Comparative procedure of photodegradation of methylene blue using N doped activated carbon loaded with hollow 3D flower like ZnS in two synergic phases of adsorption and catalytic

Structural and optical properties of silver supported α-Fe2O3 nanocomposite fabricated by Saraca asoca leaf extract for the effective photo-degradation of cationic dye Azure B

In recent decades, several nanocomposites developed by chemical synthetic routes, have been demonstrated as efficient photocatalysts for the photodegradation of hazardous organic dyes. The present investigation reports the sonochemical-assisted fabrication of silver-supported α-Fe2O3 nanocomposites (SA@Ag@IONCs) using the Saraca asoca leaf extract. The magnetic nanocomposites can be easily removed from the reaction mixture. The morphology of these materials was characterized by field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), XPS, BET surface area analyzer, UV-visible spectroscopy, photoluminescence, X-ray diffraction (XRD), and VSM techniques. The XRD and electron microscopy analyses revealed the small size and well-crystalline SA@Ag@IONC particles with spherical and buckyball structures. The large surface area of SA@Ag@IONCs was confirmed by BET analysis. The absorption edge in UV-visible spectra appeared to migrate towards high wavelengths for the SA@Ag@IONC composite, causing a change in the bandgap energy. In the case of the sonication assisted composite, the bandgap energy was 2.1 eV, making it easier for the electron to transfer from the valence band to conduction band. The decoration of ultrasmall silver onto the surfaces of the α-Fe2O3 nanocomposite, which considerably increases the capacity to absorb sunlight, enhances the efficiency of charge carrier separation, and inhibits the electron-hole recombination rate as confirmed by the reduced PL intensity, is responsible for the excellent photocatalytic degradation performance. Outcomes shown SA@Ag@IONCs have a high photodegradation rate as well as high-rate constant value at an optimized condition that is at pH 9 and 0.5 g L-1 dose of nanocomposite, photodegradation rate of Azure B is ∼94%. Trap experiment results indicated that O2˙- and h+ are the active species responsible for the photodegradation of AzB.

Study of Photocatalytic Oxidation of Micropollutants in Water and Intensification Case Study

During the last decades, heterogenous photocatalysis has shown as the most promising advanced oxidation process for the removal of micropollutants due to degradation rate, sustainability, non-toxicity, and low-cost. Synergistic interaction of light irradiation, photocatalysts, and highly reactive species are used to break down pollutants toward inert products. Even though titanium dioxide (TiO2) is the most researched photocatalyst, to overcome shortcomings, various modifications have been made to intensify photocatalytic activity in visible spectra range among which is modification with multiwalled carbon nanotubes (MWCNTs). Therefore, photocatalytic oxidation and its intensification by photocatalyst’s modification was studied on the example of four micropollutants (diclofenac, DF; imidacloprid, IMI; 1-H benzotriazole, BT; methylene blue, MB) degradation. Compound parabolic collector (CPC) reactor was used as, nowadays, it has been considered the state-of-the-art system due to its usage of both direct and diffuse solar radiation and quantum efficiency. A commercially available TiO2 P25 and nanocomposite of TiO2 and MWCNT were immobilized on a glass fiber mesh by sol-gel method. Full-spectra solar lamps with appropriate UVB and UVA irradiation levels were used in all experiments. Photocatalytic degradation of DF, IMI, BT, and MB by immobilized TiO2 and TiO2/CNT photocatalysts was achieved. Mathematical modelling which included mass transfer and photon absorption was applied and intrinsic reaction rate constants were estimated: kDF=3.56 × 10−10s−1W−0.5m1.5, kIMI=8.90 × 10−11s−1W−0.5m1.5, kBT=1.20 × 10−9s−1W−0.5m1.5, kMB=1.62 × 10−10s−1W−0.5m1.5. Intensification of photocatalysis by TiO2/CNT was observed for DF, IMI, and MB, while that was not the case for BT. The developed model can be effectively applied for different irradiation conditions which makes it extremely versatile and adaptable when predicting the degradation extents throughout the year using sunlight as the energy source at any location.

Decolorization of Azo Dyes by Chemically and Biosynthesized ZnO Nanoparticles

Dye contaminants in industrial effluents contribute significantly to environmental pollution. Conventional wastewater treatment methods are expensive and energy-consuming. These limitations could be overcome by the use of nanobioremediation processes. The present work was an effort to study decolorization of azo dyes by ZnO nanoparticles (NPs). Rubine GDB (R-GDB) and Congo Red (CR) were the azo dyes selected for the study. The ZnO NPs were successfully synthesized by chemical and biological methods. Chemical synthesis of ZnO NPs was carried out by co-precipitation method; biosynthesis was done using bacteria Bacillus subtilis. The synthesized nanoparticles were characterized by UV-Vis Spectroscopy, SEM, and XRD. The UV spectrophotometer showed peaks in the range of 300-400 nm. SEM pictures indicated the presence of NPs in the size of 100-200 nm. XRD results were analyzed based on the peaks that were seen. EDX analysis showed the presence of Zn particles and oxygen particles majorly. Decolorization efficiency was evaluated by calculating % decolorization by Meyer's method. Chemically synthesized NPs showed maximum % decolorization of the R-GDB (89.55 ± 0.44%) and CR (88.52 ± 0.90%). The biosynthesized NPs showed the least decolorization (R-GDB, 18.46 ± 0.45% and CR, 21.41 ± 1.02%). However, moderate percentages of decolorization of both the azo dyes were observed when a combination of the NPs was used (R-GDB, 36.25 ± 0.22% and CR, 39.47 ± 0.94%). Nanoparticles showed good potential for the decolorization of the azo dyes. With further optimization of the parameters, the present findings show that dye decolorization by chemically synthesized ZnO NPs could be used as a probable nanobioremediation approach to treat wastewaters.

Network structure-based decorated CPA@CuO hybrid nanocomposite for methyl orange environmental remediation

A unique network core-shell hybrid design-based cross-linked polyaniline (CPA), which was coated with CuO nanoparticles (NPs) and decorated with nitrogen-doped SWCNT/GO/cellulose N-SWCNTS-GO-CE, has been fabricated using the oxidative polymerization technique. This hybrid nanocomposite shows excellent photocatalytic degradation and an acceptable adsorption capability for Methyl Orange (MO) dye in aqueous solutions with a very slight effect for the N-SWCNTS-GO-CE CuO component. The prepared nanocomposites were used for the removal of a carcinogenic and noxious dye, Methyl Orange, from aqueous samples under various adsorption conditions. Approximately 100% degradation of 10 mg/L of Methylene orange dye was observed within 100 min at pH 6.0 using 50 mg/L CPA/N-SWCNTS-GO-CE/CuO nanocomposite under UV radiation. Additionally, significant factors were investigated on the degradation process including the contact time, MO initial concentration (Ci), solution pH, and dosage of the CuO nanocomposite. All investigated experiments were performed under UV radiation, which provided significant data for the MO degradation process. Furthermore, the recovery of the nanocomposite was studied based on the photocatalytic process efficiency. The obtained data provide the high opportunity of reusing CPA/N-SWCNTS-GO-CE/CuO nanocomposite for numerous photocatalytic processes. The CPA/N-SWCNTS-GO-CE/CuO nanocomposite was prepared via chemical oxidative copolymerization of polyaniline (PANI) with p-phenylenediamine (PPDA) and triphenylamine (TPA) in the presence of N-SWCNTS-GO-CE and CuO NPs. The morphology, structure and thermal properties of the CPA/N-SWCNTS-GO-CE/CuO nanocomposite were investigated using various techniques, including FTIR, XRD, RAMAN, SEM, MAP, EDX, TEM, TGA and DTG. Therefore, CPA/N-SWCNTS-GO-CE/CuO nanocomposite can be effectively used as a convenient and reusable adsorbent to remove hazardous dye from wastewater.

Synthesis, characterization and photo-catalytic activity of guar-gum-g-aliginate@silver bionanocomposite material

The green mechanism for the synthesis of nanoparticles and their application to the wastewater treatment is of inordinate curiosity to the research community. Herein we outline a novel method for the synthesis of silver nanoparticles via a green route using alginate-guar gum blend (GG-Alg@Ag) and their application to degrade methylene blue (MB) dye. The synthesized material was characterized by FTIR, XRD, SEM-EDX, TEM, TGA-DTG, AFM, and UV-vis techniques. A combination of RSM and CCD was employed to compute the system and optimized values of various interacting parameters such as exposure time (120 min), pH (4.98), dye concentration (194 mg L⁻¹), and catalyst dose (0.07 g) with a photodegradation capacity of 92.33% and desirability 1.0. The mechanism of degradation reaction was best elucidated by the pseudo-second-order model suggesting chemical deposition of MB on the GG-Alg@Ag surface through followed by the reduction mechanism in the occupancy of visible light. The optical studies indicated a value of 2.5 eV by Tauc's plot for bandgap energy (E_g) for GG-Alg@Ag bionanocomposite.

The green mechanism for the synthesis of nanoparticles and their application to the wastewater treatment is of inordinate curiosity to the research community.

N-Doped Carbon-Coated ZnS with Sulfur-Vacancy Defect for Enhanced Photocatalytic Activity in the Visible Light Region

In this work, N-doped carbon-coated ZnS with a sulfur-vacancy defect (ZnS@N-C) was performed for the visible-light-driven photodegradation of tetracycline hydrochloride (TCH). The obtained ZnS@N-C exhibited enhanced photocatalytic activity compared with ZnS for TCH removal. Among these ZnS@N-C composites, ZnS@N-C-3 with N-doped content of 3.01% (100 nm) presented the best visible-light photocatalytic activity and superior long-term photocatalytic stability after five cycle times for TCH removal in the visible light region. This may be ascribed to the interface between the N-doped carbon shell and ZnS with a sulfur-vacancy defect for efficient charge transfer and the restrained recombination of charge carriers. Electron spin resonance (ESR) results indicate that the ·O₂^‒ radical plays a crucial role in the enhanced photocatalytic activity of ZnS@N-C-3.

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.

ZnO nanospheres based simple hydrothermal route for photocatalytic degradation of azo dye

This novel work presents a promising application to use Zinc oxide nanospheres as nanocatalysts in photocatalytic degradation of methyl orange dye. The hydrothermal route was utilized in the synthesis process of ZnO nanospheres. The size of the synthesized ZnO nanoparticles is around 200-250 nm diameter. The synthesized nano-oxides were characterized utilizing several instruments such as X-ray diffraction, Brunauer, Emmett, and Teller (BET), and scanning electron microscope (SEM). The resulting nanoparticles are utilized as an efficient tool for degradation of methyl orange (MO) dye under UV radiation. Essential parameters were studied on degradation process involving the initial concentration of MO, pH, stirring the solution, dose of the ZnO nanospheres, the oxygen content of the solution, calcination of the nanomaterials. All activity experiments under UV radiation provide excellent results for the degradation process of MO. Also, the recovery of ZnO nanomaterials was investigated based on the photocatalytic process efficiency. The results show the high possibility of reuse ZnO nanospheres for several photocatalytic processes. Also, the nanocatalysts were applied for a real environmental sample with providing high photocatalytic performance.