A system for simulating the adsorption of organic evolving compounds (OECs) on polyethylene microplastics

Abstract

A system (100) for simulating the adsorption of organic compounds (OECs) on polyethylene (PE) microplastics using density functional theory (DFT), wherein the system (100) comprises: a molecular modeling unit (102) configured to construct and visualize molecular structures of OECs and PE microplastics; a central processing unit (104) connected to the molecular modeling unit (102) configured to optimize the molecular geometries of the OECs and PE microplastics to their ground state, the optimization being performed using a 3-parameter Lee-Yang-Parr function (B3LYP) by Becke paired with a 6-311++G(d,p) basis set within a dielectric medium; A control unit (106) connected to the central processing unit (104) uses the optimized molecular geometries to calculate and analyze the chemical reactivity parameters of OECs on the PE; an adsorption unit (108) connected to the control unit (106) and configured to simulate and evaluate the adsorption behavior of the OECs on the PE; and a display (110) configured to generate and visually verify the calculation results, including the optimized structures, chemical reactivity parameters and adsorption properties.

Description

FIELD OF THE INVENTION

[0001] The present disclosure relates to a system for simulating the adsorption of organic compounds (OECs) on polyethylene (PE) microplastics using density functional theory (DFT). More specifically, the present invention focuses on predicting the reactivity and adsorption behavior of OECs such as metronidazole, simazine, and clofibric acid on PE microplastics in aqueous environments. BACKGROUND OF THE INVENTION

[0002] Plastics have become indispensable materials in modern society, contributing significantly to comfort, safety, and technological advances in numerous applications. Their unique properties, including durability, flexibility, and resistance to degradation, have led to an exponential increase in global plastics production, which currently exceeds 368 million tons per year. However, the same properties that make plastics so valuable also contribute to their environmental permanence, especially when mishandled, leading to serious ecological and health problems.

[0003] One of the pressing environmental problems associated with plastics is the proliferation of microplastics (MPs) – plastic particles less than 5 mm in diameter. These tiny particles have been detected in a wide variety of environments, from oceans and rivers to soils and sediments, with concentrations varying considerably by location. Microplastics pose a serious threat to ecosystems due to their widespread distribution and potential to harm organisms that inadvertently ingest them.

[0004] Microplastics are broadly divided into two categories: primary and secondary. Primary microplastics are intentionally manufactured in small sizes for use in products such as cosmetics and industrial abrasives. Secondary microplastics, on the other hand, are formed from the degradation of larger pieces of plastic through processes such as physical abrasion and photooxidation. A significant portion of microplastic pollution comes from polyethylene (PE), which accounts for approximately 38% of global plastic production. PE is widely used in packaging materials, including plastic bags, bottles, and containers, and its prevalence in the environment has been linked to harmful effects on marine life, such as coral species.

[0005] The environmental impacts of microplastics are further exacerbated by their ability to adsorb and transport various emerging organic compounds (OECs), including pharmaceuticals, pesticides, and industrial chemicals. These compounds, which include substances such as metronidazole, simazine, and clofibric acid, are of particular concern due to their persistence in the environment, their potential for bioaccumulation, and their unknown long-term effects on ecosystems and human health. When microplastics and OECs coexist in aquatic environments, microplastics can easily adsorb these pollutants, increasing their mobility and potential to cause harm.

[0006] Recent studies have highlighted the complex interactions between microplastics and OECs, demonstrating that microplastics can act as carriers of these pollutants, potentially leading to combined contamination that can significantly impact organisms and ecosystems. For example, polyethylene microplastics have been shown to efficiently adsorb pesticides and antibiotics, with the extent of adsorption being influenced by environmental conditions. Despite the growing body of research on this topic, there is still a lack of theoretical studies investigating the adsorption mechanisms and reactivity of OECs to microplastics.

[0007] Given the importance of understanding these interactions, the present invention aims to fill this gap by employing quantum chemical methods, specifically density functional theory (DFT) simulations, to investigate the adsorption behavior and reactivity of OECs on PE microplastics. This approach will provide valuable insights into the molecular interactions between microplastics and pollutants, thus offering a theoretical foundation to guide future experimental work. By better understanding these interactions, this research could lead to the development of more effective materials for environmental remediation and ultimately reduce the ecological and economic costs associated with plastic pollution.

[0008] Therefore, to overcome the above limitations, there is a need to develop a system to simulate the adsorption of emerging organic compounds (OECs) on polyethylene (PE) microplastics using density functional theory (DFT).

[0009] The technical advances disclosed by the present invention overcome the limitations and disadvantages of existing and conventional systems and methods. SUMMARY OF THE INVENTION

[0010] This disclosure relates to a system that uses density functional theory (DFT) to simulate the adsorption of organic compounds onto polyethylene microplastics. By optimizing molecular structures and calculating key quantum chemical parameters, the system provides insights into the chemical reactivity, adsorption energy, and overall stability of the microplastic contaminant complexes. The system also evaluates the adsorption advantage of various OECs and generates an energy profile diagram that supports the development of materials with enhanced adsorption capabilities.

[0011] One objective of the present disclosure is to investigate the mechanisms of adsorption of metronidazole, simazine, and clofibric acid on primary polyethylene (PE) microplastics from wastewater using density functional theory (DFT).

[0012] Another objective of the present disclosure is to theoretically understand the adsorption and reactivity of OECs (OEC1 for metronidazole, OEC2 for simazine and OEC3 for clofibric acid) on PE microplastics using DFT simulations.

[0013] Another objective of the present disclosure is to create energy profile diagrams to visually represent adsorption properties and to support the development of materials with improved adsorption capabilities for environmental applications.

[0014] Another objective of the present disclosure is to evaluate the adsorption favorability of different OECs on PE microplastics based on their calculated adsorption energies and other quantum chemical descriptors.

[0015] The present disclosure is intended to provide a system for simulating the adsorption of emerging organic compounds (OECs) onto polyethylene (PE) microplastics using density functional theory (DFT), the system comprising: a molecular modeling unit configured to construct and visualize the molecular structures of OECs and PE microplastics; a computational unit connected to the molecular modeling unit and configured to optimize the molecular geometries of the OECs and PE microplastics to their ground state, wherein the optimization is performed using a B3LYP function paired with a 6-311++G(d,p) basis set within a dielectric medium; an analysis unit connected to the computational unit and utilizing the optimized molecular geometries to calculate and analyze the chemical reactivity parameters of OECs on PE;an adsorption unit connected to the analysis unit, configured to simulate and evaluate the adsorption behavior of the OECs on PE; and a data output unit configured to generate and visually verify the computational results, including the optimized structures, chemical reactivity parameters, and adsorption properties.

[0016] To further clarify the advantages and features of the present disclosure, a more detailed description of the invention will be given with reference to specific embodiments thereof illustrated in the accompanying drawings. It should be noted that these drawings represent only typical embodiments of the invention and are therefore not to be considered limiting its scope. The invention will be described and explained in additional detail and in greater detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE CHARACTERS

[0017] These and other features, aspects, and advantages of the present disclosure will be better understood when the following detailed description is read with reference to the accompanying drawings, in which like characters represent like parts throughout. Fig. 1 shows a block diagram of a system (100) for simulating the adsorption of organic compounds (OECs) on polyethylene (PE) microplastics using density functional theory (DFT) according to an embodiment of the present disclosure, and Fig. Figure 2 shows the potential energy diagram for the adsorption of PE-OEC1, PE-OEC2, PE-OEC3.

[0018] Furthermore, those skilled in the art will appreciate that elements in the drawings are shown for convenience and may not necessarily be drawn to scale. For example, the flowcharts illustrate the method by key steps to enhance understanding of aspects of the present disclosure. Moreover, with respect to device construction, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details relevant to understanding embodiments of the present disclosure in order not to clutter the drawings with details that would be readily apparent to those skilled in the art who would benefit from the description herein. DETAILED DESCRIPTION:

[0019] To facilitate an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and described in specific language. It is to be understood, however, that this is not intended to limit the scope of the invention, as such changes and further modifications to the illustrated system and such further applications of the principles of the invention as illustrated therein are contemplated as would normally occur to one skilled in the art to which the invention pertains.

[0020] It will be understood by one skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be limiting thereof.

[0021] References in this specification to "one aspect," "another aspect," or similar language mean that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Therefore, occurrences of the phrase "in one embodiment," "in another embodiment," and similar language throughout this specification may or may not all refer to the same embodiment.

[0022] The terms "comprises," "comprising," or other variations thereof are intended to cover non-exclusive inclusion, such that a process or method comprising a list of steps not only includes those steps, but may also include other steps not expressly listed or inherent in such process or method. Likewise, one or more devices or subsystems or elements or structures or components preceded by "comprises...a" does not preclude, without further limitation, the existence of other devices or other subsystems or other elements or other structures or other components or additional devices or additional subsystems or additional elements or additional structures or additional components.

[0023] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The system, methods, and examples provided herein are for illustrative purposes only and should not be considered limiting.

[0024] Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0025] Fig.1 shows a block diagram of a system (100) for simulating the adsorption of emerging organic compounds (OECs) onto polyethylene (PE) microplastics using density functional theory (DFT), the system (100) comprising: a molecular modeling unit (102) configured to construct and visualize molecular structures of OECs and PE microplastics; a central processing unit (104) connected to the molecular modeling unit (102) and configured to optimize the molecular geometries of the OECs and PE microplastics to their ground state, the optimization being performed using a 3-parameter Lee-Yang-Parr (B3LYP) function by Becke paired with a 6-311++G(d,p) basis set within a dielectric medium;a control unit (106) connected to the central processing unit (104) uses the optimized molecular geometries to calculate and analyze chemical reactivity parameters of OECs on the PE; an adsorption unit (108) connected to the control unit (106) and configured to simulate and evaluate the adsorption behavior of the OECs on the PE; and a display (110) configured to generate and visually verify the calculation results, including the optimized structures, chemical reactivity parameters, and adsorption properties.

[0026] In one embodiment, the B3LYP function is a key component used in density functional theory (DFT) calculations to optimize the molecular geometries of OECs and PE microplastics.

[0027] In one embodiment, the 6-311++G(d,p) basis set used in the density functional theory (DFT) calculations is a triple zeta basis set.

[0028] In one embodiment, the inclusion of "(d,p)" means the addition of a polarization function that helps adjust the shape of atomic orbitals, where the notation "++" indicates the inclusion of diffuse functions that serve to correct the size of atomic orbitals.

[0029] In one embodiment, the dielectric medium has a relative permittivity (ε) of 80, which corresponds to water as a solvent.

[0030] In one embodiment, the chemical reactivity parameters calculated and analyzed using the analysis unit (106) are the HOMO-LUMO energy gap (H), the chemical hardness (η), the chemical softness (S), the chemical potential (µ), the electrophilicity index (ω), and the adsorption energy (E).

[0031] A computational study using density functional theory (DFT) calculations is conducted to gain insights into chemical reactivity and better understand the adsorption process of organic electron carriers (OECs) on polyethylene (PE). The molecular structures used in this study are constructed using Gauss View 6, a graphical user interface for generating inputs and visually inspecting the outputs generated by the Gaussian 16W program (Rasheed et al., 2022). All molecules are optimized to their ground state using the B3LYP / 6-311++G(d,p) method in a dielectric medium with ε = 80, which corresponds to water as the solvent. This particular combination of B3LYP and 6-311++G(d,p) is widely known for its balance between computational accuracy and efficiency.

[0032] In one embodiment, the notation "6-311G" refers to the use of a triple zeta basis set, while the inclusion of "(d,p)" indicates the addition of a polarization function that helps refine the shape of atomic orbitals.

[0033] In one embodiment, the “++” notation denotes the inclusion of diffuse functions, which are important for correcting the size of atomic orbitals, especially for anions and molecules with weakly bound electrons.

[0034] Using these equations, various quantum chemical parameters such as the HOMO-LUMO energy gap (H), chemical hardness (η), chemical softness (S), chemical potential (µ), electrophilicity index (ω), and adsorption energy (E) are calculated. The most important orbitals in a molecule are the frontier orbitals, specifically the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). The energy difference between HOMO and LUMO reflects the kinetic and chemical stability of a molecule. A smaller HOMO-LUMO energy gap indicates greater chemical reactivity and lower kinetic stability, while a larger gap indicates the opposite. The HOMO-LUMO gap is determined using the following equation: H=EHOMO−ELUMO

[0035] The stability and reactivity of a molecule are influenced by its chemical hardness. A molecule with a large energy gap is considered hard, indicating lower chemical reactivity and higher kinetic stability. Consequently, hard molecules are less reactive. Chemical hardness (η) is calculated using the following equation: η=LUMO−HOMO2

[0036] A soft molecule has a small energy difference from a hard molecule. This difference means it has higher chemical reactivity and lower kinetic stability. Chemical softness (S) is calculated using the following equation: S=12η

[0037] The chemical potential represents the contribution of each constituent per mole to the total free energy of the system at constant temperature and pressure. It is related to the electronegativity and electron affinity of the species. A strong electrophile is identified by its chemical potential, with a high value indicating a molecule's high reactivity and a tendency to lose electrons. Chemical softness is calculated using the following equation: μ=HOMO+LUMO2

[0038] Electrophiles are positively charged or neutral species with vacant orbitals that are attracted to an electron-rich center. The electrophilic nature of a molecule depends on its electrophilicity index. The higher the electrophilicity index value, the stronger the molecule's electrophilic character. The electrophilicity index is calculated using the following equation: ω=μ22η

[0039] An electrophile is classified based on its ω value: if ω > 1.5 eV, it is considered a strong electrophile; if 0.8 < ω < 1.5 eV, it is classified as moderate; and if ω < 0.8 eV, it is considered marginal.

[0040] Adsorption energy defined as: Adsorption energy (E)=EMP−OEC−(EMP+EOEC) where E (MP-OEC) the total energy of microplastics and OEC in equilibrium is E MP the total energy of the adsorbent (PE) and E OEC the total energy of the adsorbate (OEC). A negative value of the adsorption energy indicates stronger adsorption at the surface.

[0041] The interactions between PE (adsorbent) and OECs (adsorbate) are primarily determined by their specific functional groups, which influence important intermolecular interactions, including electrostatic interactions, hydrogen bonds, van der Waals interactions, halogen bonds, and n-n interactions. These interactions are influenced by the properties of the PE and OECs as well as environmental factors. Among them, hydrogen bonding proves to be a fundamental and crucial interaction between OECs and PE. Therefore, the present invention investigates the possible formation of hydrogen bonds between OECs and PE using DFT calculations.

[0042] In the present invention, DFT-based molecular orbital descriptors help in understanding chemical reactivity at the molecular level. Table 1 shows the electronic molecular descriptors and their calculated values. The calculated energy values ​​of E H and E Lfor the resulting organic compounds are as follows: OEC1 with E H = -0.320 eV and E L = -0.166 eV, OEC2 with E H = -0.325 eV and E L = -0.138 eV and OEC3 with E H = -0.318 eV and E L = -0.168 eV. The low E H - and E L -values ​​indicate that OEC1, OEC2 and OEC3 are electrophiles or electron acceptors. Table 1. Calculated molecular properties of OECs and PE. system Dipole moment (Debye) HOMO (eV) LUMO (eV) HOMO-LUMO (H) (eV) µ (eV) η (eV) S (eV) ω (eV) PE 2.932 - 0.353 -0.011 - 0.342 - 0.182 -0.171 - 0.086 - 0.003 OEC-1 4.804 - 0.320 -0.166 - 0.154 - 0.243 -0.077 - 0.039 - 0.228 OEC-2 6.611 - 0.325 -0.138 - 0.187 - 0.231 -0.093 - 0.048 - 0.250 OEC-3 6.738 - 0.318 -0.168 - 0.149 - 0.243 -0.075 - 0.037 - 0.022 µ= chemical potential, η= chemical hardness, S= chemical softness, ω= electrophilicity index

[0043] According to the principle of hard and soft acids and bases (HSAB), the S value, which determines the interaction between species with similar hardness (or softness), is preferred. Hardness applies to species with high charge states, while "soft" applies to low charge states. In this case, the S value (softness) for OEC2 (-0.048 eV) is larger than that of OEC1 (-0.039 eV) and OEC3 (-0.037 eV).

[0044] The frontier orbitals help characterize the chemical reactivity and kinetic stability of the molecule. A molecule with a small HOMO-LUMO gap is associated with high chemical reactivity and low kinetic stability and is referred to as a "soft molecule." Analysis of the HOMO-LUMO gap for OEC1, OEC2, and OEC3 yields values ​​of -0.154 eV, -0.187 eV, and -0.149 eV, respectively, clearly demonstrating that OEC2 is the most reactive of the three isomers.

[0045] A high dipole moment provides information about the polarity of the molecule and its chemical reactivity. The dipole moment of OEC2 (6.611 eV) is larger than that of OEC1 and OEC3, indicating that OEC2 exhibits higher chemical reactivity. The chemical potential is related to the electronegativity and electron affinity of the species. The chemical potential of OEC2 (-0.23129 eV) is higher compared to OEC1 and OEC3, clearly demonstrating that OEC2 is more electrophilic.

[0046] The electrophilicity index (ω) classifies molecules as strong electrophiles (ω > 1.5 eV), moderate electrophiles (0.8 eV < ω < 1.5 eV), or marginal electrophiles (ω < 0.8 eV). A higher electrophilicity index indicates a stronger electrophilic character. OEC2 (-0.250 eV) proves to be a better electrophile compared to the other two adsorbates OEC1 (-0.228 eV) and OEC3 (-0.022 eV). Fig. Figure 3 shows the HOMO-LUMO orbitals of the different compounds.

[0047] The adsorption energy values, calculated as the difference between the energies of the complex microplastic OECs and the free components of the complex, predict the preferred adsorption site on the adsorbent. Table 2 shows the adsorption energies (E) and bond distances for these different interactions. Table 2. Bond length and adsorption energies of the PE and OEC system. Adsorbate + adsorbent system Adsorption energy (kJ / mol) Bond distance (nm) Polyethylene (PE) + Organic Emerging Compounds (OECs) PE + OE C1 -18.667 0.187 PE + OEC2 -25.548 0.177 PE + OEC3 -23.440 0.185

[0048] Fig.Figure 2 shows the potential energy diagram for the adsorption of PE-OEC1, PE-OEC2, and PE-OEC3. The PE + OEC2 system exhibits a shorter bond length and a larger negative adsorption energy, indicating that the adsorptive interaction between PE and OEC2 is preferable to that of OEC1 and OEC3. This preference for OEC2 with PE is also supported by the softness of OEC2, as determined by the HOMO-LUMO gap and its chemical potential, which is higher than that of the other two adsorbates, OEC1 and OEC3. The relative energy of the models and their stability follow the order: PE-OEC2 > PE-OEC3 ~ PE-OEC1.

[0049] The drawings and the foregoing description provide examples of embodiments. Those skilled in the art will recognize that one or more of the described elements may well be combined into a single functional element. Alternatively, certain elements may be separated into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, orders of the processes described herein may be changed and are not limited to the manner described herein. Furthermore, the actions of any flowchart need not be implemented in the order shown; nor do all actions necessarily need to be performed. Also, those actions that are not dependent on other actions may be performed in parallel with the other actions. The scope of the embodiments is in no way limited by these specific examples.Numerous variations, whether explicitly stated in the specification or not, such as differences in structure, dimensions, and material use, are possible. The scope of the embodiments is at least as broad as indicated in the following claims.

[0050] Advantages, other benefits, and solutions to problems have been described above with reference to specific embodiments. However, the advantages, benefits, solutions to problems, and any components that may cause an advantage or solution to occur or become more apparent are not to be construed as a critical, required, or essential feature or component of any or all of the claims. REFERENCES 100 A system for simulating the adsorption of organic emerging compounds (OECs) on polyethylene (PE) microplastics using density functional theory (DFT). 102 Molecular Modeling Unit 104 Central unit 106 Control unit 108 adsorption unit 110 ad QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited non-patent literature

[0000] Rasheed et al., 2022

[0031]

Claims

[1] A system (100) for simulating the adsorption of organic compounds (OECs) on polyethylene (PE) microplastics using density functional theory (DFT), the system (100) comprising: a molecular modeling unit (102) configured to construct and visualize molecular structures of OECs and PE microplastics; a central processing unit (104) connected to the molecular modeling unit (102) and configured to optimize the molecular geometries of the OECs and PE microplastics to their ground state, wherein the optimization is performed using a 3-parameter Lee-Yang-Parr (B3LYP) function from Becke paired with a 6-311++G(d,p) basis set within a dielectric medium; a control unit (106) connected to the central processing unit (104) uses the optimized molecular geometries to calculate and analyze the chemical reactivity parameters of OECs on the PE; an adsorption unit (108) connected to the control unit (106) and configured to simulate and evaluate the adsorption behavior of the OECs on the PE; and a display (110) configured to generate and visually verify the calculation results, including the optimized structures, chemical reactivity parameters, and adsorption properties. [2] The system of claim 1, wherein the B3LYP function used in the density functional theory (DFT) calculations optimizes the molecular geometries of OECs and PE microplastics. [3] The system of claim 1, wherein the 6-311++G(d,p) basis set used in the density functional theory (DFT) calculations is a triple zeta basis set. [4] The system of claim 3, wherein the inclusion of "(d,p)" means the addition of a polarization function that helps adjust the shape of atomic orbitals, the notation "++" indicating the inclusion of diffuse functions that serve to correct the size of atomic orbitals. [5] The system of claim 1, wherein the dielectric medium has a relative permittivity (ε) of 80, which corresponds to water as a solvent. [6] The system (100) according to claim 1, wherein the chemical reactivity parameters calculated and analyzed using the analysis unit (106) are the HOMO-LUMO energy gap (H), the chemical hardness (η), the chemical softness (S), the chemical potential (µ), the electrophilicity index (ω), and the adsorption energy (E).

Images