Core-shell composite nanoarchitectonics of TiO2@NiCo2S4 via thermal decomposition approach for photodegradation of congo red

In the present work, TiO2@NiCo2S4 core-shell nanocomposites have been successfully synthesized using a thermal decomposition approach using nickel acetyl acetonate and cobalt acetyl acetonate as metal salts and thiourea as source of sulfur in the presence of TiO2 microspheres in diphenyl ether at about 200 °C in air aiming at their application in photodegradation of congo red (CR), a dye pollutant. The thickness of NiCo2S4 nanoparticles (shell) could be varied using different concentrations of reagents. Various analytical techniques were used to characterize the TiO2@NiCo2S4 core-shell nanocomposites including powder XRD, FE-SEM, XPS, TEM and EDX confirming their successful synthesis. The synthesized core-shell nanocomposites exhibit notable photocatalytic activity towards degradation of an aqueous solution of congo red under sunlight. The photocatalytic degradation efficiency of TiO2@NiCo2S4 nanocomposites is better than that of TiO2-based nanocomposites, metal sulfide nanoparticles and other nanocomposites reported in the literature.

New bacterial strains isolated from Tunisian biotopes: A sustainable enzymatic approach for decolorization and detoxification of Congo Red and Malachite Green

Seven bacterial strains, isolated from various Tunisian biotopes, were investigated for Congo Red (CR) and Malachite Green (MG) decolorization. The isolated strains underwent morphological and biochemical tests, including assessments for antibiotic sensitivity as well as biofilm formation. One selected strain, ST11, was partially identified as Paenibacillus sp. strain ST11. The newly isolated crude bacterial filtrates (NICBFs) effectively decolorized CR and MG. Specifically, six and seven NICBFs were found to be effective for degrading CR (150 mg l-1) and MG (50 mg l-1), respectively. Under non-optimized conditions, CR and MG could be decolorized up to 80% within 6-12 h. The degradation products of CR and MG, characterized by UV-visible and FT-IR techniques, demonstrated both decolorization and transformation, highlighting the role of enzymes in dye degradation. Phytotoxicity and cytotoxicity studies evaluated the impact of treated and untreated CR and MG. Some NICBFs showed promise as powerful biological tools, reducing and sometimes detoxifying CR and MG, commonly used as fertilizers. The potential applications of these NICBFs in decolorization and bioremediation of dye-rich textile effluents were explored. The screening also identified environmentally friendly, cost-effective bacterial strains adaptable to various conditions through phytotoxicity and cytotoxicity studies.

Control of particle growth and enhancement of photoluminescence, adsorption efficiency, and photocatalytic activity for zinc sulfide and cadmium sulfide using CoAl-layered double hydroxide system

The fabrication of zinc sulfide (ZnS) and cadmium sulfide (CdS) hybrids was carried out by the sulfidization of Zn(II) or Cd(II) adsorbed in dodecylsulfate modified CoAl-layered double hydroxide through solid-liquid reaction. The TEM images showed the nanocrystals of ZnS (2.61 nm) or CdS (3.29 nm) orderly distributed on the nanosheets. The BET surface area of ZnS (1.13 m²/g) and CdS (0.78 m²/g) was largely improved by intercalating in the interlayer space of CoAl-layered double hydroxide system (15-20 m²/g). The spectroscopic observations further confirmed the formation of ZnS or CdS nanoparticles in the hybrid as the evidence of the blue-shifted absorption onset (39-44 nm), and the increase of the photoluminescence intensity (3-4 times) relative to those of bare ZnS and CdS. The nanohybrids could be applicable as the adsorbent and photocatalyst on purifying wastewater contaminated with Congo red dye. By the adsorptive removal, the hybrids exhibited the maximum adsorption capacity of 216-234 mg/g, resulting from the effect of CoAl-layered double hydroxide. In addition, the photocatalytic degradation was completely conducted by using CdS hybrid with the rate constant of 0.0115 min^-1, because the host-guest and/or guest-guest interactions promoted the greater optical performance, and adsorption and photocatalytic efficiencies.

Photocatalytic removal of organic dye using green synthesized zinc oxide coupled cadmium tungstate nanocomposite under natural solar light irradiation

In this work, zinc oxide coupled cadmium tungstate (ZnO-CT) was prepared as a nano-photocatalyst through a green synthesis route using lemon leaf extract and characterized based on diverse microscopic and spectroscopic techniques. To explore the applicabilties of the prepared nanocomposite (NC), its photocatalytic activity has been investigated against Congo red (CR) dye under natural solar light irradiation conditions. ZnO- CT nano-photocatalyst showcases 97% photocatalytic degradation of the CR after 90 min of natural solar light irradiation with quantum yield of 1.16 × 10^-8 molecules photon^-1. The ZnO-CT NC has shown the enhanced photocatalytic degradation performance against CR when compared to its pristine forms (e.g., ZnO (70%) or CT (44%)). According to the free radical trapping and quenching experiments, the photocatalytic activity of ZnO-CT NC appears to be driven efficiently by superoxide and hydroxyl radicals. The photocatalytic degradation kinetics for CR dye was also studied using the pseudo-first-order, diffusional, and Singh models. The high photocatalytic activity of ZnO-CT NC can be accounted for by the presence of electron-withdrawing functional groups like acids (-COOH) and aldehydes (-CHO) on its surface which helped maintain the prolonged recombination of charge carriers and enhanced stability of ZnO-CT (with moderately low leaching rate of cadmium ions (∼2-5%)).

Surface conjugation of titanium dioxide nanoparticles on nano-graphene oxide enhances photocatalytic degradation of azo dyes under sunlight

Here, conjugate of nano-graphene oxide (GO) and titanium dioxide nanoparticle (nTiO₂) was proposed for the photocatalytic degradation of two toxic azo dyes, Congo red (CR) and Methylene blue (MB), under sunlight irradiation. Furthermore, the optimized weight ratio between GO and nTiO₂ of 1:5 demonstrated the highest degradation efficiency. The nanoconjugate induced 85% degradation of 40 ppm of CR in 60 min and a complete degradation within 70 min, while it degraded more than 90% of 20 ppm of MB in 80 min. The photocatalyst can be reused for five cycles of photocatalysis. Thus, the photocatalytic potential of GO/nTiO₂ under visible light may be used as a very suitable and cost-effective photocatalyst industrially for the removal of toxic dyes from water.

Elimination of Congo Red Dye from Industrial Wastewater Using Teucrium polium L. as a Low-Cost Local Adsorbent

A novel adsorbent prepared from the leaf powder of Teucrium polium L. (TPLLP) was characterized and its ability for adsorption of Cong red (CR) was inspected. Influences of CR concentration, adsorbent dosage, time of agitation, pH of solution, and temperature on the performance of this adsorption were also examined. Three models of kinetic along with three different isotherm models were applied for analyzing the empirical data of this adsorption. Additionally, the thermodynamic constants of were decided. The surface area, pore volume, pore size, and pHZPC of Zn/Cu-TPLLP were found to be 2.6436 m2.g-1, 0.013317 cm3.g-1, 527.393 Å, and 8.8, respectively. The achieved outcomes indicate the positive influence of temperature, concentration of CR in the range of 20 to 900 mg/L, adsorbent mass in the range of 0.005 to 0.02 g, time of adsorption from 0 to 120 min, and pH from 5.5 to 8.5. Models of the 2nd order with $R^2\ge 0.995$ and Langmuir with $R^2\ge 0.990$ were the best among the other kinetic and isotherm models applied in this research. Moreover, superior capacities of 526.32, 666.67, and 909.09 (mg.g-1) were stemmed at 27, 42, and 57°C, respectively. The outcomes of the thermodynamic evidenced that this adsorption is spontaneous and a heat absorber.

Formation of Single-Walled Carbon Nanotube-Ruthenium Nanoparticles in Ethanol upon Microwave Radiation

In this work, an environmentally friendly microwave method was employed to rapidly synthesize a single-walled carbon nanotube-Ru nanoparticle (SWCNT-Ru) catalyst utilizing ethanol as the reducing agent. In general, the SWCNT-Ru nanoparticle catalyst facilitated the degradation of Congo red dye solutions, of both low and high concentrations, within eight minutes at room temperature, and possessed great recoverability and reusability properties. High-resolution transmission electron microscopy (HR-TEM) analysis of the SWCNT-Ru nanoparticle catalyst, which was synthesized with 0.05 wt. % RuCl₃ in ethanol, revealed highly dispersed Ru nanoparticles of the averaged size of 2.0 nm ± 0.5 nm onto the single-walled carbon nanotube bundles. Raman spectroscopy analysis indicated that there was no alteration to the nanotube structural framework upon the formation of the Ru nanoparticles. UV-Visible spectroscopy analysis indicated that the electronic properties of both smaller and larger diameters of SWCNTs were altered upon the coordination of the Ru nanoparticles. In addition, studies showed that when using ethanol as a reducing agent, concentrations of the RuCl₃ salt must remain below 0.10 wt. % to facilitate the production of Ru nanoparticles with efficient catalytic properties.

Mechanistic Insights into Photodegradation of Organic Dyes Using Heterostructure Photocatalysts

Due to its low cost, environmentally friendly process, and lack of secondary contamination, the photodegradation of dyes is regarded as a promising technology for industrial wastewater treatment. This technology demonstrates the light-enhanced generation of charge carriers and reactive radicals that non-selectively degrade various organic dyes into water, CO2, and other organic compounds via direct photodegradation or a sensitization-mediated degradation process. The overall efficiency of the photocatalysis system is closely dependent upon operational parameters that govern the adsorption and photodegradation of dye molecules, including the initial dye concentration, pH of the solution, temperature of the reaction medium, and light intensity. Additionally, the charge-carrier properties of the photocatalyst strongly affect the generation of reactive species in the heterogeneous photodegradation and thereby dictate the photodegradation efficiency. Herein, this comprehensive review discusses the pseudo kinetics and mechanisms of the photodegradation reactions. The operational factors affecting the photodegradation of either cationic or anionic dye molecules, as well as the charge-carrier properties of the photocatalyst, are also fully explored. By further analyzing past works to clarify key active species for photodegradation reactions and optimal conditions, this review provides helpful guidelines that can be applied to foster the development of efficient photodegradation systems.

Visible light-assisted photocatalytic mineralization of diuron pesticide using novel type II CuS/Bi2W2O9 heterojunctions with a hierarchical microspherical structure

A hierarchical CuS/Bi₂W₂O₉ heterojunction photocatalyst exhibits excellent photocatalytic activity for the degradation of diuron achieving 95% mineralization within 3 h of irradiation.