CN102079563B - Regenerative coagulant, and preparation method and using method thereof - Google Patents

Abstract

The invention relates to a renewable coagulant and methods for its preparation and use. The renewable coagulant is characterized in that it is made from waste concrete. The specific steps are: collect waste concrete, remove sand and gravel, crush, grind, pass through a 150-mesh sieve, and calcined for 2 hours. After cooling, grind to obtain concrete with a particle size of less than 0.03mm and a specific surface area of 3000-4000cm ² /g. Powder, which is a renewable coagulant. The invention makes full use of the hydration of artificial minerals such as monocalcium aluminate, dicalcium silicate, tricalcium silicate, tricalcium aluminate and tetracalcium aluminoferrite, and the electric neutralization, adsorption, and net-catching and sweeping functions of hydrolyzed products. And the synergistic effect of coagulation and precipitation to achieve a good coagulation effect, and use the good settling performance of coagulation sludge to regenerate the coagulant through the process of filtration, drying and calcination, so as to realize the repeated use of the coagulant.

Description

A kind of renewable coagulant and its preparation and use method

technical field

The invention relates to a renewable coagulant and its preparation and use method, which are used for the treatment of refractory printing and dyeing wastewater and other wastewater, and belong to the technical field of environmental protection.

Background technique

The printing and dyeing industry is a major industrial pollutant discharger. At present, the total discharge of printing and dyeing wastewater in China is 5.5×10 ⁸ t/a, accounting for about 13% of the entire industrial wastewater. The difficulties in the treatment of textile printing and dyeing wastewater are: (1) high COD, poor biodegradability; (2) high chroma, complex components, and difficult decolorization.

The treatment methods of printing and dyeing wastewater can be roughly divided into: (1) Biological treatment method, that is, the use of microbial enzymes to catalyze the degradation of organic molecules, through a series of life activities such as oxidation, reduction, hydrolysis, and compounding, and finally degrade the organic substances in the wastewater into simple inorganic substances or into various nutrients and biomass. Due to the complex composition of dye wastewater, which contains a large amount of substances that are toxic to microorganisms, the direct biochemical effect is not good, and the decolorization ability is limited, so pretreatment is often required; (2) Chemical oxidation, including advanced oxidation technology, that is, the use of oxidants to make dye molecules The unsaturated double bond of the chromophoric group is oxidized and broken to form organic or inorganic substances with a small molecular weight. Among them, the photosensitized semiconductor is used as a catalyst to treat printing and dyeing wastewater, which is a branch that has been studied more in recent years. In this method, the catalyst Most of them use titanium-based semiconductor catalysts represented by _TiO2 or other noble metal catalysts; (3) physical and chemical treatment methods, mainly including adsorption methods, electrochemical methods and coagulation methods. Adsorption method, that is, the use of porous solid materials to adsorb and separate pollutants in water; electrochemical method, that is, the use of electrolytic oxidation, electrolytic reduction, electrolytic flocculation or electrolytic flotation to destroy the structure of molecules to achieve the purpose of decolorization; coagulation method is widely used as wastewater pretreatment. Treatment operations can significantly reduce the load of biological treatment of high-turbidity and high-concentration printing and dyeing wastewater, and can also be placed after biochemical treatment to improve the decolorization rate, ensure discharge standards, or create conditions for advanced water treatment and reuse.

With the development of the dye industry and the progress of finishing technology, new auxiliaries, dyes, finishing agents and other refractory organic substances are widely used in the printing and dyeing industry, resulting in higher COD and lower BOD/COD in printing and dyeing wastewater, making wastewater treatment difficult. It is also increasing day by day. With the traditional printing and dyeing wastewater treatment process, the effluent index is difficult to meet the discharge standard. Coagulation operations are often indispensable. Choosing the right coagulant, improving the coagulation effect and reducing the treatment cost are the main contents of research and development.

Commonly used coagulants include: organic polymer coagulants (such as polyacrylamide, etc.), inorganic coagulants (such as polyaluminum chloride, polyaluminum sulfate, etc.), organic-inorganic composite coagulants (such as ferric chloride-II Methyldiallyl ammonium chloride homopolymer, polyferric chloride-dimethyldiallyl ammonium chloride homopolymer, etc.). Commonly used coagulants generally have disadvantages such as high price and poor treatment effect on hydrophilic dyes. The generated sludge cannot be reused, and solidification and stabilization treatment is required before landfill, which is costly and landfill sites are limited. In addition, the traditional coagulant treatment of printing and dyeing wastewater has a slow settling speed of alum flowers, sludge concentration, and difficulty in filtration. If the sludge is not handled properly, it is very easy to cause secondary pollution.

Contents of the invention

The purpose of the present invention is to provide a coagulant with low cost, high coagulation efficiency and strong water quality adaptability and its preparation and use method.

In order to achieve the above object, the present invention provides a renewable coagulant, which is characterized in that it is made from waste concrete.

The present invention also provides the preparation method of the above-mentioned renewable coagulant, which is characterized in that the specific steps are: collecting the discarded concrete, removing sand and gravel, crushing, grinding, passing through a 150-mesh sieve, and drying at 550-650°C Calcined for 1-2 hours, cooled, and ground to obtain a powder with a particle size of 0.03 mm or less and a specific surface area of 3000-4000 cm ² /g, which is a renewable coagulant. The fineness of the powder has a certain influence on the coagulation effect. Increasing the fineness can improve the coagulation effect, but at the same time the power consumption will increase accordingly. Dust is generated during the grinding and screening process, so dust collection equipment, such as settling chambers, cyclone dust collectors, bag dust collectors, etc., should be installed at the equipment import and export, transportation process and packaging.

When in use, the above-mentioned renewable coagulant is added to the wastewater to be treated, the amount of coagulant added is 1-15 g/L, and it is fully stirred at a certain intensity (such as a six-way mixer, 150 r/min) and then statically Set aside for 30-50 minutes, use its hydrolysis and hydration products for electrical neutralization, adsorption, net capture and sweeping, and bridging to coagulate and settle various substances in the wastewater, and use the physical and chemical processes of precipitation and adsorption to Synergistically, sludge and clean water are obtained.

The present invention also provides a recycling method for the above-mentioned renewable coagulant, which is characterized in that the specific steps are: suction filter the sludge obtained from coagulation and sedimentation, dry it, and calcinate it at a temperature of 550-650°C for 1-2 h, after cooling, grind to a powder with a particle size of less than 0.03 mm and a specific surface area of 3000-4000 cm ² /g, and use it again as a coagulant for wastewater coagulation treatment. The coagulant described in the present invention can be continuously regenerated and recycled at least 10 times. The coagulation effect of the coagulant decreases slightly with the increase of regeneration times, and the sludge after failure can be disposed of directly in landfill without additional solidification and stabilization treatment.

The main principle that the present invention realizes is as follows:

The present invention uses the substances produced by hydration and hydrolysis of artificial minerals such as calcium silicate, calcium aluminate, and calcium ferrite to coagulate and settle various substances in wastewater, and utilizes the synergistic effect of physical and chemical processes such as precipitation and adsorption. Realize the separation of pollutants and water.

(1) Monocalcium aluminate (CA) hydrates very quickly due to the extremely irregular coordination of calcium and aluminum in the crystal structure. The hydration products are different at different temperatures. The main hydration products at room temperature are CAH ₁₀ or C ₂ AH ₈ , both of which belong to the hexagonal crystal system. Crystallization of synbiotics, so as to achieve the coagulation effect of adsorption, netting and sweeping, and bridging.

The coagulated sludge is calcined and regenerated at 600 °C, and the hydration products are reduced to C _x A (0<x<1) and Al ₂ O ₃ , and put into use again, it still has the coagulation effect and can be reused repeatedly.

(2) Tricalcium silicate (C ₃ S), dicalcium silicate (C ₂ S), tricalcium aluminate (C ₃ A) and tetracalcium aluminoferrite C ₄ AF are the main minerals in Portland cement. C ₃ S and C ₂ S are hydrated to form calcium silicate hydrate (C—S—H) gel and calcium hydroxide (CH). coagulation, and can adjust the pH value. In addition, C ₃ A and C ₄ AF hydrate to form hexagonal calcium aluminate hydrate and colloidal calcium ferrite, which also have coagulation effect.

Tricalcium silicate C ₃ S has relatively strong hydration reaction ability, and the hydration reaction at room temperature can be expressed by the following formula:

or:

In the formula, C—S—H represents calcium silicate hydrate with unfixed components.

The coagulated sludge is calcined and regenerated at 600 °C, and the hydration products are reduced to C _x S (0<x<3), C _z A (0<z<3) and CaO, and they are put into use again, and still have mixed Coagulation effect, reusable and reusable.

Compared with the prior art, the present invention has the following characteristics, the technical progress is very significant, and the problems of coagulant recycling and sludge treatment and disposal are better solved, and it is positive for reducing the cost of printing and dyeing wastewater treatment and reducing the pressure of sludge treatment and disposal significance.

(1) Since the coagulant contains a variety of metal salt ions, the hydrolysis speed is fast, and for the treatment of wastewater, compared with the single metal salt coagulant, it has stronger electrical neutralization, adsorption, and sweeping capabilities, and the coagulation Better results.

(2) The regeneration of the coagulant can be realized through low-temperature calcination, the utilization rate of the coagulant can be improved, and the cost of wastewater treatment can be reduced.

(3) The sludge coagulant that has been recycled for many times (more than 10 times) does not need additional solidification and stabilization treatment when it is finally discarded, and can be directly landfilled, saving sludge treatment and disposal costs.

Description of drawings

Fig. 1 is a schematic diagram of the preparation and recycling process of the new renewable coagulant proposed by the present invention.

Detailed ways

The present invention will be further described below in conjunction with embodiment.

Example 1

As shown in FIG. 1 , it is a schematic diagram of the preparation and recycling process of the new renewable coagulant proposed by the present invention. Collect waste concrete, remove sand and gravel, crush it to a particle size of less than 25 mm, and then use an autogenous mill to grind it to a particle size of less than 2 mm, pass through a 150-mesh sieve, and calcinate at 550°C for 2 hours, and then cool , using a high-pressure roller mill to grind to obtain a powder with a particle size of 0.03 mm or less and a specific surface area of 3000-4000 cm ² /g, which is the coagulant.

The simulated dye wastewater with hydrophobic disperse scarlet dye at a concentration of 0.15 g/L had an initial pH of about 8.0 and an absorbance of 1.41. It was treated with the above coagulant, first stirred at a high speed (200 r/min) for 30 min, then stirred at a slow speed (100 r/min) for 5 h, and finally settled for 30 min, and the supernatant was taken to measure the absorbance and pH. Gradually increasing the dosage of coagulant, the coagulation dye removal rate increased accordingly, when the dosage of coagulant reached 11 g/L, the coagulation efficiency reached the best, and the dye removal rate reached 99.0%. The sludge settling performance was good, and its SV ₃₀ was measured to be 25 mL/L.

The sludge obtained by coagulation and sedimentation is suction-filtered with a Buchner funnel, dried, calcined at 550°C for 2 h, and ground to a powder with a particle size of less than 0.03 mm and a specific surface area of 3000-4000 cm ² /g after cooling. , and again as a coagulant for wastewater coagulation treatment. The removal rate of dyes in wastewater can still reach 96.3%. After 10 times of recycling, although the removal effect is slightly reduced, the removal rate can still reach 90.5%.

The coagulant has a good coagulation effect on the simulated wastewater of the hydrophobic disperse scarlet dye, has good sludge settling performance, and can be regenerated and used repeatedly.

Example 2

Collect the discarded concrete, remove the sand and gravel, first crush it to a particle size of less than 25 mm, then use an autogenous mill to grind it to a particle size of less than 2 mm, pass through a 150-mesh sieve, and calcinate at 600 °C for 2 h, after cooling , using a high-pressure roller mill to grind to obtain a powder with a particle size of less than 0.03 mm and a specific surface area of 3000-4000 cm ² /g, which is the coagulant.

The simulated dye wastewater with hydrophilic reactive brilliant blue dye at a concentration of 0.14 g/L had an initial pH of about 10.4 and an absorbance of 0.76. Treat it with the above coagulant, first stir it at a high speed (200 r/min) for 30 min, then adjust it at a slow speed (100 r/min) for 5 h, and finally settle it for 30 min, and take the supernatant to measure its absorbance and pH. Gradually increasing the dosage of coagulant, the coagulation dye removal rate increased accordingly, when the dosage of coagulant reached 5 g/L, the coagulation efficiency reached the best, and the dye removal rate reached 98.4%. The sludge settling performance was good, and its SV ₃₀ was measured to be 45 mL/L.

The sludge obtained by coagulation and sedimentation is suction-filtered with a Buchner funnel, dried, calcined at 600°C for 2 hours, and ground to a powder with a particle size of less than 0.03 mm and a specific surface area of 3000-4000 cm ² /g after cooling. , and again as a coagulant for wastewater coagulation treatment. The removal rate of dyes in wastewater can still reach 91.6%. After 10 cycles of recycling, the removal rate can still reach 88.2%.

The coagulant has good coagulation effect on simulated wastewater of hydrophilic reactive brilliant blue dye, good sludge settling performance, and can be regenerated and used repeatedly.

Example 3

Collect the discarded concrete, remove the sand and gravel, first crush it to a particle size of less than 25 mm, then use an autogenous mill to grind it to a particle size of less than 2 mm, pass through a 150-mesh sieve, and calcinate at 650 ° C for 2 h, after cooling , using a high-pressure roller mill to grind to obtain a powder with a particle size of 0.03 mm or less and a specific surface area of 3000-4000 cm ² /g, which is the coagulant.

Take the printing and dyeing wastewater discharged from a printing and dyeing factory, which is dark in color and has a foul smell, and the color is red. The water quality has been measured: pH value is 9.5, absorbance is 0.56, COD _Cr is 860 mg/L, BOD ₅ is 450 mg/L, SS is 230 mg/L, and chromaticity is 500 times. Add 500 mL of printing and dyeing wastewater samples into a 1000 mL beaker, and use the above coagulant to treat it. First, stir at a high speed (200 r/min) for 30 min, and then stir at a slow speed (100 r/min) for 5 h. The final precipitation was 50 min, and the supernatant was taken to measure its absorbance and COD. When the dosage of coagulant was gradually increased, the removal rate of coagulation dye increased. When the dosage of coagulant reached 3.8 g/L, the coagulation efficiency reached the best, and the COD _Cr removal rate reached 95.7%. Chromaticity removal rate reaches 90%.

The sludge obtained by coagulation and sedimentation is suction-filtered with a Buchner funnel, dried, calcined at 650°C for 2 hours, and ground to a powder with a particle size of less than 0.03 mm and a specific surface area of 3000-4000 cm ² /g after cooling. , as a coagulant again for wastewater coagulation treatment, the removal rate of COD _Cr in wastewater can still reach 93.6%. After 10 cycles of recycling, the removal rate can still reach 90.1%.

The coagulant has a good coagulation treatment effect on actual printing and dyeing wastewater, and has a good effect of repeated regeneration, and the sludge settles quickly, and is easy to filter and dewater.

Claims (3)

1. OnePlanting reproducible coagulating agent, it is characterized in that, is that raw material is processed by discarded concrete; Its preparation method is: collect the depleted concrete, reject sandstone, fragmentation; Grinding is crossed 150 mesh sieves, at 550-650 ℃ of temperature lower calcination 1 ~ 2 h; After the cooling, the levigate particle diameter that obtains is that 0.03 mm is following, specific surface area is 3000～4000 cm ²The powder of/g is reproducible coagulating agent.

2. the method for use of the described reproducible coagulating agent of claim 1; It is characterized in that; Concrete steps are: the described reproducible coagulating agent of claim 1 is joined in the pending waste water; The coagulating agent add-on is 1～15 g/L, leaves standstill 30～50 min after fully stirring, and obtains mud and clear water.

3. the method for use of reproducible coagulating agent as claimed in claim 2; It is characterized in that, with the mud suction filtration of coagulating sedimentation gained, drying; Place 550-650 ℃ of temperature lower calcination 1～2 h, cooling back grinding to particle diameter is below 0.03 mm, specific surface area is 3000～4000 cm ²The powder of/g is used for coagulating waste water as coagulating agent once more and handles.

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