Decolorization Of Methyl Orange Research Articles

Photoluminescence and photocatalytic activity of sol gel synthesized Mg doped TiO2 nanoparticles

The influence of magnesium doping on the optical properties, structural characteristics, and photocatalytic performance of TiO2 nanoparticles was investigated. Pure and Mg-doped TiO2 nanoparticles with varying weight percentages of magnesium were synthesized via the sol–gel method, followed by calcination at 100 °C for 12 h and annealing at 400 °C for 2 h to promote crystallization. X-ray diffraction (XRD) analyses confirmed the formation of crystalline mixed phases of anatase and rutile TiO2 nanoparticles, exhibiting their crystalline nature upon synthesis. Scanning electron microscopy (SEM) images were employed to study the morphological features of the samples, while energy dispersive spectroscopy (EDS) provided insights into their elemental composition. Photoluminescence (PL) emission spectra revealed ultraviolet (UV) to visible region emission for both pure and doped TiO2 samples. The photocatalytic activity was evaluated by monitoring the degradation of methyl orange under natural sunlight irradiation, elucidating the impact of visible light exposure. Furthermore, investigations were conducted to assess the influence of catalyst loading, initial dye concentration, and pH of the dye solution on the methyl orange removal efficiency. The 3 wt% Mg doped TiO2 exhibited 95 % of decolorization of Methyl Orange. X-ray photoelectron spectroscopy measurements was performed to verify the elemental composition and chemical valence states of each element. The scavenger test in photodegradation mechanism revealed that the main reactive species was superoxide species. The electron species resonance (ESR) measurement demonstrate that the synthesized sample shows the low spin state of Mg2+ in TiO2. The correlation between Mg doping on photocatalytic activity and crystal structure were studied. Theoretical calculations were performed to gain insights into the potential mechanism underlying the tuning of luminescent and photocatalytic properties of Mg-doped TiO2 nanoparticles, enabling a comprehensive discussion.

Ultra-fine carbon decorated TiO2/C/g-C3N4 hybrid for strong physical adsorption and efficient photodegradation of pollutants

Enhancement in the visible light absorption and efficient interfacial charge transfer is crucial for optimizing photocatalytic efficiency in the degradation of pollutants such as methyl orange (MO) and formaldehyde. This study focuses on the properties of a TiO2/C/g-C3N4 hybrid efficient photocatalyst is developed by employing an air calcination method to deposit graphitic nitride (g-C3N4) onto a carbon-modified TiO2 surface. The characterization techniques, including high-resolution transmission electron Microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS), were used to provide a comprehensive understanding of the material’s structural, morphological, thermal, and chemical properties. This hybrid catalyst is specifically engineered for the efficient decomposition of methyl orange (MO) and formaldehyde, demonstrating a significant increase in photocatalytic activity. The TiO2/C/g-C3N4 photocatalyst also exhibits an enhanced specific surface area of 181.2 m2/g, which facilitates increased physical adsorption and photo-catalytic active sites. Experimental results confirm that this catalyst effectively adsorbs MO physically even in the dark without degradation. Combining physical and photo-catalytic functions, this catalyst degrades 94 % of MO within 180 min with the initial concentration 0.2 mol/L of MO, and achieves almost 100 % decolorization of MO under visible light irradiation. Notably, the catalyst retains its high activity after 4 cycles of MO degradation, underscoring its durability and consistent performance. Additionally, the hybrid catalyst features a staggered type-II energy level configuration, which effectively enhances charge separation and boosts photocatalytic efficacy. The incorporation of an ultrafine carbon layer further augments electron mobility towards the surface, crucial for effective catalytic reactions. This study paves the way for future development of highly efficient photocatalytic materials for environmental purification.

Facile preparation of magnetic activated carbon from Peltophorum pterocarpum flowers for persulfate activation in methyl orange treatment

Herein, Peltophorum pterocarpum flowers (PPFs) were used to fabricate magnetic activated carbon (MAC) through one-pot pyrolysis with the addition of FeCl3 and KOH. XRD results proved that zero-valent iron crytals were formed in activated carbon (AC) bases. With 16.0 wt% Fe, MAC possessed a specific saturation magnetization of 35.6 emu/g, indicating its sufficient strength for magnetic separation. Furthermore, MAC had hierarchical porosity, characterized by a specific surface area of 69 m2/g and a total pore volume of 0.104 cm3/g. Subsequently, MAC was explored for activating persulfate (PS) in methyl orange (MO) decolorization. At pH 3.0, 30 °C, 5.00 mM PS, and 1.00 g/L MAC, 93.3 % MO (0.100 mM) vanished after 120 min. In reuse experiments, only 10.6 % of iron was leached from the MAC activator, and MO removal still remained at 77.7 % after five cycles. In summary, PPF-derived MAC showed effective potential in activating PS for MO elimination.

Effect of Solvothermal Time to Characteristics and Performance of Photocatalyst Bismuth‐Rich Oxyiodide for Dye Decolorization

AbstractThis study aims to explore how altering solvothermal duration influences the characteristics of the resulting products, spanning crystal structure, band gap energy, morphology, and photocatalytic performance. Bismuth‐rich oxyiodide was synthesized via the solvothermal method by dissolving Bi(NO3)3 ⋅ 5H2O and KI in ethylene glycol. The mixture underwent heating in a Teflon autoclave stainless steel at 120 °C for durations of 6, 12, 24, and 48 hours. Analysis using FTIR revealed the presence of Bi−O and I−O bonds. Diffractograms indicated that all products exhibited traits of Bi4O5I2, with slight traces of Bi5O7I. Distinct band gap energies were observed across the solvothermal durations: 2 eV for 6 hours, 2.08 eV for 12 hours, and 1.89 eV for both 24 and 48 hours, delineating temporal nuances in product properties. Noteworthy, the morphology of the 12 hour variant revealed surface pores, indicative of intricate structural features. Notably, the 12 hour product exhibited the pinnacle of photocatalytic efficacy in methyl orange decolorization under UV light. Furthermore, investigations into photocatalyst mass variations and the inclusion of additional dyes, such as rhemazol black B, further elucidated the robust photocatalytic potential inherent in the B12 variant.

Photocatalytic degradation of methyl orange and methyl violet dyes by UV/Cu2+/PDS process

ABSTRACT This research is focused on the application of the UV/Cu2+/peroxydisulfate (PDS) system for the successful decolorization of methyl orange (MO) and methyl violet (MV) dyes in aqueous media. The effects of different parameters such as the equilibrium time, initial catalyst amount, PDS concentration and pH of the media in terms of MO and MV degradation were studied. Furthermore, the photocatalytic performance of the UV/Cu2+/PDS system was also investigated by performing the degradation of MO and MV in different water systems including distilled water, synthetic wastewater and industrial wastewater samples. The results revealed 94 and 89% degradation for MO and MV dyes in the UV/Cu2+/PDS system, respectively. The radical quenching experiments showed sulfate radicals (SO4·-) as the prominent species involved in the degradation of MO and MV dyes. Overall, it was concluded that the UV/Cu2+/PDS process has the ability to be adopted for the effective elimination of contaminants from the aquatic system.

Investigating the optimum conditions for azo dye (methyl orange and methyl red) decolorization from aqueous solution using oyster mushroom (Pleurotus ostreatus): a mycoremediation approach

Since conventional dye removal techniques require a substantial amount of energy and chemicals, this study evaluated the utilization of Pleurotus ostreatus, a species of fungus, in an environmentally beneficial mycoremediation approach to decolorize two azo dyes, methyl orange (MO) and methyl red (MR), in a liquid medium. Pleurotus ostreatus was utilized under standard circumstances in the solutions containing 0.05% (w/v) MO and 0.05% (w/v) MR, without undergoing any genetic modifications. By analyzing the effects of time (6, 12, and 18 days), temperature (15 °C to 40 °C), pH (4 to 7), and inoculum volume (1 to 25 mL) on the decolorization rate of P. ostreatus, the ideal environment for the decolorization of MO and MR was determined. The highest rate of decolorization was evident at 25 °C temperature, pH 7 within 18 days of incubation, P. ostreatus could decolorize 0.05 g MO up to 97% when added in 10 mL inoculum volume on the other hand 0.05 g MR up to 93% in 15 mL inoculum volume at pH 6. Furthermore, the dye uptake rate after 18 days for MO was 59.25% and MR was 53.97% which indicated that P. ostreatus had a better uptake efficiency for MO than MR. Based on its ability to decolorize both MO and MR under suitable circumstances, the study concludes that P. ostreatus offers an appreciable mycoremediation approach for removing dye pigments from industrial wastewater.

Hibiscus sabdariffa assisted green fabrication of reduced graphene oxide and its application for methyl orange removal: Optimization employing response surface methodology

Eco-friendly fabrication of reduced graphene oxide (rGO) is of paramount importance among various carbon nanostructures. In the current research, sustainable preparation of rGO via aqueous extract of Hibiscus sabdariffa L. calyces as the green reducer of graphene oxide (GO) without utilizing hazardous chemical agents was described. The structural characteristics of the GO and rGO were studied utilizing Fourier transform infrared (FT-IR) spectroscopy, UV–Visible spectrophotometry, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The prepared nanostructure was applied as the potential adsorbent for effective methyl orange (MO) decolorization and degradation in aqueous solution. The effect of numerous independent parameters on the decolorization process involving rGO dosage, H2O2 volume, process time, and temperature were assessed and optimized via Box-Behnken design/response surface methodology BBD/RSM). A second-order model was proved to express the decolorization efficiency (D %) responses with high values of R2 and adjusted R2. Under optimal condition, the decolorization rate of MO using rGO was higher than 99 % in contact time of 31 min. The reusability of rGO for the MO removal manifested good efficiency in up to five cycles of recyclability. The findings of this research illustrate the feasibility of Hs based rGO as a suitable adsorbent for effective decolorization of MO dye from aqueous medium.

Kinetic studies on optimized extracellular laccase from Trichoderma harzianum PP389612 and its capabilities for azo dye removal

BackgroundAzo dyes represent a common textile dye preferred for its high stability on fabrics in various harsh conditions. Although these dyes pose high-risk levels for all biological forms, fungal laccase is known as a green catalyst for its ability to oxidize numerous dyes.MethodsTrichoderma isolates were identified and tested for laccase production. Laccase production was optimized using Plackett–Burman Design. Laccase molecular weight and the kinetic properties of the enzyme, including Km and Vmax, pH, temperature, and ionic strength, were detected. Azo dye removal efficiency by laccase enzyme was detected for Congo red, methylene blue, and methyl orange.ResultsEight out of nine Trichoderma isolates were laccase producers. Laccase production efficiency was optimized by the superior strain T. harzianum PP389612, increasing production from 1.6 to 2.89 U/ml. In SDS-PAGE, purified laccases appear as a single protein band with a molecular weight of 41.00 kDa. Km and Vmax values were 146.12 μmol guaiacol and 3.82 μmol guaiacol/min. Its activity was stable in the pH range of 5–7, with an optimum temperature range of 40 to 50 °C, optimum ionic strength of 50 mM NaCl, and thermostability properties up to 90 °C. The decolorization efficiency of laccase was increased by increasing the time and reached its maximum after 72 h. The highest efficiency was achieved in Congo red decolorization, which reached 99% after 72 h, followed by methylene blue at 72%, while methyl orange decolorization efficiency was 68.5%.ConclusionTrichoderma laccase can be used as an effective natural bio-agent for dye removal because it is stable and removes colors very well.

Phycoremediation of Phenolphytalein, Indigo Carmine, Methyl Orange and Eriochrome Black T By Using Chlamydomonas and Chlorella sp. (Chlorophyta)

This work aimed to evaluate the decolorization of phenolphthalein (PP), indigo carmine (IC), methyl orange (MO) and eriochrome black T (EBT) by using Chlorella and Chlamydomonas as a biosorbent. This experiment used the batch adsorption method to study the adsorption effect of pH, biomass dosage, contact time, initial dye concentration and temperature on the dyes. The adsorption of the dyes onto the cells were fitted with the Langmuir and Freundlich isotherms. The results showed that the optimum conditions for PP removal (99%) was obtained at pH 4, contact time of 120min, 35°C, algal dosage of 0.5 mg/mL and dye concentration of 100 mg/L on to the cells. The sample prepared at 25°C, 120 min, 1 mg/mL algal dosage, 25 mg/L dye concentration and at pH 4 had the best adsorption effect on IC on to the both of cells (99-98%). In addition, the optimum conditions for MO and EBT removal (99-97%) was obtained at pH 2-4, contact time of 30 min, 25°C, algal dosage of 0.5mg/mL and dye concentration of 100mg/L. The results of this study reveal that the algae cells can be utilized as an efficient and eco-friendly biosorbent for the removal of the indicator dyes from aqueous solution.

Optimization of methyl orange decolorization by bismuth(0)-doped hydroxyapatite/reduced graphene oxide composite using RSM-CCD

In the current study, the catalyst for the decolorization of methyl orange (MO) was developed HAp-rGO by the aqueous precipitation approach. Then, bismuth(0) nanoparticles (Bi NPs), which expect to show high activity, were reduced on the surface of the support material (HAp-rGO). The obtained catalyst was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques. The parameters that remarkably affect the decolorization process (such as time, initial dye concentration, NaBH4 amount, and catalyst amount) have been examined by response surface methodology (RSM), an optimization method that has acquired increasing significance in recent years. In the decolorization of MO, the optimum conditions were identified as 2.91 min, Co: 18.85 mg/L, NaBH4 amount: 18.35 mM, and Bi/HAp-rGO dosage: 2.12 mg/mL with MO decolorization efficiency of 99.60%. The decolorization process of MO with Bi/HAp-rGO was examined in detail kinetically and thermodynamically. Additionally, the possible decolorization mechanism was clarified. The present work provides a new insight into the use of the optimization process for both the effective usage of Bi/HAp-rGO and the catalytic reduction of dyes.

Synthesis and Characterization of a Photocatalytic Material from TiO2 Nanoparticles Supported on Zeolite Obtained from Ignimbrite Residue Used in Decolorization of Methyl Orange

In the present work, a TiO2/zeolite photocatalyst was synthesized by dispersing TiO2 nanoparticles obtained through the sol-gel method onto the surface of natural zeolite derived from ignimbrite residue. The zeolite was obtained from an ignimbrite rubble treatment collected from a quarry in Arequipa City, Peru. The research focused on the effect of zeolite on the TiO2 nanoparticles. The synthesized photocatalysts were characterized using various techniques, including field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray (EDS), X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), and Brunauer–Emmett–Teller surface area analysis (BET). The results revealed that the TiO2/zeolite samples displayed high crystallinity, with TiO2 being present in three phases and zeolite being present in the analcime phase. Furthermore, these samples exhibited a band gap of 3.14 eV and a high surface area compared to that of bare TiO2. Finally, the photocatalytic activity of the TiO2/zeolite composite obtained was evaluated toward the decomposition of 10 ppm and 20 ppm of methyl orange (MO) dye. The TiO2/zeolite samples demonstrated improved photocatalytic activity compared to that of pristine TiO2 under the same experimental conditions. This enhancement is primarily attributed to the increased specific surface area of the TiO2/zeolite samples, making them promising materials for future efficient and sustainable photocatalytic applications.

A coupled faradaic/electrostatic boosting strategy for decolorization of a refractory dye inside a dually-biased photoelectrochemical reactor: Time and energy saving

A green sustainable strategy for environmental remediation and treatment of dye-polluted water is the application/development of effective photoelectrochemical (PEC) reactors. Despite some recent progress in PEC systems, achieving a complete decolorization is still a challenging issue and often requires a long period of reactor operation. Herein, the authors address this interesting time/energy-related problem, demonstrating how without consuming extra electricity/chemicals, fabricating complex photoelectrodes, or changing the pH of medium, one can effortlessly promote the activity of a PEC reactor just by its coupling to a non-faradaic bias source. By applying this novel dually biased (faradaic/electrostatic) boosting strategy, we reveal that decolorization of methyl orange (a refractory dye pollutant) is significantly improved and the decolorization time (thereby energy consumption) is reduced by almost half in comparison to that of a conventional PEC reactor–operating under a single-bias (faradaic) condition. The reactor activity and its photoelectrochemical response are finally discussed in detail in terms of applied potential biases, semiconductor's band bending, open-circuit-potential displacement, electrostatic interaction and electrosorption of dye pollutant.

Merits of photocatalytic activity of synthesized (ZnxCu(1−x)Fe2O4); x = (0–1) magnetic nanoparticles for wastewater treatment

Synthesis of crystalline zinc copper ferrite nanoparticles was achieved via a simple co-precipitation method. Scanning electron microscope (SEM) is utilized to give the morphological characterization of the prepared samples. A transmission electron microscope (TEM) was employed for further identification and confirmation of the particle size and morphology. Moreover, X-ray diffraction (XRD) and Fourier transformation infrared (FTIR) spectroscopy were utilized to examine crystalline structure and chemical structure, respectively. The photocatalytic performance of Zn0.5Cu0.5Fe2O4 nanoparticles under UV light was assessed by decolorization of methyl orange (MO) azo dye. The efficiency of photocatalytic degradation of 20 ppm of MO by Zn0.5Cu0.5Fe2O4 nanoparticles 15 mg was 96% after 135 min at an ambient temperature of 25 °C and pH value of 3. Further interpretation was carried out and a proposed mechanism for the MO photodegradation over Zn0.5Cu0.5Fe2O4 nanoparticles was suggested.

Kinetic study of electron transfer process in methyl orange decolorization by shewanella in MFCs with covalent organic frameworks modified anode

As a new electrode material for electrochemical systems, covalent organic framework (COF) materials have been gradually applied to bioelectrochemical systems. In our previous study, the COFBTA-DPPD-rGO composite was synthesized via Schiff-base coupling between benzene-1,3,5-tricarbaldehyde (BTA) and 3,8-diamino-6-phenylphenanthridine (DPPD) on reduced graphene oxide (rGO) at room temperature. Here, COFBTA-DPPD-rGO modified MFC anode was used to assist microorganisms to decolorize methyl orange (MO), and the properties of MFCs were studied. The results showed that compared to the unmodified electrode MFC (28 mA m−2, 4.20 mW m−2) the current density and maximum power density of the anode MFC modified by COFBTA-DPPD-rGO (134.5 mA m−2, 21.78 mW m−2) were increased by 380.3% and 423.6%, respectively. The transferred electron number n and charge transfer coefficient α of the modified COFBTA-DPPD-rGO anode (4 and 0.43) compared to the unmodified electrode (2.4 and 0.38) were increased by 67% and 13%, respectively. The decolorization ratio of MO could reach 90.3% at 10 h. Compared with the unmodified electrode MFC (53.0%), the decolorization ratio and kinetic constant of decolorization process were enhanced by 26% and 372%, respectively. Therefore, COFBTA-DPPD-rGO could be a new choice for applying to the MFCs.

Removal of reactive dyes from textile industrial effluent using electrocoagulation in different parametric conditions of aluminum electrodes

Untreated textile industrial effluent becomes a major concern for the receiving water bodies. Extensive use of azo dyes in textile industries trigger to find latest techniques for the treatment of textile wastewater. The purpose of this study was to employ the electrocoagulation process for the effective removal of dyes from textile wastewater. The optimization of parameters was performed using the Taguchi method to analyze the conditions of electrode for efficient dye removal. The effects of different parameters including synthetic dye initial concentration, initial pH, applied voltages, interelectrode distance and contact time were studied. Different electrode pairs combination with iron to iron, iron to aluminum and aluminum to aluminum were investigated. The electrode combination of aluminum to aluminum performed better in terms of dye removal. The removal efficiency of methylene blue was achieved to 82% under optimum conditions having pH of 8, 15 V voltage, 60 min contact time and 2 cm aluminum interelectrode distance. Similarly, the optimum conditions for decolorization of methyl orange was performed and achieved 81% of removal efficiency. After the optimization of electrode and parametric conditions, real textile wastewater was treated and removal efficiency of 81% was achieved. At optimal conditions (pH 7–8, 15 V, 60 min contact time, and 20 min settling time), COD, TDS, TSS, and discoloration removal efficiencies were 79%, 91%, 75%, and 86%, respectively. The result of this study indicates the significance of EC process and its future scope for integration of this technology at industrial scale.

Photoelectrocatalytic Processes of TiO2 Film: The Dominating Factors for the Degradation of Methyl Orange and the Understanding of Mechanism.

Various thicknesses of TiO2 films were prepared by the sol-gel method and spin-coating process. These prepared TiO2 films exhibit thickness-dependent photoelectrochemical performance. The 1.09-μm-thickTiO2 film with 20 spin-coating layers (TiO2-20) exhibits the highest short circuit current of 0.21 mAcm-2 and open circuit voltage of 0.58 V among all samples and exhibits a low PEC reaction energy barrier and fast kinetic process. Photoelectrocatalytic (PEC) degradation of methyl orange (MO) by TiO2 films was carried out under UV light. The roles of bias, film thickness, pH value, and ion properties were systematically studied because they are the four most important factors dominating the PEC performance of TiO2 films. The optimized values of bias, film thickness, and pH are 1.0 V, 1.09 μm, and 12, respectively, which were obtained according to the data of the PEC degradation of MO. The effect of ion properties on the PEC efficiency of TiO2-20 was also analyzed by using halide as targeted ions. The "activated" halide ions significantly promoted the PEC efficiency and the order was determined as Br > Cl > F. The PEC efficiency increased with increasing Cl content, up until the optimized value of 30 × 10-3 M. Finally, a complete degradation of MO by TiO2-20 was achieved in 1.5 h, with total optimization of the four factors: 1.0 V bias, 1.09-μm-thick, pH 12, and 30 × 10-3 M Cl ion content. The roles of reactive oxygen species and electric charge of photoelectrodes were also explored based on photoelectrochemical characterizations and membrane-separated reactors. Hydrogen peroxide, superoxide radical, and hydroxyl radical were found responsible for the decolorization of MO.

TiO2-functionalized biochar from pistachio nutshells: adsorptive removal and photocatalytic decolorization of methyl orange

Pistachio nutshells-derived biochar (PNS-BC) was utilized as a cost-effective adsorbent for competently removing a model dye, methyl orange (MO) from wastewater. Three concentrations of TiO2; 1%, 2%, and 3% were used to decorate the biochar. Analysis of morphology, stability, and structure of the three adsorbents (PNS, PNS-BC, and the TiO2 functionalized biochar; TiO2@PNS-BC) was extensively explored using various characterization techniques. The synergistic photocatalytic-adsorptive efficiency of the three adsorbents was compared. In this regard, a Box-Behnken (BB) design-based multivariate scheme was inaugurated with the target of maximizing MO removal (%R) while using the minimum possible of chemicals and resources. The impact of five variables; %TiO2, dose of TiO2-PNS, reaction time, dye concentration, and pH on the magnitude of %R was investigated. Results show that 97.69% removal of MO could be recognized over 120 min using adsorption compared to 99.47% removal over 30 min using 3% TiO2@PNS-BC as a photocatalyst. A 3% TiO2@PNS-BC was the best catalyst (compared to 1% and 2%) with a decolorization rate constant of 0.12741 min−1, ~ 1.5 × faster compared to the decolorization of MO using adsorption alone. Adsorption of MO conformed well to Langmuir isotherm. A maximum adsorption capacity (qmax) of 142.38 mg/g was achieved. Adsorption kinetics fitted well with the pseudo-second order (PSO) model. Results obtained indicated that biochar of PNS is a promising, cost-effective, and economical adsorbent.

Paper sludge saccharification for batch and fed-batch production of bacterial cellulose decorated with magnetite for dye decolorization by experimental design

Cellulosic wastes represent a great environmental challenge, with potential conversion to product-added value through microbial fermentation. Currently, bacterial cellulose (BC) is considered a promising natural polymer for multiple applications. However, the high production cost challenges its wide application. Hence, the current study evaluated the applicability of paper sludge as a cost-effective medium for both cellulases and BC production. The local isolate Streptomyces rochei revealed the highest cellulase production titer (about 3 U/mL) at optimized conditions. For BC production, batch and fed-batch fermentation strategies were evaluated using enzymatically hydrolyzed paper sludge. The results asserted the advantage of fed-batch fermentation for advanced BC production (3.10 g/L) over batch fermentation (1.06 g/L) under the same cultivation conditions. The developed BC membranes were characterized through different instrumental analyses, which revealed an increase in fiber diameters and crystallinity under fed-batch fermentation. Furthermore, BC/magnetite (BC/Fe3O4) nanocomposite was developed by an in-situ approach. The newly developed composite was evaluated for dye removal applications, using methyl orange (MO) as a model. The dye removal conditions were optimized through Box Behnken design (BBD), which indicated maximal MO removal (83.5%) at pH 3.0 and BC/Fe3O4 concentration of 0.1 mg/dL after 60 min. Therefore, the current study asserts the good applicability of enzymatically hydrolyzed paper sludge as a medium for cost-effective BC production and the high capacity of BC/magnetite nanocomposite for MO decolorization. The study paves the way for the cost-effective implementation of BC/magnetite nanocomposite for dye removal.Graphical

Decolorization, degradation and detoxification of mutagenic dye Methyl orange by novel biofilm producing plant growth-promoting rhizobacteria

Discharge of untreated dyeing wastewater nearby water-bodies is one of major causes of water pollution. Generally, bacterial strains isolated from industrial effluents and/or contaminated soils are used for the bioremediation of Methyl orange (MO), a mutagenic recalcitrant mono-azo dye, used in textiles and biomedical. However, MO degradation by biofilm producing plant growth-promoting rhizobacteria (BPPGPR) was not studied yet. In this study, 19 out of 21 BPPGPR strains decolorized 96.3–99.9% and 89.5–96.3% MO under microaerophilic and aerobic conditions, respectively from Luria-Bertani broth (LBB) followed by yeast-extract peptone and salt-optimized broth plus glycerol media within 120 h of incubation at 28 °C. Only selected BPPGPR including Pseudomonas fluorescens ESR7, P. veronii ESR13, Stenotrophomonas maltophilia ESR20, Staphylococcus saprophyticus ESD8, and P. parafulva ESB18 were examined for process optimization of MO decolorization using a single factor optimization method. This study showed that under optimal conditions (e.g., LBB, 100 mg L−1 MO, pH 7, incubation of 96 h, 28 °C), these strains could remove 99.1–99.8% and 97.6–99.5% MO under microaerophilic and aerobic conditions, respectively. Total azoreductase and laccase activities responsible for biodegradation were also remarkably activated in the biodegraded samples under optimal conditions, while these activities were repressed under unfavorable conditions (e.g., 40 °C and 7.5% NaCl). This study confirmed that MO was degraded and detoxified by these bacterial strains through breakage of azo bond. So far, this is the first report on bioremediation of MO by the BPPGPR strains. These BPPGPR strains are highly promising to be utilized for the bioremediation of dyeing wastewater in future.

Enhanced photocatalytic activity of CeO2 and magnetic biochar-CeO2 nanocomposite prepared from Murraya koenigii stem for degradation of methyl orange under UV light

This paper discusses the synthesis and characterization of CeO2 nanoparticles (NPs), magnetic biochar-CeO2 (MBC-CeO2) nanocomposites (NCs), and their photocatalytic analysis in methyl orange (MO) degradation. MBC-CeO2 material is synthesized on the basis of carbonization of iron oxide precursor treated with Murraya koenigii (curry leaf) stem powder. CeO2 with crystallite size 7.78 nm and MBC-CeO2 with crystallite size 14 nm are identified from XRD, with band gap energies 3.16 and 2.84 eV respectively. XPS, SEM, TEM, BET, UV–visible, FTIR, and PL characterizations are conducted to study the morphology, oxygen vacancy concentration in the samples. The removal efficiency of Methyl Orange (MO) is studied by changing both pH and concentration of MO solution. The decolorization of MO is observed at an optimum level of pH 4, with a catalyst dosage of 50 mg, which obeys pseudo-first-order kinetic theory. Under 16 min UV irradiation treatment, the decolorization efficiency of the as-prepared MBC-CeO2 is 96.7 % and total organic carbon (TOC) is ∼94 %, and for the as-prepared CeO2 it is 87.5 % and ∼ 81 % respectively. The plausible degradation pathway of MO is analyzed through LC-MS method. Regression studies are conducted to assess the suitability of all models towards photocatalytic degradation. The recycling experiment showed that both MBC-CeO2 and CeO2 are excellent stable catalysts for the activation of MO.