on the molecular weight distribution of cationic tannins in gel filtration chromatograms

Cationized _Molecular mass_tannin_10,000 5,000 3,000 1,500 1,000 10 Non-crosslinked 36 56 68 82 89

Cross-linked 50 66 74 84 89 (0.103 moles of CH 2 O / 100 g) 15

The gel filtration method is described in Forss K., Kokkonen R. and Sägfors PE., "Determination of molar mass distribution of lignins by gel permeation chromatography", 1989, American Chemical Society, Symposium Series 20 397, Chapter 9, 125-133. Sephadex G-50 and 0.5 M NaOH as eluent.

The improvement in flocculation efficiency due to crosslinking is shown in Table 5.

25 Table 5

Effect of tannin cross-linking (CH 2 O) on the silica precipitation of the cationic ether prepared from it in a vessel test 30 Cross-linking degree Dosage Relative moles of CH 2 O / 100 g of silica, flock size _% _ J [_% _ 100 rpm_ 0 3.6 0.17 - 0.20 1.2 0.154 3.5 0.07 - 0.11 2.8 35 _ 12 91770

Example 3 This example further describes the effect of CH 2 O crosslinking of tannin on the flocculation efficiency of the cationic ether prepared therefrom.

5 The starting tannin is the same as in Example 1 (Stiasny number 84). For the crosslinking step, 278.7 g (ca. 43.3%) of tannin was weighed wet to give 120.7 g of dry bark extract, based on which 0.46% (0.0153 moles of CH 2 O / 100 g of bark extract) was used.

CH 2 O was added as a 37% aqueous solution and NaOH as a 5 M solution until the pH of the reaction mixture was 12. Cross-linking took place in a 1.5 L flat plate flask, allowing the reaction mixture to stand at room temperature for 2 hours and then at 45 ° C for 4 hours.

To the crosslinked mixture was added 80.19 g (GTAK, ca. 70%, active ingredient 60%) of cationization reagent (GTAK, ca. 70%, active ingredient) and the reaction mixture was homogenized with a blender (Braun). The mixture was allowed to stand for 2 hours at 20 ° C and 22 hours at 40 ° C.

The stiffening effect of formaldehyde on the reaction mixture was already visible at room temperature, but the almost solid mass flexed during etherification to a viscous liquid. After ultrafiltration, 3.6% of nitrogen was found in the neutralized crude product.

The reagent yield calculated as follows was remarkably high: ^ = 0.257 x 151.64 = 39.0 g of GTAK reagent and 14,100 g to 39.0 g * 61.0 g of tannin.

30 GTAK reagents are bound to tannin: 0.257 x 120f7_ = g61 61.0 x 0.529 13 91770

Effect of crosslinking on flocculation efficiency

Although the crosslinked cationic tannin contained 4.4% nitrogen (Example 1) and the crosslinked tannin 3.6%, both cationizations were performed on the same bark extract, so the flocculation results can be compared if the doses are calculated on the cationic tannin nitrogen. towards. It is clear from the results shown in Figure 3 that cross-linking with formaldehyde reduces the optimum dose in the vessel test and increases the relative floc size in the test performed on the PDA.

Example 4 This example shows that epichlorohydrin cross-links a non-tannin-containing hot water extract of spruce bark (Stiasny number 40), whereby the flocculation efficiency of the cation-15 product is significantly improved due to cross-linking.

2 g of spruce bark hot water extract (Stiasny number 40) dissolved in concentrated NaOH solution (0.3 g of NaOH and 2 ml of H 2 O) was stirred at 50 ° C in a glass vessel for about 1 hour. Cross-linking was performed by adding 0.1 g of epichlorohydrin (ECH) to the reaction vessel and stirring was continued at the same temperature for 10 min.

For cationization, 1 g of GTAK reagent (calculated as 100% epoxy content, 6.7 moles) was added to the crosslinked reaction mixture and heating was continued at 50 ° C for 2.5 hours. The reaction was quenched by neutralizing the mixture with 2 N HCl. The crude product was dried to constant weight at 50 ° C. A portion of the dry product (1 g) was slurried at room temperature in 160 ml of 94% ethanol, filtered and the precipitate was washed with diethyl ether and dried to constant weight in a vacuum desiccator. The purified epichlorohydrin-crosslinked cationic spruce bark extract was obtained by ethanol washing from 61% of the dry crude product and had a nitrogen content of 2.6%.

14 91770 Baseline

Grams Grams in mmoles Molar ___ ratio

Bark extract 5 Stiasny chapter 40 2 2

NaOH (40) 0.3 0.3 7.5 1.12 7 ECH (92.53) 0.1 0.1 1 GTAK (151.64) 1 1.0 6.6 1 H2O _2_ _ 10 5, 4 3.4 dry matter 63% Initial situation calculated per 100 g of shell extract: 15

Grams Grams Moles Mole _Ratio_

bark Extract

Stiasny number 40 100 100 20 NaOH (40) 15 15 0.375 1.14 7 1 ECH (92.53) 5 5 0.054 1 0.14 GTAK (151.64) 50 50 0.330 1

HjO 100 _ 270 170 dry matter 63%

Figure 4 shows the effect of crosslinking the shell extract on the silica precipitation capacity of the corresponding cationic ether 30 (Min-U-Sil-5, silica 150 mg / l) in a vessel test. The cationic tannin (2.6% nitrogen) prepared from the cross-linked shell extract gave a significantly lower optimum dose than the non-cross-linked cationic tannin (2.7% nitrogen).

»Li 15 91770

Example 5 In this example, vessel tests with colloidal silica as a reference have shown that when a small amount of Al 3+ or Fe 3+ salt is added to a solution of cationic tannin, the flocculation capacity of cationic tannin is improved. This is shown in Figure 5.

Example 6 This example describes the interaction of a cationic tannin and a linear cationic polymer on the flocculation of microcrystalline cellulose in a vessel test. The results are shown in Figure 6.

The dose of cationic tannin (0.25 ppm) selected in this experiment is not a clear cellulose dispersion alone, but when added to this amount of linear cationic polymer Fennopol K211, Kemira Oy (slightly cationic polyacrylamide; M is about 8 million) the residual turbidity reaches its minimum value in a total dose of about 0.3 ppm. In this experiment, the optimum total dose was 0.38 ppm (20% ratio of cationic tannin (3.9% nitrogen) to Fennopol K2li 66:34).

Example 7 In this experiment, cationic tannin and a combination of cationic tannin and inorganic coagulant (Al sulfate, Fe chloride) were added to pulp mill 25 wastewater that was biologically treated and thus intended to be discharged into a discharge water. The vessel test was performed on 600 ml of wastewater to which the above flocculants were added, the mixture was stirred and after a certain time was allowed to settle. Samples taken from the supernatant were assayed for solids, COD, AOX (organic chlorine), color, total phosphorus, and total nitrogen. The results are shown in Table 6. It can be seen from the results, among other things, that the amount of phosphate can be significantly reduced by adding cationic tannin either alone or in combination with 35 coagulants. The results further show that cationic tannin reduces the amount of soluble aluminum when used as a precipitant with Al sulfate.

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Claims (6)

91770 Cationic tannin useful as a flocculant, characterized in that the tannin-containing bark extract of the coniferous tree is cross-linked before it is cationized with a glycidyltrimethylammonium chloride or N- (3-chloro-2-hydroxypropyl) trimethylammonium chloride reagent. Cationic tannin according to Claim 1, characterized in that formaldehyde is used in the crosslinking. Cationic tannin according to Claim 1, characterized in that epichlorohydrin is used in the crosslinking. Composition useful as a flocculant in wastewater treatment, characterized in that it contains a cationic tannin according to one of Claims 1 to 3. Composition according to Claim 4, characterized in that it further contains an inorganic coagulant. Composition according to Claim 4 or 5, characterized in that it additionally contains a high molecular weight cationic, anionic or neutral linear polymer. 91770