Effect of Morphology Modification of BiFeO3 on Photocatalytic Efficacy of P-g-C3N4/BiFeO3 Composites.

This current study assessed the impacts of morphology adjustment of perovskite BiFeO3 (BFO) on the construction and photocatalytic activity of P-infused g-C3N4/U-BiFeO3 (U-BFO/PCN) heterostructured composite photocatalysts. Favorable formation of U-BFO/PCN composites was attained via urea-aided morphology-controlled hydrothermal synthesis of BFO followed by solvosonication-mediated fusion with already synthesized P-g-C3N4 to form U-BFO/PCN composites. The prepared bare and composite photocatalysts' morphological, textural, structural, optical, and photocatalytic performance were meticulously examined through various analytical characterization techniques and photodegradation of aqueous rhodamine B (RhB). Ellipsoids and flakes morphological structures were obtained for U-BFO and BFO, and their effects on the successful fabrication of the heterojunctions were also established. The U-BFO/PCN composite exhibits 99.2% efficiency within 20 min of visible-light irradiation, surpassing BFO/PCN (88.5%), PCN (66.8%), and U-BFO (26.1%). The pseudo-first-order kinetics of U-BFO/PCN composites is 2.41 × 10-1 min-1, equivalent to 2.2 times, 57 times, and 4.3 times of BFO/PCN (1.08 × 10-1 min-1), U-BFO, (4.20 × 10-3 min-1), and PCN, (5.60 × 10-2 min-1), respectively. The recyclability test demonstrates an outstanding photostability for U-BFO/PCN after four cyclic runs. This improved photocatalytic activity exhibited by the composites can be attributed to enhanced visible-light utilization and additional accessible active sites due to surface and electronic band modification of CN via P-doping and effective charge separation achieved via successful composites formation.

Enhanced piezocatalytic RhB degradation with ZnSnO3 Nanocube-modified Bi4Ti3O12 composite catalyst by harnessing ultrasonic energy.

With the increasing demand for effective methods to address environmental pollution, piezocatalysis has emerged as a promising approach for pollutant degradation under mechanical energy. However, the development of highly efficient piezocatalytic materials remains a challenge. This study aimed to increase the piezocatalytic activity of bismuth titanate (Bi4Ti3O12) by modifying it with zinc stannate (ZnSnO3) nanocubes. The composite catalysts were synthesized using a straightforward deposition and calcination process. The calcination process ensured the tight adhesion of ZnSnO3 nanocubes to the Bi4Ti3O12 surface, while facilitating strong interactions between ZnSnO3 and Bi4Ti3O12, which enhanced electron transfer and heterojunction structure formation. Band structure analysis indicated that Bi4Ti3O12 has higher conduction band and valence band potentials than ZnSnO3, forming a type-II heterojunction. Bi4Ti3O12 possesses a higher Fermi level than ZnSnO3, resulting in interfacial electron drift and formation of a built-in electric field, which further promotes the directional transfer and separation efficiency of charge carriers within the composite catalyst. This hypothesis was confirmed by surface photovoltage spectroscopy, piezoelectric current response, and electrochemical analysis. Consequently, the ZnSnO3/Bi4Ti3O12 composite exhibited significantly improved piezocatalytic performance in RhB degradation, achieving a degradation efficiency of 80 % within 90 min under ultrasonic vibration. The degradation rate of the optimal sample was 8.2 times that of Bi4Ti3O12 and 6.3 times that of ZnSnO3. Additionally, experiments to detect reactive species were conducted to elucidate the mechanism behind the piezocatalytic RhB degradation. Holes and hydroxyl radicals were the main reactive species. This study may offer new insights into the design of efficient piezocatalytic materials.

Efficient degradation of Rhodamine B by magnetically recoverable Fe3O4-modified ternary CoFeCu-layered double hydroxides via activating peroxymonosulfate.

Environment-friendly nano-catalysts capable of activating peroxymonosulfate (PMS) have received increasing attention recently. Nevertheless, traditional nano-catalysts are generally well dispersed and difficult to be separated from reaction system, so it is particularly important to develop nano-catalysts with both good catalytic activity and excellent recycling efficiency. In this work, magnetically recoverable Fe3O4-modified ternary CoFeCu-layered double hydroxides (Fe3O4/CoFeCu-LDHs) was prepared by a simple co-precipitation method and initially applied to activate PMS for the degradation of Rhodamine B (RhB). X-ray diffraction (XRD), fourier transform infrared spectrometer (FT-IR), scanning electron microscope (SEM), transmission electron microscopy (TEM), Brunauer-Emmett-Teller method (BET), and vibrating sample magnetometer (VSM) were applied to characterize morphology, structure, specific surface area and magnetism. In addition, the effects of several key parameters were evaluated. The Fe3O4/CoFeCu-LDHs exhibited high catalytic activity, and RhB degradation efficiency could reach 100% within 20 min by adding 0.2 g/L of catalyst and 1 mmol/L of PMS into 50 mg/L of RhB solution under a wide pH condition (3.0-7.0). Notably, the Fe3O4/CoFeCu-LDHs showed good super-paramagnetism and excellent stability, which could be effectively and quickly recovered under magnetic condition, and the degradation efficiency after ten cycles could still maintain 98.95%. Both radicals quenching tests and electron spin resonance (ESR) identified both HO• and SO4•- were involved and SO4•- played a dominant role on the RhB degradation. Finally, the chemical states of the sample's surface elements were measured by X-ray photoelectron spectroscopy (XPS), and the possible activation mechanism in Fe3O4/CoFeCu-LDHs/PMS system was proposed according to comprehensive analysis.

Multiple response optimization for high efficiency energy saving treatment of rhodamine B wastewater in a three-dimensional electrochemical reactor.

The removal of high-concentration rhodamine B (RhB) wastewater was investigated in a three-dimensional electrochemical reactor (3DER) packed with granular activated carbon (GAC) particle electrodes. Response surface methodology (RSM) coupled with grey relational analysis (GRA) was used to evaluate the effects of voltage, initial pH, aeration rate and NaCl dosage on RhB removal and energy consumption of the 3DER. The optimal conditions were determined as voltage 7.25 V, pH 5.99, aeration rate 151.13 mL/min, and NaCl concentration 0.11 mol/L. After 30 min electrolysis, COD removal rate could arrive at 60.13% with an extremely low energy consumption of 6.22 kWh/kg COD. The voltage and NaCl were demonstrated to be the most significant factors affecting the COD removal and energy consumption of 3DER. The intermediates generated during the treatment process were identified and the possible degradation pathway of RhB was proposed. It is worth noting that 3DER also showed an excellent performance in total nitrogen (TN) removal under the optimal condition. The activated chlorine generated from chloride had great contributions to eliminate carbon and nitrogen of RhB wastewater. The treatment effluent had a good biodegradability, which was suitable for subsequent biological treatment.

Multifunctional characteristics of biosynthesized CoFe2O4@Ag nanocomposite by photocatalytic, antibacterial and cytotoxic applications.

Carissa carandas, a traditional medicinal herb with a high concentration of antioxidant phytochemicals, has been used for thousands of years in the Ayurveda, Unani, and homoeopathic schools of medicine. By employing Carissa carandas bark extract as a reducing and capping agent in green biosynthesis, we extend this conventional application to produce CoFe2O4 and CoFe2O4@Ag nanocomposite. A variety of techniques have been used to characterize the synthesised nanocomposite, including UV-Vis, FTIR, XRD, FESEM, EDX, and BET. The CoFe2O4 and CoFe2O4@Ag nanocomposite demonstrated promising antibacterial action against human bacterial pathogens like B. subtilis and S. aureus as gram positive and P. aeruginosa and E. coli as gram negative with inhibition zones of 24.3 ± 0.57, 17.4 ± 0.75 and 20.5 ± 0.5, 19.8 ± 1.6 mm respectively, and the obtained results were superior to the nanocomposite without silver. Moreover, in-vitro cytotoxicity effects of biosynthesized CoFe2O4 and CoFe2O4@Ag were performed on the human breast cancer cell MCF-7. It was found that the MCF-7 cells' 50% inhibitory concentration (IC50) was 60 µg/mL. Additionally, biosynthesized CoFe2O4 and CoFe2O4@Ag nanocomposite was used to demonstrate the photocatalytic eradication of Rhodamine Blue (RhB). Due to the addition of Ag, which increases surface area, conductivity, and increased charge carrier separation, the CoFe2O4@Ag nanocomposite exhibits a high percentage of photocatalytic degradation of ⁓ 98% within 35 min under UV light irradiation. The photocatalytic performance of as-synthesised nanocomposite was evaluated using dye degradation-adsorption in both natural light and dark condition. Under dark conditions, it was found that 2 mg mL-1 CoFe2O4@Ag in RhB aqueous solution (5 ppm) causes dye adsorption in 30 min with an effectiveness of 72%. Consequently, it is anticipated that the CoFe2O4@Ag nanocomposite will be a promising photocatalyst and possibly a noble material for environmental remediation applications.

A Novel BiOBr/CAU-17 Composite with Enhanced Photo-Catalytic Performance for Dye Degradation and Removal of Tetracycline Antibiotic Under Visible Light.

In order to improve the low specific surface area and high recombinant light generation carriers of BiOBr, loading BiOBr onto suitable Metal Organic Frameworks (MOFs) is an effective strategy to unleash its efficient visible light response and intrinsic catalytic activity. In this study, using classic MOF CAU-17 as a precursor, using a straightforward co-precipitation technique, four BiOBr/CAU-17 composites with distinct MOF contents values BCAU-1, BCAU-2, BC, AU-3, and BCAU-4 were created, and their photo-catalytic characteristics were examined. The BCAU-2 composite exhibited much higher photo-catalytic degradation efficiency for Rhodamine B (RhB) and Tetracycline (TC) than the pristine materials, counter compositions, and early reported materials. XRD, SEM, TEM, XPS, and EDX results revealed the strong synergistic photo-catalytic effect of BiOBr and CAU-17. The photocatalytic degradation of TC was significantly enhanced by the BiOBr bimetal modification, with the 2 wt.% BiOBr/CAU-17 nanocomposite achieving an 87.2 % degradation of TC and 82 % Total Organic Carbon (TOC) removal within 60 min. The high photo-degradation efficiency of BCAU-2 composite should be attributed to the efficient transfer of photo-generated carriers at interfaces and the synergistic effect between BiOBr/CAU-17. Furthermore, the experiments on the capture of the active species proved that the main active free radicals involved in the degradation of RhB and TC are attributed to the photo-induced holes h+ and ⋅ O2 - under visible light. The catalyst's efficacy is corroborated by the outcomes of photoluminescence spectroscopy and photo current response. This study offers a new understanding for the design of green synthesis schemes for photo-catalytic dye degradation and removal of certain antibiotics from the aquatic environment.

Sodium alginate-encapsulated nano-iron oxide coupled with copper-based MOFs (Cu-BTC@Alg/Fe3O4): Versatile composites for eco-friendly and effective elimination of Rhodamine B dye in wastewater purification.

This study explores the effectiveness of Alginate-coated nano­iron oxide combined with copper-based MOFs (Cu-BTC@Alg/Fe3O4) composites for the sustainable and efficient removal of Rhodamine B (RhB) dye from wastewater through adsorption and photocatalysis. Utilizing various characterization techniques such as FTIR, XRD, SEM, and TEM, we confirmed the optimal synthesis of this composite. The composites exhibit a significant surface area of approximately 160 m2 g-1, as revealed by BET analysis, resulting in an impressive adsorption capacity of 200 mg g-1 and a removal efficiency of 97 %. Moreover, their photocatalytic activity is highly effective, producing environmentally friendly degradation byproducts, thus underlining the sustainability of Cu-BTC@Alg/Fe3O4 composites in dye removal applications. Our investigation delves into kinetics and thermodynamics, revealing a complex adsorption mechanism influenced by both chemisorption and physisorption. Notably, the adsorption kinetics indicate equilibrium attainment within 100 min across all initial concentrations, with the pseudo-second-order kinetic model fitting the data best (R2 ≈ 0.999). Furthermore, adsorption isotherm models, including Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich, elucidate the adsorption behavior, with the Temkin and Dubinin-Radushkevich models showing superior accuracy compared to the Langmuir model (R2 ≈ 0.98 and R2 ≈ 0.96, respectively). Additionally, thermodynamic analysis reveals a negative Gibbs free energy value (-6.40 kJ mol-1), indicating the spontaneity of the adsorption process, along with positive enthalpy (+24.3 kJ mol-1) and entropy (+82.06 kJ mol-1 K) values, suggesting an endothermic and disorderly process at the interface. Our comprehensive investigation provides insights into the optimal conditions for RhB adsorption onto Cu-BTC@Alg/Fe3O4 composites, highlighting their potential in wastewater treatment applications.

Harnessing ZnCr2O4/g-C3N4 nanosheet heterojunction for enhanced photocatalytic degradation of rhodamine B and ciprofloxacin.

Utilizing semiconductors for photocatalytic processes in water bodies as an approach to environmental remediation has gained considerable attention. Theoretical band position calculations revealed a type-II step-scheme charge flow mechanism for ZnCr2O4/g-C3N4 (ZCr/gCN), emphasizing effective heterojunction formation due to synergies between the materials. A composite of agglomerated nanoparticle ZnCr2O4 (Zinc chromium oxide - ZCr)/g-C3N4 (graphitic carbon nitride - gCN) nanosheets was synthesized using the ultrasonication and leveraging the heterojunction to enhance degradation efficiency and active sites participation. The synthesized sample was characterized by XRD, XPS, FTIR, BET, HRSEM, EDX, HRTEM, EIS PL, and UV-visible spectroscopy. XRD analysis confirmed the successful formation of pure ZnCr2O4, g-C3N4 (gCN), and their composite without any secondary phases. Optical investigations demonstrated a red shift (444-470 nm) in UV-visible spectra as ZnCr2O4 content increased. Morphological assessment via HRSEM unveiled agglomerated nanoparticle and nanosheet structures. FTIR analysis indicated the presence of gCN with the tri-s-triazine breathing mode at 807 cm-1, and the identification of octahedral Zn-O (598.11 cm-1) and tetrahedral Cr-O (447.01 cm-1) metal bonds within the spinel structure of ZnCr2O4. A Surface area of 134.162 m2/g was noticed with a microporous structure of pore radius 1.484 nm. Notably, the 15% ZCr/gCN composite achieved a remarkable 93.94 % (Rhodamine B-RhB) and 74.36 % (Ciprofloxacin - CIP) within 100 and 120 min, surpassing the performance of pure gCN. Improved degradation was attributed to higher charge separation (photo-excited electrons and holes), reducing charge recombination, as supported by photoluminescence and photoelectrochemical analyses. The presence of active species like superoxide during degradation was confirmed through a scavenger test. The stability analysis confirms the sample's stable nature (without secondary phase formation) after degradation. This work underscores the potential of ZnCr2O4 based metal-free compounds intended for effective environmental remediation.

Morphological influence of BiVO4 nanostructures on peroxymonosulfate activation for highly efficient catalytic degradation of rhodamine B.

Bismuth vanadate (BiVO4) nanostructured films were prepared and successfully applied for peroxymonosulfate (PMS) activation for the degradation of rhodamine B (RhB) in aqueous solution. The BiVO4 thin films were obtained by thermal reaction between electrodeposited bismuth (Bi) films and vanadium precursor. The as-prepared BiVO4 porous, nanoflowers, and cluster nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and BET analysis. The catalytic performance of BiVO4 nanostructures has been carefully evaluated in activating PMS for the degradation of RhB. The nanoflower-like BiVO4 nanostructures exhibit the best catalytic activity. Under optimized conditions, the complete catalytic degradation of RhB using BiVO4 nanoflowers/PMS system was achieved in 17 min at room temperature as revealed by high-performance liquid chromatography (HPLC) analysis. Quenching experiments suggested that sulfate radicals are the main active species in the degradation process. Additionally, BiVO4 catalyst remained stable without any apparent activity loss after five cycling runs.

Direct Z-scheme CeO2@LDH core-shell heterostructure for photodegradation of Rhodamine B by synergistic persulfate activation.

Photocatalytic activation of persulfate (PAPS) is considered an efficient and green approach for the mitigation of organic pollutants because of its advantages in low energy consumption and high reusability of photocatalysts. Herein, direct Z-scheme CeO2@LDH heterojunction photocatalyst with a core-shell structure is constructed. We reveal that CeO2@LDH exhibits excellent persulfate (PS) activation performance and high degradation efficiency of RhB under visible light irradiation. Control experiments by quenching catalytically active radicals and analysis of electron paramagnetic resonance (ESR) spectra suggest that the sulfate radical (SO4·-) generated by photocatalytic activation of PS, together with superoxide radical (·O2-) and hydroxyl radical (·OH), degrade pollutants synergistically. Density functional theory (DFT) calculations indicate that the built-in electric field across the surface of CeO2 and LDH is the intrinsic driving force for the efficient transfer of hot carriers in the Z-scheme heterojunction. The construction of this transfer path can effectively engineer the interfacial band structure and inhibit the recombination of photogenerated electron-hole pairs and promote their transportation. Meanwhile, electrons were found to accumulate at the conduction band (CB) of LDHs and holes populate at valence band (VB) of CeO2, generating more active species for photodegradation of RhB. We demonstrate that the Z-scheme heterojunction photocatalyst activated PS system (Z-scheme/PS) is a promising method to degrade RhB and potentially organic pollutants in general.

[Photocatalytic Degradation of Rhodamine B with Micro-SiC/Graphene Composite Under Visible Light Irradiation].

To develop low consumption and an environmentally friendly degradation technology for organic pollutants, micro-SiC/graphene composite materials were synthesized by photocatalytic reduction, and the composition and morphology of the prepared materials were characterized by XRD, FTIR, Raman spectroscopy, XPS, and SEM. Rhodamine B (RhB) was selected as the simulated pollutant to investigate the photocatalytic activity and stability of composite materials under visible light irradiation. The degradation mechanism was preliminarily discussed by active species capture experiments. Results show that the lives of photogenerated electron and photogenerated hole of SiC were prolonged when combined with graphene, which improved the photocatalytic activity and stability of composite materials. The degradation efficiency of RhB reached 92.7% with the composite material of SiC/graphene ratio (1:0.8) under 60 min irradiation, and the degradation process accorded with the first-order reaction kinetic equation. The contribution of main active species for photocatalytic degradation followed with a decreasing order of photogenerated hole (h+), superoxide anion radical (·O2-), photogenerated electron (e-), and hydroxyl radical (·OH).

Enhancement on the removal of Rhodamine B (RhB) by means of the Enlarged Anode Electric Biological (EAEB) reactor.

The Enlarged Anode Electric Biological (EAEB) Reactor was proposed, as an alternative to the common BAF. The goal of this research was to develop a new process for simultaneously removing, NH4+-N and Rhodamine B (RhB) from dyeing wastewater. The performance of EAEB was evaluated based on COD, NH4+-N and RhB removal efficiency in the effluent. The study found that the removal rate of RhB, which is a characteristic of the inoculation and start period, reaches 80% in EAEB and 30% in common BAF. A current intensity of 0.5 A, HRT of 3.5 h, and electrode area of 0.13 m2 were identified as operating parameters that could guarantee excellent RhB removal efficiency. It is worth noting that the removal of RhB in the two reactors was mainly concentrated in the 80 cm-140 cm area (measuring upwards at the top of the support layer). The removal rate of EAEB in this area was 97.7%, and the common BAF was 84.3%. Besides, in each segment of EAEB, the removal effect of RhB was better than in common BAF. This study elucidated the synergistic effects of electricity and biofilm on contaminant removal and identified important roles of improvements to the anode electro-biodegradation process. As compared to conventional technologies, the proposed process provides a highly efficient new alternative to dyeing wastewater treatment technology.

Heterogeneous activation of hydrogen peroxide by cysteine intercalated layered double hydroxide for degradation of organic pollutants: Performance and mechanism.

A novel cysteine intercalated copper aluminum layered double hydroxide (CuAl-Cys-LDH) was synthesized and applied as heterogeneous catalyst for activating hydrogen peroxide (H2O2) to degrade rhodamine B (RhB) and 4-Nitrophenol (4-NP). The effects of initial pH, CuAl-Cys-LDH dosage, and H2O2 concentration on RhB and 4-NP removal were comprehensively investigated. The results indicated the intercalation of cysteine into the interlayer of LDH greatly enhanced its catalytic activity and stability. With 0.2 g/L CuAl-LDH and 50 mM H2O2, 93.7% of RhB and 80.2% of 4-NP could be removed in the CuAl-Cys-LDH activated H2O2 system. While the CuAl- LDH activated H2O2 system could only degrade 51.2% of RhB and 46.8% of 4-NP under the identical experimental conditions. Significantly, the CuAl-Cys-LDH catalyzed H2O2 system exhibited high degradation efficiency within a wide pH range from 4.0 to 10.0. Based on the electron paramagnetic resonance (EPR) tests and radical quenching experiments, it was inferred that •OH radical was the dominant species responsible for organic contaminants degradation. Mechanism study revealed that the intercalated cysteine in the interlayer of LDH strongly accelerated the rate-determining conversion of Cu(II) to Cu(I) by oxidation itself to cystine, thus enhanced the catalytic efficiency for H2O2 activation to produce •OH radicals. The findings of this work indicated that CuAl-Cys-LDH is a conveniently prepared and highly efficient and stable catalyst for the degradation of organic contaminants in environmental remediation.

Peat moss-derived biochar for sonocatalytic applications.

Peat-moss derived biochar was used as a sonocatalyst for the degradation of rhodamine B (RhB) at different ultrasonic frequencies (40 kHz and 300 kHz). The biochar was prepared by pyrolysis of peat-moss at 300 °C under N2-saturated conditions. High removal efficiency was achieved when biochar (1000 mg L-1) was used as a sonocatalyst in the 40 kHz system, and high removal could be achieved by pre-adsorption and radical oxidation reactions on the surface of the biochar. This was validated in experiments employing radical scavengers. Sonochemiluminescence images and real images of the systems with no biochar, 100 mg L-1 biochar, and 1000 mg L-1 biochar also supported this observation. On the other hand, the addition of the biochar was less effective than expected for the degradation of RhB at 300 kHz. This was due to low dispersion of the biochar in solution in the high frequency system, where relatively weaker sonophysical effects could be obtained.

Orthogonal synthesis of a novel hybrid layered material containing three different zincous components and its photocatalytic property investigation.

A novel hybrid layered material-Schiff Base-Zinc Complexes intercalated ZnCr-LDHs-supported ZnO-was synthesized by one-step coprecipitation method and characterized by XRD, UV-vis DRS, SEM, TEM, BET, ICP-AES and XPS analysis. The influences of the three Zn components (intercalated between the layers, supported on the surface, distributed in the host layers of the layered material) on the crystallinity and the photocatalytic activity of ZnO/ZnCr-SalenZn-LDHs for Rhodamine B (RhB) degradation were studied in detail by orthogonal design. The results showed that the percentage of the three components has a great effect on the structure and photocatalytic performance of ZnO/ZnCr-SalenZn-LDHs. The SalenZn intercalated between the layers and the Zn distributed in the layers of the layered material were the main influencing factors, and the ZnO supported on the surface of the layered material was the secondary influencing factor. The optimum initial molar ratios were SalenZn:Cr = 0.5, Zn:Cr = 3, and ZnO:Cr = 0.75, respectively, and the photocatalytic degradation efficiency of RhB reached 96.9%. In addition, a possible mechanism of photocatalysis was discussed from the perspectives of photogenerated reactive species and photoinduced carries transfer. While, the regeneration of the best photocatalytic material was also investigated in detail.

Synthesis of hollow lantern-like Eu(III)-doped g-C3N4 with enhanced visible light photocatalytic perfomance for organic degradation.

A series of hollow structure lantern-like Eu(III)-doped g-C3N4 (xEu-CN, x = 1, 2, 3) was firstly synthesized by heating a mixture of melamine, HNO3 and Eu2O3 at 500 °C for 2 h. The phase, morphology and optical properties of the serial xEu-CN samples were characterized by different techniques, including TEM, XRD, FT-IR, SEM, XPS, BET, UV-vis, PL, photocurrent, and EIS. The results indicated that Eu doping extraordinarily enhanced the photocatalytic activity of pure g-C3N4, and the 2Eu-CN exhibited the highest photocatalytic performance with a 98% (82%) degradation rate for RhB (TC), 6.03 (1.71)-fold of pure g-C3N4(CN). The higher photocatalytic efficiency is ascribed to the synergy effect of Eu(III) and the hollow structures, which led to a larger surface specific area, bandgap narrowing, enhanced light harvesting ability and efficient charge separation.

Bismuth oxide decorated graphene oxide nanocomposites synthesized via sonochemical assisted hydrothermal method for adsorption of cationic organic dyes.

Bismuth oxide decorated graphene oxide (Bi2O3@GO) nanocomposites were successfully synthesized by sonochemical method followed by hydrothermal treatment. The structural, morphology/microstructure and functional groups were investigated through X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM) and Fourier Transform Infrared (FTIR) spectroscopy, respectively. In the FESEM and TEM studies, well dispersed Bi2O3 nanoparticles of size 3-5nm were found uniformly distributed throughout the surface and edges of GO sheets. The HRTEM measurements on the Bi2O3 nanoparticle decorated graphene oxide shows imaged lattice spacing of 3.2Å corresponding to (111) plane of Bi2O3 which confirms the successful synthesis of bismuth oxide decorated graphene oxide (Bi2O3@GO) nanocomposite. The synthesized nanocomposite was employed for adsorption and removal of cationic organic dyes like RhB from industrial wastewater. The effect of various parameters, viz., contact time, temperature, pH and amount of adsorbent on the adsorption capability as well as dye removal capacity of the adsorbent was studied in detail. Under optimized conditions, like, contact time (65min), amount of adsorbent (5mg), temperature (35°) and pH (4), the adsorption capacity of GO and Bi2O3@GO were recorded and the percentage of removal was found to be 64% and 80.7% for GO and Bi2O3@GO, respectively. The Bi2O3@GO nanocomposite shows higher adsorption capacity (320mg/g) as compare to only GO (224mg/g). The adsorption isotherm follows both the Temkin as well as Langmuir isotherm having heat of sorption 65.88 with Langmuir constant of 13.13 corresponding to the complete monolayer coverage of 387.44mg/g. The adsorption kinetics also follow, both pseudo first order and intraparticle diffusion model with adsorption capacity of 84.91mg/g and intra particle diffusion rate constant of 10.53mg/g min1/2 for Bi2O3@GO nanocomposites. Our results suggest that the prepared Bi2O3@GO nanocomposites possess potential application as high-performance renewable adsorbent for removal of toxic dyes from wastewater.

Environmental application of millimetre-scale sponge iron (s-Fe0) particles (IV): New insights into visible light photo-Fenton-like process with optimum dosage of H2O2 and RhB photosensitizers.

In this study, we firstly develop the photo-Fenton-like system with millimetric sponge iron (s-Fe0), H2O2, visible light (vis, λ≥420nm) and rhodamine B (RhB), and present a comprehensive study concerning the mechanism. Thus, we investigate (1) the adsorption of RhB onto s-Fe0, (2) the photo-Fenton-like removal of RhB over iron oxides generated from the corrosion of s-Fe0, (3) the homogeneous photo-Fenton removal of RhB over Fe2+ or Fe3+, (4) the Fe3+-RhB complexes, and (5) the photo-Fenton-like removal of tetrabromobisphenol A (TBBPA). The results show that neither the adsorption process over s-Fe0 nor the photo-Fenton-like process over FeOOH, Fe3O4 and Fe2O3, achieved efficient removal of RhB. For comparison, in homogeneous photo-Fenton process, the presence of Fe3+ ions, rather than Fe2+ ions, effectively eliminated RhB. Furthermore, the UV-vis spectra showing new absorbance at∼285nm indicate the complexes of RhB and Fe3+ ions, adopting vis photons to form excited state and further eject one electron via ligand-to-metal charge-transfer to activate H2O2. Additionally, efficient TBBPA removal was obtained only in the presence of RhB. Accordingly, the s-Fe0- based photo-Fenton-like process assisted with dyestuff wastewater is promising for removing a series of persistent organic pollutants.

Synthesis of magnetic CoFe2O4/ordered mesoporous carbon nanocomposites and application in Fenton-like oxidation of rhodamine B.

CoFe2O4/ordered mesoporous carbon (OMC) nanocomposites were synthesized and tested as heterogeneous peroxymonosulfate (PMS) activator for the removal of rhodamine B. Characterization confirmed that CoFe2O4 nanoparticles were tightly bonded to OMC, and the hybrid catalyst possessed high surface area, pore volume, and superparamagnetism. Oxidation experiments demonstrated that CoFe2O4/OMC nanocomposites displayed favorable catalytic activity in PMS solution and rhodamine B degradation could be well described by pseudo-first-order kinetic model. Sulfate radicals (SO4-·) were verified as the primary reactive species which was responsible for the decomposition of rhodamine B. The optimum loading ratio of CoFe2O4 and OMC was determined to be 5:1. Under optimum operational condition (catalyst dosage 0.05 g/L, PMS concentration 1.5 mM, pH 7.0, and 25 °C), CoFe2O4/OMC-activated peroxymonosulfate system could achieve almost complete decolorization of 100 mg/L rhodamine B within 60 min. The enhanced catalytic activity of CoFe2O4/OMC nanocomposites compared to that of CoFe2O4 nanoparticles could be attributable to the increased adsorption capacity and accelerated redox cycles between Co(III)/Co(II) and Fe(III)/Fe(II).