CN111269623B

CN111269623B - Method for preparing coating by using gypsum whisker residues

Info

Publication number: CN111269623B
Application number: CN202010088330.6A
Authority: CN
Inventors: 王波; 孙桂红; 赵镇东; 高旭
Original assignee: Yantai University
Current assignee: Yantai University
Priority date: 2020-02-12
Filing date: 2020-02-12
Publication date: 2021-09-07
Anticipated expiration: 2040-02-12
Also published as: CN111269623A

Abstract

The invention discloses a method for preparing a coating by using gypsum whisker residues, which is characterized by comprising the following steps: adding sodium alginate and polyvinyl alcohol into water, heating and dissolving to prepare an aqueous solution, adding gypsum whisker residues, shell slaked lime, calcined ball clay, a ZIF-67-loaded shell-derived Co-based catalyst and magnetic nanoparticles, and uniformly stirring to prepare the water-based coating. Through scientific design of the preparation process of the gypsum whisker and the method for designing the function of the pigment and filler and preparing the magnetic nanoparticles according to the chemistry of the filter residue, a sustainable development gypsum whisker application industrial chain which is green, environment-friendly, low in cost and high in added value is created.

Description

Method for preparing coating by using gypsum whisker residues

Technical Field

The invention belongs to the field of paint preparation, and particularly relates to a method for preparing a paint by using gypsum whisker residues.

Background

The gypsum whisker is also called calcium sulfate whisker, is a fibrous crystal and has wide application prospect in the fields of building materials, chemical industry, environmental protection and the like. The composite material has the effects of high tensile strength, high toughness, fire resistance, flame retardance, wear resistance and chemical corrosion resistance, and the diameter is generally 0.1-8 mu m and the length is 0-300 mu m.

The quantity of industrial by-product gypsum in China is very large, and when titanium dioxide is produced by adopting a sulfuric acid method, lime (or carbide slag) is added to treat acid wastewater so as to neutralize a large amount of acid wastewater, so that C is produced_aSO₄·2H₂O is industrial waste residue as main component. With the increasing demand of coatings and plastics, the titanium dioxide industry has a steadily increasing trend. 6-10 tons of titanium gypsum can be produced when 1 ton of titanium dioxide is produced, the comprehensive utilization rate is about 10 percent, and the titanium gypsum is a byproduct gypsum with the lowest utilization rate. The large amount of emission not only occupies land, pollutes environment and destroys ecological balance, but also brings huge economic burden to titanium white enterprises and influences on expanded reproduction. The main methods for preparing the gypsum whisker by using the titanium gypsum comprise a normal-pressure salt method, a hydrothermal method, an organic solvent method and the like, and have excessive equipment and technical problems. Low gypsum whisker yield, high cost and market demandThe demand is less. The industrialization of the gypsum whisker needs to solve the key preparation technology, reduce the cost and develop the market application. One of the technical difficulties in preparing white gypsum whiskers from titanium gypsum is secondary pollution caused by improper disposal of waste water and waste residues. Because no ideal comprehensive utilization technology causes a large amount of accumulation, the method has practical significance for scientific and efficient technical treatment.

Disclosure of Invention

The invention aims to provide a green process for preparing gypsum whiskers by titanium gypsum, and a process flow for preparing the gypsum whiskers by the titanium gypsum is designed, so that the key preparation technology is solved, the industrialization is achieved, and the application field of whisker materials is expanded. Through scientific design of the preparation process of the gypsum whisker and the method for designing the function of the pigment and filler and preparing the magnetic nanoparticles according to the chemistry of the filter residue, a sustainable development gypsum whisker application industrial chain which is green, environment-friendly, low in cost and high in added value is created.

The scheme of the invention is as follows: a method for preparing coating by utilizing gypsum whisker residue, a process for preparing powder by titanium gypsum pretreatment: drying the blocky titanium gypsum at 105 ℃ for 24h, grinding for 30min, covering the ground titanium gypsum with a preservative film, and aging for more than 7 d.

And (3) a decoloring treatment process: adding ionized water into the pretreated titanium gypsum powder, and magnetically stirring and dispersing. Adding concentrated hydrochloric acid for dissolving, neutralizing with shell slaked lime, and filtering to obtain clear liquid and filter residue. And putting the filter residue product into a vacuum drying oven, and drying at the temperature of 200 ℃ until the weight is constant. The preparation of the shell slaked lime selects oyster shell with low iron content and high whiteness to calcine at 900 ℃, and keeps the temperature for 2 h. Cooling, taking out, placing in air, and automatically pulverizing to obtain white powder. Oyster shell need not to grind, and low price, the waste of utilizing is environmental protection.

The preparation process of the whisker comprises the following steps: adding sodium sulfate, triethanolamine and glycerol as crystal modifier into the clear liquid, stirring and dissolving completely. The resulting solution was poured into a 500ml glass bottle, the lid was sealed and tightened and placed in a vacuum oven, the temperature was set at 160 ℃ and heated for 4 h. And opening the reactor after the reaction is completely cooled, performing suction filtration on an SHB-IIIA circulating water type multipurpose vacuum pump, and finally drying the reactor in a vacuum drying oven at 45 ℃ for 24 hours. The prepared gypsum whisker has large length-diameter ratio, good dispersibility and 98 percent of whiteness. The conventional concentrated sulfuric acid crystal transfer agent is adopted, the crystal whisker is short and small, the agglomeration effect is obvious, a plurality of dendritic crystals are arranged, the disorder dispersibility is poor, and the length is uneven. The order of adding concentrated sulfuric acid is to add a crystal transformation procedure after the hydrothermal synthesis reaction is finished. Sodium sulfate is used as a crystal transformation agent instead of concentrated sulfuric acid, and the hydrothermal synthesis reaction and the crystal transformation are carried out integrally. Good growing of crystal whisker, easy dispersion, reduced acid pollution, simple process and low cost, and is beneficial to the subsequent application of waste liquid.

The calcined ball clay preparation process comprises the following steps: the ball clay is placed in a corundum crucible and put in a high-temperature furnace for calcination in a reducing atmosphere. The calcining temperature is 860 ℃, the temperature is kept for 1h, the mixture is cooled and taken out and placed in the air for 48h, and the color is changed from white to pink.

The preparation process of the ZIF-67 loaded shell-derived Co-based catalyst comprises the following steps: the ratio of cobalt nitrate to dimethylimidazole is 1: 4 was dissolved in 50ml of methanol and stirred at room temperature for 6 hours to prepare ZIF-67. Soaking abalone shell in 0.8g of nickel nitrate and 0.2g of ZIF-67 solution, and drying in an oven at 60 ℃ for 12 h. Heating the mixture in a tube furnace to 350 ℃, keeping the temperature for 2h, and increasing the temperature at a rate of 1 ℃/min.

The preparation process of the magnetic nanoparticles comprises the following steps: the filter residue after decolorization mainly contains ferric hydroxide and a small amount of gypsum whiskers. Can be used for producing pigment fillers of coatings and preparing magnetic nano particles Fe₃O₄. Adding triethanolamine and urea into the filter residue, stirring, mixing, placing into autoclave, drying at 200 deg.C for 8 hr. Cooling, filtering, magnetizing and dispersing. The mass volume ratio of the filter residue, the urea and the triethanolamine is 3:1-2: 30.

The preparation process of the coating comprises the following steps: the formula takes sodium alginate and polyvinyl alcohol as main organic film forming substances, filter residue, shell hydrated lime and calcined ball soil are hydrated to generate cement to form an inorganic film, and a photocatalyst and magnetic nanoparticles form a composite photocatalytic system. The filter residue contains crystal whiskers, which has the functions of strengthening and preventing the coating from cracking. The ferric hydroxide is red in color and porous, and the ambient temperature is adjusted. The shell has porosity and is loaded with ZIF-67 assembled CaCO₃a/Co based MOF catalyst. But because the MOF has poor conductivity, the synergistic magnetic nano particles form a composite catalyst system, photo-generated electrons generate more active free radicals under the illumination condition,decompose pollutants and purify air. The application range of the water-based paint is as follows: both indoor and outdoor applications are possible. The base material is cement, stone, metal and the like, forms patterns with various colors, and has multiple functions of alkali resistance, weather resistance, heat insulation, humidity adjustment, crack resistance, self-cleaning property and the like.

The invention has the advantages that:

1. the green and clean production process design for preparing the gypsum whisker from the titanium gypsum realizes an industrial chain of green environmental protection, low cost and high added value and sustainable development.

2. The application of pigment and filler of filter residue and the preparation of magnetic nano particles are a customized process line for preparing gypsum whisker reinforced cement-based materials from titanium gypsum.

3. The paint has the functions of no toxicity, no smell, water resistance, alkali resistance, air purification, wave absorption and the like, and is suitable for indoor and outdoor use. Can also be popularized and applied as a tree whitening agent.

Drawings

FIG. 1 is an XRD pattern of gypsum whisker and filter residue;

FIG. 2 is an SEM photograph of ZIF-67;

FIG. 3 is an XRD pattern of a ZIF-67 supported shell derived Co based catalyst.

Detailed Description

The following examples are provided to illustrate the present invention.

Example 1 a method of preparing a coating using gypsum whisker residue, comprising the steps of:

step 1: preparing titanium gypsum powder, namely drying 1kg of blocky titanium gypsum for 24h at 95 ℃, cooling, grinding for 30min in a ball mill, controlling the screen residue of a 80-micron square-hole sieve to be less than 3.2%, covering the powder with a preservative film, and aging for 7 d;

step 2: and (3) decoloring, weighing 5g of pretreated titanium gypsum powder, adding 100ml of deionized water, and dissolving in a 250ml beaker by magnetic stirring. Adding 7ml of concentrated hydrochloric acid, stirring for 2min to fully dissolve the agglomerated titanium gypsum, and standing for 5min after stirring;

and step 3: preparing shell slaked lime, collecting 500g oyster shell, cleaning, removing sand, calcining at high temperature of 900 deg.C, and maintaining the temperature for 2 hr. Naturally cooling, taking out and stacking at room temperature, and automatically pulverizing into white powder;

and 4, step 4: preparing crystal whisker, adding shell slaked lime to regulate the pH value to 7, standing for 5min to allow undissolved titanium gypsum to naturally precipitate, and obviously observing solid-liquid separation. Filtering the layered clear liquid on a funnel, putting filter residues into a vacuum drying oven, and setting the temperature to be 200 ℃ to constant weight;

and 5: and (3) preparing calcined ball clay, namely placing the ball clay in a corundum crucible, and calcining in a high-temperature furnace in a reducing atmosphere. Calcining at 860 ℃, preserving heat for 1h, cooling, taking out, and placing in air for 48h to change the color from white to pink;

step 6: preparing a ZIF-67 loaded shell-derived Co-based catalyst, wherein the ratio of cobalt nitrate to dimethyl imidazole is 1: 4 was dissolved in 50ml of methanol and stirred at room temperature for 6 h. Soaking abalone shell in solution of 0.8g nickel nitrate and 0.2g zif-67, and oven drying at 60 deg.C for 12 h. Heating the mixture in a tube furnace to 350 ℃, keeping the temperature for 2h, and increasing the temperature at a rate of 1 ℃/min;

and 7: and (3) preparing magnetic nanoparticles, namely adding 3g of filter residue into 30ml of triethanolamine, adding 1.8g of urea, stirring, mixing, putting into an autoclave, putting into a drying box, and keeping the temperature at 200 ℃ for 8 hours. Cooling, filtering, magnetizing and dispersing;

and 8: the coating is prepared by adding 3g of sodium alginate and 10g of polyvinyl alcohol into 100ml of water, heating and dissolving to prepare an aqueous solution, then adding 3g of waste residue, 5g of shell hydrated lime, 5g of calcined ball clay, 3g of photocatalyst and 0.25g of magnetic nanoparticles, and uniformly stirring. The prepared water-based paint has the functions of water resistance, alkali resistance, air purification and the like, and can be used indoors and outdoors.

Example 2 a method of preparing a coating using gypsum whisker residue, comprising the steps of:

step 1: preparing titanium gypsum powder, namely drying 1kg of blocky titanium gypsum for 24 hours at 105 ℃, cooling, grinding for 30 minutes in a ball mill, controlling the fineness to be less than 3.2 percent of the screen residue of a square-hole sieve with the fineness of 80 mu m, covering the powder with a preservative film, and aging for 8 days;

step 2: and 6g of pretreated titanium gypsum powder is weighed and added into 100ml of deionized water to be magnetically stirred and dissolved in a 250ml beaker. Adding 8 ml of concentrated hydrochloric acid, stirring for 2min to fully dissolve the agglomerated titanium gypsum, and standing for 5min after stirring;

and step 3: preparing hydrated lime, namely taking 500g of oyster shells, cleaning and removing sand, calcining at high temperature of 900 ℃, and keeping the temperature for 2 hours. Naturally cooling, taking out and stacking at room temperature. After absorbing water, the mixture becomes white powder;

and 4, step 4: preparing crystal whisker, adding shell slaked lime to regulate the pH value to 7, standing for 5 minutes to allow undissolved titanium gypsum to naturally precipitate, and obviously observing solid-liquid separation. Filtering the layered clear liquid on a funnel, putting filter residues into a vacuum drying oven, and setting the temperature to be 200 ℃ to constant weight;

and 5: and (3) preparing calcined ball clay, namely containing the ball clay by using a crucible, and calcining the ball clay in a high-temperature furnace in a reducing atmosphere. Calcining at 860 ℃, preserving heat for 1h, cooling, taking out, and placing in air for 48h to change the color from white to pink;

step 6: and (3) preparing magnetic nanoparticles, namely adding 3g of filter residue into 30ml of triethanolamine, adding 1.8g of urea, stirring, mixing, putting into an autoclave, putting into a drying box, and keeping the temperature at 200 ℃ for 8 hours. Cooling, filtering, magnetizing and dispersing;

and 7: the coating is prepared by adding 10g of polyvinyl alcohol into 100ml of water, heating and dissolving to prepare an aqueous solution, then adding 5g of waste residue, 5g of shell hydrated lime, 5g of calcined ball clay and 0.1g of magnetic nano particles, and uniformly stirring. The prepared water-based paint has the characteristics of water resistance, alkali resistance, wave absorption and the like.

Example 3 a method of preparing a coating using gypsum whisker residue, comprising the steps of:

and 5: and (3) preparing the coating, namely adding 10g of shell hydrated lime into water, stirring and standing for 24h, adding 3g of waste residues, and uniformly stirring. The paint has the functions of corrosion resistance, heat reflection and the like, and is suitable for being applied as a tree whitening agent.

Test examples

1. Raw materials:

shell: the shell is obtained from seafood processing shop in vegetable market. Oyster shell, high calcium content and good whiteness.

Abalone shells, which contain fluorescent substances and are used as carriers of the photocatalyst.

Shell slaked lime: cleaning oyster shell, calcining at 900 deg.C in high temperature furnace, and maintaining the temperature for 2 hr. Naturally cooling and taking out chamber

And (5) warm stacking. After absorbing water, the mixture became white powder.

Glycerol: analytically pure, Tianjin Bodi chemical Co., Ltd.

Triethanolamine: analytically pure, Tianjin Bodi chemical Co., Ltd.

Dimethyl imidazole: guangdong Wenjiang chemical reagents, Inc.

Cobalt nitrate hexahydrate: analytically pure, Shanghai Meclin.

Nickel nitrate hexahydrate: analytically pure, Shanghai Meclin.

Ethanol: analytically pure, chemical reagents of national drug group, ltd.

Methanol: analytically pure, chemical reagents of national drug group, ltd.

Sodium sulfate: analytical purity, Henjin chemical reagents manufacturing Co., Ltd.

Concentrated hydrochloric acid: analytically pure, Tianjin Bodi chemical Co., Ltd.

Polyvinyl alcohol 1750 ± 50: chemical agents of the national drug group, ltd.

Sodium alginate: sanfeng Biotechnology Ltd.

Urea: analytically pure, Tianjin, Convergence Hangzhou chemical science and technology Co.

Ball clay: tabac ceramics ltd.

Titanium gypsum: the chemical compositions are shown in Table 1.

TABLE 1 chemical composition of raw materials%

2. The test method comprises the following steps:

2.1 preparation method of Gypsum whisker

Crushing 1kg of titanium gypsum by using a hammer, drying in a drying oven at 105 ℃ and preserving heat for 24h, cooling and then grinding in a ball mill for 30min, covering the ground powder with a preservative film and aging for more than 7 d.

The white gypsum whisker preparation process flow comprises the following steps:

titanium gypsum powder → decolorization → hydrothermal reaction → filtration → drying → gypsum whisker

↓

Color filler ← drying ← filter residue → drying → hydrothermal synthesis → magnetic nano-particles

2.2 preparation method of calcined ball clay

The ball clay is placed in a corundum crucible and put in a high-temperature furnace for calcination in a reducing atmosphere. The calcining temperature is 860 ℃, the temperature is kept for 1h, the mixture is cooled and taken out and placed in the air for 48h, and the color is changed from white to pink.

2.3 preparation method of ZIF-67-loaded shell-derived Co-based MOF catalyst

The ratio of cobalt nitrate to dimethylimidazole is 1: 4 is dissolved in 50ml of deionized water, stirred for 6h at room temperature, and then the purple precipitate zif-67 is obtained by centrifugation, and is washed three times by the deionized water and once by methanol in the centrifugation process, and is dried for 10h at 60 ℃.

Soaking abalone shells in 0.8g of nickel nitrate and 0.2g of zif-67 ethanol solution, and drying in an oven at 60 ℃ for 12 h. Heating the mixture in a tube furnace to 350 ℃, keeping the temperature for 2h, and increasing the temperature at a rate of 1 ℃/min.

2.4 preparation method of magnetic nanoparticles

Adding 30ml of triethanolamine into 3g of filter residue, adding 1.8g of urea, stirring, mixing, putting into an autoclave, putting into a drying box, keeping the temperature at 200 ℃ for 8 hours. Cooling, filtering, magnetizing and dispersing.

2.5 coating application

An aqueous solution was prepared by adding 3g of sodium alginate and 10g of polyvinyl alcohol to 100ml of water and dissolving them by heating. Adding 4g of filter residue, 5g of shell slaked lime, 5g of calcined ball clay, 3g of photocatalyst and 0.5g of magnetic nano particles, uniformly stirring, and coating the mixture on the surfaces of outdoor stone and indoor cement walls by using a brush.

3. Test and result analysis

3.1 coating Heat resistance test results

Four rectangular paper boxes with the length of 8cm, the width of 8cm and the height of 20cm are manually manufactured by using corrugated paper as a raw material, and a small opening is formed in the upper end of each paper box so that a thermocouple can be inserted into each paper box. The four cartons are marked as A, B, C and D respectively, the carton A is used as a control group and is not treated, the inner wall of the carton B is coated with paint, the outer wall of the carton C is coated with paint, and the inner wall and the outer wall of the carton D are coated with paint. And simultaneously dried at room temperature for 48 hours.

500ml of water heated to 68 ℃ was put into four paper boxes at the same time, cooled naturally at room temperature, and the change in water temperature with time was recorded. Parallel experiments were performed multiple times and averaged to exclude chance. The results are shown in Table 2.

TABLE 2 test results of heat resistance of coating

Numbering	1min	8min	15min	20min	30min	45min
							Blank space	65.5	62.5	60.5	58.5	55	50.7
Coating on outer wall	67.1	64.5	61.8	59.5	56.1	52.0
							Inner wall coating	67.3	64.6	62.1	60.3	57.3	52.6
Coating brush for inner and outer walls	67.2	64.7	62.2	60.7	57.3	52.5

Table 2 shows that the outer wall coating can reduce 7% of heat loss, and the inner wall coating and the inner and outer wall coating can reduce about 10% of heat loss. The coating has the effects of heat insulation and preservation, and has the effect of adjusting the room temperature so as to reduce the waste of energy.

3.2 coating weatherability Observation

Painting indoor and outdoor paint, and observing for 8 months. The coating without filter residue falls off and cracks. As shown in figure 1, the filter residue contains gypsum whiskers, so that the crack resistance is enhanced. Therefore, the coating prepared from the filter residue has good decorative effect, is green and environment-friendly, nontoxic and tasteless, and has low price, sulfate resistance and atmospheric aging resistance.

3.3 detection of wave-absorbing Property of coating

And (3) making a closed space by using a gypsum board, and coating the space with the coating. The noise instrument tests show that the sound absorption coefficient fluctuation is 0.2-0.8 in the ranges of 125HZ, 250HZ, 500HZ, 1000HZ, 2000HZ and 4000HZ, and the coating has good absorption performance for medium and high frequency electromagnetic waves and certain absorption performance for low frequency.

3.4 detection of self-cleaning Properties of coatings

The shell is porous and supports the ZIF-67 derived Co-based catalyst. ZIF-67 is a three-dimensional framework compound (MOF) formed by coordination of cobalt nitrate hexahydrate and 2-methylimidazole, and a metal center Co is unsaturated coordination and has a large number of empty metal active sites. The figure 2 shows that the shape is regular and the crystallization is good. The main component of the shell is CaCO illustrated by FIG. 3₃Loaded with Co₃O₄The organic-inorganic frame material is assembled, the process is simple and convenient, and the cost is low. But due to poor conductivity, the catalyst system is combined with the nano-magnetic particles to form a composite catalyst system. Under the condition of illumination, more photogenerated electrons are generated to excite O₂ ^-OH and CO₃ ^-Free radicals are generated to decompose toxic and harmful substances, and the air purifier has the capability of purifying air. Warp beamAnd through rainwater and snow water scouring and atmospheric erosion, the surface of the coating is observed to be clean, no dirt exists, and the color is bright.

Although specific embodiments of the invention have been described above, it will be understood by those skilled in the art that the specific embodiments of the invention described are illustrative only and are not limiting to the scope of the invention, and that equivalent modifications and variations can be made by those skilled in the art without departing from the spirit of the invention, which is to be covered by the appended claims.

Claims

1. A method for preparing coating by utilizing gypsum whisker residues is characterized by comprising the following steps: adding sodium alginate and polyvinyl alcohol into water, heating and dissolving to prepare an aqueous solution, adding gypsum whisker residues, shell slaked lime, calcined ball clay, a ZIF-67-loaded shell-derived Co-based catalyst and magnetic nanoparticles, and uniformly stirring to prepare the water-based coating;

preparing the gypsum whisker residues, namely 1) pretreating titanium gypsum to prepare powder, drying blocky titanium gypsum for 24 hours at 105 ℃, cooling and grinding for 30 minutes to prepare powder, and covering a plastic film in the air for aging for more than 7 days;

2) a decoloring treatment process, namely adding a proper amount of pretreated titanium gypsum powder into concentrated hydrochloric acid for dissolving, adding shell slaked lime for adjusting the pH value to 7, and filtering to form clear liquid and filter residue; putting the filter residue product into a vacuum drying oven, and drying at 200 ℃ to constant weight;

the preparation of the shell slaked lime selects oyster shells with less iron and high whiteness to be calcined at 900 ℃, and the temperature is kept for 2 hours; cooling, taking out, placing air, and automatically pulverizing to obtain white powder; the weight parts of the raw materials are as follows: 0-5 parts of sodium alginate, 1-10 parts of polyvinyl alcohol, 3-5 parts of gypsum whisker residues, 5-10 parts of shell hydrated lime, 0-6 parts of calcined ball clay, 0-4 parts of a catalyst and 0-0.5 part of magnetic nanoparticles;

preparing calcined ball clay, namely holding the ball clay by a crucible, and calcining the ball clay in a high-temperature furnace in a reducing atmosphere; calcining at 860 ℃, preserving heat for 1h, cooling, taking out, and placing in air for 48h to change the color from white to pink; the preparation method of the ZIF-67 loaded shell-derived Co-based catalyst comprises the following steps of (1) preparing cobalt nitrate and dimethyl imidazole in a mass ratio: 4, dissolving in methanol, and stirring at room temperature for 6 hours; soaking the abalone shell in a solution of nickel nitrate and zif-67, wherein the mass ratio of the nickel nitrate to the zif-67 is 4:1, and drying the abalone shell in an oven at 60 ℃ for 12 hours; heating the mixture in a tube furnace to 350 ℃, keeping the temperature for 2h, and increasing the temperature at a rate of 1 ℃/min;

preparing the magnetic nanoparticles, namely adding triethanolamine into filter residues for dissolving, adding urea, stirring, mixing, putting into a still kettle, putting into a drying box, and keeping the temperature at 200 ℃ for 8 hours; cooling, filtering, magnetizing and dispersing; the mass volume ratio of the filter residue, the urea and the triethanolamine is 3:1-2: 30.