Synthesis of mesoporous Fe/Al/La trimetallic oxide for photodegradation of various water-soluble dyes: Kinetic, mechanistic, and pH studies

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

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.

Efficient removal of basic yellow 28 dye from water using facilely synthesized ZnO and Mg3B2O6 nanostructures

Basic yellow 28 dye, used extensively in the textile and leather industries, poses significant environmental and health risks, including allergic reactions, skin irritation, and respiratory problems. This study reports the Pechini sol-gel synthesis of novel ZnO/Mg3B2O6 nanostructures for the decontamination of basic yellow 28 dye from aqueous solutions. The nanostructures were synthesized by calcining at 650 and 850 °C for 5 h, producing ZM650 and ZM850, respectively. The average crystallite sizes were 39.28 nm for ZM650 and 51.03 nm for ZM850. BET surface areas were 70.71 m2/g for ZM650 and 48.13 m2/g for ZM850. FE-SEM and HR-TEM analyses revealed distinct morphological structures, with ZM650 exhibiting a dense aggregation of rod-like particles and ZM850 showing larger clusters. The maximum adsorption capacities were 381.68 mg/g for ZM650 and 303.03 mg/g for ZM850. The optimum adsorption was observed at a pH of 10, a contact time of 70 min, and a temperature of 298 K. Regeneration using a 6 M HCl solution demonstrated efficient reusability over five cycles. The adsorption process followed pseudo-second-order kinetics and the Langmuir isotherm, indicating monolayer adsorption. Also, the adsorption process was found to be physical and exothermic.

Solvothermal synthesis of 3D rod-shaped Ti/Al/Cr nano-oxide for photodegradation of wastewater micropollutants under sunlight: a green way to achieve SDG:6

Waterbodies are day-by-day polluted by the various colored micropollutants, e.g., azo dyes enriched (carcinogenic, non-biodegradable) colored wastewater from textile industries. Water pollution has become a serious global issue as ~ 25% of health diseases are prompted by pollution as reported by WHO. Around 1 billion people will face water scarcity by 2025 and this water crisis is also a prime focus to the UNs' sustainable development goal 6 (SDG6: clean water and sanitation). To prevent the water pollution caused by micropollutants, a mesoporous, 3D rod-like nano-oxide Ti/Al/Cr (abbreviated as TAC) has been synthesized via the solvothermal method. TAC degraded all classes of azo dyes (mono, di, tri, etc.) with > 90% efficiency under renewable energy source solar irradiation within the pH range 2-11. The detailed study was done on the photodegradation of carcinogenic di-azo dye Congo red (CR) which is banned in many countries. TAC showed 90.64 ± 2% degradation efficiency for CR at pH 7. The proposed photodegradation mechanism of CR was confirmed by the high-resolution liquid chromatography-mass spectroscopy (HRLC-MS) analysis obeying the Pirkanniemi path. The photodegradation obeyed the pseudo-1st-order kinetics and was reusable up to successive 5 cycles which can be an efficient tool to meet the UNs' SDG:6.

Highly efficient adsorption of congo red and methyl orange dyes using mesoporous α-Mn2O3 nanoparticles synthesized with Pyracantha angustofolia fruit extract

Due to the many applications of manganese oxides in water treatment, this research aimed to synthesize α-Mn2O3 nanoparticles through a green method and investigate the dye adsorption capacity of them. The α-Mn2O3 nanoparticles were successfully synthesized using KMnO4 and aqueous extract of Pyracantha angustofolia fruits under hydrothermal conditions and calcination. The products were identified using Fourier transform infrared (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and scanning electron microscopy (SEM) analyses. The adsorption capacity of methyl orange (MO) and Congo red (CR) dyes were evaluated at different concentrations (25, 50, and 75 ppm) using α-Mn2O3 nanoparticles. Results revealed the spherical and porous structure of α-Mn2O3 nanoparticles with a specific surface area of 21.7 m2.g-1. Dye removal significantly increased with pH decrement. The adsorption capacity for MO and CR was 73.07 and 70.70 mg.g-1, respectively. The adsorption data of both dyes followed a pseudo-second-order kinetic model. The best fitted models for MO and CR adsorption were the Langmuir isotherm and the Dubinin-Radushkevich, respectively. In addition, a possible adsorption mechanism was proposed for both dyes. The findings showed that α-Mn2O3 nanoparticles are very efficient adsorbents for removing anionic dyes.

Humic acid-nanoceria composite as a sustainable adsorbent for simultaneous removal of uranium(VI), chromium(VI), and fluoride ions from aqueous solutions

In this article, the multifunctional behavior of novel, efficient, and cost-effective humic acid-coated nanoceria (HA@CeO2 NPs) was utilized for the sorptive removal of U(VI), Cr(VI), and F- ions at different conditions. The production cost of HA@CeO2 was $19.28/kg and was well characterized by DLS, FESEM, HRTEM, FTIR, XRD, XPS, and TGA. Batch adsorption study for U(VI) (at pH ~ 8), Cr(VI) (at pH ~ 1), and F- (at pH ~ 2) revealed that the maximum percentage of sorption was > 80% for all the cases. From the contact time experiment, it was concluded that pseudo-second-order kinetics followed, and hence, the process should be a chemisorption. The adsorption study revealed that U(VI) and Cr(VI) followed the Freundlich isotherm, whereas F- followed the Langmuir isotherm. Maximum adsorption capacity for F- was 96 mg g-1. Experiments in real water suggest that adsorption is decreased in Kaljani River water (~ 12% for Cr(VI) and ~ 11% for F-) and Kochbihar Lake water (25.04% for Cr(VI) and 20.5% for F-) because of competing ion effect. Mechanism was well established by the kinetic study as well as XPS analysis. Because of high adsorption efficiency, HA@CeO2 NPs can be used for the removal of other harmful water contaminants to make healthy aquatic life as well as purified drinking water.

Synthesis of novel antibacterial nanocomposite CuO/Ag-modified zeolite for removal of MB dye

Novel CuO/Ag nanocomposites added zeolite (CAZ) were successfully fabricated, and their effectiveness as an antibacterial on S. aureus and MB removal was evaluated. EDX, XRD, and FTIR confirm the presence of the elemental compositions of CAZ. Friable CuO nanorods (10-70 nm in diameter) existed on the surface of the zeolite. Pure zeolite had a higher band gap (5.433 eV) and lower MB removal efficiency than CAZ. The adsorption method by CAZ was more effective at removing MB than photodegradation. 0.10 CAZ had the highest removal effectiveness (~ 99%) and adsorption capacity (~ 70.4 mg g-1) of MB. The inhibitory zone diameter for 0.005 CAZ against S. aureus was 20 mm, while 0.01 CAZ had a diameter of 17 mm. Azithromycin, ceftriaxone, and erythromycin antibiotics demonstrated lower or no efficacy against S. aureus than CAZ. Significant antibacterial activities and wastewater treatment were achieved by CAZ. The combination of photodegradation and adsorption enhanced pollutant removal. It will be interesting to study further the optimal molar ratio for MB removal (0.10 CAZ) in future investigations.

Investigation on water defluoridation via batch and continuous mode using Ce-Al bimetallic oxide: Adsorption dynamics, electrochemical and LCA analysis

With variable atomic ratios, Ce-Al bimetallic oxides were fabricated using the sol-gel combustion method and utilized for efficient fluoride removal. The synthesized bimetallic oxides were extensively studied using advanced characterization techniques, including TGA, XRD, FTIR, BET surface area analysis, EDX-assisted FESEM, XPS and impedance analysis. These techniques facilitate the interpretation of the chemical and physical properties of the synthesized material. The Ce-Al (1:1) bimetallic oxide was selected as an adsorbent for the defluoridation. The Ce-Al (1:1) oxide demonstrates a moderately high surface area of 108.67 m²/g. The sorption behaviour of fluoride on Ce-Al (1:1) was thoroughly investigated using batch and column modes. The maximum fluoride removal efficiency (99.4%) was achieved at a temperature of 45 °C and pH of 7.0 using an adsorbent dose of 0.18 g/L for 35 min. Pseudo-second-order kinetic model appropriately describes the sorption process. Freundlich's adsorption isotherm was more pertinent in representing fluoride adsorption behaviour. The maximum fluoride adsorption capacity is 146.73 mg/g at 45 °C. Thermodynamics study indicates fluoride adsorption on Ce-Al (1:1) bimetallic oxide is spontaneous and feasible. The adsorption mechanism was interpreted through XPS spectra, indicating that the physisorption process is mainly responsible for fluoride adsorption. An in-depth investigation of the adsorption dynamics was carried out using mass transfer models and found that the external diffusion process limits the overall adsorption rate. An electrochemical investigation was performed to understand the effect of fluoride adsorption on the electrochemical behaviour of bimetallic oxide. The fixed-bed column adsorption study suggested that the lower flow rate and increased bed height favourably impacted the overall defluoridation process, and column adsorption results were suitably interpreted through both the Adam-Bohart model and Yoon-Nelson dynamics model. The sustainable aspect of the defluoridation process was elucidated in terms of carbon footprint measurement using life cycle assessment analysis. The carbon footprint of the entire treatment process was calculated as 0.094 tons/year.