Modified hydroxyethyl cellulose scale inhibitor for inhibiting silica scale and preparation method thereof

Abstract

A preparation method and use of a modified hydroxyethyl cellulose scale inhibitor for inhibiting silica scale are provided. The scale inhibitor is prepared by grafting reaction with hydroxyethyl cellulose as a raw material, ammonium persulfate as an initiator and N-(3-dimethylaminopropyl) methyl acrylamide as a graft monomer. The grafting reaction can introduce grafting chains containing amide group and tertiary amine group into a cellulose molecular chain, so that it can effectively disperse scale forming substances and obtain the efficient environment-friendly scale inhibitor. The scale inhibitor can effectively inhibit the generation of silica scale and prevent the increase of scale particle size, the scale inhibitor is used in a reverse osmosis system, which can effectively alleviate the decline of the membrane flux. The scale inhibitor has a good application prospect in controlling the silica scale on the surface of the reverse osmosis membrane.

Claims

1. A method for inhibiting silica scale, comprising: adding a modified hydroxyethyl cellulose scale inhibitor to water in one of a cooling water and a reverse osmosis system in a range of 5 mg.Math.L.sup.−1 to 500 mg.Math.L.sup.−1; wherein the modified hydroxyethyl cellulose scale inhibitor is obtained by graft copolymerization of hydroxyethyl cellulose in nitrogen atmosphere, and a structural formula of the modified hydroxyethyl cellulose scale inhibitor is shown as following Chemical Formula I: ##STR00004## where n is in a range of 0.04 to 2.00; wherein the modified hydroxyethyl cellulose scale inhibitor is a grafted hydroxyethyl cellulose obtained by a reaction of the hydroxyethyl cellulose and N-(3-dimethylaminopropyl) methyl acrylamide.

2. The method for inhibiting silica scale according to claim 1, wherein the hydroxyethyl cellulose modified scale inhibitor is obtained by the graft copolymerization with the hydroxyethyl cellulose as a raw material, ammonium persulfate as an initiator and the N-(3-dimethylaminopropyl) methyl acrylamide as a graft monomer according to following Reaction Formula I: ##STR00005##

3. The method for inhibiting silica scale according to claim 2, wherein the hydroxyethyl cellulose modified scale inhibitor is a grafted carboxymethyl cellulose obtained by a preparation method including: dissolving the hydroxyethyl cellulose in water to prepare a solution with a mass percentage concentration of 1% to 10% of the hydroxyethyl cellulose; adding the ammonium persulfate with a mole number being 1% to 5% of a mole number of the hydroxyethyl cellulose into the solution as the initiator; adding the N-(3-dimethylaminopropyl) methyl acrylamide with a mass ratio to the hydroxyethyl cellulose being 0.1:1 to 1.5:1 into the solution for the graft copolymerization at 45° C. to 75° C. for 0.5 hours to 5 hours to obtain products; and obtaining the grafted carboxymethyl cellulose by using one of ethanol and acetone as a precipitant to precipitate and separate the products; wherein the mole number is an amount of substance.

4. The method for inhibiting silica scale according to claim 2, wherein the hydroxyethyl cellulose modified scale inhibitor is a grafted carboxymethyl cellulose obtained by a preparation method including: dissolving the hydroxyethyl cellulose in water to prepare a solution with a mass percentage concentration of 10% of the hydroxyethyl cellulose; adding the ammonium persulfate with a mole number being 5% of a mole number of the hydroxyethyl cellulose into the solution as the initiator; adding the n-(3-dimethylaminopropyl) methyl acrylamide with a mass ratio to the hydroxyethyl cellulose being 1:1 into the solution for the graft copolymerization at 70° C. for 3 hours to obtain products; and obtaining the grafted carboxymethyl cellulose by using acetone as a precipitant to precipitate and separate the products; wherein the mole number is an amount of substance.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 illustrates a schematic diagram of a synthesis of a modified hydroxyethyl cellulose scale inhibitor.

(2) FIG. 2 illustrates Fourier-transform infrared spectra of hydroxyethyl cellulose and a modified hydroxyethyl cellulose scale inhibitor.

(3) FIG. 3 illustrates the scale inhibition efficiency of a modified hydroxyethyl cellulose scale inhibitor in a static scale inhibition experiment.

(4) FIG. 4 illustrates the comparison of the reverse osmosis membrane flux with and without adding a modified hydroxyethyl cellulose scale inhibitor.

DETAILED DESCRIPTION OF EMBODIMENTS

(5) The disclosure is further described below through embodiments. It should be understood that these embodiments are explanations and examples of the disclosure and do not limit the scope of the disclosure in any form.

Embodiment 1

(6) Dissolving hydroxyethyl cellulose (a viscosity of the hydroxyethyl cellulose is 80 milli-pascal seconds (mPa.Math.s) to 125 mPa.Math.s) in pure water to prepare a solution with a mass percentage concentration of 10% hydroxyethyl cellulose, stirring under nitrogen atmosphere to make the solution evenly, then adding ammonium persulfate into the solution as an initiator (the addition amount of the ammonium persulfate is 5% of a mole number of the hydroxyethyl cellulose), then adding N-(3-dimethylaminopropyl) methyl acrylamide (the mass ratio of the N-(3-dimethylaminopropyl) methyl acrylamide to the hydroxyethyl cellulose is 1:1) after pH adjustment into the solution for reacting at 70° C. for 3 hours to obtain products, and then preparing a modified hydroxyethyl cellulose scale inhibitor material by using acetone as a precipitant to precipitate and separate the products and drying. A content of the N-(3-dimethylaminopropyl) methyl acrylamide is 43% according to mass fraction, and the degree of substitution n is 1.0. As illustrated in FIG. 2, which illustrates Fourier-transform infrared spectra of the hydroxyethyl cellulose and the modified hydroxyethyl cellulose scale inhibitor material. It can be seen from FIG. 2 that in the Fourier-transform infrared spectroscopy of the modified hydroxyethyl cellulose scale inhibitor material, 1530 cm.sup.−1 is a N—H characteristic absorption peak on an amide group, which is proved that the modified hydroxyethyl cellulose scale inhibitor material is successfully prepared. FIG. 3 illustrates a scale inhibition efficiency of a modified hydroxyethyl cellulose scale inhibitor in a static scale inhibition experiment. It can be seen from FIG. 3 that for supersaturated silicon dioxide solution (the concentration is recorded as 500 mg.Math.L.sup.−1 in silicon dioxide), the scale inhibition efficiency of silicon dioxide is obtained by determining the content of reactive silicon dioxide by spectrophotometry. When a dosage of the scale inhibitor is 30 mg.Math.L.sup.−1, a residual concentration of the silicon dioxide after 12 hours is 395 mg.Math.L.sup.−1, while the residual concentration of reactive silicon dioxide without the scale inhibitor is 225 mg.Math.L.sup.−1, achieving 79% scale inhibition efficiency. The scale inhibition performance of the scale inhibitor in the reverse osmosis system is evaluated by a cross-flow high-pressure flat membrane instrument. The quality of the permeate is automatically recorded according to a balance to calculate the permeation flux. It can be seen from FIG. 4 that the addition of the scale inhibitor increases the normalized flux of commercial reverse osmosis membrane from 73% to more than 80% after 4 hours.

(7) The structural formula of the modified hydroxyethyl cellulose scale inhibitor material is shown as following Chemical Formula I:

(8) ##STR00003##

Embodiment 2

(9) Dissolving hydroxyethyl cellulose (a viscosity of the hydroxyethyl cellulose is 250 mPa.Math.s to 450 mPa.Math.s) in pure water to prepare a solution with a mass percentage concentration of 1% hydroxyethyl cellulose, stirring under nitrogen atmosphere to make the solution evenly, then adding ammonium persulfate into the solution as an initiator (the addition amount of the ammonium persulfate is 1% of a mole number of the hydroxyethyl cellulose), then adding N-(3-dimethylaminopropyl) methyl acrylamide (the mass ratio of the N-(3-dimethylaminopropyl) methyl acrylamide to the hydroxyethyl cellulose is 0.3:1) after pH adjustment into the solution for reacting at 50° C. for 1 hour to obtain products, and then preparing a modified hydroxyethyl cellulose scale inhibitor material by using acetone as a precipitant to precipitate and separate the products and drying. A content of the N-(3-dimethylaminopropyl) methyl acrylamide is 17% according to mass fraction, and the degree of substitution n is 0.26. In a static scale inhibition experiment, for supersaturated silicon dioxide solution (the concentration is recorded as 500 mg.Math.L.sup.−1 in silicon dioxide), the scale inhibition efficiency of silicon dioxide is obtained by determining the content of reactive silicon dioxide by spectrophotometry. When a dosage of the scale inhibitor is 80 mg.Math.L.sup.−1, a residual concentration of the silicon dioxide after 12 hours is 360 mg.Math.L.sup.−1, while the residual concentration of reactive silicon dioxide without the scale inhibitor is 225 mg.Math.L.sup.−1, achieving 72% scale inhibition efficiency. The scale inhibition performance of the scale inhibitor in the reverse osmosis system is evaluated by a cross-flow high-pressure flat membrane instrument, the quality of the permeate is automatically recorded according to a balance to calculate the permeation flux, and the addition of the scale inhibitor increases the normalized flux of commercial reverse osmosis membrane from 73% to more than 80% after 4 hours.

Embodiment 3

(10) Dissolving hydroxyethyl cellulose (a viscosity of the hydroxyethyl cellulose is 100 mPa.Math.s to 200 mPa.Math.s) in pure water to prepare a solution with a mass percentage concentration of 7% hydroxyethyl cellulose, stirring under nitrogen atmosphere to make the solution evenly, then adding ammonium persulfate into the solution as an initiator (the addition amount of the ammonium persulfate is 4% of a mole number of the hydroxyethyl cellulose), then adding N-(3-dimethylaminopropyl) methyl acrylamide (the mass ratio of the N-(3-dimethylaminopropyl) methyl acrylamide to the hydroxyethyl cellulose is 0.1:1) after pH adjustment into the solution for reacting at 65° C. for 5 hours to obtain products, and then preparing a modified hydroxyethyl cellulose scale inhibitor material by using acetone as a precipitant to precipitate and separate the products and drying. A content of the N-(3-dimethylaminopropyl) methyl acrylamide is 8% according to mass fraction, and the degree of substitution n is 11. In a static scale inhibition experiment, for supersaturated silicon dioxide solution (the concentration is recorded as 500 mg.Math.L.sup.−1 in silicon dioxide), the scale inhibition efficiency of silicon dioxide is obtained by determining the content of unpolymerized silicon dioxide by spectrophotometry. When a dosage of the scale inhibitor is 200 mg.Math.L.sup.−1, a residual concentration of the silicon dioxide after 12 hours is 350 mg.Math.L.sup.−1, while the residual concentration of reactive silicon dioxide without the scale inhibitor is 225 mg.Math.L.sup.−1, achieving 70% scale inhibition efficiency. The scale inhibition performance of the scale inhibitor in the reverse osmosis system is evaluated by a cross-flow high-pressure flat membrane instrument, the quality of the permeate is automatically recorded according to a balance to calculate the permeation flux, and the addition of the scale inhibitor increases the normalized flux of commercial reverse osmosis membrane from 73% to more than 80% after 4 hours.

Embodiment 4

(11) Dissolving hydroxyethyl cellulose (a viscosity of the hydroxyethyl cellulose is 1000 mPa.Math.s to 1500 mPa.Math.s) in pure water to prepare a solution with a mass percentage concentration of 2% hydroxyethyl cellulose, stirring under nitrogen atmosphere to make the solution evenly, then adding ammonium persulfate into the solution as an initiator (the addition amount of the ammonium persulfate is 2% of a mole number of the hydroxyethyl cellulose), then adding N-(3-dimethylaminopropyl) methyl acrylamide (the mass ratio of the N-(3-dimethylaminopropyl) methyl acrylamide to the hydroxyethyl cellulose is 1.5:1) after pH adjustment into the solution for reacting at 75° C. for 0.5 hours to obtain products, and then preparing a modified hydroxyethyl cellulose scale inhibitor material by using acetone as a precipitant to precipitate and separate the products and drying. A content of the N-(3-dimethylaminopropyl) methyl acrylamide is 57% according to mass fraction, and the degree of substitution n is 1.72. In a static scale inhibition experiment, for supersaturated silicon dioxide solution (the concentration is recorded as 500 mg.Math.L.sup.−1 in silicon dioxide), the scale inhibition efficiency of silicon dioxide is obtained by determining the content of unpolymerized silicon dioxide by spectrophotometry. When a dosage of the scale inhibitor is 20 mg.Math.L.sup.−1, a residual concentration of the silicon dioxide after 12 hours is 385 mg.Math.L.sup.−1, while the residual concentration of reactive silicon dioxide without the scale inhibitor is 225 mg.Math.L.sup.−1, achieving 77% scale inhibition efficiency. The scale inhibition performance of the scale inhibitor in the reverse osmosis system is evaluated by a cross-flow high-pressure flat membrane instrument, the quality of the permeate is automatically recorded according to a balance to calculate the permeation flux, and the addition of the scale inhibitor increases the normalized flux of commercial reverse osmosis membrane from 73% to more than 80% after 4 hours.

Embodiment 5

(12) Dissolving hydroxyethyl cellulose (a viscosity of the hydroxyethyl cellulose is 5000 mPa.Math.s to 6400 mPa.Math.s) in pure water to prepare a solution with a mass percentage concentration of 5% hydroxyethyl cellulose, stirring under nitrogen atmosphere to make the solution evenly, then adding ammonium persulfate into the solution as an initiator (the addition amount of the ammonium persulfate is 3% of a mole number of the hydroxyethyl cellulose), then adding N-(3-dimethylaminopropyl) methyl acrylamide (the mass ratio of the N-(3-dimethylaminopropyl) methyl acrylamide to the hydroxyethyl cellulose is 0.6:1) after pH adjustment into the solution for reacting at 55° C. for 2 hours to obtain products, and then preparing a modified hydroxyethyl cellulose scale inhibitor material by using acetone as a precipitant to precipitate and separate the products and drying. A content of the N-(3-dimethylaminopropyl) methyl acrylamide is 28% according to mass fraction, and the degree of substitution n is 0.55. In a static scale inhibition experiment, for supersaturated silicon dioxide solution (the concentration is recorded as 500 mg.Math.L.sup.−1 in silicon dioxide), the scale inhibition efficiency of silicon dioxide is obtained by determining the content of unpolymerized silicon dioxide by spectrophotometry. When a dosage of the scale inhibitor is 40 mg.Math.L.sup.−1, a residual concentration of the silicon dioxide after 12 hours is 375 mg.Math.L.sup.−1, while the residual concentration of reactive silicon dioxide without the scale inhibitor is 225 mg.Math.L.sup.−1, achieving 75% scale inhibition efficiency. The scale inhibition performance of the scale inhibitor in the reverse osmosis system is evaluated by a cross-flow high-pressure flat membrane instrument, the quality of the permeate is automatically recorded according to a balance to calculate the permeation flux, and the addition of the scale inhibitor increases the normalized flux of commercial reverse osmosis membrane from 73% to more than 80% after 4 hours.

Comparative Embodiment 1

(13) The commercially available hydroxyethyl cellulose is selected as the comparison, in a static scale inhibition experiment, for supersaturated silicon dioxide solution (the concentration is recorded as 500 mg.Math.L.sup.−1 in silicon dioxide), the scale inhibition efficiency of silicon dioxide is obtained by determining the content of reactive silicon dioxide by spectrophotometry. When a dosage of the scale inhibitor is 160 mg.Math.L.sup.−1, a residual concentration of the silicon dioxide after 12 hours is 255 mg.Math.L.sup.−1, while the residual concentration of reactive silicon dioxide without the scale inhibitor is 225 mg.Math.L.sup.−1, compared with the grafted hydroxyethyl cellulose, it has low scale inhibition efficiency, poor polymerization inhibition effect on silicon dioxide, and no obvious scale inhibition effect on silicon dioxide.

Comparative Embodiment 2

(14) Dissolving hydroxyethyl cellulose (a viscosity of the hydroxyethyl cellulose is 100 mPa.Math.s to 200 mPa.Math.s) in pure water to prepare a solution with a mass percentage concentration of 7% hydroxyethyl cellulose, stirring under nitrogen atmosphere to make the solution evenly, then adding ammonium persulfate into the solution as an initiator (the addition amount of the ammonium persulfate is 4% of a mole number of the hydroxyethyl cellulose), then adding 3-chloropropylamine (the mass ratio of the 3-chloropropylamine to the hydroxyethyl cellulose is 1:1) after pH adjustment into the solution for reacting at 65° C. for 3 hours to obtain products, and then preparing a modified hydroxyethyl cellulose scale inhibitor material by using ethanol as a precipitant to precipitate and separate the products and drying. In a static scale inhibition experiment, for supersaturated silicon dioxide solution (the concentration is recorded as 500 mg.Math.L.sup.−1 in silicon dioxide), the scale inhibition efficiency of silicon dioxide is obtained by determining the content of unpolymerized silicon dioxide by spectrophotometry. When a dosage of the scale inhibitor is 50 mg.Math.L.sup.−1, a residual concentration of the silicon dioxide after 12 hours is 200 mg.Math.L.sup.−1, while the residual concentration of unpolymerized silicon dioxide without the scale inhibitor is 225 mg.Math.L.sup.−1, compared with the selected grafted monomer n-(3-dimethylaminopropyl) methyl acrylamide, the grafted 3-chloropropylamine has a negative effect, and the residual content of silicon dioxide after use is lower than that without adding chemicals.