Novel ZnS/Carbon Nanofiber Photocatalyst for Degradation of Rhodamine 6G: Kinetics Tracking of Operational Parameters and Development of a Kinetics Model

Photocatalytic degradation of ciprofloxacin by MMT/CuFe2O4 nanocomposite: characteristics, response surface methodology, and toxicity analyses

The photocatalytic degradation of ciprofloxacin (CIP) was examined by loading spinel ferrite copper (CuFe2O4) nanoparticles onto montmorillonite (MMT) under irradiation using UV light. The laboratory parameters were optimized using response surface methodology (RSM), and maximum efficiency (83.75%) was achieved at a pH of 3, CIP concentration of 32.5 mg/L, MMT/CuFe2O4 dose of 0.78 g/L, and irradiation time of 47.50 min. During the photocatalysis process, the experiments on radical trapping demonstrated the generation of hydroxyls (•OH), superoxide (•O2-) radical, electrons (e-), and holes (h+). A low rate drop (below 10%) in the CIP degradation during the six consecutive reaction cycles corroborated the remarkable recyclability and stability of the MMT/CuFe2O4. The acute toxicity of the treated solution was determined using Daphnia Magna, by applying photocatalysis, which was indicative of a marked decline in the toxicity. Comparing the findings of the degradation using UV and the degradation process using visible light represented results with close resemblance to each other at the end of the reaction time. Besides, under UV and visible light, the particles in reactor are easily activated when the pollutant mineralization exceeded 80%.

Green construction of metal- and additive-free citrus peel-derived carbon dot/g-C3N4 photocatalysts for the high-performance photocatalytic decomposition of sunset yellow

In this study, novel, metal-free, CP-derived CDs/g-C₃N₄ nanocomposites (CDCNs) were created by introducing citrus peel-derived carbon dots (CP-derived CDs) into graphite carbon nitride (g-C₃N₄) by a green hydrothermal method. The CDCNs were revealed to have superior photoelectrochemical properties relative to pristine g-C₃N₄ for the photocatalytic degradation of the food dye sunset yellow (SY) under visible light. For SY decomposition, the recommended catalyst contributed almost 96.3% to the photodegradation rate after 60 min of irradiation, showing satisfactory reusability, structural stability and biocompatibility. Moreover, a mechanism for enhanced photocatalytic SY degradation was proposed according to band analysis, free radical trapping and electron paramagnetic resonance (EPR) results. A possible pathway for SY photodegradation was also predicted from UV-visible (UV-Vis) spectroscopy and high-performance liquid chromatography (HPLC) results. The constructed nonmetallic nanophotocatalysts afford a novel route for the elimination of harmful dyes and for the resource conversion of citrus peels.

Sphagnum perichaetiale Hampe biomass as a novel, green, and low-cost biosorbent in the adsorption of toxic crystal violet dye

In this study, the Sphagnum perichaetiale Hampe biomass was collected, characterized, and used as a biosorbent in the removal of crystal violet from water. The chemical and morphological results suggest that even after minimal experimental procedures, the biomass presented interesting properties regarding the adsorption of contaminants. Results of adsorption showed that the pH was not a relevant parameter and the best adsorbent dosage was 0.26 g L^-1. The kinetic results presented an initial fast step and the equilibrium was reached after 180 min. For the equilibrium data, the best adjustment occurred for the Sips model, reaching a maximum adsorption capacity of 271.05 mg g^-1 and the removal percentage obtained in the maximum adsorbent dosage was 97.11%. The thermodynamic studies indicated a reversible process and that the mass-transfer phenomena is governed by the physisorption mechanism. In addition to its great performance as a biosorbent, Sphagnum perichaetiale biomass also presents economic and sustainable benefits, as its production does not require costs with reagents or energy, usually used in chemical and physical activation. The reversible process indicated that the biosorbent could be reused, decreasing the costs related to the treatment of the effluents. Thus, Sphagnum perichaetiale biomass can be considered an efficient low-cost and eco-friendly biosorbent.

Dual-Functional Solar-to-Steam Generation and SERS Detection Substrate Based on Plasmonic Nanostructure

Solar-to-steam (STS) generation based on plasmonic materials has attracted significant attention as a green method for producing fresh water. Herein, a simple in situ method is introduced to fabricate Au nanoparticles (AuNPs) on cellulose filter papers as dual-functional substrates for STS generation and surface-enhanced Raman spectroscopy (SERS) sensing. The substrates exhibit 90% of broadband solar absorption between 350 and 1800 nm and achieve an evaporation rate of 0.96 kg·m^-2·h^-1 under 1-sun illumination, room temperature of 20 °C, and relative humidity of 40%. The STS generation of the substrate is stable during 30 h continuous operation. Enriched SERS hotspots between AuNPs endow the substrates with the ability to detect chemical contamination in water with ppb limits of detection for rhodamine 6G dye and melamine. To demonstrate dual-functional properties, the contaminated water was analyzed with SERS and purified by STS. The purified water was then analyzed with SERS to confirm its purity. The developed substrate can be an improved and suitable candidate for fresh water production and qualification.

Light driven Aspergillus niger-ZnS nanobiohybrids for degradation of methyl orange

Inorganic-microbial hybrid systems have potential to be sustainable, efficient and versatile chemical synthesis platforms by integrating the light-harvesting properties of semiconductors with microbial cells. Here, we demonstrate light-driven photocatalytic semiconducting Aspergillus niger cells-ZnS nanoparticles for enhanced removal of the dye methyl orange. Chemically synthesized ZnS nanoparticles exhibited a zinc blende pattern in X-ray diffraction, had a dimension of 20-90 nm with a band gap (E_bg) of 3.4 eV at 1.83 × 10¹⁸ photons/second. Biologically synthesized ZnS nanoparticles of 40-90 nm showed a hexagonal pattern in the X-ray powder diffraction spectra with an E_bg 3.7 eV at 1.68 × 10¹⁸ photons/second. At a methyl orange (MO) concentration of 100 mg/L, dosage of 0.5 × 10⁵ mol catalyst and pH 4, a 97.5% and 98% removal efficiency of MO was achieved in 90 min and 60 min for, respectively, chemically and biologically synthesized ZnS nanobiohybrids in the presence of UV-A light. The major degradation products of photocatalysis for chemically synthesized ZnS nanobiohybrids were naphtholate (C₁₀H₇O m/z 143) and hydroquinone (C₉H₅m/z 113). For the biologically synthesized ZnS nanobiohybrids, the degradation products were hydroquinone (C₉H₅m/z 113) and 2-phenylphenol (C₁₂H₁₀O m/z 170).

Antibiotics in livestock wastewater treatment by using biomass-derived activated carbon supported ZnS nanomaterials

A new type of composite photocatalyst material was successfully prepared through the ultrasound-assisted coprecipitation method precipitate of zinc sulfide (ZnS) nanomaterials on peach wood activated carbon (PAC). The optimization of ZnS@PAC demonstrates excellent photocatalytic performance by using the response surface method (RSM), which is essential for improving photocatalytic performance. In this model it was found that the photocatalytic degradation of enrofloxacin (ENR) increased with microwave heating power and ZnS concentration, whereas it decreased with increasing activation time. The RSM model predicts that under certain conditions (microwave heating power 800 W, activation time 3 h, ZnS 0.5 mol·L^-1), the maximum degradation rate of ENR in livestock and poultry wastewater is 97.81%. By empirical testing under the optimum conditions with 97.35% degradation the accuracy of the designed model was proven using RSM and the mechanism of the photocatalytic process was studied.

Ultrasound-assisted Synthesis of Ag-ZnS/rGO and its Utilization in Photocatalytic Degradation of Tetracycline Under Visible Light Irradiation

Recent improvements based on heterojunction nanocomposites have opened new possibilities in photocatalysis. In this research, an ultrasound-assisted coprecipitation method was used to fabricate silver, zinc sulfide and reduced graphene oxide (Ag-ZnS/rGO) nanocomposite, and characterization results indicated that 3% Ag-ZnS spherical nanoparticles are successfully embedded in rGO matrix. The potential of the Ag-ZnS/rGO, as a visible light active photocatalyst, was assessed through optimizing degradation of Tetracycline (TC) by response surface methodology. It was found that the photocatalytic degradation of TC increased with an increase in the amount of nanocomposite and irradiation time, whereas it decreased with increasing the initial TC concentration. Under the optimal conditions (10 mg L^-1 of TC, 1.25 g L^-1 of Ag-ZnS/rGO, at pH = 7, and irradiation duration 110 min), more than 90% of the TC was degraded. The study of the mechanism of the photocatalytic process disclosed that the synergistic role of surface plasmon resonance (SPR) induced by Ag nanoparticles and p-type semiconductor feature of rGO leads to ZnS semiconductor stimulation in the visible light region. Eventually, a pseudo-first order kinetics model was developed based on the proposed mechanism. The obtained results highlight the role of Ag-ZnS/rGO nanophotocatalyst toward degradation of some antibiotics under visible light.