METHOD FOR THE SELECTIVE REMOVAL OF MERCURY IONS FROM WATER USING A COVALENT ORGANIC POLYMER BASED ON THIOUREA

Description

2. High efficiency can be achieved. Nitrogen (N), oxygen (O), and sulfur (S) are elements with relatively high electronegativity that exhibit strong electrophilic properties. Groups containing N, O, or S atoms can provide free electron pairs, thereby improving their bonding ability with mercury ions. Coordination bonds and chelation represent the strongest types of interaction. Such bonds, based on the heteroatoms N, O, or S, can undergo coordination reactions with mercury ions to form metal complexes, thereby removing mercury from the water. Covalent organic polymers (COPs) are already being investigated as adsorbents for mercury. Most adsorbents for mercury use rigid aromatic monomers for the synthesis of the COP backbone, which potentially limits the number of heteroatoms such as sulfur and nitrogen at the mercury chelate formation sites on the COP surface and thus leads to a low saturation adsorption capacity.Although various COPs for mercury removal have been described, improvements regarding the type and density of the chelate groups are still needed to achieve a high adsorption capacity and effective mercury adsorption over a wider pH range. Against this background, the present invention is proposed. CONTENT OF THE PRESENT INVENTION The objective of the present invention is to provide a process for the selective removal of mercury ions from water using a thiourea-based covalent organic polymer in order to overcome the aforementioned problems in the state of the art. To achieve the aforementioned objective, the present invention offers the following solutions.Technical solution of the present invention: a manufacturing process of an eccentric organic polymer based on thiourea, comprising the following steps: mixing ammonium thiocyanate, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine and water, subsequently adding concentrated hydrochloric acid to the mixture and reacting to obtain (1,3,5-triazine-2,4,6-tris(4-aminophenyl))tris(thiourea); and mixing (1,3,5-triazine-2,4,6-tris(4-aminophenyl))tris(thiourea), a polycyclic aromatic polyaldehyde, mesitylene and dioxane, carrying out freeze-thaw cycles to remove oxygen and subsequent sealing, and then carrying out- a heating reaction to obtain the covalent organic polymer based on thiourea 35. BE2025 / 7040 3 Preferably, the polycyclic aromatic polyaldehyde is thiophene-2,5-dicarboxaldehyde, thieno[3,2-b]thiophene-2,5-dicarboxaldehyde or benzo[1,2-b:3,4-b':5,6-b'']trithiophene-2,5,8-tricarboxaldehyde.Preferably, the mass ratio of ammonium thiocyanate, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, water, and concentrated hydrochloric acid is 1–1.1 g : 150–180 mg : 5–155 ml : 550–650 μl. Preferably, the reaction temperature is 85–95°C and the reaction time is 14–16 hours. Preferably, the molar ratio of (1,3,5-triazine-2,4,6-tris(4-aminophenyl))tris(thiourea), the polycyclic aromatic polyaldehyde, mesitol-10-ethylene, the dioxane, and the acetic acid is 0.06–0.07 mmol : 0.05–0.15 mmol : 2–3 ml : 2–3 ml : 1–2 ml. Preferably, the concentration of the acetic acid is 5–7 M. Preferably, the heating reaction is carried out at a temperature of 120–125°C over a period of 3–3.5 days. 15 Technical solution II of the present invention: a covalent organic polymer based on thiourea, produced by the manufacturing process described above, is provided.Technical Solution III of the present invention: An application of the above-described covalent organic polymer based on thiourea for the remediation of waters contaminated with mercury-20 is provided. Technical Solution IV of the present invention: A method for the selective removal of mercury ions from water using a covalent organic polymer based on thiourea is provided, wherein the covalent organic polymer based on thiourea is used for the selective removal of mercury ions from waters contaminated with mercury-25. Thiourea derivatives are organic compounds containing sulfur atoms and amino groups and exhibiting an exceptionally high content of the heteroatoms S and N. They can form stable complexes by forming metal-thiourea chelations and metal-nitrogen chelations through the respective bonding of sulfur and nitrogen atoms with metal ions.Thiourea-based polymer materials exhibit strong adsorption capacity and specific detection capabilities and are frequently used in dye adsorption, sensitive detection, and heavy metal adsorption. The present invention effectively binds heavy metal mercury ions by introducing thiourea groups into incovalent organic polymers (COP), where these thiourea groups serve as strong anchoring sites for mercury ions. This results in improved selective removal of mercury ions and enables highly efficient treatment of mercury-contaminated waters. The present invention reveals the following technical effects. With this invention, tricovalent organic polymers based on thiourea5 (TS-COPs) as adsorbents for mercury were successfully synthesized by means of a Schiff base reaction mechanism and a solvothermic method, namely TS-TD, TS-TTD and TS-BTT.The thiourea within the polymer structure exhibits a unique sulfur-nitrogen configuration and shows excellent affinity for mercury. Among these, the thiourea-based covalent organic polymer TS-TTD shows a maximum adsorption capacity that surpasses most polymeric adsorbents. The mercury removal mechanism is primarily based on the chelating coordination between sulfur-containing groups (thiourea) and Hg²⁺ ions. TS-TD, TS-TTD, and TS-BTT all exhibit mercury adsorption over a wide pH range (pH 1–7) with maximum equilibrium adsorption capacities of 45815. mg·g⁻¹, 516 mg·g⁻¹ or 378 mg·g⁻¹. In the presence of twelve other competing metal cations, TS-COPs also exhibit excellent Hg²⁺ removal capacity. This demonstrates the potential of the thiourea-based covalent organic polymers prepared in this invention for applications in mercury adsorption. 20 DESCRIPTION OF THE DRAWING Fig.Fig. 1 shows a schematic diagram of the synthesis process of the decovalent organic polymer TS-COPs; Fig. 2 shows the Fourier transform infrared spectra (a–c) and the X-ray diffraction diagrams (d–f) of the TS-COPs; Fig. 3 shows the N₂ adsorption-desorption isotherms and the pore size distributions (a–c) as well as the thermogravimetric curves (d–f) of the TS-COPs at 77 K; Fig. 4 shows scanning electron microscope images of TS-COPs at different magnifications (a–c); Fig. 5 shows the adsorption of Hg(II) by TS-COPs under different pH conditions 30 (a–c), the kinetic adsorption isotherms of Hg(II) on TS-COPs (d–f) and the thermodynamic adsorption isotherms of Hg(II) on TS-COPs (g–i); Fig. 6 shows the competitive adsorption of TS-COPs in the presence of 12 commonly occurring cations; Fig. 7 illustrates the reusability of TS-COPs (a) and a performance comparison with other materials in the same category (b); and BE2025 / 7040 5 Fig.Figure 8 shows the total spectrum of TS-TTD before mercury adsorption and TS-TTD@Hg after mercury adsorption (a), the refined Hg4f spectrum of TS-TTD@Hg (b), the refined N1s spectrum of TS-TTD and TS-TTD@Hg (c), and the refined S2p spectrum of TS-TTD and TS-TTD@Hg (d). 5. DETAILED DESCRIPTION Various embodiments of the present invention are described in detail below. These descriptions are not to be regarded as limitations of the present invention, but rather as more detailed descriptions of certain aspects, features, and embodiments of the present invention. 10. It is to be understood that the terms described in the present invention serve only to describe specific embodiments and are not to be used to limit the present invention. In addition, the value ranges specified in the present invention are to be understood as the specific disclosure of each intermediate value between the upper and lower limits of this range.15 Any smaller range between any given value or range of statements and any other given value or intermediate value within the range is also included in the present invention. The upper and lower limits of these smaller ranges can be included or excluded from the range independently of each other. 20 Unless otherwise specified, all technical and scientific terms used herein have the same meaning as they are generally understood by persons skilled in the field of the present invention. While the present invention describes only preferred methods and materials, any method and material similar or equivalent to that described herein may also be used in carrying out 25 or testing the present invention. All documents mentioned in this description are incorporated by reference to disclose and describe methods and / or materials that refer to the aforementioned documents. hen.In the event of a conflict with any incorporated documents, the contents of this specification shall prevail. 30 Various modifications and variations may be made to the specific embodiments of the present invention without departing from the scope or spirit of the present disclosure, which is obvious to persons skilled in the art. Other embodiments obtained from the description of the present invention are also obvious to persons skilled in the art. The descriptions 35 and embodiments of the present invention are only examples. BE2025 / 7040 6 As used herein, “including”, “comprise”, “include”, “contain”, and the like are all open-ended terms, i.e., meaning “including” but not “limited to”. It should be noted that all aspects of the present invention which are not described in detail here represent common practices in this field and are not of central importance to the present invention.Embodiment 1 In this embodiment, tricovalent thiourea-based organic polymers (TS-COPs) are produced, namely TS-TD, TS-TTD and TS-BTT, whereby the specific manufacturing process was as follows: Materials: Ethanol, acetic acid, tetrahydrofuran, ammonium thiocyanate, 1,3,5-trimethylbenzene, 1,4-dioxane, 2,4,6-tris(4-aminophenyl)-1,3,5-triazine, thiophene-2,5-dicarboxaldehyde, thieno[3,2-b]thiophene-2,5-dicarboxaldehyde, benzo[1,2-b:3,4-b':5,6- b'']trithiophene-2,5,8-tricarboxaldehyde,Ni(NO₃)₂·6H₂O,La(NO₃)₃·6H₂O,Mg(NO₃)₂·6H₂O,15 Zn(NO₃)₂ 6H₂O,Co(NO₃)₂ 6H₂O,Cu(NO₃)₂ 3H₂O,Cd(NO₃)₂ 4H₂O,KNO₃,Ca(NO₃)₂,SrCl₂, CsCl. All of the above reagents are purchased from commercial suppliers and are of analytical grade and are not further purified.Preparation method: Synthesis of the monomer (1,3,5-triazine-2,4,6-tris(4-aminophenyl))tris(thiourea) 20 1.078 g of ammonium thiocyanate (Atc) is weighed and dissolved in 10 ml of deionized water. The mixture is added dropwise at 0°C to a 25 ml round-bottom flask containing 170 mg of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine. After stirring for 30 minutes, 600 μl of concentrated HCl are added, and the mixture is allowed to react at 90°C for 15 hours. After cooling to room temperature, the product is washed with deionized water and ethanol, then filtered to collect the product. The product is 12 Dried for several hours at 60°C under vacuum to obtain 145.6 mg of orange-colored product, yield: 85.64%. 1HNMR(400MHz,DMSO-d6)δ10.10(s,1H),8.67(s,2H),7.80(s,2H). Covalent organic polymers TS-COPs: Synthesis of TS-TD, TS-TTD and TS-BTT30 (1,3,5-triazine-2,4,6-tris(4-aminophenyl))tris(thiourea) (35.4 mg, 0.067 mmol), thiophene-2,5-dicarboxaldehyde (14.01 mg, 0.1 mmol), mesitylene (2 ml) and dioxane (2 ml) are placed in a 25 ml Schlenk flask.The mixture is sonicated for 20 minutes to achieve complete homogeneity. After adding 1 ml of 6M acetic acid, the sonication is continued for a further 10 minutes. The Schlenk flask is rapidly frozen in liquid nitrogen and, before sealing, subjected to three freeze-thaw cycles for deacidification. The reaction proceeds undisturbed for 3 days at 120°C. After completion of the reaction, the mixture is cooled to room temperature. The material is collected by filtration and washed with methanol, THF, acetone, water, and ethanol. The collected material is then dried for 12 hours in a vacuum drying oven at 60°C and ground into a dark brown powder, achieving a yield of 68%. TS-TTD and TS-BTT are prepared by copolymerization under identical conditions as TS-TD, wherein thiophene-2,5-dicarboxaldehyde is replaced by an equimolar amount of thieno[3,2-b]thiophene-2,5-dicarboxaldehyde or benzo[1,2-b:3,4-b':5,6-b'']trithiophene-2,5,8-tricarboxaldehyde. Fig. 10Figure 1 showed a schematic diagram of the synthesis process of the covalent organic polymer TS-COPs. 1. Characterization of Covalent Organic Polymers TS-COPs: The pH value of the solution is measured with an mpH meter (PHS-25, Leici); Fourier transform infrared spectroscopy (FT-IR) is performed in the range of 4000 cm⁻¹ to 500 cm⁻¹ using an infrared spectrometer (Nicolet Summit X); powder X-ray diffraction (XRD) is performed with a D8 ADVANCE diffractometer; the thermal stability of the material is analyzed using a thermogravimetric differential thermal analyzer (Diamond TGA); the specific surface area and pore size distribution (BET) of the polymers are determined using nitrogen adsorption-desorption isotherms at low temperature (77 K) using a BELSORP MAX analyzer. Calculated for specific surface area and pore size. Scanning electron microscopy (SEM) images are taken with a Sigma300 SEM.X-ray photoelectron spectroscopy (AxisUltraDLD) (XPS) characterizes the adsorbent TS-COPs before and after adsorption. The results are shown in Fig. 2. Fig. 2 shows the Fourier transform infrared (FT-IR) spectra (a–c) and the X-ray diffraction diagrams (d–f) of the TS-COPs. Fig. 2a–Fig. 2c show the FT-IR spectra of the TS-COPs. Compared to the monomer, the FT-IR spectra of TS-TD, TS-TTD, and TS-BTT show a marked attenuation of the characteristic CHO peak (at 1706 cm⁻¹, 1706 cm⁻¹ or 1661 cm⁻¹), the disappearance of the characteristic NH₂ peaks (in the range 30,300–3400 cm⁻¹) and the appearance of distinct new peaks at 1601 cm⁻¹, 1606 cm⁻¹, and 1593 cm⁻¹. These peaks are attributed to stretching vibrations of imine bonds (C=N), indicating the occurrence of Schiff base reactions and the successful formation of polymers. Figures 2d–2f show the XRD spectra of TS-COPs.In the XRD spectral profiles of the three-polymer materials TS-COPs, no distinct effervescence peaks are observed, indicating disordered and amorphous arrangements of atoms within the polymer matrix, which is consistent with an amorphous structure. Fig. 3 shows the N₂ adsorption-desorption isotherms and the pore size distribution (a–c) as well as the thermogravimetric curves (d–f) of the TS-COPs at 77 K. Fig. 3a–Fig. Figure 3 shows specific surface areas of 30.661 m² g⁻¹, 15.103 m² g⁻¹ and 14.851 m² g⁻¹ for TS-5 TD, TS-TTD and TS-BTT. TS-TD exhibits a pore size distribution that is predominantly in the micropore range (mainly at 1.32 nm), TS-TTD shows a pore size distribution that extends over micropores (mainly at 1.29 nm) and mesopores (mainly at 2.50 nm and 3.47 nm), while TS-BTT has a pore size distribution that is concentrated on micropores (mainly at 1.32 nm and 1.49 nm). The thermal stability of TS-COPs is investigated by thermogravimetric analysis (TGA) (Fig. 3d–Fig.3f) and exhibits excellent thermal stability, characterized by three distinct weight-loss phases. All three polymer adsorbents show a slight weight loss at about 200°C, which is attributable to the evaporation of solvents from the pores. Notably, TS-TD, TS-TTD, and TS-BTT retain 65.82%, 75.48%, and 73.25% of their original weight, respectively, at about 400°C, which is attributable to the decomposition or volatilization of certain small molecules of organic compounds. At 800°C, TS-COPs show weight losses of 62.55%, 55.73%, and 56.76%, respectively, which may be due to partial car- This is due to the oxidation of the materials. This demonstrates the excellent thermal stability of all three adsorbents under high-temperature conditions. Fig. 4 shows scanning electron microscope (SEM) images of TS-COPs at different magnifications (a–c). Figs. 4a–4c show SEM images of the polymeric adsorbents TS-COPs at a scale of 200 nm and 500 nm.The recordings show that TS-TD exhibits relatively sharp, block-like structures formed by the irregular aggregation of numerous such blocks; TS-TTD displays a coral-like morphology, while TS-BTT shows a plant-fiber-like structure. All three exhibit a non-porous structure. To evaluate the effectiveness of the TS-COPs in removing Hg(II), a series of adsorption experiments are carried out, including investigations into the influence of pH, adsorption kinetics, adsorption isotherms, competitive adsorption, and adsorbent reusability. 2. Adsorption test for mercury: 0.6769 g of HgCl₂ is weighed out and dissolved in a 0.05% K₂Cr₂O₇ solution acidified with 5% HNO₃, and then filled to 1000 mL. This serves to stabilize Hg²⁺ and prevents its reduction or loss by adsorption to the vessel walls. A stable Hg²⁺ stock solution with a concentration of 500 mg / L⁻¹ is thus successfully prepared for long-term storage.Typically, 10 mg of adsorbent are mixed with 50 ml of Hg(II) solutions of varying concentrations. After reaching mercury adsorption equilibrium, 2 ml of the suspension are filtered through a 0.22 µm filter head. The filtrate is then diluted and analyzed for its residual mercury content using inductively coupled plasma mass spectrometry (ICP-MS). The formula for calculating the removal efficiency of mercury is as follows: Removal efficiency (%) = (C0 - Ce) / Ce × 100% (1) where C0 is the initial concentration; Ce is the equilibrium concentration of Hg²⁺ at the respective time. 10 2.1 Influence of the pH value on adsorption 10 mg TS-COPs adsorbents are thoroughly mixed with 50 mL of a Hg(II) solution (50 mg·L⁻¹) at a mpH value of 1–7. After reaching adsorption equilibrium of the mercury, 2 mL of the suspension are filtered with a 0.22 µm filter head. The mercury content in the filtrate is analyzed by ICP-MS after dilution of the filtrate. 15 2.2. Adsorption Kinetics of Hg(II) To investigate the adsorption kinetics of mercury, 10 mg of TS-COPs adsorbent is mixed with 50 ml of a 50 mg / L Hg(II) solution in an Erlenmeyer flask and placed on a shaker. Samples are taken at intervals of 30 min, 1 h, 2 h, 3 h, 6 h, 9 h, 12 h, 24 h, and 48 h. A 2 ml suspension is filtered through a 0.22 µm-20 filter head, and the mercury content in the filtrate is analyzed by ICP-MS after dilution of the filtrate. To better understand the adsorption kinetics, the experimental kinetic data are analyzed using pseudo-first-order and pseudo-second-order models as follows: Pseudo-first-order model: (−) = −(2)25 Pseudo-second-order model: = + (3) Here, qₜ and qₑ denote the adsorption capacity at time t(h) and at equilibrium (in mg·g⁻¹), respectively, and K₁(min⁻¹) and K₂(g·mg⁻¹min⁻¹) denote the diffusion rate constants for the pseudo-first-order and pseudo-second-order processes, respectively. 2.3. Adsorption Isotherms of Hg(II) 30 In the adsorption isotherm experiments, 10 mg of TS-COPs adsorbent is mixed with 50 ml of Hg(II) solutions of different initial concentrations (10, 50, 75, 100, 125, 150, 200 mg·L⁻¹) in Erlenmeyer flasks. The mixtures are treated with ultrasound until complete dispersion of the adsorbent and then placed on a shaking platform. After reaching mercury adsorption equilibrium, the supernatant is collected. A 2 ml suspension is filtered through a 0.22 µm filter head, and the mercury content in the filtrate is analyzed by ICP-MS after dilution of the filtrate solvent. The equilibrium adsorption capacity (mg·g⁻¹) is calculated using the following formula: = () × (4) V denotes the volume of the solution (ml); m denotes the amount of adsorbent used (g); C₀ and Ce denote the initial concentration and the equilibrium concentration of Hg²⁺, respectively.To further clarify the nature of adsorption and the interactions between TS-COPs and Hg²⁺, the adsorption data are analyzed using the Langmuir isotherm and Freundlich isotherm models: = / (1+)(5)10 ln=+ (6) where b denotes the Langmuir constant (L·g⁻¹); Ce represents the equilibrium concentration of mercury ions (mg·L⁻¹); qm indicates the adsorption capacity (mg·g⁻¹); qe denotes the equilibrium adsorption capacity (mgg⁻¹); and KF represents the Freundlich isotherm constant (mg·g⁻¹).15 Fig. 5 shows the adsorption of Hg(II) by TS-COPs at different pH Conditions (a–c), the kinetic adsorption isotherms of Hg(II) on TS-COPs (d–f) and the thermodynamic adsorption isotherms of Hg(II) on TS-COPs (g–i). The results in Fig. 5a–Fig. 5c show that within the spH range of 1–7, the adsorption of mercury by TS-COPs remains largely independent of the mpH value, which demonstrates the broad applicability of the adsorbent. Fig. 5d–Fig.Figure 5 illustrates the adsorption of Hg²⁺ by TS-COPs in aqueous solutions over different contact times. The results show that TS-TD exhibits rapid adsorption in the first three hours with a 50 mg·L⁻¹Hg²⁺ solution, followed by gradual adsorption over the next forty-plus hours, reaching an equilibrium adsorption capacity of 25,206 mg·g⁻¹. TS-TTD shows faster adsorption kinetics and reaches adsorption equilibrium within about three hours. It adsorbed Hg²⁺ rapidly within the first hour, with the amount of adsorption increasing slowly during the subsequent adsorption process and eventually reaching an equilibrium adsorption capacity of 25,206 mg·g⁻¹. TS-BTT, due to its lowest sulfur content, exhibits the slowest adsorption kinetics and achieves a final equilibrium adsorption capacity of 165 mg / g.To elucidate the kinetic mechanisms, the experimental data on adsorption kinetics are analyzed and fitted using pseudo-first and pseudo-second order kinetic models. BE2025 / 7040 11 The coefficients of determination R² for the pseudo-first-order kinetic models of TS-TD, TS-TTD, and TS-BTT are 0.931, 0.988, and 0.945, respectively. The R² values ​​for the pseudo-second-order kinetic models are 0.980, 0.997, and 0.981, respectively. The R² values ​​for the pseudo-second-order kinetic models are higher than those for the pseudo-first-order models. The higher R² values ​​for the second-order kinetic models indicate a better fit to the experimental data compared to the pseudo-first-order models. This suggests that the adsorption rate is reduced by chemically- The adsorption mechanisms are determined, thereby establishing chemical adsorption as the primary kinetic principle. The adsorption results are shown in Fig. 5g–Fig. 5i.If the Hg²⁺ concentration of the solution is below 125 mg·L⁻¹, the adsorption capacity increases rapidly with increasing initial Hg²⁺ concentration. Above 125 mg·L⁻¹, the adsorption capacity increases only slightly with further increasing concentration, as the adsorption sites of the adsorbent are largely saturated with Hg²⁺ until an equilibrium is finally reached. The equilibrium adsorption capacities are determined as follows: TS-TD has 458 mg·g⁻¹, TS-TTD has 516 mg·g⁻¹, and TS-BTT15 has 378 mg·g⁻¹. The adjustment of the adsorption data using the long- The Muir model yields coefficients of determination (R²) of 0.983, 0.988, and 0.974 for TS-TD, TS-TTD, and TS-BTT. This indicates monolayer adsorption of Hg²⁺ on the material surfaces. 3.Competitive Adsorption Experiments 20 For the competitive adsorption experiments, a mixed metal ion solution (Hg²⁺, Ni²⁺, Sr²⁺, Cs²⁺, La³⁺, Mg²⁺, K⁺, Ca²⁺, Mn²⁺, Co²⁺, Zn²⁺, Cd²⁺, Ce²⁺) with an initial concentration of 100 mg·L⁻¹ is prepared by directly dissolving the corresponding hydrochloride or nitrate salts in water. This is then diluted to a concentration of 10 mg·L⁻¹ and adjusted to a pH of 4 using a pH meter. The mixture is placed on a shaking platform 25 and shaken for 12 hours at room temperature. 2 mL The suspension is filtered through a 0.22 µm filter head, and the residual mercury content in the filtrate is analyzed by ICP-MS after dilution of the filtrate solvent. Fig. 6 shows the competitive adsorption of TS-COPs in the presence of 12 commonly occurring cations. As shown in Fig.Figure 6 shows the selective adsorption results of mercury ions (Hg²⁺) by the three polymer adsorbents in the presence of 12 frequently occurring competing metal cations (Ni²⁺, Sr²⁺, Cs⁺, La³⁺, Mg²⁺, K⁺, Ca²⁺, Mn²⁺, Co²⁺, Zn²⁺, Cd²⁺, Ce²⁺) for a 10 mg / L mixed solution. The results show that TS-TD, TS-TTD, and TS-BTT exhibit almost 35 adsorption sites under conditions with 12 competing ions due to their numerous adsorption sites and high adsorption capacity. Achieve 100% removal efficiency for Hg²⁺. This demonstrates the excellent interference resistance of these two adsorbents in the removal of Hg²⁺ from water and underlines the potential of TS-TD, TS-TTD, and TS-BTT for practical applications. 4. Repeatability Experiment To investigate the reusability of the TS-COPs adsorbent, five consecutive adsorption-desorption cycles are performed. 10 mg of adsorbent is added to 50 ml of a 10 mg·L⁻¹ mercury(II) solution in a 100 ml Erlenmeyer flask.The mixture is shaken for 12 hours to achieve mercury adsorption equilibrium. The supernatant is then collected, and 2 ml of the suspension is filtered through a 0.22 µm filter head. The filtrate is diluted and analyzed for residual mercury content using ICP-MS. The adsorbed 10 t of adsorbent collected by filtration is desorbed by soaking for 12 hours in a 0.5 M thiourea solution acidified with 50 ml of a 0.5 M MHCl solution. After desorption, the adsorbent is filtered and collected, then dried overnight in a vacuum drying oven at 60°C before being reused in the next cycle. Fig. 7 illustrates the reusability of TS-COPs (a) and their performance compared with others of the same category (b). As shown in Fig. 7, TS-TD and TS-TTD maintain Hg²⁺ removal efficiencies of over 90% after five adsorption-desorption cycles in a 10 mg·L⁻¹Hg²⁺ solution, while TS-BTT maintains a removal efficiency of over 80% under the same conditions.Given the excellent mercury ion adsorption capacity, favorable interference resistance, and the resulting recyclability of TS-TD, TS-TTD, and TS-BTT, these materials offer broad application possibilities for the adsorption and removal of Hg²⁺ ions from aqueous solutions. Covalent organic polymers (COPs) are being investigated as adsorbents for mercury. Most adsorbents for mercury may possess only a limited number of heteroatoms, such as sulfur and nitrogen, at the mercury chelation sites on the COP surface, leading to relatively low saturation adsorption capacities. Various COPs for mercury removal have been reported. Fig. 7b compares the maximum adsorption capacities of the adsorbent produced in this invention with those of similar polymer adsorbents. TS-TTD surpasses most 30 polymer adsorbents in their maximum adsorption capacity. Thiourea derivatives possess exceptionally high concentrations of heteroatoms (S,N).Sulfur and nitrogen atoms form stable complexes with Hg²⁺ ions via metal-thiol chelation and metal-nitrogen chelation, respectively. In the present work, the introduction of thiourea and thiophene functional groups into the structure increases both the diversity and the density of chelation sites, thereby achieving a high adsorption capacity. BE2025 / 7040 13 4. Adsorption Mechanism of Mercury To further investigate the adsorption mechanism, X-ray photoelectron spectroscopy (XPS) of the adsorbents TS-TD, TS-TTD and TS-BTT is performed before mercury adsorption and again of adsorbents TS-TD@Hg, TS-TTD@Hg and TS-BTT@Hg after mercury adsorption. All refined spectra are calibrated according to the 5 standards for organic polymers, with the C-C / C=C / CH peak in the refined C1s spectrum being corrected to 284.80 eV. TS-TTD, which exhibits the most effective adsorption, is selected as a representative example for detailed analysis. After Hg²⁺- Adsorption shows TS-TTD two new binding energy peaks (see Fig.8b) at 105.22 eV and 101.17 eV, respectively. These peaks correspond to Hg4f₅ / ₂ and Hg4f₇ / ₂, respectively, confirming the successful adsorption of mercury ions by TS-TTD. The refined N1s and S2p spectra of TS-TTD before and after mercury adsorption are shown in Fig. 8.

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