Loss In Degradation Efficiency Research Articles

Boosting the performance of LaCoO3/MoS2 perovskite interface for sustainable decontaminants under visible light-driven photocatalysis

The novel composite LaCoO3/MoS2 hybrid nanostructure was synthesized via a combination of sol-gel, hydrothermal, and ultrasonication methods. Alizarin Red S (ARS) and Rhodamine B (RhB) were employed as a model pollutant, to assess the photodegradation efficiency of synthesized catalysts. The effect of MoS2 (2.5%, 5%, 7.5%, and 10%) on LaCoO3 (LCO) and its photocatalytic performance was studied. The properties of synthesized catalysts were assessed using various material characterization techniques. The photocatalytic dye degradation of ARS and RhB was investigated under visible light. Among the synthesized catalyst LM-5% composite (LaCoO3 with 5% MoS2) is determined to be the best photocatalyst as it degrades 96 % (ARS) and 90 % (RhB) in 40 min and 80 min, respectively. The photocatalyst is stable even after multiple runs and exhibits negligible loss in degradation efficiency during the cyclic test. Trapping experiments reveal the significance of superoxide anion and hydroxyl radicals against the photodegradation of ARS and RhB. The kinetics of photodegradation of ARS and RhB by LM-5% is found to be 5.70 × 10−2 and 2.25 × 10−2 min−1, respectively. Herein, we demonstrated a catalyst possessing excellent photodegradation activity which may ignite the possibilities of using efficient photocatalysts for environmental remediation.

Light-Driven Catalytic Activity of Green-Synthesized SnO2/WO3-x Hetero-nanostructures.

This work reports an environmentally friendly and economically feasible green synthesis of monometallic oxides (SnO2 and WO3) and their corresponding mixed metal oxide (SnO2/WO3-x) nanostructures from the aqueous Psidium guajava leaf extract for light-driven catalytic degradation of a major industrial contaminant, methylene blue (MB). P. guajava is a rich source of polyphenols that acts as a bio-reductant as well as a capping agent in the synthesis of nanostructures. The chemical composition and redox behavior of the green extract were investigated by liquid chromatography-mass spectrometry and cyclic voltammetry, respectively. Results acquired by X-ray diffraction and Fourier transform infrared spectroscopy confirm the successful formation of crystalline monometallic oxides (SnO2 and WO3) and bimetallic SnO2/WO3-x hetero-nanostructures capped with polyphenols. The structural and morphological aspects of the synthesized nanostructures were analyzed by transmission electron microscopy and scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy. Photocatalytic activity of the synthesized monometallic and hetero-nanostructures was investigated for the degradation of MB dye under UV light irradiation. Results indicate a higher photocatalytic degradation efficiency for mixed metal oxide nanostructures (93.5%) as compared to pristine monometallic oxides SnO2 (35.7%) and WO3 (74.5%). The hetero-metal oxide nanostructures prove to be better photocatalysts with reusability up to 3 cycles without any loss in degradation efficiency or stability. The enhanced photocatalytic efficiency is attributed to a synergistic effect in the hetero-nanostructures, efficient charge transportation, extended light absorption, and increased adsorption of dye due to the enlarged specific surface area.

Investigation of the Degradation Behavior of Cyclophosphamide by Catalytic Ozonation Based on Mg(OH)2

Metal hydroxides, owing to their catalytic active sites for the decomposition of O3 to Reactive Oxygen Species (ROS), have been adapted for catalytic ozonation of micropollutants in wastewater. In this study, commercial Mg (OH)2 was used for the degradation of cyclophosphamide (CYP) by ozone. The crystal phase was confirmed by X-ray powder Diffraction (XRD). Percent degradation of 10 ppm CYP after 30 min by O3 and Mg (OH)2/O3 was 56 and 93, respectively, suggesting enhanced decomposition of O3 to ROS by the catalyst. The presence of ROS was further confirmed using pCBA as a probe, which showed that the concentration of ROS was eight times higher in the presence of Mg (OH)2/O3 than O3 alone. Catalytic ozonation experiments in the presence of scavengers showed that OH· radicals play a significant role in the degradation of CYP. The catalyst was found to be reusable for at least three cycles without significant loss in degradation efficiency. To study the compatibility of Mg (OH)2 for wastewater treatment applications, synthetic effluent was spiked with CYP and subjected to ozonation by Mg(OH)2/O3. The TOC of CYP before and after the treatment showed that Mg (OH)2/O3 not only degrades CYP but also mineralizes to a certain extent unlike O3 alone.

Visible light‐assisted degradation of binary mixture of dyes using purple tea‐mediated zinc oxide nanoparticles

AbstractThis work presents completely a new, green, and non‐expensive route of synthesis of zinc oxide (ZnO) nanoparticles (NPs) using purple tea leaves. The crystalline nature of purple tea‐mediated ZnO NPs (PT‐ZnO NPs) was confirmed by XRD and SAED analyses. Further characterizations of PT‐ZnO NPs were done using UV‐vis spectroscopy, FTIR spectroscopy, SEM‐EDX, and TEM. The size of synthesized NPs was calculated to be 15.1 nm which presented spherical morphology with some sorts of agglomeration. The PT‐ZnO NPs when applied as visible light‐driven photocatalyst for degradation of dyes, Malachite green (MG) and Rhodamine B (RB) showed that degradation was found to be higher in their binary solution (MG‐RB) than in their single solution (MG/RB). MG 95% and RB 35% was degraded in their binary solution where as in their respective single dye solution MG 89% and RB 22% got degraded within the experimental time. The highly pure, PT‐ZnO NPs are considered to have comparable photocatalytic activity with respect to most of the reported works and hence might find a way for its practical application for waste water treatment in the real world. The PT‐ZnO NPs could be reused at least for five times without any significant loss in degradation efficiency.

Visible light sensitive hexagonal boron nitride (hBN) decorated Fe2O3 photocatalyst for the degradation of methylene blue

The role of the carbon-based two-dimensional (2D) structures such as graphene or graphene oxide on the properties of metal oxide/2D composites materials are extensively studied for the environmental applications like photocatalysis. However, the metal oxide/inorganic 2D structure-based composites are less explored. In this regard, we have explored the α-Fe2O3/inorganic 2D hexagonal boron nitride (hBN) composite as an efficient visible light photocatalyst for the degradation of methylene blue (MB). A systematic investigation on the role of varying the weight percent of hBN on the photocatalytic efficiency for MB degradation under visible light was studied. The α-Fe2O3/(x) hBN (x = 1, 5, 10 wt%) composites were characterized by various analytical and spectroscopic techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The bandgap tuning with varying compositions of α-Fe2O3/(x) hBN (x = 1, 5, 10 wt%) were investigated by UV–vis diffuse reflectance spectroscopy (UV DRS) and the bandgap values were found to decrease with addition of hBN (1.56 eV for 5 wt%) compared to bare α-Fe2O3 (2.02 eV). The composite α-Fe2O3 with 5 wt% of hBN (FB2) showed an enhanced methylene blue (MB) degradation of ~ 91% with a high rate constant value of 5.03 × 10–4 s−1. This was ~ 3.3 times higher than the rate constant observed for the MB degradation using bare hematite. The material after photocatalysis process was retrieved by simple sedimentation process and reused for four cycles with no loss in degradation efficiency. The as-prepared composite material may have application in recycling and reuse of water in textile industries.

Areca nut (Areca catechu) husks and Luffa (Luffa cylindrica) sponge as microbial immobilization matrices for efficient phenol degradation

Immobilization of microorganisms is a widely adopted strategy for the efficient degradation of hazardous organic compounds like phenol. Microorganisms can be immobilized in synthetic or natural matrices. In this work dried areca nut (Areca catechu) husks and luffa (Luffa cylindrica) sponge fibers were used as alternative and inexpensive natural matrices for microbial cell immobilization. The potential of these immobilization systems for the effective bioremediation of phenolic wastewater was explored. A bacterial consortium was isolated by enriching a sludge sample from a petroleum refinery in high phenol concentrations. The mixed bacterial culture was capable of degrading 1000 mg L−1 of phenol in suspension cultures. The bacterial consortium was immobilized on the lignocellulosic matrices. Phenol degradation studies were performed in batches to optimize the physicochemical parameters. Optimum pH and temperature for phenol degradation was found to be 8.0 and 37 °C. At an optimum pH and temperature, the areca nut husk and luffa sponge systems immobilized with the mixed culture could degrade 1000 mg L−1 phenol in 28 h and 30 h respectively. The highest experimental degradation rates in areca nut husk and luffa sponge systems were 0.37 h−1 and 0.21 h−1 respectively at 200 mg L−1 phenol. Degradation kinetic studies were carried out using several inhibition models. Further studies revealed that both matrices with immobilized microbes could be reused for several successive batch degradation experiments and stored at 4 °C for several weeks without any noticeable loss in degradation efficiency.

Synthesis of panos extract mediated ZnO nano-flowers as photocatalyst for industrial dye degradation by UV illumination

Green synthesis of zinc oxide has gained extensive attention as a reliable, sustainable, and eco-friendly protocol to reduce the destructive effects associated with the traditional synthesis methods commonly utilized in laboratory and industry. Here for the first time, we have synthesized quaker ladies flower type ZnO (ZnO/QNF) from panos extract (extract from four panax plants such as Panax ginseng, Acanthopanax senticosus, Kalopanax septemlobus and Dendropanax morbifera). The synthesized ZnO materials was characterized using powder X-ray diffraction, Fourier infrared spectroscopy, X-ray photoelectron spectroscopy and Transmission electron microscope. The newly synthesized ZnO/QNF was applied for the removal of industrial dyes such as methylene blue (MB), Eosin Y (EY) and Malachite green (MG) under UV illumination. The photocatalyst degraded the 15 mg L−1 MB, EY and MG to >99% within 80, 90 and 110 min of contact time, respectively. In addition, the ZnO/QNF photocatalyst removed the low concentrated 5 mg L−1 of MB, EY, and MG within 30, 35 and 40 min of contact time, respectively. The pedal structure provided all the active sites available for the easy interaction with dye molecule under UV, and that enabled fast kinetics of dye degradation than the many other benchmark materials reported previously. The ZnO photocatalyst could be reused minimum of five cycles without any significant loss in degradation efficiency.

Evaluation of an ultrasonic-assisted mechanical stirring technique for the synthesis of an efficient nano-photocatalyst

Photocatalysis has emerged as an efficient technique for the removal of contaminants from wastewater. In this work, conventional mechanical stirring was compared with ultrasonic-assisted mechanical stirring for the synthesis of an efficient nano-photocatalyst (Al2O3)1−x(ZnO) x Fe2O3. The photocatalytic activity of (Al2O3)1−x(ZnO) x Fe2O3 synthesized by both techniques was compared for the degradation of methyl orange dye (MO) under visible light irradiation. Important process parameters were optimized during the study and the results indicated that the photocatalyst synthesized by ultrasonic-assisted mechanical stirring was more efficient with 93.5% photocatalytic activity for the degradation of MO dye than that synthesized by using a simple mechanical stirring technique which resulted in photocatalytic activity of 83.7%. (Al2O3)0.75(ZnO)0.25Fe2O3 nano-photocatalysts synthesized by both methods were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray analysis, dynamic light scattering and BET surface area analysis. The results indicated that the particle size of the (Al2O3)0.75(ZnO)0.25Fe2O3 catalyst synthesized by ultrasonic-assisted mechanical stirring was significantly smaller and the surface area larger than the particles prepared by the conventional mechanical stirring method. A cyclic study evaluated the reusability of the photocatalyst and found minimal loss in degradation efficiency after seven cycles. The optimal photocatalyst produced in this study can degrade higher concentrations of MO with a higher efficiency using a lower or similar catalyst dose compared to other materials published in the literature.

Construction of highly efficient and stable ternary AgBr/Ag/PbBiO2Br Z-scheme photocatalyst under visible light irradiation: Performance and mechanism insight

In this work, the novel ternary AgBr/Ag/PbBiO2Br Z-scheme photocatalysts were synthesized via a CTAB-assisted calcination process. The AgBr/Ag/PbBiO2Br composites were employed for the degradation of rhodamine B (RhB) and antibiotic bisphenol A (BPA) under visible light irradiation. Results showed that the obtained AgBr/Ag-3/PbBiO2Br displayed optimal photocatalytic performance, which could remove almost all RhB within 25 min and effectively decompose 82.3% of BPA in 120 min. Three-dimensional excitation-emission matrix fluorescence spectra (3D EEMs) were utilized for the purposes of fully grasping the behaviors of RhB molecules during the reaction process. Meanwhile, the effects of initial RhB concentration and co-existent electrolytes were investigated from the viewpoint of practical application. In addition, there was no obvious loss in degradation efficiency even after four cycles. The enhanced photocatalytic performances of AgBr/Ag/PbBiO2Br could be credited to the accelerated interfacial charge transfer process and the improved separation of the photogenerated electron-hole pairs. The existence of a small amount of metallic Ag played a significant role in preventing AgBr from being further photocorroded, resulting in the formation of a stable Z-scheme photocatalyst system. This study demonstrated that using metallic Ag as an electron mediator to construct Z-scheme photocatalytic system provided a feasible strategy in promoting the stability of Ag-based semiconductors.

Degradation of 1-butanol by solvent-tolerant Enterobacter sp. VKGH12

Abstract Biodegradation of solution-phase 1-butanol by solvent-tolerant Enterobacter sp. VKGH12 (NCIM 5221), which utilizes 1-butanol as its sole source of carbon and energy, was investigated. At an initial loading of 0.4% and 0.8% (v/v) 1-butanol, freely suspended cells degraded 76% and 26%, whereas calcium alginate-immobilized cells degraded 96% and 92% 1-butanol, respectively, in batch cultures. At these loadings, alginate-immobilized cells could be reused for 10 and 7 cycles, respectively, without significant loss in degradation efficiency. A packed-bed reactor containing immobilized cells efficiently degraded 1-butanol at a flow rate of 25–75 ml h −1 at an initial loading of 0.4% (v/v), and could be continuously operated for 10 days at an influent concentration of 0.4% (v/v) 1-butanol without a loss in degradation efficiency. The results suggest the application of immobilized solvent-tolerant bacterium in treatment of solvent waste streams.