Dye Degradation Rate Research Articles

High-efficiency degradation catalytic performance of a novel Angelica sinensis polysaccharide-silver nanomaterial for dyes by ultrasonic cavitation.

Currently, the polluted wastewater discharged by industry accounts for the major part of polluted bodies of water. As one of the industrial wastewaters, dye wastewater is characterized by high toxicity, wide pollution, and difficulty in decolorization degradation. In this paper, a novel composite nanomaterial catalyst of silver was prepared by using Angelica sinensis polysaccharide (ASP) as a reducing and stabilizing agent. And the optimum reaction conditions explored are VAgNO3=5mL (300mM) and vASP=7% (w/v) for 6h at 90°C. In addition, the ASP-Ag nanocatalyst was characterized by several techniques. The results demonstrated that ASP-Ag nanoparticles were successfully synthesized. Degradation rate, which provides a numerical visualization of the percentage reduction in pollutant concentration. With the wrapping of ASP, the ultrasonic catalytic degradation rates of different organic dyes including rhodamine B (RB), methylene blue (MB), and methyl orange (MO) were from 88.2%, 88.7%, and 85.2% to 96.1%, 95.2% and 93.5% at room temperature, respectively. After the experiments, when cdyes=10mg/L, the highest degradation rate can be observed under cAPS-AgNPs=10mg/L with the most powerful cavitation frequency f=59kHz. The effect of ultrasonic frequency on the acoustic pressure distribution in the reactor was investigated by using COMSOL Multiphysis@ software to propose the mechanism of ultrasonic degradation and the mechanism was confirmed by OH radical trapping experiments. It indicates that OH produced by the ultrasonic cavitation effect plays a determinant role in the degradation. And then, the intermediate products of the dye degradation process were analyzed by gas chromatography and mass spectrometry (GC-MS), and the possible degradation processes of dyes were proposed. The resulting products of degradation are SO42-, NH4+, NO3-, N2, CO2 and H2O. Finally, the recycling degradation experiments showed that catalyst maintains a high degradation rate within reusing 5 cycles. Thus, this catalyst is highly efficient and recyclable.

Photodegradation of methyl orange dye by using Azadirachta indica and chemically mediated synthesized cobalt doped α-Fe2O3 NPs through co-precipitation method

In current study, the Co-precipitation method was successfully used for the synthesis of Cobalt (Co) doped hematite (α-Fe2O3) nanoparticles (NPs). The synthesized Co-doped α-Fe2O3 NPs were analyzed by various characterization techniques. The chemical and greenly synthesizedα-Fe2O3 NPs had an average crystallite size of 22.63 and 16.02 nm as analyzed by XRD respectively. The Raman peaks marks the crystalline nature and hematite phase of Fe2O3 nanoparticles. The spherical shape of the Co-doped α-Fe2O3 NPs in both chemical and green methods is determined by the SEM pictures. UV–visible absorption studies marked the values of band gap i.e. 2.28 and 2.61 eV for chemical and green synthesized Co-doped α-Fe2O3 respectively. By employing the use of methyl orange dye, the photocatalytic action of α-Fe2O3 NPs was analyzed. The findings have shown that an appropriate amount of Co-dopant can significantly lead into an increase in the number of hydroxyl radicals produced from α-Fe2O3 NPs. They cause increase the methyl orange dye degradation rate. The results have shown that Azadirachta indica extract has the potential to produce α-Fe2O3-NPs in an environmentally safe manner. This research concluded that the α-Fe2O3 NPs have better photocatalytic potential with aqueous Azadirachta indica leaves extract.

Designing of a magnetically recoverable (Ce+3, +4/Fe+2. Fe+3) oxide@ 2D g-C3N4 surface for enhanced photo-Fenton catalytic degradation of Bismarck-Brown R and Congo red dyes: kinetics, optical properties,and mechanistic pathway studies

ABSTRACT Co-precipitation-assisted hydrothermal synthesis was employed to synthesize Fe3O4/CeO2 nanohybrids over 2D g-C3N4 (CF@GCN) for photo-Fenton catalytic degradation of Bismarck brown R (BBR) and Congo Red (CR) dyes. Initially, Fe loading was deployed in CF@GCN with different sets of molar ratios of Fe against the 1 mole of Ce (Ce: Fe=1:0.2-1). Among different sets, the one with 0.8 moles of Fe against the 1 mole of Ce (C1F0.8@GCN) performed excellently for BBR and CR dye degradation via aiding in the photo-Fenton process. Morphological, structural, compositional, and electronic states of the final nanocomposite were evaluated using powder X-ray diffraction, transmission electron microscopy/high-resolution transmission electron microscopy, selected area electron diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. BET analysis of the final nanocomposite showed an excellent surface area of 56.76 m2g−1, allowing for effective degradation. UV–vis spectrophotometry, UV-DRS, and PL (photoluminescence) techniques were performed to monitor the optical properties of the final nanocomposite. Taulc’s plots estimated the band gaps of catalysts, and the final nanocomposite’s band gap was 2.2 eV, which was key for capturing photons from the light source and functioning the degradation process. Further, operating parameters such as catalyst dose, dye concertation, pH, H2O2 dose, and contact time studies were done with the final nanocomposite. C1F0.8@GCN degraded BBR up to 94.5 % within 30 minutes with a first-order rate constant of 0.09747 min−1 and CR dye up to 97.7 % within 45 minutes with a first-order rate constant of 0.07391 min−1. All results supported a nanocomposite of Fe3O4 nanoparticles and CeO2 nanorods grown over 2D g-C3N4 sheets. As predicted, composing Fe3O4 sped up catalyst recovery. Also, the final nanocomposite’s dye degradation rate was consistent till the 6th run. So, the study proposes a cost-effective plan for dealing with organic water contaminants like hazardous dyes.

Near-Infrared (NIR) Silver Sulfide (Ag2S) Semiconductor Photocatalyst Film for Degradation of Methylene Blue Solution.

A silver sulfide (Ag2S) semiconductor photocatalyst film has been successfully synthesized using a solution casting method. To produce the photocatalyst films, two types of Ag2S powder were used: a commercialized and synthesized powder. For the commercialized powder (CF/comAg2S), the Ag2S underwent a rarefaction process to reduce its crystallite size from 52 nm to 10 nm, followed by incorporation into microcrystalline cellulose using a solution casting method under the presence of an alkaline/urea solution. A similar process was applied to the synthesized Ag2S powder (CF/syntAg2S), resulting from the co-precipitation process of silver nitrate (AgNO3) and thiourea. The prepared photocatalyst films and their photocatalytic efficiency were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and UV-visible spectroscopy (UV-Vis). The results showed that the incorporation of the Ag2S powder into the cellulose films could reduce the peak intensity of the oxygen-containing functional group, which indicated the formation of a composite film. The study of the crystal structure confirmed that all of the as-prepared samples featured a monoclinic acanthite Ag2S structure with space group P21/C. It was found that the degradation rate of the methylene blue dye reached 100% within 2 h under sunlight exposure when using CF/comAg2S and 98.6% for the CF/syntAg2S photocatalyst film, and only 48.1% for the bare Ag2S powder. For the non-exposure sunlight samples, the degradation rate of only 33-35% indicated the importance of the semiconductor near-infrared (NIR) Ag2S photocatalyst used.

Oxone® induced textile dyes degradation using cobalt-doped alumina catalyst

Cobalt-doped alumina catalyst calcined at 500 ?C (CoA-500) was investigated in the degradation of anionic textile dye Orange G in the presence of Oxone?. Different reaction parameters were altered in order to study their influence on Orange G degradation. The increase of the Oxone? dosage, mass of the catalyst and temperature was beneficial for the dye degradation rate. The best catalytic performance was obtained in the range of the initial solution pH = 6-8. Simultaneous degradation of both Orange G and cationic textile dye Basic blue 41, was also tested. The degradation of the Basic blue 41 did not occur while Orange G was present in the system. CoA-500 was found to be efficient catalyst in the Oxone? induced catalytic degradation of textile dyes.

In2S3 Growth Templated by Aluminogermanate Double‐Walled Imogolite Nanotubes Toward Efficient Visible Light Photocatalysts

Different strategies combining semiconductors and nanomaterials have been explored to enhance the performance of visible light photocatalysts. This work reports the hydrothermal growth of In2S3 on the aluminogermanate double‐walled imogolite nanotubes and the photocatalytic properties of the resulting composites. The reaction conditions are optimized to ensure the linear growth of In2S3, while preserving the tubular structure of imogolite nanotubes. The imogolite–In2S3 composites show enhanced photocatalytic degradation of methyl orange compared to the control In2S3, exhibiting a fourfold increase in the photocatalytic dye degradation rate constant. Interestingly, these composites present a negative photocurrent response, indicating the generation of mobile holes, whereas both In2S3 and imogolite by themselves exhibit typical positive photocurrent behavior. The improvement in the photocatalytic dye degradation and the negative photocurrent response is attributed to the interface formation between In2S3 and imogolite in these composites and the p‐type character of the latter. Templating the colloidal synthesis of semiconducting nanoparticles in confined spaces could bring a step change in the design of catalytic and photocatalytic materials.

Insulator polymers achieve efficient catalysis under visible light due to contact electrification

Under the limitation of the carrier yield and mobility of semiconductor photocatalysts and the reaction domain, it seems that the photocatalytic efficiency cannot be greatly improved. Here, an efficient contact-electro-catalysis (CEC) system based on droplet triboelectric nanogenerator (TENG) is developed. Instead of using traditional semiconductor catalysts, the electric charge transferred during the electrification process of the contact between water droplets and polytetrafluoroethylene (PTFE) is used to participate in catalysis, and the output electrical signal can also monitor the degree of catalysis. The important role of light in the circulation of this CEC system is studied and discussed for the first time. It is proved that the contact electrification at the liquid-solid interface is accompanied by the generation of a large number of strong oxidizing radicals. The efficient transport of charge carriers driven by mechanical force and the active oxygen species distributed in the whole domain greatly improve the degradation rate of dyes. The experimental data show that the degradation efficiency of crystal violet (CV) reaches 90% within 38 s, and the rate constant k is as high as 3.7 min−1. This is a breakthrough in the field of catalysis.

Improved ionic organic pollutant degradation under visible light by Ag SPR-promoted phosphorus-doped g-C3N4/AgBr/Bi2WO6 with excellent charge transfer capacity and high surface area

Graphite carbon nitride (g-C3N4) has a strong photocatalytic capability to degrade ionic organic compounds due to its unique electrical structure with numerous marginal amino groups. A photocatalyst was fabricated via a facile in-situ sedimentation–calcine–hydrothermal method by anchoring AgBr and Bi2WO6 onto the framework of phosphorus-doped g-C3N4 (PCAB). The photocatalyst has been proven to have good photocatalytic degradation effect on different ionic organic pollutants. The removal rate of tetracycline, the target pollutant, can reach 99.2%, which was 1.83 times higher than that of g-C3N4 within 60 min under visible light. Moreover, the degradation rates of dyes containing azo bonds and -SO3H can reach 100% within 20 min, as determined by the electrical relationship between the catalyst and the dye. The excellent performance can be attributed to the synergistic effect of the formation of mid-gap in g-C3N4 after phosphorus doping, improvements in charge carrier transfer and the low recombination rate based on the construction of dual Z-scheme heterojunction and Ag bridge. In addition, cycling experiments and characterizations illustrated the high stability and reusability of PCAB. The main active species during photocatalytic process was·O2−, whereas h+ and·OH played a minimal role. Ultimately, a dual Z-scheme mechanism was proposed to explain the photocatalytic reaction.

Remediation of groundwater contaminated with dye using carbon dots technology: Ecotoxicological and microbial community responses.

Groundwater pollution poses a serious threat to the main source of clean water globally. Nanoparticles have the potential for remediation of polluted aquifers; however, environmental safety concerns associated with in situ deployments of such technology include potential detrimental effects on microorganisms in terms of toxicity and functional disruptions. In this work, we evaluated a new and ecofriendly approach using carbon dots (CDs) as Fenton-like catalysts to catalyse the degradation of dye-containing groundwater samples. This investigation aimed at evaluating the efficacy of a novel remediation technology in terms of dye degradation and toxicity reduction while assessing its impacts on aquatic microorganisms. Uncontaminated Australian groundwater samples were spiked with methylene blue and incubated in the dark, at 18°C, under slow agitation, using CDs at 0.5mgmL-1 and H2O2 at 73.5mM for 25h. The dye degradation rate was determined as well as the toxicity of the treated solutions using the Microtox® bioassay. Further, to determine the changes in the groundwater microbial community, 16S rRNA sequencing was used and evenness and diversity indices were analysed using Pielou's evenness and Simpson index, respectively. This study revealed that dye-containing groundwater were effectively treated by CDs showing a degradation rate of 78-82% and a significant 4-fold reduction in the toxicity. Characterisation of the groundwater microbiota revealed a predominance of at least 60% Proteobacteria phylum in all samples where diversity and evenness were maintained throughout the remediation process. The results showed that CDs could be an efficient approach to treat polluted groundwater and potentially have minimum impact on the environmental microbiome.

Production of CuCoO2 nanoparticle/SnO2 nanofiber heterostructures for visible light photocatalytic applications

p-type CuCoO2/n-type SnO2 heterostructured photocatalysts were produced and used, for the first time, in photocatalysis applications for the removal of organic pollutants in wastewater. The heterostructures were obtained by decoration of hydrothermally derived CuCoO2 nanoparticles (NPs) on electrospun SnO2 nanofibers (NFs). Microstructural, morphological, optical, and electrochemical properties of SnO2, CuCoO2, and the heterostructures were characterized in detail. The photocatalytic activities of CuCoO2/SnO2 (0.25–1.25 wt% CuCoO2) were systematically examined and the highest activity was obtained for the SnO2 sample containing 0.35 wt% CuCoO2 and almost all the methylene blue (MB) dye (98.1 %) was degraded within 90 min. Compared to the SnO2, 0.35 wt% CuCoO2-SnO2 exhibited 83 % increase in degradation rate of MB dye. This increase in photocatalytic activity was attributed to the narrow band gap CuCoO2 absorbing more light together with SnO2, thus generating more electron (e-)-hole (h+) pairs and more successful charge separation thanks to the p-n junction they formed.

Uncovering the Role of Surface-Attached Ag Nanoparticles in Photodegradation Improvement of Rhodamine B by ZnO-Ag Nanorods.

ZnO nanorods decorated with metal nanoparticles have sparked considerable interest in recent years thanks to their suitability for a wide range of applications, such as photocatalysis, photovoltaics, antibacterial activity, and sensing devices. In this study, we prepared and investigated the improved solar-light-assisted photocatalytic activity of ZnO nanorods (NRs) decorated with Ag nanoparticles (NPs) using a conventional rhodamine B (RB) dye as a model water pollutant. We showed that the presence of Ag NPs on the surface of ZnO NRs significantly increases the degradation rate of RB dye (~0.2432 min−1) when compared to bare ZnO NRs (~0.0431 min−1). The improved photocatalytic activity of ZnO-Ag was further experimentally tested using radical scavengers. The obtained results reveal that ˙OH and ˙O2− radicals are main active species involved in the RB dye photodegradation by ZnO-Ag NRs. It was concluded that efficient charge separation plays a major role in photocatalytic activity improvement.

Photocatalytic degradation of Reactive Black dye using ZnO-CeO2 nanocomposites.

This study presents the photocatalytic efficiency of ZnO-CeO2 nanocomposites for the degradation of a model Reactive Black (RB) dye. Nano-CeO2 was synthesized using cerium nitrate precursor solution via chemical precipitation. Synthesized nano-CeO2 was mixed with ZnO nanoparticles in different mass ratios to obtain ZnO-CeO2 heterojunction photocatalyst. The morphology of the nanocomposites was examined using transmission electron microscope (TEM). X-ray diffraction patterns of the CeO2 corresponded well with (1 1 1) plane of cubic-phase CeO2. The band gap of the ZnO-CeO2 nanocatalyst synthesized was determined to be 3.08 eV, which was lower than that of the pristine CeO2 and ZnO powders, respectively. The results indicate that 1:1 wt. ratio ZnO-CeO2 nanocomposite provides about 85% RB degradation within 90 min under UV light under alkaline pH conditions. Degradation rate of RB dye achieved with ZnO-CeO2 nanocomposite was almost 1.5 times greater than that obtained with pristine ZnO. Increasing CeO2 ratio beyond 1:1 wt. ratio did not significantly increase RB degradation. The results demonstrate that addition of CeO2 to ZnO results in lowering its band gap energy and aids charge carrier separation resulting in enhanced oxidation of RB dye under UV light.

Electronic structure modulation of multi-walled carbon nanotubes using azo dye for inducing non-radical reaction: Effect of graphitic nitrogen and structural defect

Multiwalled carbon nanotube (MWCNT) have a great potential for advanced oxidation process as a metal free catalyst. However, there catalytic activity is very low and needs to be appropriately tuned. Herein, we demonstrate a novel synthesis method for tuning the defect and surface functionality of MWCNT using azo dyes and the catalytic performance was tested for the degradation of different organic contaminates using PMS as an oxidant. The content, type of heteroatom functional groups, and the defect parameters were optimized by varying the pH and concentration of the organic dye. The quenching effect showed that singlet oxygen (1O2) is the primary reactive species generated by graphitic nitrogen, which can be boosted by the degree of graphitic structure disruption in MWCNT. The Linear sweep voltammetry (LSV) also confirmed that extrinsic doping enhanced the non-radical degradation by increasing the direct charge transfer rate from MB to PMS. Moreover, the designed catalyst showed a fast degradation performance with 35.1 kJ/mol activation energy and achieved the highest dye degradation rate and even surpassed some state-of-the-art metal-based and metal-free catalysts. The effect of inorganic anions study has also confirmed its industrial applicability.

Morphology normalization of peony flower-like Bi2O2CO3 boosts photocatalytic seawater purification

The development of sunlight as the driving force to purify the marine environment is an energy-saving, environmentally friendly and sustainable technology. The construction of photocatalysts with morphology normalization is expected to guide the adjustment of light absorption properties and electron transfer paths, thereby enhancing the photocatalytic performance. Herein, the peony flower-like Bi2O2CO3 (BOC) with morphology normalization was successfully prepared by the simple hydrothermal technology in the presence of polyvinylpyrrolidone (PVP) as polymer microreactor. The normalized peony flower-like BOC effectively broadens the light absorption range, improves the carrier separation efficiency, and prompts more active oxygen species (•O2−) generation. Compared with the amorphous BOC, the photocatalytic degradation rate of organic dyes for normalized peony flower-like BOC is increased by at least 2.3 times. The normalized peony flower-like BOC with good ion anti-interference ability exhibited excellent photocatalytic performance for decomposing organic pollutants in real seawater. The degradation efficiency of RhB in seawater under natural light is 98.7%. The detailed degradation intermediates were probed in depth by liquid chromatograph-mass spectrometer, and speculate the possible photocatalytic mechanism. This work opens up fresh ideas for the design of photocatalysts on efficient seawater purification.

Study of catalytic activity of G-SrO nanoparticles for degradation of cationic and anionic dye and comparative study photocatalytic and electro & photo-electrocatalytic of anionic dye degradation

Cationic dye (methylene blue) and anionic dye (carmine) degradation were demonstrated by SrO and G-SrO NPs. Furthermore, the carmine dye was degraded using two promising technologies: photocatalysis and electro& photo-electrocatalytic oxidation. Analyses of the synthesized photocatalysts were carried out utilizing optical techniques such as Fourier transforms infrared (FTIR), X-ray diffraction (XRD), UV–visible absorption, and Scanning Electron Microscopy (SEM). The FTIR results showed that no band for graphene appeared. The XRD data revealed that the nanocomposite has a cubic structure typical of SrO, which is highly crystalline. The energy band gap (EBG) decreases from 6 eV to 3.87 eV for SrO and 0.25 G-SrO, respectively. SEM images showed that incorporating graphene into SrO might enhance the surface area.For photocatalytic applications, the results revealed that the 0.25G-SrO catalyst achieved 99.5% degradation of MB dye and kinetic degradation rates of 0.04718 min−1 within 70min by photocatalysis under UV light irradiation. In comparison, 0.1G-SrO catalyst reached 79.03% degradation of carmine and kinetic degradation rates of 0.01182 min−1 within 125 min. The carmine dye was completely degraded with 8 min and 6 min irradiation time by electro and photo-electro catalytic. According to this research, SrO's photocatalytic activity was improved by incorporating graphene under UV light; besides comparing photocatalysis and electro &photo-electro catalytic processes to verify which technique is best for treating carmine in effluents.

Remarkable Recycling Process of ZnO Quantum Dots for Photodegradation of Reactive Yellow Dye and Solar Photocatalytic Treatment Process of Industrial Wastewater.

The mineralization of five industrial sunlight-exposed wastewater samples was investigated, and the recycling process of ZnO quantum dots (ZQDs) for five reusable times was estimated under the approved Egyptian Environmental Law COD (Chemical Oxygen Demand), which has to be less than 1000 ppm. An improved sol-gel process at a low calcination temperature that ranged between 350 and 450 °C was employed to synthesize ZnO quantum dots (ZQDs). The purity, high crystallinity, and structure of the prepared catalysts were determined by TEM and XRD analysis. The energy bandgap, the crystal size values, and the surface area for Z1 and Z2 were determined based on the TEMs, DRSs, and EBTs, which were equal to 6.9 nm, 3.49 eV, and 160.95 m2/g for Z1 and 8.3 nm, 3.44 eV, and 122.15 m2/g for Z2. The investigation of the prepared samples was carried out by studying the photocatalytic activity and photoluminescence, and it was found that the degradation rate of reactive yellow dye as an industrial pollutant of the Z1 sample was significantly higher than other samples, by 20%. The data collection has shown that photocatalytic efficiency decreases with an increase in the crystallite size of ZQDs.

Removal of dye pollution by an oxidase derived from mutagenesis of the Deuteromycete Myrothecium with high potential in industrial applications

It is estimated that over 700,000 tons of synthetic dyes are produced annually, 15% of which are emitted as effluents. These highly stable dyes enter the world water ecosystems and stay in the environment, and eventually cause adverse impacts to the environment. Current wastewater treatment methods, such as filtration, coagulation, and chemical oxidation, have sideeffects, including toxic residue formation, membrane fouling, bioaccumulation, and secondary pollutant formation. Given the issues mentioned, it is necessary to study how to improve the degradation of synthetic dye with a cost-effective and ecofriendly approach. Natural oxidation provides a greener option. Recently, Deuteromycetes fungus Myrothecium verrucaria G-1 (M. verrucaria G-1) has shown great potential in producing high level of dye oxidase. This study aims to generate a dye oxidase hyperproducer, 3H6 from M. verrucaria G-1 by using atmospheric and room temperature plasma (ARTP) coupled with ultraviolet (UV) irradiation. This method increases oxidase production by nearly 106.15%. After a simple precipitation and dialysis, this mutant oxidase increases by 1.97-fold in a specific activity with dye degradation rates at 70% for Mmethylene blue (MB) and 85% for Congo red (CR). It is found that the genetic stability of 3H6 remains active for ten generations. The size of oxidase is 65 kDa, and optimum temperature for reaction is 30 °C with 4.5 pH. This study presents that the first combined mutagenesis approach by ARPT-UV on fungus species generates an impressive increment of acid dye oxidases production. As such, this method presents a cost-effective alternative to mitigate hazardous dye pollution.

α-MnO2 Nanowire Structure Obtained at Low Temperature with Aspects in Environmental Remediation and Sustainable Energy Applications

Hydrothermally obtained α-MnO2 nanowire characterizations confirm the tetragonal crystalline structure that is several micrometers long and 20–30 nm in diameter with narrow distributions in their dimensions. The absorption calculated from diffuse reflectance of α-MnO2 occurred in the visible region ranging from 400 to 550 nm. The calculated band gap with Quantum Espresso using HSE approximation is ~2.4 eV for the ferromagnetic case, with a slightly larger gap of 2.7 eV for the antiferromagnetic case, which is blue-shifted as compared to the experimental. The current work also illustrates the transformations that occur in the material under heat treatment during TGA analysis, with the underlying mechanism. Electrochemical studies on graphite supports modified with α-MnO2 compositions revealed the modified electrode with the highest electric double-layer capacitance of 3.444 mF cm−2. The degradation rate of an organic dye—rhodamine B (RhB)—over the compound in an acidic medium was used to examine the catalytic and photocatalytic activities of α-MnO2. The peak shape changes in the time-dependent visible spectra of RhB during the photocatalytic reaction were more complex and progressive. In two hours, RhB degradation reached 97% under sun irradiation and 74% in the dark.

Statistical Optimization of Zinc Oxide Nanarod Synthesis for Photocatalytic Degradation of Methylene Blue

In this work, synthesis process parameters of Zinc Oxide nanorods (ZnO NRs) photocatalyst is optimized using Taguchi Method to obtain the highest degradation rate of Methylene Blue dye, MB. The Taguchi L27 (38) orthogonal array technique was used to determine the optimum conditions for the synthesis of the nanostructured photocatalyst. Eight important synthesis process parameters were chosen in the analysis while the effects of the parameters were studied using signal-to-noise (S/N) ratio analysis using minitab-16. The ZnO NRs photocatalyst was synthesized via solution process route based on the parameters obtained from the layout of the orthogonal arrays. The optimized synthesized nanorods was then characterized using field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), photoluminescence (PL), ultraviolet-visible near-infrared (UV-VIS-NIR), and Raman spectroscopies while the photodegradation of MB was determined by UV-VIS spectrum analysis under ultraviolet light irradiation. The results show that ZnO NRs with hexagonal wurtzite structure and bandgap energy of 3.25 eV have been obtained. The Taguchi analysis based on simulated experimental runs predicted the highest MB degradation percentage of 17.12% that can be achieved under optimum process conditions. Meanwhile, experimental photocatalytic degradation of MB using ZnO NRs synthesized under the same optimum condition achieved a degradation percentage of 17.27%, which deviates only 0.88% from the predicted value. This analysis could give an approach to optimize the synthesis process to ensure the good performance of nano-photocatalyst for the photodegradation of organic contaminations in industrial wastewater in a short time and cost-effective process.

Composition controllable alga-mediated green synthesis of covellite CuS nanostructure: An efficient photocatalyst for degradation of toxic dye

A facile, convenient and green method has been devised for the synthesis of a covellite phase copper sulfide nanoparticles (CuSNPs) using aqueous extract of a green alga, Chlorella ellipsoidea. The algal phytochemicals are conjectured to have served as both reducing and capping agent. The absorption features in the NIR region of the UV–visible-NIR spectrum confirmed the formation of covellite copper sulfide nanostructures. The FTIR spectrum of the as-synthesized CuSNPs indicated the involvement of functional groups of biomolecule as surface-ligands on the outer surface of the nanoparticle. The XRD reflections were indexed to hexagonal phase covellite CuS structure. The TEM study revealed a predominantly spherical morphology of particle size in the range of 9–23 nm with some agglomeration. The dark field microscope images also confirm the formation of CuS nanoparticles. EDX analysis of the synthesized nanoparticles confirms the presence of only ‘Cu’ and ‘S’ indicating formation of pure CuS nanoparticles. The as-synthesized nanoparticles exhibited excellent photocatalytic property for the degradation of a water soluble toxic methylene blue dye under scattered sunlight. The dye degradation (rate = 0.03692 min−1) was ascertained to be pseudo-first order with regression coefficient, R2 being 0.96884. The photocatalyst is readily recoverable and showed excellent stability even after four cycles.