CN110929426A - Membrane pollution simulation analysis method - Google Patents
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Abstract
The invention discloses a membrane pollution simulation analysis method, which is characterized in that by means of the polymer module function of Materials Studio software, a final optimization model is determined by building membrane material models such as classical polymer membranes, inorganic membranes and the like and conventional pollutant models such as inorganic, organic, colloid, microorganism and the like through systematic calculation and optimization, and a calculation interface model for different water solutions is built on the basis of the final optimization model. Meanwhile, a designed operation basic environment aperiodic system and periodic systems such as membrane materials and pollutants are subjected to reliable structural optimization and energy calculation by combining molecular mechanics and dynamics methods, and operation parameters are regulated and controlled to obtain a series of two-dimensional and three-dimensional result parameters such as membrane surface parameters, molecular configuration parameters, interaction parameters and water body solution components under long-term operation. The membrane pollution simulation analysis method can be used for performing various types of simulation aiming at different water bodies and different membranes, and is flexible, simple and novel.
Description
Technical Field
The invention belongs to the field of interdisciplines of material physics, and relates to a membrane pollution simulation analysis method.
Background
The membrane separation technology is widely applied to the field of water treatment due to the characteristics of easy operation, low energy consumption, high efficiency and the like. However, in practical operation, the biggest obstacle limiting its application is the problem of membrane fouling during filtration. Research has been conducted to date, and ultrafiltration membrane fouling is mainly caused by the fact that inorganic colloidal particles, soluble organic matter macromolecules, microorganisms and the like which are abundantly present in sewage gradually form a fouling layer on the membrane surface in the filtration process due to adsorption, interception and the like, and the fouling layer is gradually deposited on the membrane surface, so that membrane pores are narrowed or blocked, membrane flux is reduced, membrane performance is sharply reduced, the service life of the membrane is seriously reduced, membrane replacement frequency is greatly increased, and system operation cost is further improved. The method for measuring the membrane replacement frequency in industry is mainly through flux reduction and effluent quality reduction, but the method can only reflect the overall change of a membrane system and cannot actually represent the pollution degree of the membrane module through long-time operation. Therefore, the frequency of replacing the film cannot be accurately and efficiently determined.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provides a membrane pollution simulation analysis method and provides a constructive guide for accurately and efficiently making a membrane replacement frequency.
The technical scheme of the invention is summarized as follows: a membrane pollution simulation analysis method comprises the following steps:
(1) building a membrane material structure model and a pollutant model;
(2) and (3) building and calculating different water body solution filtering models according to the real solution filtering state of the two models built in the step (1).
The membrane material in the step (1) comprises a single-component polymer membrane material or 2-3 polymer blended membrane materials in polyvinylidene fluoride (PVDF), polyether sulfone (PES), Polysulfone (PSF), Polyamide (PAN), polymethyl methacrylate (PMMA), polypropylene (PP), polyvinyl chloride (PVC), Polyethylene (PE) and Cellulose Acetate (CA);
the building steps of the polymer film material structure model are as follows:
firstly, defining a repeating Unit of head and tail atoms of the selected polymer film material in a Materials Studio software polymer creation module, and using a Build Polymers/Repeat Unit tool;
constructing a polymer polymerization degree threshold domain with polymerization degree of 1-100 based on the repeating units, and using a Buildpolymers/Homopolymer tool;
secondly, filling 1-200 chains based on a Monte Carlo method (Amorphous Cell module/Amorphous Cell calibration/Setup/Task/defined Layer tool) on the basis of the single-chain initial model, building an Amorphous film three-dimensional space configuration of the polymer film material, and setting the void percentage of the built Amorphous polymer film according to the actual film pore structure;
thirdly, on the basis of the polymer amorphous film, performing geometric Optimization (ForciteCalculation/Setup/Task/Geometry Optimization tool) and annealing Calculation (ForciteCalculation/Setup/Task/Anneal tool), extracting a global optimal configuration, performing sufficient dynamic balance (ForciteCalculation/Setup/Task/Dynamics tool) under the conditions of fixed temperature and pressure, and counting the configuration characteristics of the amorphous film based on the structure of the dynamic balance;
and finally, calculating cohesive energy density based on the dynamic trajectory of the dynamic balance structure, and inspecting the strength of the intermolecular interaction force, thereby forming a selected polymer film material structure model with a stable structure.
The inorganic membrane material in the step (1) comprises a single-component inorganic membrane material of Carbon Nano Tubes (CNT), graphite, Graphene Oxide (GO) and cement or 2-3 inorganic substance blended membrane materials;
the building steps of the inorganic membrane material structure model are as follows:
firstly, the selected inorganic membrane material is arranged in a material Studio software inorganic substance creating module, an initial structure model of the inorganic membrane material is created by setting proper Size and functional Groups, and a Build menu/Build trinogranics/Size tool and a Build Inorganics/Groups tool are used;
then, geometric optimization and annealing calculation are carried out on the obtained initial structure model of the inorganic membrane material, a global optimal configuration is extracted, sufficient dynamic balance is carried out under the conditions of fixed temperature and pressure, and the characteristics of the configuration are counted based on the structure of the dynamic balance;
and then, according to the dynamic track of the obtained dynamically balanced inorganic membrane material structure model, calculating cohesive energy density, and investigating the strength of the intermolecular interaction force, thereby forming a selected inorganic membrane material structure model with a stable structure.
And (3) using tools and creating steps and a polymer film material structure model building step.
The step (1) contaminants include, but are not limited to, calcium carbonate (CaCO)3) Calcium sulfate (CaSO)4) The inorganic pollutants of (a), organic pollutants containing proteins (bovine serum albumin, ovalbumin, β -microglobulin), humic acids, colloidal pollutants containing silicic acid compounds, ferro-aluminium compounds, algae, and microbial pollutants of bacteria (staphylococcus aureus, escherichia coli).
Building an inorganic pollutant model: the crystal structure can be introduced according to the crystal information, and Build inorganic nano particles with various sizes are constructed by using a Build/Nanostructure/nanocruster tool; the Sketch tool was used to construct the anion, cation and water molecule structures: the rest steps are the same as the building steps of the polymer film material structure model;
building an organic pollutant model: carrying out initial state model building on the selected organic pollutants according to components and structures, and constructing a molecular structure by using Build Polymers/Repeat Unit tools and Sketch tools: the rest steps are the same as the building steps of the polymer film material structure model;
building a colloid pollutant model: constructing structures of negative ions, positive ions and water molecules according to the actual structures; the rest steps are the same as the organic pollutant model building process.
Building a microbial pollutant model: the steps are the same as the organic pollutant model building process.
The different water body solution filtration models in the step (2) comprise one or more models of but not limited to a single membrane material-solution model, a single membrane material-single pollutant-solution model, a single membrane material-composite pollutant-solution model and a composite membrane material-composite pollutant-solution model;
building a water body solution filtering model:
firstly, inputting the built membrane material model and the pollutant model into Materials Studio software, activating the built model file (". xsd"), and modifying the Cell Parameters (by using a Lattice Parameters/Lattice type tool and a Lattice Parameters/Advanced/Cell Origin tool);
isosurface was then created using Tool/Atom volumes & Surfaces, flipping the isosurface (translation of the molecular layer through 3D Movement): then, filling a solution by using a Monte Carlo-based method (Amorphous Cell module), building a solution and an Amorphous film structure, and deleting an isosurface after building;
and finally, performing geometric optimization and annealing calculation on the built model, extracting a global optimal configuration, performing sufficient dynamic balance under the conditions of fixed temperature and pressure, counting the characteristics of the configuration based on the structure of the dynamic balance, and building a structural model of the polymer film material by using tools and steps.
And (3) calculating filtering models of different water solutions in the step (2):
firstly, the calculation interfaces and processes of different water body solution filtering models can perform reliable structure optimization and energy calculation on a designed operation basic environment aperiodic system and periodic systems such as membrane materials and pollutants by using a molecular mechanics dynamics method; the method comprises the steps that a Smart tool comprising a plurality of structure optimization methods and automatic adjustment optimization methods and a plurality of temperature control functions (Vehicity Scale, Nose, Andersen, Berendsen and NHL) and a plurality of pressure control functions (Andersen, Berendsen, Parrinello and Souza-Martins) realize configuration simulation and structure anisotropy maximization, and batch processing of calculation tasks such as calculation and analysis of structures of a plurality of membrane materials and interaction energy is realized;
secondly, calculating result parameters of different water body solution filtering models comprise two-dimensional/three-dimensional space distribution information of atoms, wherein the two-dimensional/three-dimensional space distribution information of adsorption structures, molecular configuration changes, interaction energy, interaction force real-time changes and the like are obtained when molecular dynamics simulation is carried out under the condition of large temperature and pressure range changes; meanwhile, the dynamics calculation track file and the structure-related properties can be obtained: a correlation function file such as a bond length, a bond angle, a torsion angle time distribution curve, a concentration distribution curve, a density field, a radial distribution function (coordination number), probability distribution of a radius of gyration, spatial orientation, average speed along a certain direction, a temperature distribution curve, a diffusion coefficient, a dipole autocorrelation function, a stress autocorrelation function, an ensemble fluctuation function, a distance orientation rotation correlation function (dielectric relaxation, dipole relaxation), a displacement time correlation function, a speed autocorrelation function (diffusion coefficient) and the like; finally extracting the change curve of the interaction energy and the solution composition along with the time after the simulation is finished, the solution concentration curve and the pollutant configuration parameters, and evaluating the membrane performance from the surface pollution phenomenon of the macroscopic material corresponding to the microscopic molecular scale.
Has the advantages that:
1. according to the invention, by building membrane material models such as classical polymer membranes, inorganic membranes and the like and conventional pollutant models such as inorganic, organic, colloid, microorganism and the like, various types of simulation can be carried out on different water bodies and different membranes, and calculation can be carried out through a platform, so that the method is flexible, simple and novel.
2. The invention evaluates the membrane performance from the surface pollution phenomenon of the macroscopic material corresponding to the microscopic molecular scale, and has important guiding significance for the membrane component replacement frequency and the membrane material preparation optimization.
Drawings
FIG. 1 is a schematic diagram of a polyvinylidene fluoride membrane-calcium carbonate-water solution interaction model;
FIG. 2 is a schematic diagram of a polyamide membrane-bovine serum albumin-aqueous solution interaction model;
FIG. 3 is a schematic diagram of a cellulose acetate membrane-Escherichia coli-aqueous solution interaction model;
FIG. 4 is a schematic diagram of a carbon nanotube film-silicic acid compound-aqueous solution interaction model;
FIG. 5 is a schematic diagram of a model of graphene oxide membrane-humic acid-water solution interaction;
FIG. 6 is a schematic diagram of a polypropylene membrane-calcium sulfate-water solution interaction model.
Has the advantages that:
the comprehensive evaluation of simulation shows that the organic matter membrane has the best permeability, but the maximum interaction energy with the surface of the pollutant and the most serious surface pollution condition, and the pollution degree is reduced along with the increase of the surface hydrophilicity of the organic matter membrane, and the pollution resistance of the hydrophilic membrane is better than that of the hydrophobic membrane under the same condition. Meanwhile, the interaction energy of bacteria and all the membrane surfaces is the largest, and the design of antibacterial property modification on the membrane surfaces is important.
Detailed Description
The invention is further described below with reference to the following figures and specific examples.
Example 1: polyvinylidene fluoride membrane-calcium carbonate-water body solution interaction model building and calculating
Initial state model building of polyvinylidene fluoride (PVDF) membrane: firstly, defining a repeating Unit of PVDF head and tail atoms in a Materials Studio software polymer creation module, and using a Build Polymers/Repeat Unit/VDF tool, wherein an initial polymer file is named as VDF.xsd; calling a VDF (visual desktop Format) xsd file to construct a polymer with the polymerization degree of 50, and constructing a single-Chain initial model by using a Buildpolymers/Homopolymer/Chain Length/50 tool; secondly, filling 100 chains based on a Monte Carlo method (Amorphous Cell module/Amorphous Cell calibration/Setup/Task/ConsinedLayer tool), building an Amorphous film three-dimensional space configuration of the PVDF film, and setting the void percentage of the built polymer Amorphous film according to the actual film pore structure; thirdly, on the basis of the polymer amorphous film, performing geometric Optimization (a Forcite Calculation/Setup/Task/Geometry Optimization tool) and annealing Calculation (a Forcite Calculation/Setup/Task/analysis tool), extracting a global optimal configuration, performing sufficient dynamic balance (the Forcite Calculation/Setup/Task/Dynamics tool) under the conditions of fixed temperature and pressure, and counting the configuration characteristics of the amorphous film based on the structure of the dynamic balance; finally, based on the dynamic locus of the dynamic balance structure, calculating cohesive energy density, and investigating the strength of the interaction force among molecules, thereby forming a selected PVDF membrane structure model of a stable structure, which is named as PVDF.xsd;
calcium carbonate (CaCO)3) Initial state model building: first, in the Materials Studio software inorganics creation module, according to CaCO3Setting molecular formula calcium carbonate molecular Size, creating an initial structure model, and using a Build menu/BuildInorganics/Size tool; simultaneously, using a Sketch tool to construct structures of anions, cations and water molecules, then, carrying out geometric optimization and annealing calculation on the obtained calcium carbonate material initial state structure model, extracting global optimal configuration, carrying out sufficient dynamic balance under the conditions of fixed temperature and pressure, and counting the configuration characteristics of the calcium carbonate material based on the structure of the dynamic balance; then, according to the dynamic track of the obtained dynamically balanced inorganic membrane material structure model, calculating cohesive energy density, and investigating the strength of the intermolecular interaction force, thereby forming the selected CaCO with a stable structure3Structural model, named CaCO3Xsd. The construction steps of the tool and the creation steps are the same as those of a PVDF membrane material structure model;
building a polyvinylidene fluoride membrane-calcium carbonate-water solution filtering model: firstly, the constructed PVDF membrane structure model file (PVDF. xsd) and CaCO3Structure model file (CaCO)3Xsd) into the Materials Studio software, activating the built model file, modifying the cell parameters-Length: a, b and c are all 30.0 multiplied by 10-10m, Angles: α, γ all 90o (using the Lattice Parameters/Lattice type/3D tricinic Tool and the Lattice Parameters/Advanced/Cell Origin Tool), then, using the Tool/Atom Vluminaces&Surfaces creates iso-Surfaces, flips the iso-Surfaces (translation of the molecular layer through 3D Movement): thereafter, using a Monte Carlo-based method (Amorphous Cell Module/Amorphous Cell calibration/Task/packaging, with a sensitivity of 0.9g/cm3) Drawing H2Filling a solution into an O molecular structure, building a solution and an amorphous film structure, and deleting an isosurface after building; finally, the built model is geometrically processedOptimizing, annealing and calculating, extracting a global optimal configuration, carrying out sufficient dynamic balance under the conditions of fixed temperature and pressure, counting the characteristics of the configuration based on the structure of the dynamic balance, and using tools and steps as the steps of building a PVDF membrane material structure model.
Calculating a polyvinylidene fluoride membrane-calcium carbonate-water body solution filtering model: firstly, the calculation interfaces and processes of different water body solution filtering models can perform reliable structure optimization and energy calculation on a designed operation basic environment aperiodic system and periodic systems such as membrane materials and pollutants by using a molecular mechanics dynamics method; the method comprises the steps that a Smart tool comprising a plurality of structure optimization methods and automatic adjustment optimization methods and a plurality of temperature control functions (Vehicity Scale, Nose, Andersen, Berendsen and NHL) and a plurality of pressure control functions (Andersen, Berendsen, Parrinello and Souza-Martins) realize configuration simulation and structure anisotropy maximization, and batch processing of calculation tasks such as calculation and analysis of structures of a plurality of membrane materials and interaction energy is realized; secondly, calculating result parameters of different water body solution filtering models comprise two-dimensional/three-dimensional space distribution information of atoms, wherein the two-dimensional/three-dimensional space distribution information of adsorption structures, molecular configuration changes, interaction energy, interaction force real-time changes and the like are obtained when molecular dynamics simulation is carried out under the condition of large temperature and pressure range changes; meanwhile, the dynamics calculation track file and the structure-related properties can be obtained: bond length, bond angle, torsion angle time distribution curve, concentration distribution curve, density field, radial distribution function (coordination number), probability distribution of radius of gyration, spatial orientation, average velocity in a certain direction, temperature distribution curve, diffusion coefficient, dipole autocorrelation function, stress autocorrelation function, ensemble fluctuation function, distance orientation rotation correlation function (dielectric relaxation, dipole relaxation), displacement time correlation function, velocity autocorrelation function (diffusion coefficient), and the like.
Finally extracting the change curves of the interaction energy and the solution composition along with time, the solution concentration curve and the pollutant configuration parameters after the simulation is finished, and finding that the interaction energy of the polyvinylidene fluoride membrane and the calcium carbonate is higher, the filtered calcium carbonate only exists on the surface of the membrane, the adhesion is basically avoided in the membrane body, the change of the solution composition and the concentration is smaller, and the result of the size screening effect is consistent with that of the larger size of the calcium carbonate compared with the surface aperture of the macroscopic membrane, so that the polyvinylidene fluoride membrane has better pollution resistance to the calcium carbonate.
Example 2: establishing and calculating interaction model of polyamide membrane-bovine serum albumin-water body solution
Initial state model building of Polyamide (PAN) membrane: firstly, defining repeating units of PAN head and tail atoms in a Materials Studio software polymer creation module, and naming an initial polymer file as AN.xsd; calling an AN.xsd file, constructing a polymer with the polymerization degree of 100, and constructing a single-chain initial model; secondly, filling 150 chains based on a Monte Carlo method, building an amorphous thin film three-dimensional space configuration of the PAN, and setting the void percentage of the built PAN amorphous thin film according to the actual pore structure of the PAN; then, the creating step and the tool using step are the same as those of the initial model building step of the PVDF membrane in the embodiment 1, and the structural model of the PAN membrane with the stable structure is obtained and named as PAN.
Bovine Serum Albumin (BSA) initial state model set up: firstly, in a Materials Studio software organic matter creating module, setting the Size of a bovine serum albumin molecule and a functional group according to a BSA molecular formula to create an initial structure model, and using a Build menu/Build Inorganics/Size tool and a Build Inorganics/groups tool; thereafter, the procedure was followed using tools like example 1- -calcium carbonate (CaCO)3) And (3) an initial state model building step to obtain a BSA structure model of a stable structure, which is named as BSA.
Establishing and calculating a polyamide membrane-bovine serum albumin-water solution filtering model: the steps of establishing and using tools are the same as those of the polyvinylidene fluoride membrane-calcium carbonate-water solution filtration model and the calculation step in the embodiment 1.
Finally, extracting the change curve of the interaction energy and the solution composition along with the time after the simulation is finished, the solution concentration curve and the pollutant configuration parameters, and finding that the interaction energy of the polyamide membrane and the bovine serum albumin is low, the bovine serum albumin is firmly attached to the surface of the membrane after filtration, the membrane body is basically not attached, the solution composition and the concentration change are large, the polyamide membrane is basically intercepted in the filtration process and is consistent with the result of the macroscopic size screening effect, and the situation that the pollution resistance of the polyamide membrane to the bovine serum albumin is poor is also explained.
Example 3: cellulose acetate membrane-escherichia coli-water solution interaction model building and calculation
Initial state model building of Cellulose Acetate (CA) membrane: firstly, defining a repeating unit of a head atom and a tail atom of CA in a Materials Studio software polymer creating module, and naming an initial polymer file as CA-0. xsd; calling a CA-0.xsd file, constructing a polymer with the polymerization degree of 80, and constructing a single-chain initial model; secondly, filling 100 chains based on a Monte Carlo method, building a three-dimensional space configuration of the amorphous film of the CA film, and setting the percentage of gaps of the built amorphous film of the CA film according to the actual film pore structure; then, the step of creating and the step of constructing the initial model of the PVDF membrane in the same manner as in embodiment 1 are performed, and a CA membrane structure model of a stable structure is obtained, which is named as CA.
E.coli (Coli) initial state model building: firstly, setting the Size of escherichia Coli according to a Coli molecular structure in Materials Studio software, creating an initial structure model, and using a Build menu/Build enterprises/Size tool; thereafter, the procedure was followed using tools like example 1- -calcium carbonate (CaCO)3) And (5) an initial state model building step to obtain a Coli structure model with a stable structure, which is named Coli.
Constructing and calculating a cellulose acetate membrane-escherichia coli-water solution filtering model: the steps of establishing and using tools are the same as those of the polyvinylidene fluoride membrane-calcium carbonate-water solution filtration model and the calculation step in the embodiment 1.
Finally extracting the change curve of the interaction energy and the solution composition along with time, the solution concentration curve and the pollutant configuration parameters after the simulation is finished, and finding that the interaction energy of the cellulose acetate membrane and the escherichia coli is higher, the escherichia coli is rarely attached to the membrane surface after filtration, and the membrane surface has better hydrophilicity; the solution composition and concentration change is large, and the solution is basically intercepted in the filtering process, which indicates that the cellulose acetate membrane has strong inhibition effect on escherichia coli.
Example 4: building and calculating carbon nanotube film-silicic acid compound-water solution interaction model
Carbon Nanotube (CNT) film initial state model building: firstly, defining a repeating unit of a CNT head and tail atom in a Materials Studio software polymer creating module, and naming an initial polymer file as CNT-0. xsd; calling a CNT-0.xsd file to construct a single-chain initial model; secondly, filling 100 chains based on a Monte Carlo method, building an amorphous thin film three-dimensional space configuration of the CNT film, and setting the percentage of gaps of the built CNT amorphous thin film according to the actual film pore structure; then, the creating step and the tool building step are the same as those in embodiment 1, namely, the initial state model building step of the PVDF film, and a CNT film structure model with a stable structure is obtained, which is named as CNT.
Initial state model building of silicic acid compound (SiO): firstly, setting the Size of a silicic acid compound according to the SiO molecular structure in Materials Studio software, creating an initial structure model, and using a Build menu/BuildInorganics/Size tool; thereafter, the procedure was followed using tools like example 1- -calcium carbonate (CaCO)3) And an initial state model building step, namely obtaining a SiO structure model of a stable structure, which is named as SiO.
Building and calculating a carbon nanotube film-silicic acid compound-water solution filtering model: the steps of establishing and using tools are the same as those of the polyvinylidene fluoride membrane-calcium carbonate-water solution filtration model and the calculation step in the embodiment 1.
Finally, the interaction energy, the solution composition change curve with time, the solution concentration curve and the pollutant configuration parameters after the simulation is finished are extracted, and the fact that the carbon nanotube film and the silicic acid compound have high interaction energy, the silicic acid compound is rarely attached to the surface after filtration, the solution composition and concentration change are large, and the carbon nanotube film is basically intercepted in the filtration process is found, namely the carbon nanotube film has strong performance of resisting the silicic acid compound pollution.
Example 5: graphene oxide film-humic acid-water solution interaction model building and calculation
Establishing an initial state model of a Graphene Oxide (GO) film: firstly, defining a repeating unit of GO head and tail atoms in a Materials Studio software polymer creation module, and naming an initial polymer file as GO-0. xsd; calling a GO-0.xsd file to construct a single-chain initial model; secondly, filling 150 chains based on a Monte Carlo method, building an amorphous thin film three-dimensional space configuration of the GO film, and setting the percentage of gaps of the built GO amorphous thin film according to the actual film pore structure; and then, a step of establishing and a step of establishing an initial state model of the PVDF membrane by using a tool are the same as those in the embodiment 1, so that a GO membrane structure model with a stable structure is obtained and named as GO.
Building an initial state model of Humic Acid (HA): firstly, setting the Size of humic acid according to HA molecular structure in Materials Studio software, creating an initial structure model, and using a Build menu/Build enterprises/Size tool; thereafter, the procedure was followed using tools like example 1- -calcium carbonate (CaCO)3) And an initial state model building step to obtain an HA structure model of a stable structure, which is named as HA.
Establishing and calculating a graphene oxide film-humic acid-water solution filtering model: the steps of establishing and using tools are the same as those of the polyvinylidene fluoride membrane-calcium carbonate-water solution filtration model and the calculation step in the embodiment 1.
Finally, extracting the change curve of the interaction energy and the solution composition along with time, the solution concentration curve and the pollutant configuration parameters after the simulation is finished, and finding that the interaction energy of the graphene oxide film and the humic acid is higher, the humic acid is hardly attached to the surface after the filtration, the solution composition and concentration change are larger, and the graphene oxide film is basically intercepted in the filtration process, thereby showing that the graphene oxide film has very strong humic acid pollution performance.
Example 6: establishing and calculating polypropylene film-calcium sulfate-water body solution interaction model
Initial state model building of polypropylene (PP) film: and (3) establishing and using a tool in the same steps as the step of establishing the initial state model of the PVDF membrane in the embodiment 1 to obtain the PP membrane structure model with a stable structure, which is named as PP.
Calcium sulfate (CaSO)4) Initial state model building: procedure for creation and use of tools like example 1- -calcium carbonate (CaCO)3) An initial state model building step to obtain the CaSO with a stable structure4Structural model, named CaSO4.xsd。
Building and calculating a polypropylene film-calcium sulfate-water solution filtering model: the steps of establishing and using tools are the same as those of the polyvinylidene fluoride membrane-calcium carbonate-water solution filtration model and the calculation step in the embodiment 1.
Finally extracting the change curve of interaction energy and solution composition along with time, the concentration curve of the solution and the configuration parameters of pollutants after the simulation is finished, and finding that the interaction energy of the polypropylene film and calcium sulfate is lower, and the filtered calcium sulfate is attached to the surface of the film and tends to permeate into the film body; the composition and concentration of the solution are changed slightly, and a small part of the solution is intercepted and attached to the surface of the membrane in the filtration process, so that the polypropylene membrane has lower calcium sulfate pollution resistance.
The following table shows the membrane materials and contaminants in the other 76 examples:
it should be understood that the embodiments and examples discussed herein are illustrative only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims.
Claims (7)
1. A membrane pollution simulation analysis method is characterized by comprising the following steps:
(1) building a membrane material structure model and a pollutant model;
(2) and (3) building and calculating different water body solution filtering models according to the real solution filtering state of the two models built in the step (1).
2. The method of claim 1, wherein the membrane fouling is analyzed by simulation,
the membrane material in the step (1) comprises a single-component polymer membrane material selected from polyvinylidene fluoride, polyethersulfone, polysulfone, polyamide, polymethyl methacrylate, polypropylene, polyvinyl chloride, polyethylene and cellulose acetate or 2-3 polymer blend membrane materials selected from the group;
the building steps of the polymer film material structure model are as follows:
firstly, defining a repeating Unit of head and tail atoms of the selected polymer film material in a Materials Studio software polymer creation module, and using a Build polymers/Repeat Unit tool;
constructing a polymer polymerization degree threshold domain with the polymerization degree of 1-100 based on the repeating units, and using Build Polymers/Homopolymer tool;
secondly, filling 1-200 chains based on a Monte Carlo method on the basis of the single-chain initial model, building an amorphous film three-dimensional space configuration of the polymer film material, and setting the percentage of gaps of the built amorphous polymer film according to the actual film pore structure;
thirdly, geometric optimization and annealing calculation are carried out on the basis of the polymer amorphous film, a global optimal configuration is extracted, sufficient dynamic balance is carried out under the conditions of fixed temperature and pressure intensity, and the configuration characteristics are counted on the basis of a dynamic balance structure;
and finally, calculating cohesive energy density based on the dynamic trajectory of the dynamic balance structure, and inspecting the strength of the intermolecular interaction force, thereby forming a selected polymer film material structure model with a stable structure.
3. The method according to claim 1, wherein the inorganic membrane material of step (1) comprises a single-component inorganic membrane material selected from carbon nanotube, graphite, graphene oxide, cement, or a mixture of 2-3 inorganic membrane materials;
the building steps of the inorganic membrane material structure model are as follows:
firstly, the selected inorganic membrane material is placed in a material Studio software inorganic substance creating module, an initial structure model of the inorganic membrane material is created by setting proper Size and functional Groups, and a Build Inorganics/Size tool and a Build menu/Build Inorganics/Groups tool are used;
then, geometric optimization and annealing calculation are carried out on the obtained initial structure model of the inorganic membrane material, a global optimal configuration is extracted, sufficient dynamic balance is carried out under the conditions of fixed temperature and pressure, and the characteristics of the configuration are counted based on the structure of the dynamic balance;
and then, according to the dynamic track of the obtained dynamically balanced inorganic membrane material structure model, calculating cohesive energy density, and investigating the strength of the intermolecular interaction force, thereby forming a selected polymer membrane material structure model with a stable structure.
4. The method according to claim 1, wherein the step (1) contaminants include, but are not limited to, one or more of inorganic contaminants including calcium carbonate and calcium sulfate, organic contaminants including protein (bovine serum albumin, ovalbumin, β -microglobulin), humic acid, colloidal contaminants including silicic acid compounds, ferro-aluminum compounds, algae, and microbial contaminants including bacteria (staphylococcus aureus and escherichia coli).
5. The method of claim 1, wherein the membrane fouling is analyzed by simulation,
building an inorganic pollutant model: the crystal structure can be introduced according to the crystal information, and Build inorganic nano particles with various sizes are constructed by using a Build/Nanostructure/nanocruster tool; using Sketch tool to construct the structures of the anion, cation and water molecules; then, geometric optimization and annealing calculation are carried out on the obtained initial structure model of the inorganic membrane material, a global optimal configuration is extracted, sufficient dynamic balance is carried out under the conditions of fixed temperature and pressure, and the characteristics of the configuration are counted based on the structure of the dynamic balance; and then, calculating cohesive energy density according to the dynamic track of the obtained dynamic balance structure model, and inspecting the strength of the intermolecular interaction force to further form a selected inorganic pollutant structure model with a stable structure.
Building an organic pollutant model: carrying out initial model building on the selected organic pollutants according to components and structures, and constructing a molecular structure by using a Build polymers/Repeat Unit tool and a sketch tool; the rest steps are the same as the organic pollutant model building process.
Building a colloid pollutant model: constructing structures of negative ions, positive ions and water molecules according to the actual structures; the rest steps are the same as the organic pollutant model building process.
Building a microbial pollutant model: the steps are the same as the organic pollutant model building process.
6. The method of claim 1, wherein the membrane fouling is analyzed by simulation,
the different water body solution filtration models in the step (2) comprise one or more models of but not limited to a single membrane material-solution model, a single membrane material-single pollutant-solution model, a single membrane material-composite pollutant-solution model and a composite membrane material-composite pollutant-solution model;
building a water body solution filtering model:
firstly, inputting a built membrane material model and a built pollutant model into Materials Studio software, activating a built model file (". xsd"), and modifying cell parameters;
then, using a Tool/Atom Vlumes & Surfaces to create an isosurface, then turning over the isosurface, then filling a solution by using a Monte Carlo-based method, building a solution and amorphous film structure, and deleting the isosurface after building;
and finally, performing geometric optimization and annealing calculation on the built model, extracting a global optimal configuration, performing sufficient dynamic balance under the conditions of fixed temperature and pressure, and counting the configuration characteristics of the model based on a dynamic balance structure.
7. The method of claim 1, wherein the membrane fouling is analyzed by simulation,
and (3) calculating filtering models of different water solutions in the step (2):
firstly, the calculation interfaces and processes of different water body solution filtering models can perform reliable structure optimization and energy calculation on a designed operation basic environment aperiodic system and periodic systems such as membrane materials and pollutants by using a molecular mechanics dynamics method; smart tools including various structure optimization methods and automatic adjustment optimization methods, various temperature control functions and various pressure control functions realize configuration simulation and structural anisotropy maximization, and batch processing of calculation tasks such as calculation and analysis of various membrane material structures and interaction energy is realized;
secondly, calculating result parameters of different water body solution filtering models comprise two-dimensional/three-dimensional space distribution information of atoms, wherein the two-dimensional/three-dimensional space distribution information of adsorption structures, molecular configuration changes, interaction energy, interaction force real-time changes and the like are obtained when molecular dynamics simulation is carried out under the condition of large temperature and pressure range changes; meanwhile, the dynamics calculation track file and the structure-related properties can be obtained: a plurality of correlation function files of bond length, bond angle, torsion angle time distribution curve, concentration distribution curve, density field, radial distribution function, probability distribution of gyration radius, space orientation, average speed along a certain direction, temperature distribution curve, diffusion coefficient, dipole autocorrelation function, stress autocorrelation function, ensemble fluctuation function, distance pointing rotation correlation function, displacement time correlation function and speed autocorrelation function; the change curve of kinetic energy, potential energy and composition thereof along with time, the pressure and temperature distribution curve, the lattice parameter and density distribution curve, the adsorption capacity-time curve, the pollutant configuration parameter and the solution concentration curve after the long-term filtration process is simulated and simulated can be obtained.
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