CN108328804B

CN108328804B - Method for treating platinum-containing wastewater

Info

Publication number: CN108328804B
Application number: CN201810331938.XA
Authority: CN
Inventors: 曾坚贤; 吕超强; 刘国清; 曾令玮; 董志辉; 曾杰辉; 马溢昌
Original assignee: Hunan University of Science and Technology
Current assignee: Hunan University of Science and Technology
Priority date: 2018-04-13
Filing date: 2018-04-13
Publication date: 2020-11-03
Anticipated expiration: 2038-04-13
Also published as: CN108328804A

Abstract

The invention belongs to the technical field of chemical mass transfer and separation, and particularly relates to a method for treating platinum-containing wastewater, which comprises the following steps: (1) naturally settling; (2) treating the organic suspended matter; (3) treating high-concentration heavy metal; (4) pumping the supernatant treated in the step (3) to a transfer pool, and adjusting the pH value; (5) film treatment: pumping the wastewater in the step (4) to a membrane filtration device for membrane filtration, wherein a membrane component in the membrane filtration device comprises a Pt (IV) ion imprinting blending membrane; (6) membrane backwashing: and (4) taking out the Pt (IV) ions in the step (5) and backwashing, thereby recovering the Pt (IV) ions. The method disclosed by the invention is simple and strong in purification capacity, effectively removes harmful substances in the sewage, simultaneously recovers the target platinum, and obviously improves the environmental protection benefit and the economic benefit.

Description

Method for treating platinum-containing wastewater

Technical Field

The invention belongs to the technical field of chemical mass transfer and separation, and particularly relates to a method for treating platinum-containing wastewater.

Background

With the progress of industrial chemical combination urbanization, a large amount of wastewater is generated, the main sources are industrial wastewater and municipal sewage, and the industrial wastewater mainly refers to wastewater, sewage and waste liquid generated in the industrial production process, wherein the wastewater contains industrial production materials, intermediate products and products which are lost along with water, and pollutants generated in the production process. With the rapid development of industry, the variety and quantity of waste water are rapidly increased, the pollution to water bodies is more and more extensive and serious, and the health and the safety of human beings are threatened.

At present, the treatment methods of waste water are many and can be divided into four main categories according to the functions: the patent CN1232446C discloses a water treatment method, which applies a catalytic reduction method of a nano metal-membrane composite electrode to remove oxidation state pollutants in polluted water.

In the prior art, a molecular imprinting technology and a membrane preparation technology are combined to prepare a molecular imprinting blending membrane, the selective adsorption principle of membrane filtration and an imprinted polymer is fully utilized, the membrane is applied to water treatment, the pollutant emission is reduced, simultaneously, a target object can be selectively recovered, and the environmental protection benefit and the economic benefit are improved. However, the imprinting blend membrane prepared in the prior art usually has the phenomenon that the template molecules (ions) are embedded too deeply by the membrane matrix and are not easy to elute, so that the adsorption capacity and the adsorption rate of the imprinting blend membrane are greatly reduced.

In view of the above, it is desirable to provide a method for treating platinum-containing wastewater, which can effectively improve environmental and economic benefits.

Disclosure of Invention

The invention aims to provide a preparation method of an ion imprinting blending membrane which is stable in structural performance, not easy to peel off, high in adsorption capacity and high in adsorption rate.

The above purpose is realized by the following technical scheme: a method for treating platinum-containing wastewater comprises the following steps:

(1) and (3) natural sedimentation: removing turbidity matters and solid particles in the platinum-containing wastewater;

(2) treating the organic suspended matter;

(3) and (3) high-concentration heavy metal treatment: pumping the supernatant treated in the step (2) to a heavy metal treatment pool, adding an alkaline agent, and precipitating heavy metal ions;

(4) pumping the supernatant treated in the step (3) to a transfer pool, and adjusting the pH value;

(5) film treatment: pumping the wastewater in the step (4) to a membrane filtration device for membrane filtration, wherein membrane components in the membrane filtration device comprise Pt (IV) ion imprinting blend membranes, and the wastewater in the step (4) is filtered by the Pt (IV) ion imprinting blend membranes, and the Pt (IV) ion imprinting blend membranes adsorb and retain Pt (IV) ions in the wastewater;

(6) membrane backwashing: removing Pt (IV) ions in the step (5) and backwashing, and recovering Pt (IV) ions;

the preparation method of the Pt (IV) ion imprinting blending membrane comprises the following steps:

(S1) Synthesis of macromolecular chain transfer agent: adding methyl methacrylate, an RAFT reagent and a thermal initiator into a reactor according to a preset proportion, adding a solvent, sealing under protective gas for reaction, precipitating and filtering after the reaction is finished, and drying the obtained solid product to constant weight;

(S2) Synthesis of amphiphilic Block functional Polymer: adding 4-vinylpyridine, a thermal initiator and the macromolecular chain transfer agent synthesized in the step (S1) into a reactor according to a predetermined proportion, adding a solvent, sealing for reaction, precipitating and filtering after the reaction is finished, and drying the obtained solid product to constant weight;

(S3) synthesis of template ion-polymer complex: dispersing the amphiphilic block functional polymer synthesized in the step (S2) in a container filled with Pt (IV) template ion aqueous solution, sealing for reaction, filtering after the reaction is fully performed, washing with deionized water and freeze-drying;

(S4) casting: dissolving the template ion-polymer complex and the membrane substrate in the step (S3) in a solvent according to a predetermined ratio, stirring for a predetermined time to uniformly mix to obtain a casting solution, standing the casting solution for a predetermined time to remove bubbles, pouring the casting solution into a membrane forming plate, tiling the casting solution into uniform thin membranes, rapidly immersing the thin membranes into a deionized water bath at a predetermined temperature to perform membrane solidification, and washing the membranes to remove residual solvent;

(S5) elution: eluting Pt (IV) template ions by using an eluent to wash the membrane prepared in the step (S4) to obtain the Pt (IV) ion imprinting and blending membrane.

The method disclosed by the invention is simple and strong in purification capacity, effectively removes harmful substances in the sewage, simultaneously recovers the target platinum, and obviously improves the environmental protection benefit and the economic benefit.

The amphiphilic block functional polymer prepared by the invention comprises an A block and a B block, wherein the A block is a hydrophobic chain segment, has a polymer which has good compatibility with a membrane matrix and contains unsaturated bonds and is used for being entangled and fixed with the membrane matrix material; the B block is a hydrophilic chain segment, has the binding capacity with metal ions and contains a hydrophilic polymer with unsaturated bonds. In the present invention, the monomer for the A block is Methyl Methacrylate (MMA), and the monomer for the B block is 4-vinylpyridine (4 VP).

In the preparation process, MMA and RAFT reagent are firstly used for polymerization, then the obtained macromolecular chain transfer agent PMMA-RAFT is used as a macromolecular chain transfer agent to be polymerized with 4VP, finally, an amphiphilic block copolymer polymethyl methacrylate-poly (4-vinylpyridine) abbreviated as PMMA-b-P4VP is obtained, a PMMA-b-P4VP functional polymer is combined with template ions to form a metal organic compound, then a solvent such as dimethylacetamide (DMAc) is used for blending the compound and polyvinylidene fluoride (PVDF), and finally, the ionic imprinting blend membrane is prepared by using ionic water as a coagulation bath and using a non-solvent induced phase separation method (NIPS).

During the solidification process of the membrane matrix, the amphiphilic block functional polymer migrates to the membrane surface (also called surface segregation), so that the metal template moves to the surface of the membrane, and 3D cavities complementary to the metal template are formed on the surface of the solidified membrane after elution. The hydrophilic block of the functional polymer can rapidly move to the surface of the membrane through surface segregation in the membrane forming process, the membrane is not easy to elute due to too deep embedding of template ions by PVDF, and meanwhile, more hydrophilic blocks are arranged on the surface of the membrane to generate more binding sites, so that target ions can be rapidly combined with the binding sites on the surface of the membrane, and finally the selective adsorption capacity of the ion imprinting blending membrane is increased, the adsorption speed is high, and the service life is prolonged. Thirdly, with the membrane structure formed in such a way, the hydrophobic chains in the functional polymer can be sufficiently tightly entangled with the membrane matrix, so that it is difficult to peel off from the surface of the blotting membrane. The ion imprinting blending membrane gets rid of the limitation of using a cross-linking agent in the traditional imprinting process, and in addition, the synthesis of the amphiphilic block functional polymer can control the length of a B block by controlling the reaction time, so that the adsorption capacity and the adsorption rate of the ion imprinting blending membrane are improved.

Preferably, the further technical scheme is as follows: the specific steps in the step (2) are as follows: and (3) pumping the supernatant treated in the step (2) to an organic matter treatment system, wherein the organic matter treatment system comprises an anaerobic reactor, a biological sterilizer and a photochemical reactor which are sequentially connected.

Preferably, the further technical scheme is as follows: the organic matter treatment system also comprises an oil separator, and the rear end of the oil separator is connected with the anaerobic reactor.

Preferably, the further technical scheme is as follows: in the step (S1) and the step (S2), the RAFT agent, the thermal initiator, and the solvent are trithioester, azobisisobutyronitrile, and N, N-dimethylformamide, respectively.

The further technical scheme is as follows: the film substrate and the solvent in the step (S4) are polyvinylidene fluoride and N, N-dimethylacetamide, respectively.

Polyvinylidene fluoride (PVDF) is a semi-crystalline polymer with strong hydrophobicity, can be rapidly cured in water, has a good film forming effect, can be well intertwined and fixed with PMMA, has a stable ion imprinting blending film structure, and is not easy to fall off.

Further, the template ions are Pt (IV), and the template ion solution is a chloroplatinic acid solution.

The further technical scheme is as follows: the eluent in the step (S5) is a mixed solution of thiourea and hydrochloric acid. Experiments prove that the mixed solution of thiourea and hydrochloric acid with proper concentration has good elution effect on the Pt (IV) ions of the template.

The further technical scheme is as follows: removing polymerization inhibitor from methyl methacrylate by a flash chromatography column filled with alkaline alumina before use, and sealing at 2 ℃ and keeping out of the sun; recrystallizing the azodiisobutyronitrile in absolute ethyl alcohol for three times before use, and sealing and storing at 2 ℃ in a dark place; the polyvinylidene fluoride is dried in vacuum at 90 ℃ for 24h to remove water before use.

The further technical scheme is as follows: the specific process in the step (S1) is as follows: dissolving 15.0g of methyl methacrylate, 0.1g of trithiocarbonate reagent and 0.2g of azobisisobutyronitrile in 36.9mL of N, N-dimethylformamide, adding the mixed solution into a reactor, sealing, degassing, filling nitrogen in the reactor, placing the reactor in a preheated oil bath at 70 ℃ and keeping continuous stirring for reaction for 6 hours, cooling to room temperature after the reaction is finished, diluting the reacted mixture with tetrahydrofuran, precipitating in excessive low-temperature methanol for three times, and finally, vacuum-drying the obtained macromolecular chain transfer agent for 24 hours at 40 ℃.

The further technical scheme is as follows: the specific process in the step (S2) is as follows: 2.0g of the macromolecular chain transfer agent synthesized in step (S1), 3.0g of 4-vinylpyridine and 1mg of azobisisobutyronitrile were dissolved in 12.3mL of dimethylformamide; adding the mixed solution into a reactor, sealing, degassing, filling nitrogen into the reactor, placing the reactor in a preheated oil bath at 70 ℃ and keeping continuous stirring for reaction for 6 hours, cooling to room temperature after the reaction is finished, diluting the reacted mixture with dichloromethane, and precipitating in excessive low-temperature methanol for three times; finally, the amphiphilic block functional polymer obtained was dried under vacuum at 40 ℃ for 24 hours.

The further technical scheme is as follows: the specific process in the step (S3) is as follows: 4.00g of amphiphilic block functional polymer was dispersed in 100mL of a solution containing 50mg of template platinum (IV) ion at pH 0.5 ± 0.1, then sealed and kept under constant stirring at 25 ℃ for 24 hours, and then the resulting mixture was filtered, washed with deionized water and freeze-dried.

The further technical scheme is as follows: the specific processes in the steps (S4) and (S5) are: dissolving the template ion-polymer complex prepared in the step (S3) and polyvinylidene fluoride in N, N-dimethylacetamide according to a ratio of 3: 10, and mechanically stirring at 60 ℃ for 8 hours to prepare a casting solution, wherein the template ion-polymer complex and polyvinylidene fluoride together account for 15% of the weight of the casting solution, standing the casting solution for at least 3 hours to completely release bubbles, pouring the obtained casting solution on a clean glass plate, flatly paving the film into a uniform film at room temperature by using a scraper fixed to a gap of 250 micrometers, rapidly immersing the film in a deionized water bath at 25 ℃ for film solidification, and washing the formed film to remove residual solvent; elution of template ions was performed by rinsing the membrane with 1mol/L HCl solution containing 1% by weight of thiourea, and a pt (iv) ion imprinted blend membrane was obtained.

The further technical scheme is as follows: the synthetic process route of the trithioester is as follows: mixing n-dodecyl mercaptan, acetone and methyl trioctyl ammonium chloride in a mixing container, cooling, slowly dripping NaOH solution of a predetermined amount under the protection of nitrogen, continuously stirring for a predetermined time, and adding CS solution₂Is allowed to stand for a predetermined time after the solution turns red, a predetermined amount of CHCl is added₃Then adding a predetermined amount of NaOH solution, reacting for a predetermined time, and then adding a predetermined amount of water and concentrated hydrochloric acid; and (3) aerating to remove redundant acetone, performing suction filtration, collecting solids, adding isopropanol, filtering out insoluble solids, and spin-drying an isopropanol solution to obtain solids, and repeatedly recrystallizing the obtained solids in n-hexane to obtain yellow solid trithioester.

The further technical scheme is as follows: the specific process for synthesizing the trithioester comprises the following steps: RSH (n-dodecyl mercaptan) (48mL, 40.38g, 0.2mol), acetone (160mL), and methyltrioctylammonium chloride (phase transfer agent) (3.6mL, 3.2g, 0.008mol) were mixed into a 1L three-necked flask, cooled to 10 ℃ and protected with nitrogen. Slowly adding 50% NaOH solution (16.7g, time is more than 20min), continuing stirring for 15min, adding acetone (25mL, 20g, 0.3mol) solution dissolved with CS2(12mL, 15.2g, 0.2mol), adding CHCl3(24mL, 35.6g, 0.3mol) once after the solution turns red for 10min, adding 80g of 50% NaOH solution for more than 30min, reacting for one day, and adding 300mL of water and 50mL of concentrated hydrochloric acid. (the sequence of water and hydrochloric acid is not so-called and does not affect) (preferably, hydrochloric acid is added first) and then treatment is carried out: aerating (4-6h) to remove excessive acetone, filtering, collecting solid, adding 500mL isopropanol, filtering to remove insoluble solid, spin-drying isopropanol solution, and recrystallizing the obtained solid in n-hexane (80-100mL) for multiple times to obtain yellow solid. (filtrate is collected and then concentrated for recrystallization) (product color is matched, and recrystallization is not continued).

According to the invention, proper functional monomers are selected according to different target ions, and an amphiphilic block copolymer is synthesized by adopting a reversible addition fragmentation chain transfer polymerization (RAFT) method, wherein a hydrophobic chain segment can be effectively entangled with a film forming matrix to be effectively anchored in the film matrix after film forming, and a hydrophilic chain segment is enriched on the film surface due to surface segregation, so that a multifunctional film surface with hydrophilicity and ion recognition and combination capability is finally formed.

The ion imprinted membrane prepared by the invention does not need an additional crosslinking step, and after the membrane is cured and formed, metal ions are directly fixed on the membrane material and can generate effective recognition sites after elution. Compared with the complex crosslinking process required in the preparation of the traditional ion imprinting material, the method has certain convenience.

Experiments prove that the ion imprinted membrane prepared by the invention can show higher affinity to target ions, has large saturated adsorption capacity, high adsorption rate and high reusability, and only has about 5% of initial adsorption capacity loss after five cycles.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and, together with the description, serve to explain the invention and not to limit the invention.

FIG. 1 is a nuclear magnetic resonance hydrogen spectrum of PMMA and various PMMA-b-P4VP prepared by the invention;

FIG. 2 is an infrared spectrum of PMMA and various PMMA-b-P4VP prepared by the present invention;

FIG. 3 is an SEM image of various molds made in accordance with the present invention;

FIG. 4 is an ATR-FTIR spectrum of various molds made in accordance with the present invention;

FIG. 5 is a graph of static contact angle data for films of various molds made in accordance with the present invention;

FIG. 6 is a graph of dynamic contact angle data for films of various molds made in accordance with the present invention;

FIG. 7 is a graph of pure water flux data for membranes of various molds made in accordance with the present invention;

FIG. 8 is a graph showing the pH effect of an ion imprinted co-blended membrane prepared according to an embodiment of the present invention;

FIG. 9 is a schematic diagram of the selective adsorption results of an ion imprinted co-mixed membrane prepared according to an embodiment of the present invention;

FIG. 10 is a graph showing the results of a dynamic separation curve of an ion imprinted co-blended membrane prepared according to an embodiment of the present invention;

FIG. 11 is a graph showing the results of an adsorption study of an ion imprinted co-mixed membrane prepared according to an embodiment of the present invention in a filtration cycle system;

FIG. 12 is a schematic process diagram for the preparation of amphiphilic block functional polymers according to one embodiment of the present invention;

fig. 13 is a flowchart of a method for treating platinum-containing wastewater according to an embodiment of the present invention.

Detailed Description

The present invention will now be described in detail with reference to the drawings, which are given by way of illustration and explanation only and should not be construed to limit the scope of the present invention in any way. Furthermore, features from embodiments in this document and from different embodiments may be combined accordingly by a person skilled in the art from the description in this document.

Experimental materials

The main raw materials are shown in Table 1

Table 1 main reagent table in experiment

Examples

Removing polymerization inhibitor from methyl methacrylate by flash chromatography column filled with alkaline alumina before use, and sealing at 2 deg.C and keeping away from light; recrystallizing azobisisobutyronitrile in absolute ethyl alcohol for three times before use, sealing and storing at 2 ℃ in a dark place; before use, the polyvinylidene fluoride is dried in vacuum at 90 ℃ for 24h to remove water.

Synthesis of trithioester: reacting RSH (n-dodecyl mercaptan) (48 m)L, 40.38g, 0.2mol), acetone (160mL) and methyltrioctylammonium chloride (phase transfer agent) (3.6mL, 3.2g, 0.008mol) were mixed in a 1L three-necked flask, cooled to 10 ℃ and blanketed with nitrogen. Slowly adding 50% NaOH solution (16.7g, time more than 20min), stirring for 15min, and adding CS₂(12mL, 15.2g, 0.2mol) in acetone (25mL, 20g, 0.3mol) for more than 20min, after the solution turns red for 10min, CHCl was added in one portion₃(24mL, 35.6g, 0.3mol), 80g of 50% NaOH solution was added over 30min, the reaction was carried out for one day, 300mL of water and 50mL of concentrated HCl were added. (the sequence of water and hydrochloric acid is not so-called and does not affect) (preferably, hydrochloric acid is added first) and then treatment is carried out: aerating (4-6h) to remove excessive acetone, filtering, collecting solid, adding 500mL isopropanol, filtering to remove insoluble solid, spin-drying isopropanol solution, and recrystallizing the obtained solid in n-hexane (80-100mL) for multiple times to obtain yellow solid. (filtrate is collected and then concentrated for recrystallization) (product color is matched, and recrystallization is not continued).

Preparation of Pt (IV) ion imprinting blend membrane

(S1) Synthesis of macromolecular chain transfer agent: dissolving 15.0g of methyl methacrylate, 0.1g of trithiocarbonate reagent and 0.2g of azobisisobutyronitrile into 36.9mL of N, N-dimethylformamide, adding the mixed solution into a reactor, sealing, degassing, filling nitrogen into the reactor, then continuously stirring and reacting for 6 hours in a preheated oil bath at 70 ℃, cooling to room temperature after the reaction is finished, diluting the reacted mixture with tetrahydrofuran, precipitating in excessive low-temperature methanol for three times, and finally, vacuum-drying the obtained macromolecular chain transfer agent for 24 hours at 40 ℃; the product was designated PMMA-RAFT.

(S2) Synthesis of amphiphilic Block functional Polymer: 2.0g of the macromolecular chain transfer agent synthesized in step (S1), 3.0g of 4-vinylpyridine and 1mg of azobisisobutyronitrile were dissolved in 12.3mL of dimethylformamide; adding the mixed solution into a reactor, sealing, degassing, filling nitrogen into the reactor, placing the reactor in a preheated oil bath at 70 ℃ and keeping continuous stirring for reaction for 6 hours, cooling to room temperature after the reaction is finished, diluting the reacted mixture with dichloromethane, and precipitating in excessive low-temperature methanol for three times; finally, drying the obtained amphiphilic block functional polymer for 24 hours in vacuum at 40 ℃; the product was designated PMMA-b-P4 VP.

(S3) synthesis of template ion-polymer complex: dispersing 4.00g of amphiphilic block functional polymer in 100mL of a solution containing 50mg of template platinum (IV) ions and having a pH of 0.5 +/-0.1, sealing and keeping constant stirring at 25 ℃ for 24 hours, then filtering the resulting mixture, washing with deionized water and freeze-drying;

(S4) casting: dissolving the template ion-polymer complex prepared in the step (S3) and polyvinylidene fluoride in N, N-dimethylacetamide according to a ratio of 3: 10, and mechanically stirring at 60 ℃ for 8 hours to prepare a casting solution, wherein the template ion-polymer complex and polyvinylidene fluoride together account for 15% of the weight of the casting solution, standing the casting solution for at least 3 hours to completely release bubbles, then pouring the obtained casting solution on a clean glass plate, and flatly paving the casting solution at room temperature by using a scraper fixed to a gap of 250 mu m to form a uniform film; the film was then rapidly immersed in a 25 ℃ deionized water bath for film coagulation, followed by rinsing of the formed film to remove residual solvent.

(S5) elution: elution of template ions was performed by rinsing the membrane with 1mol/L HCl solution containing 1% by weight of thiourea, and a pt (iv) ion imprinted blend membrane was obtained. Denoted as Pt (IV) -IIM.

2. Preparation of non-imprinted blend membranes

The preparation method of the non-imprinted blend membrane is the same as above, except that no template ion is added.

3. Structure and performance characterization of amphiphilic block functional polymer PMMA-b-P4VP

(1) Nuclear magnetic resonance hydrogen spectrum (¹H NMR)

The nuclear magnetic resonance hydrogen spectra of PMMA and three amphiphilic block functional polymers PMMA-B-P4VP are shown in figure 1, wherein PP1, PP2 and PP3 are amphiphilic block functional polymers with three B block lengths respectively (the block length PP1 < PP2 < PP 3). Chemical shifts at 3.60ppm can be assigned to methoxy-CO-CH₃(MMA peak at a). In addition, the chemical shift at 1.25ppm is related to the hydroxyl groups at the RAFT termination. Such asOf three PMMA-b-P4VP copolymers¹The most significant change in this spectrum was shown by HNMR, which showed new chemical shifts at both 8.33ppm and 6.38ppm, which were assigned to the CH group of the pyridine ring (peak of 4VP at c-d). Other chemical shifts are also within¹Marking on HNMR spectrum. As can be seen from the figure, the chemical shift areas of 8.33ppm and 6.38ppm increase with polymerization time (from 2h to 10 h). These results indicate that the PMMA-b-P4VP copolymer has the same composition and that the hydrophilic chains P4VP are different in length among the different PMMA-b-P4VP amphiphilic block copolymers.

(2) Infrared Spectrum (FTIR)

The infrared spectrum of PMMA and three amphiphilic block functional polymers PMMA-b-P4VP is shown in figure 2, and the main absorption peaks are marked in the figure. At 1730cm^-1The peak of (a) is attributed to stretching vibration of a carbonyl group (C ═ O group is present in the PMMA segment). Compared with the PMMA spectrum, the polymer structure is obviously changed after RAFT polymerization of 4VP and PMMA. As shown, at 1599cm^-1And 1556cm^-1There are two new absorption bands corresponding to C ═ N and C — C stretching vibrations on the aromatic pyridine ring in the P4VP segment. This demonstrates the successful synthesis of the block functional polymer PMMA-b-P4VP after RAFT polymerization of 4VP and PMMA. The ratio of the B block peak intensity to the a block peak intensity increases with increasing reaction time. This also indicates that PMMA-B-P4VP block functional polymers of different B block lengths were synthesized.

¹The results of H NMR and FTIR demonstrate that the synthesized amphiphilic functional polymer is the desired product. In addition, because the molecular chains of PMMA and PVDF have an entanglement effect, when the amphiphilic functional polymer has a hydrophobic PMMA chain segment with higher molecular weight, the amphiphilic functional polymer can be firmly anchored on the PVDF of the membrane matrix, and the loss of the hydrophilic P4VP chain segment can be reduced to the maximum extent in the membrane preparation process.

(3) Gel Permeation Chromatography (GPC)

GPC analysis data of PMMA, PP1, PP2, and PP3 are shown in Table 2, and number average molecular weight (Mn), weight average molecular weight (Mw), Z average molecular weight (Mz), and peak molecular weight are shown in Table 2Amount (Mp) and degree of dispersion of the copolymer. From the results of GPC measurement, it was found that the number average molecular weights of PP1, PP2 and PP3 were 7.05X 10, respectively⁴，7.57×10⁴And 7.86X 10⁴g/mol. The number average molecular weight of PMMA was 6.45X 10⁴. It can be seen that the molecular weight of the diblock copolymer is much greater than that of PMMA. These results indicate that PMMA-B-P4VP block functional polymers with different B block molecular weights were successfully prepared. In conclusion, the amphiphilic block functional polymer PMMA-b-P4VP is successfully synthesized.

TABLE 2 GPC analysis data

^aDetection from GPC

Structure and performance characterization of Pt (IV) ion imprinting blend membrane

The casting solutions consisted of PVDF, additives, PP 1-PP 3 as described above, and various solvents such as DMAc, DMF or a mixture of DMF and THF as listed in Table 3.

TABLE 3 composition of casting solutions

(1) Scanning Electron Microscope (SEM)

Eight M0-M7 membranes were co-prepared, and the morphology of the surface and cross-section of the PVDF/PMMA-b-P4VP membranes was analyzed using SEM and is shown in FIG. 3. As can be seen from the figure, the PVDF/PMMA-b-P4VP films (M1 to M7) have substantially the same structural characteristics as the pure PVDF film (MO). Consists of a dense surface and a porous bottom layer with finger-shaped structures. However, PVDF/PMMA-b-P4VP films (M1 to M7) exhibited larger finger-like porous structures than pure PVDF film (MO). The formation of larger fingers on the porous bottom layer of PVDF/PMMA-b-P4VP membranes (M1 to M7) was due to the presence of the P4VP segment of the amphiphilic copolymer PMMA-b-P4VP in the casting solution, resulting in instantaneous delamination of the casting solution and thus formation of larger fingers. However, analysis of M1, M2 and M3 revealed that the film thickness followed the trend of M1 < M2 < M3, which is likely due to the amphiphilic copolymer PP3 with the longest P4VP chain in the M3 cast film solution, and that PP3 moved the fastest towards the film surface (faster is PP2 and slower is PP1) when the cast film solution was immersed in a water coagulation bath, and then formed the film skin layer quickly. The film shrinkage is lowest as further solvent flows from the dope solution and is stopped by the skin layer. Therefore, M3, which is about 125 μ M thick, is the thickest of the three. M4 prepared using DMF as the solvent had a smaller thickness compared to M3. This is probably due to the stronger solvent power of DMAc over PVDF compared to DMF. In other words, the mutual affinity between PVDF and DMAc is stronger than DMF, resulting in some entanglement of the solvents in the membrane system. But this was not confirmed. In addition, M5, which is about 29.47 μ M thick, is the thinnest of all films (MO to M7). This phenomenon is probably due to the formation of a porous (pore diameter from 200 to 300nm) network structure on the membrane surface at the initial stage of membrane formation. The solvent flows out during the phase inversion process, and the film shrinkage is the highest. Another possible reason may be that more THF in the mixed solvent evaporates, resulting in a thinner film being produced by phase inversion. Therefore, M5 is the thinnest. Similar phenomena are also observed by Yang et al. In addition, the presence of a spongy sublayer was observed between the skin and the large gaps of the fingers. This can be explained by the local evaporation of THF in the solvent mixture. The polymer concentration increases at the membrane surface, resulting in slower delamination and delayed large void formation. According to the analysis of M3 and M6, when a small amount of copolymer was added, the film thickness M6 < M3 was found. This result can be explained by thermodynamic factors. When small amounts of copolymer are used as additives in casting film solutions, transient liquid-liquid delamination can be induced, and the total film thickness increases with increasing copolymer concentration. However, further increases in copolymer concentration may retard the phase inversion rate and produce thinner films. Thus, film thickness M7 < M3.

(2) Porosity of the membrane

Eight membranes M0-M7 were prepared in total, and the porosity of the different membranes is shown in Table 4, and the porosity of M1-M3 is increased gradually, which can be confirmed by previous SEM analysis. With the increase of polymerization time, the hydrophilic chain P4VP is lengthened, and after film formation, the size of cross-section film pores is increased, so that the pore volume is increased and the porosity is increased. For M6, M3, M7, as the ratio of functional polymer to PVDF increased from 20% to 40%, the porosity of the membrane also increased, which is a result of enhanced porogenic action of the hydrophilic chains P4 VP. In addition, since the size of the skin pores of M5 is much larger than that of other membrane pores, the porosity is also larger by comprehensive analysis based on the principle that the smaller the membrane volume, the larger the porosity.

Table 4 porosity analysis data

a porosity of the membrane matrix is determined by ethanol soaking.

b determination of the film thickness from SEM images

(3) ATR-FTIR spectroscopy of films

The attenuated total reflection infrared spectra of M0-M7 are shown in FIG. 4, and the wave number of MO in the film is 1181cm^-1And 1072cm^-1Respectively correspond to-CF₂And C-F, 900-800cm^-1The vibrational peak in the range of (a) is attributed to the crystalline vibrational peak of PVDF; according to the analysis result of the amphiphilic block functional polymer PMMA-b-P4VP, the corresponding stretching vibration peak 1730cm^-1、1599cm^-1、1556cm^-1Respectively belonging to carbonyl C ═ O, C ═ N and C-C stretching vibration existing in an aromatic pyridine ring; as shown in FIG. 4(M1-M7) for the PMMA-b-P4VP/PVDF film, characteristic stretching vibration peaks respectively ascribed to PMMA-b-P4VP and PVDF appeared in the spectrum. 1730cm after film formation^-1The peak at (A) moved to 1728cm^-1This is a result of the interaction of the PMMA segment with the PVDF. The analysis shows that good compatibility behavior occurs between the amphiphilic functional polymer PMMA-b-P4VP and PVDF, and the compatibility behavior is required.

(4) Contact angle of film surface

Fig. 5 and 6 show the static and dynamic contact angles of the membrane, as shown, the static contact angle of the PVDF membrane is 74.5 °, reflecting its strong hydrophobicity. After being blended with PMMA-b-P4VP, the contact angles of the prepared PMMA-b-P4VP/PVDF blended film are all reduced, and the hydrophilicity of the PMMA-b-P4VP/PVDF blended film is enhanced; these analyses demonstrate that during the NIPS membrane fabrication process, the hydrophilic segments can effectively migrate to the surface of the membrane, and thus the hydrophilicity of the blot blend membrane can be enhanced by these effectively enriched hydrophilic groups. For M6, M3, M7, there was a tendency for the contact angle to decrease as the ratio of amphiphilic block polymer to PVDF increased from 20% to 40%. The explanation for this phenomenon is: in the NIPS process, the hydrophilic segment P4VP in the amphiphilic block polymer migrates to the surface of the membrane due to surface segregation, so that the hydrophilicity of the membrane surface is enhanced. In addition, the contact angle at which M5 started was large because the film surface was rough, while M3 among the dynamic contact angles exhibited a rapidly decaying dynamic contact angle, thus indicating that the film pores thereof had strong hydrophilicity. The MO film still exhibits strong hydrophobicity, so its dynamic contact angle does not undergo large decay over the test time. M1 exhibited enhanced hydrophilicity compared to MO. In the NIPS process, hydrophilic segments migrate to the upper surface of the membrane and to the surface of the membrane pores, and these enriched P4VP segments increase with increasing amphipathic copolymer content, resulting in further enhancement of membrane hydrophilicity. On the other hand, the presence of a macroporous structure also leads to a sharp decrease in the dynamic contact angle in a short time.

(4) Pure water flux

The effect of the different membranes on pure water flux is outlined in figure 7. Pure PVDF Membrane (MO) did not detect an effective pure water flux at an operating pressure of 0.1MPa due to its strong hydrophobicity. For M1-M3, the pure water flux of the amphiphilic block polymers is obviously increased due to the introduction of the amphiphilic block polymers, and in addition, when the synthesis time of the functional polymers is increased, the pure water flux of the PMMA-b-P4VP/PVDF blended membrane is increased from 61.77 to 80.44L M^-2h^-1. This is because the lengthening of the hydrophilic chain P4VP increases the size of the cross-sectional membrane pores, i.e., the membrane pores increase in size and enhance the passage of pure water, thus having a larger pure water flux. When the solvent is DMF + THF, the pure water flux of PMMA-b-P4VP/PVDF blended film is much larger than that of other solvent blended films, becauseThe size of the skin pores of the membrane is larger, so that the water resistance is reduced and the pure water flux is increased.

Performance study of Pt (IV) ion imprinted blend membranes

(1) Influence of pH

As shown in fig. 8, the imprinted blend membrane showed higher affinity for pt (iv) ions in the pH range of 0.5 to 3, but the adsorption capacity rapidly decreased as the pH of the solution increased to 3 to 4.5. These results may be attributed to the following reasons: at lower pH values, the metal ion platinum is reacted under acidic conditions with [ PtCl ] on the one hand₆]^2-The form exists; on the other hand, the ligand groups of functional polymers can be protonated in acidic solutions and then interact electrostatically [ PtCl ]₆]^2-Is attracted to the functional polymer and acts. At pH 3 to 4.5, the functional polymer is reacted with [ PtCl ] due to reduced protonation of the ligand groups of the functional polymer₆]^2-The electrostatic interaction between them is reduced and the adsorption capacity is reduced. In addition, when the pH value is higher than 4.5, Pt (OH) is used as platinum ion₄The form of the precipitate exists, so further adsorption tests are difficult to perform. Therefore, in order to obtain IIM with maximum adsorption of Pt (IV), the pH of the solution should be adjusted to 0.5.

(2) Selective adsorption

To evaluate the selective separation characteristics of Pt (IV) -IIM, competitive adsorption of various ions was investigated in a ternary mixed solution containing both Pt (IV), Cu (II) and Ni (II). The absorption amounts of Pt (IV) -IIM and NIM for Pt (IV), Cu (II) and Ni (II), respectively, are shown in FIG. 9. It can be seen that Pt (IV) -IIM has high selectivity to Pt (IV), and the existence of Cu (II) and Ni (II) ions in the solution at pH 0.5 + -0.1 has no significant effect on the adsorption amount of Pt (IV), which indicates that Pt (IV) -IIM can maintain good adsorption selectivity to platinum ions in the case of competing ions. This is because the imprinting effect of the imprinting process makes pt (iv) -IIM specifically recognize platinum ions. Pt (IV) -IIM preferentially recognizes Pt (IV), which demonstrates the successful formation of imprinted holes and the excellent shape memory effect of Pt (IV) -IIM. K of Pt (IV)_dThe value is obviously higher than that of other metalsK of ion_dThe value is obtained. Thus, the selectivity coefficients for Pt (IV) -IIM for Pt (IV)/Cu (II) and Pt (IV)/Ni (II) are 13.689 and 23.228, respectively. Obviously, in the acid aqueous solution with three metal ions coexisting, Pt (IV) -IIM has strong selective adsorption on Pt (IV).

(3) Pt (IV) separation during membrane filtration

Using 5mg/L of an aqueous Pt (IV) solution as the feed stock solution, the effective filtration area of the membrane was 38.5cm²Filtration experiments of Pt (IV) -IIM were performed at pH 0.5. + -. 0.1, and the breakthrough curves are shown in FIG. 10. Since there are many ion binding sites on the surface and pore walls of the original membrane, the pt (iv) ions in the feed stock solution were effectively adsorbed in the first 40 minutes. With the available binding sites occupied, a portion of the pt (iv) ions in the feed solution cannot be adsorbed and begin to leak. When the available binding sites are fully occupied, the permeate solution concentration reaches a maximum value, which is the feed stock solution concentration. Thus, the area is 38.5cm²The membrane of (2) can process 120mL of the feed stock solution until the breakthrough time (40 minutes). Furthermore, the content of P4VP chains was relatively low in this study. In practical application, the Pt (IV) adsorption capacity can be improved by introducing more P4VP chains into the membrane.

(4) Regeneration

To investigate the reusability of pt (iv) -IIM, the adsorption-elution cycle was repeated five times with the same pt (iv) -IIM under optimal conditions. The Pt (IV) -IIM which had been adsorbed to saturation was regenerated with 1mol/L HCl solution containing 1 wt% thiourea. The maximum adsorption capacity per cycle is shown in FIG. 11, and it is understood that Pt (IV) -IIM maintains a high adsorption level after 5 cycles. The initial adsorption capacity was only lost by about 5.1%, indicating that the pt (iv) -IIM is chemically stable and can be recycled many times while ensuring effective platinum absorption.

The method for treating the platinum-containing wastewater, as shown in the figure 13, comprises the following steps:

(2) treatment of organic suspensions: pumping the supernatant treated in the step (2) to an organic matter treatment system, wherein the organic matter treatment system comprises an oil separator, an anaerobic reactor, a biological sterilizer and a photochemical reactor which are sequentially connected;

(5) film treatment: pumping the wastewater in the step (4) to a membrane filtration device for membrane filtration, wherein a membrane module in the membrane filtration device comprises a Pt (IV) ion imprinting blending membrane prepared in the above example 1, and the wastewater in the step (4) is filtered by the Pt (IV) ion imprinting blending membrane, and the Pt (IV) ion imprinting blending membrane adsorbs and retains Pt (IV) ions in the wastewater;

(6) membrane backwashing: and (4) taking out the Pt (IV) ions in the step (5) and backwashing, thereby recovering the Pt (IV) ions.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims

1. A method for treating platinum-containing wastewater is characterized by comprising the following steps:

(2) treating the organic suspended matter;

2. The method for treating platinum-containing wastewater according to claim 1, wherein the specific steps in the step (2) are as follows: and (3) pumping the supernatant treated in the step (2) to an organic matter treatment system, wherein the organic matter treatment system comprises an anaerobic reactor, a biological sterilizer and a photochemical reactor which are sequentially connected.

3. The method of treating platinum-containing wastewater according to claim 2, wherein the organic matter treatment system further comprises an oil separator, and a rear end of the oil separator is connected to the anaerobic reactor.

4. The method for treating platinum-containing wastewater according to any one of claims 1 to 3, wherein in the steps (S1) and (S2), the RAFT agent, the thermal initiator and the solvent are trithioester, azobisisobutyronitrile and N, N-dimethylformamide, respectively; the membrane substrate and the solvent in the step (S4) are polyvinylidene fluoride and N, N-dimethylacetamide, respectively; the eluent in the step (S5) is a mixed solution of thiourea and hydrochloric acid.

5. The method for treating platinum-containing wastewater according to claim 4, wherein the methyl methacrylate is subjected to removal of polymerization inhibitor by a flash column filled with basic alumina before use, and is sealed and stored at 2 ℃ in a dark place; recrystallizing the azodiisobutyronitrile in absolute ethyl alcohol for three times before use, and sealing and storing at 2 ℃ in a dark place; the polyvinylidene fluoride is dried in vacuum at 90 ℃ for 24h to remove water before use.

6. The method for treating platinum-containing wastewater according to claim 5, wherein the specific process in the step (S1) is: dissolving 15.0g of methyl methacrylate, 0.1g of trithiocarbonate reagent and 0.2g of azobisisobutyronitrile in 36.9mL of N, N-dimethylformamide, adding the mixed solution into a reactor, sealing, degassing, filling nitrogen in the reactor, placing the reactor in a preheated oil bath at 70 ℃ and keeping continuous stirring for reaction for 6 hours, cooling to room temperature after the reaction is finished, diluting the reacted mixture with tetrahydrofuran, precipitating in excessive low-temperature methanol for three times, and finally, vacuum-drying the obtained macromolecular chain transfer agent for 24 hours at 40 ℃.

7. The method for treating platinum-containing wastewater according to claim 6, wherein the specific process in the step (S2) is: 2.0g of the macromolecular chain transfer agent synthesized in step (S1), 3.0g of 4-vinylpyridine and 1mg of azobisisobutyronitrile were dissolved in 12.3mL of dimethylformamide; adding the mixed solution into a reactor, sealing, degassing, filling nitrogen into the reactor, placing the reactor in a preheated oil bath at 70 ℃ and keeping continuous stirring for reaction for 6 hours, cooling to room temperature after the reaction is finished, diluting the reacted mixture with dichloromethane, and precipitating in excessive low-temperature methanol for three times; finally, the amphiphilic block functional polymer obtained was dried under vacuum at 40 ℃ for 24 hours.

8. The method for treating platinum-containing wastewater according to claim 7, wherein the specific process in the step (S3) is: 4.00g of amphiphilic block functional polymer was dispersed in 100mL of a solution containing 50mg of template platinum (IV) ion at pH 0.5 ± 0.1, then sealed and kept under constant stirring at 25 ℃ for 24 hours, and then the resulting mixture was filtered, washed with deionized water and freeze-dried.

9. The method for treating platinum-containing wastewater as claimed in claim 8, wherein the specific processes in the steps (S4) and (S5) are as follows: dissolving the template ion-polymer complex prepared in the step (S3) and polyvinylidene fluoride in N, N-dimethylacetamide according to a ratio of 3: 10, and mechanically stirring at 60 ℃ for 8 hours to prepare a casting solution, wherein the template ion-polymer complex and polyvinylidene fluoride together account for 15% of the weight of the casting solution, standing the casting solution for at least 3 hours to completely release bubbles, pouring the obtained casting solution on a clean glass plate, flatly paving the film into a uniform film at room temperature by using a scraper fixed to a gap of 250 micrometers, rapidly immersing the film in a deionized water bath at 25 ℃ for film solidification, and washing the formed film to remove residual solvent; elution of template ions was performed by rinsing the membrane with 1mol/L HCl solution containing 1% by weight of thiourea, and a pt (iv) ion imprinted blend membrane was obtained.

10. The method for treating platinum-containing wastewater according to claim 6, wherein the synthetic process route of the trithioester is as follows: mixing n-dodecyl mercaptan, acetone and methyl trioctyl ammonium chloride in a mixing container, cooling, slowly dripping NaOH solution of a predetermined amount under the protection of nitrogen, continuously stirring for a predetermined time, and adding CS solution₂Is allowed to stand for a predetermined time after the solution turns red, a predetermined amount of CHCl is added₃Then adding a predetermined amount of NaOH solution, reacting for a predetermined time, and then adding a predetermined amount of water and concentrated hydrochloric acid; and (3) aerating to remove redundant acetone, performing suction filtration, collecting solids, adding isopropanol, filtering out insoluble solids, and spin-drying an isopropanol solution to obtain solids, and repeatedly recrystallizing the obtained solids in n-hexane to obtain yellow solid trithioester.