Gamma-irradiated copper-based metal organic framework nanocomposites for photocatalytic degradation of water pollutants and disinfection of some pathogenic bacteria and fungi

Abstract

Background: Although there are many uses for metal-organic framework (MOF) based nanocomposites, research shows that these materials have received a lot of interest in the field of water treatment, namely in the photodegradation of water contaminants, and disinfection of some pathogenic bacteria and fungi. This is brought on by excessive water pollution, a lack of available water, low-quality drinking water, and the emergence of persistent micro-pollutants in water bodies. Photocatalytic methods may be used to remove most water contaminants, and pathogenic microbes, and MOF is an excellent modifying and supporting material for photocatalytic degradation.

Methods: This work involved the fabrication of a unique Cu-MOF based nanocomposite that was exposed to gamma radiation. The nanocomposite was subsequently employed for photocatalytic degradation and as an antimicrobial agent against certain harmful bacteria and fungi. The produced Cu-MOf nanocomposite was identified by XRD, SEM, and EDX. Growth curve analysis, UV lighting impact, and antibiofilm potential have been carried out to check antimicrobial potential. Additionally, the membrane leakage test was used to determine the mechanism of the antimicrobial action. In an experimental investigation of photocatalytic activity, a 50 mL aqueous solution including 10.0 ppm of Rhodamine B (RB) was used to solubilize 10 mg of Cu-MOF. It has been investigated how pH and starting concentration affect RB elimination by Cu-MOF. Ultimately, RB elimination mechanism and kinetic investigations have been carried out.

Results: SEM images from the characterization techniques demonstrated the fact that the Cu-MOF was synthesized effectively and exhibited the Cu-MOF layers' flake-like form. Uneven clusters of rods make up each stratum. The primary peaks in the Cu-MOF's diffraction pattern were found at 2θ values of 8.75^◦, 14.83^◦, 17.75^◦, 21.04^◦, 22.17^◦, 23.31^◦, 25.41^◦, and 26.38^◦, according to the XRD data. After 135 min of UV irradiation, only 8% of RB had undergone photolytic destruction. On the other hand, the elimination resulting from adsorption during a 30-min period without light was around 16%. Conversely, after 135 min, Cu-MOF's photocatalytic breakdown of RB with UV light reached 81.3%. At pH 9.0, the greatest removal of RB at equilibrium was found, and when the amount of photocatalyst rose from 5 to 20 mg, the removal efficiency improved as well. The most sensitive organism to the synthesized Cu-MOF, according to antimicrobial data, was Candida albicans, with a documented MIC value of 62.5 µg mL^-1 and antibacterial ZOI as 32.5 mm after 1000 ppm treatment. Cu-MOF also showed the same MIC (62.5 µg mL^-1) values against Staphylococcus aureus and Escherichia coli, and 35.0 and 32.0 mm ZOI after 1000 ppm treatment, respectively. Ultimately, it was found that Cu-MOF (1000 µg/mL) after having undergone gamma irradiation (100.0 kGy) was more effective against S. aureus (42.5 mm ZOI) and E. coli (38.0 mm ZOI).

Conclusion: From the obtained results, the synthesized MOF nanocomposites had promising catalytic degradation of RB dye and high antimicrobial potential which encouraging their use in wastewater treatment against some pathogenic microbes and polluted dyes. Due to the exceptional physicochemical characteristics of MOF nanocomposites, it is possible to create and modify photocatalytic nanocomposites in a way that improves their recovery, efficiency, and recyclability.

Keywords: 1, 2, 3-triazoles; Antimicrobial activity; Cu-MOFs; Gamma-rays; Nanocomposites; Photocatalytic degradation.

Scheme 1

Synthetic procedures of the target molecule STHC

Fig. 1

H¹NMR spectrum of STHC

Fig. 2

C¹³NMR spectrum of STHC

Scheme 2

The proposed mechanism of Cu-MOF synthesis

Fig. 3

Field-emission scanning electron microscopy images of the Cu-MOF at different magnifications

Fig. 4

a Energy-Dispersive X-ray analysis EDX of Cu-MOF. b XRD spectrum of Cu-MOF

Fig. 5

a UV-Vis. spectrum of Rhodamine B (RB) at different concentration, b calibration curve using (2.5 – 20.0 mg/L) of RB and c Removal of RB within 135 minutes due to photolysis without the catalyst (black line), photocatalysis under UV irradiation (Red line).

Fig. 6

a Showing the variation of RB removal (%) with time at different solution pH (3.0, 5.0, 7.0 and 9.0) (10 mg g of Cu-MOF in 50 ml of 10 mg/L RB at 25 ^oC). b Point of zero charge (PZC) of Cu-MOF.

Fig. 7

a The variation of percent removal as a function of contact time at different initial RB concentrations (5.0 – 15.0 mg/L) at pH 9 and 10.0 mg Cu-MOF and b Effect of the photocatalyst dose on the removal efficiency of RB (50 ml RB solution (10 mg/L), Temp. = 25 ^oC and pH 9).

Fig. 8

a Kinetics plots for linear fitting of data obtained from pseudo-first-order reaction model for RB degradation under UV light irradiation and 10 mg catalyst, 50 mL of 5, 10, and 15 mg /L dye concentration, and b Shows a relation of apparent pseudo-first-order rate constants vs. initial concentration of RB.

Fig. 9

Proposed mechanism of photocatalytic degradation of RB by Cu-MOF nanocomposites

Fig. 10

The effect of Cu-MOF nanocomposites on the growth curve of (a) S. aureus, and (b) E. coli

Fig. 11

The effect of Cu-MOF nanocomposites on the protein leakage from S. aureus, and E. coli cell membranes

Fig. 12

The UV effect on the antibacterial activity of Cu-MOF nanocomposites against S. aureus (a),and E. coli (b)

Fig. 13

Presents the predicted mechanism of reaction of the produced Cu-MOF nanocomposites toward the bacterial cell. These reactions include the following: 1) Cu-MOF nanocomposites adheres to the bacterial cell's exterior and causes membrane failure, endocytosis, the formation of endosomes, and changed transport potential, 2) Cu-MOF nanocomposites harm the electron transport chain; 3) Cu-MOF nanocomposites prevents ions from passing through the bacterial cell, 4) Cu-MOF nanocomposites produces and increases ROS, suggesting that the wall of the bacterial cell is beginning to weaken, 5) Cu-MOF nanocomposites enters bacterial cells and interacts with organelles (such as DNA) to change how those components operate and cause lysis of the cells, (6) Cu-MOF nanocomposites interacts with metabolism and enzymes, (7) Cu-MOF nanocomposites disrupts the cell membrane, causing internal organelles to seep out, and (8) Cu-MOF nanocomposites inhibits the membrane protein. In the cytoplasm and layer, where the existence of a proton motive force could lead the pH to drop below 3.0 and induce the discharge of copper ions, MOF nanocomposite might also function as a carrier to effectively release copper ions. The figure was designed by BioRender.com