CN111409213B - Waste mixed plastic full-priority flotation separation method based on calcium sulfate pretreatment - Google Patents
Waste mixed plastic full-priority flotation separation method based on calcium sulfate pretreatment Download PDFInfo
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- CN111409213B CN111409213B CN201910013273.2A CN201910013273A CN111409213B CN 111409213 B CN111409213 B CN 111409213B CN 201910013273 A CN201910013273 A CN 201910013273A CN 111409213 B CN111409213 B CN 111409213B
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- 229920003023 plastic Polymers 0.000 title claims abstract description 159
- 239000004033 plastic Substances 0.000 title claims abstract description 159
- 238000005188 flotation Methods 0.000 title claims abstract description 129
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 title claims abstract description 65
- 238000000926 separation method Methods 0.000 title claims abstract description 58
- 239000002699 waste material Substances 0.000 title claims abstract description 36
- 239000004676 acrylonitrile butadiene styrene Substances 0.000 claims abstract description 58
- 229920003229 poly(methyl methacrylate) Polymers 0.000 claims abstract description 40
- 239000004926 polymethyl methacrylate Substances 0.000 claims abstract description 40
- 238000000034 method Methods 0.000 claims abstract description 36
- 239000002245 particle Substances 0.000 claims abstract description 31
- 238000009210 therapy by ultrasound Methods 0.000 claims description 22
- 230000008569 process Effects 0.000 claims description 21
- 238000005273 aeration Methods 0.000 claims description 13
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 5
- 238000011084 recovery Methods 0.000 abstract description 31
- 239000000203 mixture Substances 0.000 abstract description 4
- XECAHXYUAAWDEL-UHFFFAOYSA-N acrylonitrile butadiene styrene Chemical compound C=CC=C.C=CC#N.C=CC1=CC=CC=C1 XECAHXYUAAWDEL-UHFFFAOYSA-N 0.000 description 54
- 229920000122 acrylonitrile butadiene styrene Polymers 0.000 description 54
- 239000004800 polyvinyl chloride Substances 0.000 description 49
- 229920000915 polyvinyl chloride Polymers 0.000 description 49
- 239000010410 layer Substances 0.000 description 29
- 235000011132 calcium sulphate Nutrition 0.000 description 20
- 238000004140 cleaning Methods 0.000 description 18
- 238000007667 floating Methods 0.000 description 17
- 238000003756 stirring Methods 0.000 description 13
- WUOACPNHFRMFPN-UHFFFAOYSA-N alpha-terpineol Chemical compound CC1=CCC(C(C)(C)O)CC1 WUOACPNHFRMFPN-UHFFFAOYSA-N 0.000 description 11
- 239000007864 aqueous solution Substances 0.000 description 11
- SQIFACVGCPWBQZ-UHFFFAOYSA-N delta-terpineol Natural products CC(C)(O)C1CCC(=C)CC1 SQIFACVGCPWBQZ-UHFFFAOYSA-N 0.000 description 11
- 229940116411 terpineol Drugs 0.000 description 11
- 238000005516 engineering process Methods 0.000 description 10
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- 239000007788 liquid Substances 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 239000004088 foaming agent Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 239000000080 wetting agent Substances 0.000 description 2
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- 239000004793 Polystyrene Substances 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 235000011114 ammonium hydroxide Nutrition 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 239000001110 calcium chloride Substances 0.000 description 1
- 229910001628 calcium chloride Inorganic materials 0.000 description 1
- 239000001175 calcium sulphate Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 1
- CSNNHWWHGAXBCP-UHFFFAOYSA-L magnesium sulphate Substances [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
- B29B17/02—Separating plastics from other materials
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
- B29B17/02—Separating plastics from other materials
- B29B2017/0203—Separating plastics from plastics
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29B—PREPARATION OR PRETREATMENT OF THE MATERIAL TO BE SHAPED; MAKING GRANULES OR PREFORMS; RECOVERY OF PLASTICS OR OTHER CONSTITUENTS OF WASTE MATERIAL CONTAINING PLASTICS
- B29B17/00—Recovery of plastics or other constituents of waste material containing plastics
- B29B17/02—Separating plastics from other materials
- B29B2017/0213—Specific separating techniques
- B29B2017/0217—Mechanical separating techniques; devices therefor
- B29B2017/0248—Froth flotation, i.e. wherein gas bubbles are attached to suspended particles in an aerated liquid
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/62—Plastics recycling; Rubber recycling
Abstract
The invention relates to a waste mixed plastic full-priority flotation separation method based on calcium sulfate pretreatment. The technical scheme is as follows: crushing a mixture formed by combining any two or more of PMMA, PVC, PS and ABS into mixed plastic particles, and using CaSO to obtain the particles4After pretreatment, PMMA, PS, ABS and PVC plastics are obtained in sequence through full-priority flotation separation. The method has the characteristics of simple operation, low cost, high separation efficiency, high recovery rate and purity and the like.
Description
Technical Field
The invention relates to a waste mixed plastic full-priority flotation separation method based on calcium sulfate pretreatment, and belongs to the technical field of waste plastic recovery.
Background
The rapid development and the large use of the plastic industry have led to a dramatic increase in the amount of waste plastics. Incineration and landfill are traditional ways of treating waste plastics, which not only cause serious environmental pollution, but also cause a great deal of waste of plastic resources. Therefore, the recycling research of waste plastics has attracted high attention worldwide. The recycling of the waste plastics mainly comprises three stages: collection, sorting and recycling, and sorting of plastics is the key and difficult point of recycling of waste plastics. The sorting technology of the waste plastics mainly comprises manual sorting, floating and sinking sorting, flotation, selective dissolution, electric sorting, spectrum sorting and the like. The manual sorting labor intensity is high, and the separation efficiency is low; the floating and sinking separation is to separate the waste mixed plastics based on the difference of the densities, and the waste plastics with similar densities cause poor applicability of the method; the solvents used for selective dissolution are mostly toxic and costly, and the electro-and spectroscopic sorting generally requires expensive sorting equipment and yields are low. The existing flotation technology capable of separating PMMA, PVC, PS and ABS comprises a boiling water treatment technology, a chemical oxidation technology, an advanced oxidation technology, an ammonia water treatment technology, an alkali treatment technology, a mechanochemical technology, a wetting agent inhibition technology and the like. The main problems of the technologies include the application of more chemical reagents which are not allowed by environmental supervision departments, higher energy consumption, poor test reproducibility, change of the chemical structure of the plastic surface layer and the like. Therefore, the development of a separation method with low cost, strong applicability and high separation efficiency is of great significance.
Disclosure of Invention
The invention provides a waste mixed plastic full-priority flotation separation method based on calcium sulfate pretreatment, aiming at overcoming the defects of the prior art in the separation of waste mixed plastics and aiming at realizing the separation and recovery of the mixed plastics with high selectivity and high recovery rate.
A waste mixed plastic full-priority flotation separation method based on calcium sulfate pretreatment is characterized in that waste mixed plastic is placed in a calcium sulfate solution and pretreated at the temperature of not lower than 20 ℃, and the pretreated waste mixed plastic is subjected to a priority flotation process to realize the separation of all plastics in the waste mixed plastic;
the waste mixed plastic comprises N of PMMA (polymethyl methacrylate), PVC (polyvinyl chloride), PS (polystyrene) and ABS (acrylonitrile-butadiene-styrene plastic), wherein N is an integer not less than 2.
The present invention has innovatively found that, in the case of a mixed plastic containing two or more of MMA, PVC, PS, and ABS, the difference between the components in the mixed plastic can be amplified by pretreating the mixed plastic with a calcium sulfate solution under the above-mentioned temperature conditions, and the components in the mixed plastic can be separated with high selectivity and high recovery rate by the preferential flotation method.
It was found that pretreatment in calcium sulfate solution at the temperature conditions described is critical to achieve selective separation of mixed plastics. The inventor researches and discovers that calcium sulfate is used as a modifier, and the mixed plastic can be differentially modified by controlling the temperature of the pretreatment process, so that the high-selectivity separation of each component of the mixed plastic can be unexpectedly realized.
Preferably, the particle size of the waste mixed plastic is 0.5-5 mm.
The inventor further finds that the solute concentration of the calcium sulfate solution in the pretreatment process is further regulated, and the recovery rate and selectivity of the plastic are further improved.
Preferably, the concentration of the solute of the calcium sulfate solution is 0.01-5 g/L; preferably 0.09 to 0.2 g/L.
The mass ratio of calcium sulfate in the calcium sulfate solution in the pretreatment process to the mixed plastic is further regulated and controlled, and the recovery rate and selectivity of the plastic are further improved.
Preferably, the calcium sulfate in the calcium sulfate solution is 0.0001-0.1 times of the total mass of the mixed plastic.
The inventor further researches and discovers that controlling the pretreatment temperature and time under the pretreatment condition helps to further improve the separation effect of the mixed plastics.
The temperature of pretreatment is 20-60 ℃; further preferably 40-60 ℃; more preferably 40 to 45 ℃.
The pretreatment process is carried out under the stirring condition, and the preferable stirring speed is 800-1200 r/min.
Preferably, the pretreatment time is 1-30 min; more preferably 10 to 30 min.
The invention is applied to the field of mixed plastic separation by adopting a preferential flotation method for the first time. The mixed plastics can be gradually floated and separated according to the priority order of PMMA, PS, ABS and PVC through the pretreatment process; thereby achieving the separation of each plastic component with high selectivity and high recovery rate.
In the invention, the preferential flotation process comprises N-1 times of flotation which are carried out in sequence.
In the present invention, if the mixed plastic is two types (N ═ 2) of PMMA, PS, ABS and PVC, the mixed plastic is subjected to the above-described pretreatment, and subjected to primary flotation, a plastic component that floats relatively preferentially is obtained from the upper layer of the flotation, and the lower layer is another plastic component, in the order of the above-described preferential flotation.
When the mixed plastics are three plastics (N is 3) of PMMA, PS, ABS and PVC, the mixed plastics are pretreated, first flotation is carried out, plastic components which float upwards relatively preferentially are obtained from the upper layer of the flotation according to the preferential flotation sequence, and the lower layer is the rest two mixed plastics. The mixed plastic of the lower layer is subjected to a second flotation, wherein the plastic floating preferentially relative to the plastic is located in the upper layer. Thereby realizing the selective separation of the three plastics.
When the mixed plastic is three plastics (N is 4) of PMMA, PS, ABS and PVC, the mixed plastic is pretreated, first flotation is carried out, plastic components (PMMA) which float upwards relatively preferentially are obtained from the upper layer of the flotation according to the preferential flotation sequence, and the remaining three mixed plastics (PS, ABS and PVC) are arranged at the lower layer. And carrying out secondary flotation on the mixed plastic of the lower layer, wherein the plastic floating preferentially relatively is positioned on the upper layer (PS), and the mixed plastic of the lower layer is ABS and PVC. And carrying out third flotation on the ABS and PVC on the lower layer to enable the ABS to float upwards, thereby realizing the selective separation of the four plastics.
Preferably, when N is more than or equal to 3, the mixed plastic at the bottom layer of the previous flotation is subjected to ultrasonic treatment and then subjected to flotation.
Research finds that when the mixed plastics are three or more of PMMA, PS, ABS and PVC, the pretreated mixed plastics are subjected to first flotation, so that plastic components floating relatively preferentially float upwards in the mixed plastics, and the mixed plastics sinking in the first flotation are subjected to ultrasonic treatment before the next flotation, so that the difference of the surface properties of the sinking mixed plastics in the first flotation is amplified, and the subsequent flotation and recovery are facilitated.
For example, when the mixed plastic is three plastics (N ═ 3) of PMMA, PS, ABS and PVC, the mixed plastic is subjected to the pretreatment, and subjected to the first flotation, plastic components that float relatively preferentially are obtained from the upper layer of the flotation, and the remaining two mixed plastics are obtained from the lower layer in the order of the preferential flotation. The lower layer of mixed plastic is subjected to ultrasonic treatment (to differentiate the properties of the lower layer of mixed plastic), and then subjected to secondary flotation, wherein the plastic floating relatively preferentially is positioned on the upper layer. Thereby realizing the selective separation of the three plastics.
For example, the mixed plastics are three plastics (N ═ 4) of PMMA, PS, ABS and PVC, the mixed plastics are subjected to the pretreatment, and after the first flotation, PMMA is obtained from the upper layer of the flotation, and the remaining three mixed plastics (PS, ABS and PVC) are obtained from the lower layer in the order of the preferential flotation. And (3) carrying out ultrasonic treatment on the mixed plastic at the lower layer, and then carrying out secondary flotation to enable PS to float upwards, wherein the mixed plastic at the lower layer is ABS and PVC. And carrying out secondary ultrasonic treatment on the lower layer mixed plastic subjected to the secondary flotation, and then carrying out tertiary flotation to enable the ABS to float upwards, wherein the bottom layer is PVC. Thereby realizing the selective separation of the four plastics.
Research shows that the first flotation of the pretreated mixed plastics can achieve a flotation recovery rate of 95% or more. In order to further improve the selectivity and the recovery rate of the mixed plastics of the lower layer of the first flotation, the ultrasonic power and the ultrasonic time can be controlled.
Preferably, the method comprises the following steps: the ultrasonic power is 100-600W.
The ultrasonic treatment time is 10min or more; preferably 10-30 min.
The inventor researches and discovers that the selectivity and the recovery rate of the lower mixed plastic after the first flotation can be unexpectedly ensured by controlling the ultrasonic power and the ultrasonic time.
The medium of the sonication process may be an aqueous solution.
After ultrasonic treatment, performing solid-liquid separation on the mixed plastic solution system after ultrasonic treatment, wherein the solid obtained by separation is the mixed plastic after ultrasonic treatment, and performing subsequent flotation on the mixed plastic after ultrasonic treatment.
In the invention, the flotation operation method can refer to the existing method.
Preferably, the medium for each flotation is water. Adding foaming agent in the flotation process, wherein the dosage of the foaming agent is 1-15 mg/L.
Preferably, the aeration amount is 100-800 mL/min.
Preferably, the time for each flotation does not exceed 20 min.
The invention provides a waste mixed plastic full-priority flotation separation method based on calcium sulfate pretreatment, which specifically comprises the following steps:
the method comprises the following steps: firstly, crushing waste mixed plastics into mixed plastic particles with the particle size of about 0.5-5 mm, and then placing the obtained particles in CaSO4The suspension is pretreated at the temperature of more than 20 ℃, and finally, the first flotation separation is carried out.
Step two: firstly, ultrasonic treatment 1 is carried out on the first flotation sinking product for a period of time at normal temperature, and then the second flotation separation is carried out after solid-liquid separation.
Step three: firstly, ultrasonic treatment 2 is carried out on the secondary flotation sinking product for a period of time at normal temperature, and then the third flotation separation is carried out after solid-liquid separation.
The technical scheme is based on the weak interaction force difference of calcium sulfate molecules and plastic surface molecules to carry out selective adhesion, so that the plastic is hydrophilic and sinks in the flotation process. It was preliminarily determined that the weak interaction may be cation-pi interaction and hydrogen bonding.
Advantageous effects
The invention innovatively realizes the selective separation of the mixed plastics with high selectivity and high recovery rate by the pretreatment of the calcium sulfate solution and the preferential flotation method.
According to the method, the recovery rate of the plastic subjected to the first flotation can be ensured to be up to 95% or more through the pretreatment, and researches also find that the recovery rate and the selectivity of the mixed plastic at the lower layer subjected to the first flotation can be ensured to be up to 90% or more by further performing ultrasonic treatment on the mixed plastic at the lower layer subjected to the first flotation.
The technical scheme of the invention does not need the technical barrier of adding a wetting agent as generally known in the prior art, and the high-selectivity separation between plastics can be realized by the simple pretreatment and flotation method.
In addition, the inventor also unexpectedly finds that the method can ensure the stability of the process effect of each batch of treatment compared with the prior art.
Drawings
FIG. 1 is a process flow diagram of example 1.
Detailed Description
The invention is further illustrated by the following examples, which are not to be construed in any way as imposing limitations upon the scope thereof. On the contrary, it is to be clearly understood that resort may be had to various other embodiments, modifications, and equivalents thereof which, after reading the scanning herein, may suggest themselves to those skilled in the art without departing from the spirit of the present invention and the scope of the appended claims.
Example 1
Cleaning and crushing mixed plastic containing PMMA, PVC, PS and ABS, taking 5g of plastic particles (the mass ratio of PMMA: PVC: PS: ABS is 1: 1: 1) with the particle diameter of 3-5 mm, and containing 0.1g/LCaSO at the temperature of 60 DEG C4And (2) magnetically stirring 100mL of the aqueous solution, wherein the stirring time is 15-30 min, the rotating speed is 800-1200 r/min, filtering to obtain plastic particles, performing flotation separation, wherein the applicable flotation conditions comprise 200mg/L of terpineol, 700-800 mL/min of aeration amount and 3min of flotation time, and the purity and recovery rate of PMMA are 97.1% and 97.3% respectively obtained by separation through flotation I. Then ultrasonic treatment (power 200W, ultrasonic time 15min) is carried out on the sinking products (PVC, PS and ABS), and then secondary flotation is carried out to obtain the floating product PS with purity of 92.3 percent and recovery rate of 94.6 percent and the sinking mixed products ABS and PVC. And (3) carrying out ultrasonic treatment on the sinking product (with the power of 100W and the ultrasonic time of 30min), and carrying out third flotation on the treated plastic mixture to obtain the ABS with the purity of 93.1%, the recovery rate of 99.3%, the PVC with the purity of 98.3% and the recovery rate of 93.4%.
Example 2
Cleaning and crushing mixed plastic containing PVC, PS and ABS, taking 4g of plastic particles with the particle diameter of 3-5 mm (the mass ratio of PVC to PS to ABS is 1: 1: 1), and using 100mL of CaSO with the concentration of 0.2g/L at the temperature of 45 DEG C4The aqueous solution entersPretreating, stirring for 10min, rotating at 200-300 r/min, filtering, cleaning, performing flotation separation, wherein the applicable flotation conditions comprise terpineol 200mg/L, aeration amount 700-800 mL/min and flotation time 3min, performing flotation I separation to obtain a floating product PS with purity of 95.6% and a recovery rate of 96.8%, performing ultrasonic treatment (power 600W and ultrasonic time 10min) on sinking products (PVC and ABS), and performing secondary flotation to obtain a floating product ABS with purity of 94.2%, a recovery rate of 97.1%, a sinking product PVC with purity of 97.5% and a recovery rate of 94.6%.
Example 3
Cleaning and crushing mixed plastic containing PVC, ABS and PMMA, taking 2g of plastic particles with the particle diameter of 3-5 mm (the mass ratio of PMMA to PVC to ABS is 1: 1: 1), and using 100mL of CaSO with the concentration of 0.09g/L at the temperature of 40 DEG C4And (3) treating the aqueous solution for 10min, wherein the stirring speed in the treatment process is 800r/min, filtering and cleaning are carried out, then flotation separation is carried out, the applicable flotation conditions are that terpineol is 200mg/L, the aeration quantity is 700-800 mL/min, the flotation time is 3min, the purity of the floating product PMMA obtained after the first flotation is 96.4%, and the recovery rate is 94.7%. The sinking mixture (PVC and ABS) is subjected to ultrasonic treatment (power 150W, ultrasonic time 25min), and then secondary flotation is carried out to obtain a floating product ABS with purity of 91.6%, recovery rate of 92.8%, a sinking product PVC with purity of 91.2% and recovery rate of 99.8%.
Example 4
Cleaning and crushing mixed plastic containing PVC and PMMA, taking 2 grams of plastic particles with the particle size of 3-5 mm respectively, and treating for 30min by using 100mL of CaSO4 aqueous solution with the concentration of 0.01g/L under the condition of 60 ℃, wherein the optimal flotation conditions are terpineol 200mg/L, the aeration quantity is 700-800 mL/min, and the flotation time is 3 min. The floating product PMMA obtained by flotation has the purity of 93.80 percent, the recovery rate of 98.21 percent, the sinking product PVC has the purity of 98.71 percent and the recovery rate of 94.23 percent.
Example 5
Cleaning and crushing mixed plastic containing PVC and PMMA, taking 2g of plastic particles with the particle size of 3-5 mm respectively, and using 100mL of CaSO with the concentration of 5g/L at the temperature of 20 DEG C4Treating the aqueous solution for 4min, wherein the optimal flotation conditions comprise 200mg/L of terpineol, 700-800 mL/min of aeration amount and flotationThe selection time is 3 min. The floating product PMMA obtained by flotation has the purity of 99.80 percent, the recovery rate of 92.23 percent, the sinking product PVC has the purity of 91.14 percent and the recovery rate of 99.91 percent.
Comparative example 1
The main difference compared with example 1 is that CaCl is used2The pretreatment agent is specifically operated as follows:
cleaning and crushing mixed plastic containing PVC, PS, ABS and PMMA, taking 4g of plastic particles (the mass ratio of PMMA: PVC: ABS: PS is 1: 1: 1) with the particle size of 3-5 mm, and using 100mL of CaCl with the concentration of 2g/L at the temperature of 40 DEG C2And (3) treating the aqueous solution for 15min, wherein the stirring speed in the treatment process is 800r/min, filtering, cleaning and then performing flotation separation, wherein the flotation conditions comprise 200mg/L of terpineol, 700-800 mL/min of aeration and 3min of flotation time. PVC, PS, ABS and PMMA float upwards, and flotation separation of mixed plastics cannot be realized. CaCl2Complete dissolution in water does not achieve surface adhesion.
Comparative example 2
The main difference compared with example 1 is that MgSO is used4The pretreatment agent is specifically operated as follows:
cleaning and crushing mixed plastic containing PVC, PS, ABS and PMMA, taking 4g of plastic particles with the particle diameter of 3-5 mm (the mass ratio of PMMA: PVC: ABS: PS is 1: 1: 1), and using 100mL of MgSO (MgSO) with the concentration of 2g/L at the temperature of 40 DEG4And (3) treating the aqueous solution for 15min, wherein the stirring speed in the treatment process is 800r/min, filtering, cleaning and then performing flotation separation, wherein the flotation conditions comprise 200mg/L of terpineol, 700-800 mL/min of aeration and 3min of flotation time. PVC, PS, ABS and PMMA float upwards, flotation separation of mixed plastics cannot be realized, MgSO4Complete dissolution in water does not achieve surface adhesion.
Comparative example 3
Compared with the example 1, the main difference is that the pretreatment temperature is 10 ℃, and the specific operation is as follows:
cleaning and crushing mixed plastic containing PVC, PS, ABS and PMMA, taking 4g of plastic particles with the particle diameter of 3-5 mm (the mass ratio of PMMA: PVC: ABS: PS is 1: 1: 1), and using 100mL of concentrated plastic particles at 10 DEG CCaSO with degree of 2g/L4And (3) treating the aqueous solution for 15min, wherein the stirring speed in the treatment process is 1000r/min, filtering, cleaning and then performing flotation separation, wherein the flotation conditions comprise 200mg/L of terpineol, 700-800 mL/min of aeration and 3min of flotation time. PVC, PS, ABS and PMMA float upwards, and flotation separation of mixed plastics cannot be realized. CaSO at too low a temperature4Cannot adhere to the plastic surface.
Comparative example 4
The main difference compared to example 1 is that the concentration of pretreated calcium sulphate is below the lower limit of the invention, the specific procedure is as follows:
cleaning and crushing mixed plastic containing PVC, PS, ABS and PMMA, taking 4g of plastic particles with the particle diameter of 3-5 mm (the mass ratio of PMMA: PVC: ABS: PS is 1: 1: 1), and using 100mL of CaSO with the concentration of 0.005g/L at the temperature of 40 DEG C4And (3) treating the aqueous solution for 15min, wherein the stirring speed in the treatment process is 1000r/min, filtering, cleaning and then performing flotation separation, wherein the flotation conditions comprise 200mg/L of terpineol, 700-800 mL/min of aeration and 3min of flotation time. PVC, PS, ABS and PMMA float upwards, and flotation separation of mixed plastics cannot be realized. Too low a concentration without sufficient CaSO4The method is adhered to the surface of the plastic, and the plastic floats upwards completely.
Example 6
Compared with the example 2, the main difference is that after the first flotation, the ultrasonic treatment is replaced by stirring, and the operation is as follows:
cleaning and crushing mixed plastic containing PVC, PS and ABS, taking 4g of plastic particles with the particle diameter of 3-5 mm (the mass ratio of PVC to ABS to PS is 1: 1: 1), and using 100mL of CaSO with the concentration of 1g/L at 40 DEG C4And (3) treating the aqueous solution for 15min, wherein the stirring speed in the treatment process is 1000r/min, filtering, cleaning and then performing flotation separation, wherein the flotation conditions comprise 200mg/L of terpineol, 700-800 mL/min of aeration and 3min of flotation time. The floating purity and yield of PMMA are 97.32% and 99.21% respectively, the sinking product is a mixture of PS and ABS, after stirring for 20min at 500r/min, the floating rates of ABS and PS are 40.12% and 60.41% respectively, and more accurate separation cannot be realized.
Example 7
After the first flotation, ultrasound with non-preferred power is used, and the operation is as follows:
cleaning and crushing PS and ABS mixed plastic, taking 4g of plastic particles with the particle size of 3-5 mm, wherein the PS and the ABS are respectively two grams, and 100mL of 1g/L CaSO is used4The solution was treated at 50 ℃ for 35min and subjected to flotation. The flotation conditions comprise 200mg/L of terpineol, 700-800 mL/min of aeration amount and 3min of flotation time. The floating rates of PS and ABS are respectively 2.26% and 3.31%, the ABS and PS are pretreated under the same condition and then are subjected to ultrasonic treatment for 60min under the condition of 50W power, the floating rates of PS and ABS are respectively 60.30% and 53.77%, and the flotation separation of ABS and PS cannot be realized. According to the embodiment and the proportion, the mixed plastics can be sequentially floated and separated according to the priority of PMMA, PS, ABS and PVC by the pretreatment of calcium sulfate and the preferable flotation method. Research also finds that the selectivity and the recovery rate of the bottom layer mixed plastic can be ensured on the premise of ensuring the flotation rate and the recovery rate of the plastic subjected to the first flotation by further controlling the calcium sulfate pretreatment parameters and carrying out ultrasonic treatment on the bottom layer mixed plastic subjected to the first flotation.
Claims (7)
1. A waste mixed plastic full-priority flotation separation method based on calcium sulfate pretreatment is characterized by comprising the following steps: the waste mixed plastic is placed in a calcium sulfate solution and is pretreated at the temperature of 20-60 ℃, and the pretreated waste mixed plastic is subjected to a preferential flotation process to realize the separation of all plastics in the waste mixed plastic;
the concentration of the solute of the calcium sulfate solution is 0.01-5 g/L;
the waste mixed plastic comprises N of PMMA, PVC, PS and ABS, and N is an integer not less than 2;
the preferential flotation process comprises N-1 times of flotation which are carried out in sequence;
when N is more than or equal to 3, performing ultrasonic treatment on the mixed plastic at the bottom layer of the previous flotation and then performing flotation;
the ultrasonic power is 100-600W; the ultrasonic treatment time is 10min or more;
and in the preferential flotation process, the plastics in the mixed plastics are sequentially floated and separated according to the priority of PMMA, PS, ABS and PVC.
2. The waste mixed plastic full-priority flotation separation method based on calcium sulfate pretreatment as claimed in claim 1, characterized in that: the concentration of the solute of the calcium sulfate solution is 0.09-0.2 g/L.
3. The waste mixed plastic full-priority flotation separation method based on calcium sulfate pretreatment as claimed in claim 1, characterized in that: the temperature of the pretreatment is 40-60 ℃.
4. The waste mixed plastic full-priority flotation separation method based on calcium sulfate pretreatment as claimed in claim 1, characterized in that: the pretreatment time is 1-30 min.
5. The waste mixed plastic full-priority flotation separation method based on calcium sulfate pretreatment as claimed in claim 1, characterized in that: the ultrasonic time is 10-30 min.
6. The waste mixed plastic full-priority flotation separation method based on calcium sulfate pretreatment according to any one of claims 1 to 5, characterized in that: the medium of each flotation is water, the aeration quantity is 100-800 mL/min, and the time of each flotation is not more than 20 min.
7. The waste mixed plastic full-priority flotation separation method based on calcium sulfate pretreatment as claimed in claim 1, characterized in that: the particle size of the waste mixed plastic is 0.5-5 mm.
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