Synthesis of a novel heterogeneous photocomposite catalyst ZnCo2O4 / g-C3N4 / Cu for the treatment of water and wastewater pollutants

Abstract

Design and synthesis of a new heterogeneous photocomposite catalyst ZnCo2O4 / g-C3N4 / Cu for the treatment of water and wastewater pollutants. This invention is related to the field of environment and can remove some persistent and organic pollutants of water and wastewater, such as some pharmaceutical pollutants (antibiotics). Therefore, there are various methods for the destruction and removal of pollutants, and advanced oxidation processes are an effective and efficient technology for the decomposition and destruction of dangerous, non-degradable and resistant organic pollutants. The main mechanism of this method is oxidation-reduction reactions and the production of highly active species. Among advanced oxidation processes, the use of photocatalytic reactions has been considered as an environmentally friendly method. In the present work, the design and synthesis of a new heterogeneous photocomposite catalyst ZnCo2O4 / g-C3N4 / Cu in the field of water and wastewater treatment was able to remove and destroy some pollutants such as a number of antibiotics (nitroimidazole group). This method is economical, recyclable and reusable, non-toxic, high production speed and also produces safe materials at the end of the reaction.

Description

Description of the invention Title of the invention Synthesis of a novel heterogeneous photocomposite catalyst ZnCo2O4 / g-C3N4 / Cu for the treatment of water and wastewater pollutants Technical background of the relevant invention This invention is related to the field of environment and can remove some persistent and organic pollutants from water and wastewater, such as some pharmaceutical pollutants (antibiotics). Technical problem and stating the objectives of the invention Persistent organic pollutants cannot be removed by conventional treatment methods because these methods cause the transfer of pollution from one phase to another and cause the production of new pollutants. Therefore, the use of new and efficient treatment methods such as advanced oxidation processes is essential. Among advanced oxidation processes, the use of heterogeneous semiconductor nanophotocatalysts as an environmentally friendly method, the ability to recover and reuse, the use of atmospheric oxygen as an oxidant, the possibility of performing the process under ambient conditions, and the possibility of complete mineralization of organic materials to water, carbon dioxide, and mineral acids have attracted much attention. A description of the state of the prior art and the history of developments related to the claimed invention. No invention or research has been conducted on the design and synthesis of the ZnCo2O4 / g-C3N4 / Cu composite heterogeneous nanocatalyst so far, but research and studies have been conducted on single or two components of the above nanocatalyst. For example: In 2019, Maryam Salimi and her colleagues investigated the efficiency of a number of D-g-C3N4 Bi5O7I composites for the photocatalytic degradation of metronidazole under visible light irradiation. The optimal photocatalytic efficiency was obtained at a pH of 10 and a catalyst dosage of 0.8 g / L. It was found that the changes in catalyst performance were negligible at least in four consecutive cyclic periods. In 2020, Yufang et al. successfully fabricated a CaFe2O4 / ZnCo2O4 composite photocatalyst for tetracycline degradation. The results showed that in the best reaction system (ZC-30), the tetracycline degradation rate reached 88% within 100 minutes of exposure to 300W xenon lamp light, and recycling experiments confirmed that the synthesized photocatalyst showed good stability after 3 cycles. In 2020, Zhenzhen Jiang and colleagues studied zinc cobaltite-bismuth erbium tungstate (ZnCo2O4–) nanocomposites. BiErWO6) was successfully synthesized by a simple hydrothermal method. Under visible light irradiation, the photocatalytic degradation efficiency of the nanocomposite with 15 wt% ZC composition showed an excellent degradation rate of 91.24% of ciprofloxacin drug within 120 min. Safajo and colleagues conducted research in 2021 on RGO / Cu nanocomposites for photocatalytic degradation of organic pollutants in water and wastewater. This combination can remove 91% and 72% of rhodamine and methylene blue dyes, respectively. Whereas the designed 3-component nanocatalyst ZnCo2O4 / g-C3N4 / Cu was synthesized for the first time and investigated on the degradation process of the pharmaceutical pollutant metronidazole. The results showed that the ZnCo2O4 / g-C3N4 / Cu nanocomposite presented an excellent photocatalytic performance towards the degradation of metronidazole under sunlight irradiation. The prepared catalyst was easily separated and recycled for at least eight cycles without significant loss of efficiency. The use of natural sunlight source, very low amount of photocatalyst (0.02 g / L), short reaction time (30 min), high degradation efficiency (98%), neutral pH, low operating costs, ease of recovery and reuse of the catalyst are the notable and outstanding points of this method compared to other researches. Providing a solution to an existing technical problem along with an accurate, sufficient, and integrated description of the invention Synthesis of g-C3N4NSs: Sequential polymerization and liquid exfoliation methods have been used to prepare g-C3N4NSs. In a typical experiment, 5 g of melamine powder was poured into a covered crucible and calcined at 550 °C (heating rate 5 °C / min) for 2.5 h. The resulting dense yellow solid was cooled to ambient temperature. It was then ground thoroughly to obtain a uniform bulk g-C3N4 powder. After that, 0.1 g of the obtained g-C3N4 bulk powder was dissolved in 100 ml of deionized water and sonicated for 6 h. Then, the obtained suspension was centrifuged (5000 rpm) to remove the remaining undepilated g-C3N4. Finally, g-C3N4NSs were obtained after drying in vacuum. Synthesis of ZnCo2O4 / g-C3N4 nanoparticles: 0.14 mmol of hexahydrate zinc nitrate Zn(NO3)2·6H2O and 0.28 mmol of hexahydrate cobalt nitrate Co(NO3)2·6H2O were dispersed in 80 mL of distilled water for 30 min. Then, 2 M NaOH solution was added dropwise to the mixture at room temperature to adjust the pH of the zinc solution to 10. The obtained suspension was stirred vigorously for 30 min at room temperature, then 0.5 g of previously synthesized g-C3N4NSs was added to the solution. The obtained suspension was refluxed for 1 h. After that, the obtained solution was centrifuged, washed repeatedly with deionized water and dried in vacuum. Finally, the obtained powder was heated at 350 °C for 2 h to obtain the desired ZnCo2O4 / g-C3N4. Synthesis of ZnCo2O4 / g-C3N4 / Cu: One gram of ZnCo2O4 / g-C3N4 was added to 30 mL of ethanol and sonicated for 30 min. Then, two mmol of copper acetate was added to 15 mL of ethanol and stirred for one hour. 30 mL of 0.1 M aqueous NaBH4 solution was added dropwise to the resulting suspension under vigorous stirring. After 4 h, the resulting ZnCo2O4 / g-C3N4 / Cu was separated by centrifugation, washed repeatedly with distilled water and ethanol, and dried in vacuo at 60 °C. Explanation of shapes, maps and diagrams Map 1 Synthesis of ZnCo2O4 / g-C3N4 / Cu nanocomposite: (Figure 1 Map file) Map 2 Nanophotocatalytic mechanism under light that causes photocatalytic degradation of metronidazole in the presence of ZnCo2O4 / g-C3N4 / Cu (Figure 2 Map file) Table 1 - Comparison of the photocatalytic efficiency of ZnCo2O4 / g-C3N4 / Cu with some other photocatalytic systems Figure 3 - Wastewater treatment system containing antibiotics A clear and precise statement of the advantages of the claimed invention over prior inventions. The designed nanocatalyst has the ability to degrade at wavelengths of 200-800 nm, which includes visible light, ultraviolet light, and sunlight, while according to studies and research, many catalysts are only active in the visible or ultraviolet light range. Among the advantages of this method are the use of natural sunlight, the neutrality of the reaction environment, short reaction time, very small amount of photocatalyst, high efficiency in the degradation process, the use of air as an oxidant, low operating cost, and ease of recycling the catalyst at least eight times with only a 9% decrease in degradation efficiency. Based on Table 1 in the map file, the photocatalytic efficiency of ZnCo2O4 / g-C3N4 / Cu has been compared with some other photocatalytic systems, which shows the superior ability of the aforementioned nanophotocatalytic system compared to other methods and previous research. Description of at least one implementation method for implementing the invention By designing and building a reactor, installing it at the wastewater outlet, and using this method and material in the designed reactor, it is possible to remove and destroy the target pollutant. Explicit mention of the industrial application of the invention This method can be used in various industries, including: pharmaceutical industries, hospital and clinic wastewater, paint industries, household wastewater, etc.

Claims

Claim What is claimed: Claim 1) What is claimed is the heterogeneous photocomposite catalyst ZnCo2O4 / g-C3N4 / Cu in the claimed invention for the treatment of water and wastewater to remove antibiotic pharmaceutical pollutants (nitroimidazole class) which includes the following components: - ZnCo2O4 which is composed of zinc nitrate hexahydrate Zn(NO3)2·6H2O and cobalt nitrate hexahydrate Co(NO3)2·6H2O - g-C3N4 which is obtained from melamine powder. - Cu Claim 2) With respect to claim 1: Synthesis of g-C3N4 NSs: Sequential polymerization and liquid exfoliation methods have been carried out to prepare g-C3N4 NS. In a typical experiment, 5 g of melamine powder was poured into a covered crucible and calcined at 550°C with a heating rate of 5°C / min for 2.5 hours. The resulting dense yellow solid was cooled to ambient temperature and then ground thoroughly to obtain a uniform bulk g-C3N4 powder. After that, 0.1 g of the obtained g-C3N4 bulk powder was dissolved in 100 ml of deionized water and sonicated for 6 hours. Then, the obtained suspension was centrifuged (5000 rpm) to remove the remaining non-exfoliated g-C3N4. Finally, g-C3N4 NSs were obtained after drying in vacuum. Claim 3) According to claim 1: Synthesis of ZnCo2O4 / g-C3N4 nanoparticles 0.1 mmol of zinc nitrate hexahydrate Zn(NO3)2·6H2O and 0.28 mmol of cobalt nitrate hexahydrate Co(NO3)2·6H2O were dispersed in 80 ml of distilled water for 30 min. Then 2 M NaOH solution was added dropwise to the mixture at ambient temperature to adjust the pH of the solution to 10. The obtained suspension was stirred vigorously for 30 min. Then 0.5 g of previously synthesized g-C3N4 NSs was added to the solution. The obtained suspension was refluxed for 1 h. After that, the obtained solution was centrifuged, washed repeatedly with deionized water and dried in vacuum. Finally, the resulting powder was heated at 350 °C for 2 h to The desired ZnCo2O4 / g-C3N4 is obtained. Claim 4) Regarding claim number 1: Synthesis of ZnCo2O4 / g-C3N4 / Cu: One gram of ZnCo2O4 / g-C3N4 was added to 30 ml of ethanol and sonicated for 30 minutes. Then, two mmol of copper acetate was added to 15 ml of ethanol and stirred for one hour. 30 ml of 0.1 M NaBH4 aqueous solution was added dropwise to the resulting suspension under vigorous stirring. After 4 hours, the resulting ZnCo2O4 / g-C3N4 / Cu was separated by centrifugation, washed repeatedly with distilled water and ethanol, and dried in vacuum at 60°C. Claim 5) Regarding claim 1: An example of a method for performing antibiotic degradation experiments using the synthesized nanophotocatalyst is as follows: Antibiotic (metronidazole) degradation experiments were conducted at room temperature in a 500 ml batch reactor. In all experiments, the solutions were exposed to sunlight from 11 am to 3 pm. A magnetic stirrer (350 rpm) was used continuously to ensure the homogeneity of the suspension. Continuous oxygen supply was performed using an air pump. The degradation ability of ZnCo2O4 / g-C3N4 / Cu was tested by evaluating various factors including pH (3, 5, 7, 9 and 11), contact time (up to 60 min), catalyst amount (0.05 – 0.005 g / L) and metronidazole drug concentration (10-30 mg / L). Before exposure to sunlight, the reaction solution was incubated in the dark for 30 min. It was stirred to ensure the equilibrium of adsorption and desorption. Then, at certain time intervals (5 minutes) of the reaction, 2 ml of the suspension was sampled and then centrifuged to separate the photocatalyst from the solution. Finally, the concentration was determined.The soluble metronidazole residue was analyzed at a wavelength of 320 nm using a spectrophotometer. Claim 6) Regarding claim 8: The prepared photocatalyst was analyzed using XRD, XPS, FE-SEM, DRS, TEM, FT-IR, EDS and elemental mapping techniques. The kinetics of antibiotic (metronidazole) degradation and the efficiency of operational parameters including initial drug dose (10-30 mg / L), photocatalyst dose (0.05-0.005 g / L), pH (3-11) and contact time (5-30 min) on the degradation process of the target drug were investigated. The results showed that the ZnCo2O4 / g-C3N4 / Cu nanocomposite presented excellent photocatalytic performance towards antibiotic degradation under sunlight irradiation. The increased photocatalytic activity of this nanocomposite can be attributed to the synergistic photo-effects between ZnCo2O4, g-C3N4 and Cu. The prepared catalyst was easily separated and recycled for at least eight cycles without significant reduction in efficiency. Using natural sunlight source, very low amount of photocatalyst (0.02 g / L), short reaction time (30 minutes), high efficiency of the degradation process (98%), neutral pH, low operating costs, ease of recovery and reuse of the catalyst are the notable points of the present method.

Images