Method for preparing wastewater flocculant by using waste white clay

Abstract

The present application relates to a kind of methods for preparing waste water flocculants with waste clay, comprising: 1) first, waste clay is solvent extraction pretreatment, remove the oil, metal ions and other impurities therein.2) waste clay after solvent extraction separation is treated by thermochemical activation, increase its specific surface area and porosity, improve the adsorption performance of activated waste clay.3) waste clay after activation is chemically modified to enhance its flocculation performance.4) the modified waste clay is crushed and screened;To obtain the particle size distribution suitable for the application of flocculant.5) the treated waste clay is mixed with water, polyacrylamide, polyethyleneimine, to obtain waste clay flocculant solution or suspension.The present application is simple in waste clay regeneration mode, and the treatment condition is mild, on the one hand, waste clay is resourceized and harmless treatment, on the other hand, efficient waste water treatment flocculant is prepared.

Description

TECHNICAL FIELD

[0001] The present application belongs to wastewater treatment, and particularly relates to a method for preparing a wastewater flocculant from waste clay. BACKGROUND

[0002] In the process of petroleum refining, food processing and chemical production, clay is used as an adsorbent to remove impurities, color, odor and other by-products in the product. The clay that loses adsorption capacity is waste clay. Waste clay contains a large amount of oil, which can pollute the environment if not properly treated, and is also a waste of resources. There are many waste clay treatment technologies at present, such as pressing method, centrifugal method, solvent method, pyrolysis method, steam method, etc. to recover oil from waste clay, but the oil in waste clay cannot be completely removed, and waste clay cannot be recycled. In order to further improve the utilization rate of waste clay, incineration method, air isolation carbonization method and calcination method are used to burn or carbonize the residual substances at high temperature into harmless substances, so that waste clay can be regenerated and utilized. However, in the process of high-temperature heat treatment, the original structure and porosity of the clay are destroyed, and the adsorption capacity of the clay is reduced, which seriously affects the use efficiency.

[0003] Patent 201110176508.3 and patent 201810467634.6 use waste clay to prepare adsorbents, which are calcined and carbonized to make the waste clay have adsorption performance similar to activated carbon to adsorb pollutants in water. However, after high-temperature treatment, the adsorption capacity is low and the stability is poor.

[0004] Therefore, by proper treatment and processing, waste clay is converted into flocculant under mild conditions for removing suspended solids, colloids and part of dissolved substances in water. Not only does it reduce environmental pollution, but also realizes the recycling of resources. It is in line with the concept of circular economy and sustainable development, and helps to promote environmental protection and resource conservation. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art, and provides a method for preparing a wastewater treatment flocculant from waste clay. The waste clay regeneration method is simple and the treatment conditions are mild. On the one hand, the waste clay is treated in a resourceful and harmless manner, and on the other hand, a high-efficiency wastewater treatment flocculant is prepared.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A method for preparing a wastewater flocculant from waste clay, comprising the following method steps:

[0008] 1) Pretreatment: firstly, the waste clay is pretreated by solvent extraction to remove oil, metal ions and other impurities. The solvent is mixed with the waste clay and stirred for 1-3 h, the volume of the solvent is 2-5 times the volume of the waste clay, and the temperature is room temperature; after stirring, solid-liquid separation is carried out by a centrifuge to obtain the waste clay after extraction separation.

[0009] 2) Activation treatment: the waste clay after solvent extraction separation is subjected to thermal chemical activation treatment to increase its specific surface area and porosity, and improve the adsorption and flocculation performance of the activated waste clay. The chemical activator is a sodium hydroxide solution with a mass concentration of 1%-5%, the volume is 1-3 times the volume of the waste clay, and is placed in a reaction kettle, and the temperature is programmed to 150-200°C at a heating rate of 5-10°C / min, and the temperature is kept for 8-15 hours; after the reaction is completed, the activated waste clay is cooled to room temperature, and washed with deionized water until the waste water is neutral, to obtain the activated waste clay.

[0010] 3) Chemical modification: the activated waste clay is subjected to chemical modification to enhance its flocculation performance. The chemical modification is an organic silicon compound and an organic phosphorus compound, and the volume ratio of the chemical modifier to the waste clay is (1-5):1, and the room temperature immersion time is 12-24 h; after the reaction is completed, the waste water is washed with deionized water until it is neutral, and dried to remove water, to obtain the modified waste clay.

[0011] 4) Crushing and screening: the modified waste clay is crushed and screened to obtain a particle size distribution suitable for the application of the flocculant.

[0012] 5) Preparation of flocculant: the treated waste clay is mixed with water, polyacrylamide and polyethyleneimine to obtain a waste clay flocculant solution or suspension.

[0013] The solvent is an ionic liquid extractant, and the components are 1-butyl-3-methylimidazolium hexafluorophosphate and 1-octyl-3-methylimidazolium hexafluorophosphate, and the ratio is 1:0.5-1.

[0014] The extraction solvent after extraction separation in step 1) is regenerated with a 5%-8% mass concentration of sodium hydroxide solution.

[0015] In the chemical modification, the ratio of the organic silicon compound to the organic phosphorus compound is 1:(0.5-2).

[0016] After crushing and screening in step 4), the particle size of the flocculant is 500-1000 mesh.

[0017] In step 5), the treated waste clay is stirred and mixed with water, polyacrylamide and polyethyleneimine at room temperature for 3-20 h, and the mass ratio of the waste clay to water, polyacrylamide and polyethyleneimine is 5:(10-30):(0.001-0.005):(0.001-0.003).

[0018] Compared with the prior art, the present application has the advantages of:

[0019] 1) The present application uses solvent extraction method to separate and recover oil in waste white clay, and has high oil recovery efficiency and high recovery purity.

[0020] 2) The waste white clay after oil removal is directly reacted to prepare a flocculant, the method is simple, there is no secondary pollution, and the waste white clay is maximized in resource utilization.

[0021] 3) The flocculant is applied to treat the effluent from the secondary sedimentation tank after biochemical treatment of industrial wastewater, and under the condition of the same dosage, compared with the traditional PAC and PFS flocculants, the COD removal rate of the wastewater is increased by more than about 26 percentage points, the color removal rate is increased by about 15-20 percentage points, and the suspended solids removal rate is increased by about 7-15 percentage points. DETAILED DESCRIPTION

[0022] The present application will be further described below by way of examples, but the present application is not limited to the scope of the examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0023] Example 1:

[0024] A certain amount of waste white clay was taken into a stirrer, 3 times the volume of ionic liquid extractant was added, stirring for 2.5 h, centrifugal separation to obtain pretreated waste white clay, 3% mass concentration of sodium hydroxide solution was added, the volume was 2 times the volume of the waste white clay, and was added into a reaction kettle, stirring and heating to 150℃ at a heating rate of 7℃ / min, and reaction for 10 h. After the reaction was completed, the activated waste white clay was cooled to room temperature and washed with deionized water until the waste water was neutral. 3 times the volume of chemical modifier was used for room temperature immersion for 15 h, the ratio of the organic silicon compound to the organic phosphorus compound was 1:1.1, after the reaction was completed, deionized water was used for washing until the waste water was neutral, drying, crushing and sieving, the particle size of the flocculant was 800 mesh, and the mass ratio of water, polyacrylamide and polyethyleneimine was 5:25:0.001:0.0015, stirring and mixing at room temperature for 15 h to obtain liquid flocculant I.

[0025] The composition of the ionic liquid extractant was 1-butyl-3-methylimidazolium hexafluorophosphate and 1-octyl-3-methylimidazolium hexafluorophosphate, and the ratio was 1:0.6.

[0026] The extraction solvent after extraction and separation was regenerated by using 7% mass concentration of sodium hydroxide solution.

[0027] Example 2:

[0028] A certain amount of waste white clay is added into a stirrer, 4 times the volume of ionic liquid extractant is added, stirred for 2 hours, centrifugal separation is carried out to obtain the pretreated waste white clay, a mass concentration of 4% sodium hydroxide solution is added, the volume is 2.5 times the volume of the waste white clay, is added into a reaction kettle, is stirred and heated to 160 DEG C, the heating rate is 8 DEG C / min, the reaction is carried out for 8 hours, after the reaction is completed, the activated waste white clay is cooled to room temperature, and is washed with deionized water until the waste water is neutral, to obtain the activated waste white clay. 4 times the volume of the chemical modifier is used for room temperature immersion for 14 hours, the ratio of the organic silicon compound to the organic phosphorus compound is 1:1, after the reaction is completed, the waste water is washed with deionized water until the waste water is neutral, drying, crushing and screening, the particle size of the flocculant is 1000 meshes, the mass ratio of water, polyacrylamide and polyethyleneimine is 5:20:0.0015:0.001, stirring and mixing at room temperature for 13 hours, to obtain the liquid flocculant II.

[0029] The ionic liquid extractant is composed of 1-butyl-3-methylimidazolium hexafluorophosphate and 1-octyl-3-methylimidazolium hexafluorophosphate, and the ratio is 1:0.7.

[0030] The extraction solvent after extraction and separation is regenerated by using a mass concentration of 6% sodium hydroxide solution.

[0031] Example 3:

[0032] A certain amount of waste white clay is added into a stirrer, 3.5 times the volume of ionic liquid extractant is added, stirred for 3 hours, centrifugal separation is carried out to obtain the pretreated waste white clay, a mass concentration of 5% sodium hydroxide solution is added, the volume is 3 times the volume of the waste white clay, is added into a reaction kettle, is stirred and heated to 180 DEG C, the heating rate is 8 DEG C / min, the reaction is carried out for 8 hours, after the reaction is completed, the activated waste white clay is cooled to room temperature, and is washed with deionized water until the waste water is neutral, to obtain the activated waste white clay. 4.5 times the volume of the modifier is used for room temperature immersion for 15 hours, the ratio of the organic silicon compound to the organic phosphorus compound is 1:1.5, after the reaction is completed, the waste water is washed with deionized water until the waste water is neutral, drying, crushing and screening, the particle size of the flocculant is 1000 meshes, the mass ratio of water, polyacrylamide and polyethyleneimine is 5:20:0.002:0.001, stirring and mixing at room temperature for 15 hours, to obtain the liquid flocculant II.

[0033] The ionic liquid extractant is composed of 1-butyl-3-methylimidazolium hexafluorophosphate and 1-octyl-3-methylimidazolium hexafluorophosphate, and the ratio is 1:0.5.

[0034] The extraction solvent after extraction and separation is regenerated by using a mass concentration of 4% sodium hydroxide solution.

[0035] Performance test of the product of the application:

[0036] The flocculants prepared in the embodiments 1-3 of the present application were used to treat the effluent from the biochemical secondary sedimentation tank of coal chemical industry under the same conditions as the commercially available polymeric ferric sulfate (PFS) and polymeric aluminum chloride (PAC), and the comparison results are shown in Table 1.

[0037] Table 1 treatment effects of different flocculants on the effluent from the secondary sedimentation tank

[0038] Flocculant Dosage (g / L) COD removal rate Color removal rate Suspended solids removal rate PAC 0.12 46.1％ 70％ 80％ PFS 0.12 52.2％ 75％ 85％ Flocculant I 0.12 78.2％ 92％ 95％ Flocculant II 0.12 82.7％ 95％ 95％ Flocculant III 0.10 80.1％ 90％ 92％

[0039] In combination with Table 1, the treatment effect of the flocculants prepared in the present application on the effluent from the biochemical secondary sedimentation tank of coal chemical industry is better than that of the commercially available flocculants.

[0040] The above description is only the preferred embodiments of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can make equivalent replacements or changes according to the technical solution and the inventive concept of the present application within the technical range disclosed by the present application, and still fall within the protection scope of the present application.

Claims

1. A method for preparing a flocculant for waste water using waste white clay, characterized by, The method comprises the following steps: 1) Pretreatment: first, the waste clay is pretreated by solvent extraction, the solvent is mixed with the waste clay and stirred for 2-3 h, the volume of the solvent is 3-4 times the volume of the waste clay, and the temperature is room temperature; after stirring, solid-liquid separation is performed by a centrifuge to obtain waste clay after extraction separation; 2) Activation treatment: the waste clay after solvent extraction separation is subjected to thermal chemical activation treatment, the chemical activator is a sodium hydroxide solution with a mass concentration of 3-5%, the volume is 2-3 times the volume of the waste clay, and is placed in a reaction kettle, heated to 150-180℃, the heating rate is 7-8℃ / min, and the temperature is kept for 8-15 hours; after the reaction is completed, the activated waste clay is cooled to room temperature and washed with deionized water until the waste water is neutral, and the activated waste clay is obtained; 3) Chemical modification: the activated waste clay is subjected to chemical modification, the chemical modifier is an organic silicon compound and an organic phosphorus compound, the volume ratio of the chemical modifier to the waste clay is (3-4.5):1, and the room temperature immersion time is 14-15 h; after the reaction is completed, the waste clay is washed with deionized water until the waste water is neutral, dried to remove water, and the modified waste clay is obtained; 4) Crushing and screening: the modified waste clay is crushed and screened; 5) Preparation of flocculant: the treated waste clay is mixed with water, polyacrylamide and polyethyleneimine to obtain a waste clay flocculant suspension; The solvent is an ionic liquid extractant, and the components are 1-butyl-3-methylimidazolium hexafluorophosphate and 1-octyl-3-methylimidazolium hexafluorophosphate, and the ratio is 1:(0.5-0.7); In the chemical modification, the ratio of the organic silicon compound to the organic phosphorus compound is 1:(1-1.5); After step 4) crushing and screening, the particle size of the flocculant is 800-1000 mesh; In step 5), the treated waste clay is stirred and mixed with water, polyacrylamide and polyethyleneimine at room temperature for 13-15 h, and the mass ratio of the waste clay to water, polyacrylamide and polyethyleneimine is 5:(20-25):(0.001-0.002):(0.001-0.0015).

2. The method for preparing a flocculant for waste water using waste white clay according to claim 1, characterized in that, In step 1), the extraction solvent after extraction separation is regenerated by using a sodium hydroxide solution with a mass concentration of 4-7%.