Oxidation Of Rhodamine B Research Articles

Visible-light-driven Z-scheme La-MOF/BiOBr heterojunction for the efficient removal of rhodamine B and hexavalent chromium from wastewater

Addressing the formidable challenge of treating significant quantities of organic dyes and heavy metal chromium in tannery wastewater, this study synthesized a novel Z-scheme La-MOF/BiOBr composite heterojunction photocatalyst via the hydrothermal method and established an efficient visible-light photocatalytic system. To comprehensively evaluate the photocatalytic redox activity, rhodamine B (RhB) and heavy metal Cr(VI) were selected as target pollutants. Kinetic analysis revealed that the optimal LM-BB-50 catalyst achieved over 99 % degradation of RhB and Cr(VI) within 15 min illumination, indicating the remarkable enhancement of Z-scheme heterojunction in photocatalytic oxidation and reduction efficiency. Based on various photoelectric analysis techniques, it was elucidated that the superior activity of the Z-scheme heterojunction originated from the modulation of the band structure upon La-MOF and BiOBr integration, significantly improving visible light absorption, electron-hole pair separation efficiency, and endowing the energy band with robust redox capabilities. Free radical capture and quenching experiments confirmed that photogenerated holes and superoxide radicals played a crucial role in RhB oxidation, while photogenerated electrons were the primary active species for Cr(VI) reduction.

Visible-light-driven BiOI and GO/BiOI photocatalysts for organic pollutants degradation and hydrogen production using low power sources

BiOI and (3 wt%)GO/BiOI visible-light-driven photocatalysts were obtained by a one-pot solvothermal method and successfully applied to the degradation of single and binary dye solutions of rhodamine B (RhB) and methylene blue (MB) and H2 production using very low-power sources. The GO/BiOI with hierarchical flower morphologies exhibited the highest activity, achieving RhB and MB photodegradation percentages (%Xdye) of 100% and 80%, respectively, in 240 min employing a simple 19 W white LED array. Furthermore, GO/BiOI dosage and RhB initial concentration play an essential role in dye degradation, and scavenger assays confirmed that holes and superoxides are the main species causing RhB oxidation. TOC analysis determined an efficiency of 70%, and after three uses, the GO/BiOI attained a %XRhB of 84%. The H2 evolution was performed under 2 W UV light, yielding 323.25 μmol/h∙g of H2 for BiOI, and the addition of GO nanosheets increased the photoactivity of GO/BiOI up to 63% (509.61 μmol/h∙g). The catalytic activity of GO/BiOI is superior to values reported in the literature considering nominal power consumption (kWh) vs. efficiency of RhB degradation or H2 production.

Synthesis of Au‐decorated WO3 nanoplates for simultaneous oxidation of RhB and reduction of Cr(VI) under visible light irradiation

AbstractTungsten oxide (WO3) nanoplates were synthesized by a simple chemical precipitation technique. These nanoplates were decorated by Au nanoparticles via photoreduction route. The obtained samples were characterized by field emission scanning electron microscopy, X‐ray diffractometry and UV–vis diffuse reflectance spectroscopy to investigate their morphological, structural and optical properties. The SEM images show the plate morphology with the size in the range of 50–150 nm, their thickness ≈10 nm; spherical‐like Au nanoparticles ≈20 nm were attached to the surface of the WO3 plates. These materials were applied for the simultaneous photocatalytic degradation of Rhodamine B (RhB) and Cr(VI) under visible light. Due to the efficient separation of photoinduced charge carriers and the enhanced visible light absorption ability, the photocatalytic performance of Au‐decorated WO3 nanoplates was higher. The main active species responsible for the photodegradation reactions were identified by different scavengers and a photocatalytic mechanism was proposed. This work represents that WO3 nanoplates are a promising candidate for the degradation of organic and inorganic pollutants from the industrial wastewater under sun light exposure.

Highly efficient visible-LED-driven photocatalytic degradation of tetracycline and rhodamine B over Bi2WO6/BiVO4 heterostructures decorated with silver and graphene synthesized by a novel green method.

Visible-light-driven Bi2WO6/BiVO4 (BWO/BVO) heterostructures were obtained by joining BWO and BVO n-type semiconductors. A novel and green metathesis-assisted molten salt route was applied to synthesize BWO/BVO. This route is straightforward, high-yield, intermediate temperature, and was successful for obtaining BWO/BVO heterostructures with several ratios (1:1, 1:2, 2:1 w/w). Besides, the 1BWO/1BVO was decorated with Ag nanoparticles (Ag-NPs, 6 wt.%) and graphene (G, 3 wt.%), applying simple and environmentally responsible procedures. The heterostructures were characterized by XRD, Raman, UV-Vis DRS, TEM/HRTEM, PL, and Zeta potential techniques. Ag-NPs and G effectively boosted the photocatalytic activity of 1BWO/1BVO for degrading tetracycline (TC) and rhodamine B (RhB) pollutants. A lab-made 19-W blue LED photoreactor was designed, constructed, and operated to induce the photoactivity of BWO/BVO heterostructures. The low-ratedpower consumption of the photoreactor (0.01-0.04 kWh) vs. the percent degradation of TC or RhB (%XTC = 73, %XRhB = 100%) is one of the outstanding features of this study. Besides, scavenger tests determined that holes and superoxides are the main oxidative species that produced TC and RhB oxidation. Ag/1BWO/1BVO exhibited high stability in reuse photocatalytic cycles.

Magnetically Separable Mixed-Phase α/γ-Fe2O3 Catalyst for Photo-Fenton-like Oxidation of Rhodamine B

Iron oxides are widely used as catalysts for photo-Fenton-like processes for dye oxidation. In this study, we report on the synthesis of an α/γ-Fe2O3 mixed-phase catalyst with magnetic properties for efficient separation. The catalyst was synthesized using glycine–nitrate precursors. The synthesized α/γ-Fe2O3 samples were characterized using scanning electron microscopy, X-ray diffraction spectroscopy (XRD), Raman shift spectroscopy, X-ray photoelectron spectroscopy (XPS), and vibrating sample magnetometer (VSM). The diffraction peaks were indexed with two phases, α-Fe2O3 as the main phase (79.6 wt.%) and γ-Fe2O3 as the secondary phase (20.4 wt.%), determined using the Rietveld refinement method. The presence of Fe2+ was attributed to oxygen vacancies. The mixed-phase α/γ-Fe2O3 catalyst exhibited remarkable photo-Fenton-like degradation performance for Rhodamine B (RhB) in neutral pH. The effects of operating parameters, including H2O2 concentration, catalyst concentration, and RhB concentration, on the degradation efficiency were investigated. The removal rates of color were 99.2% after 12 min at optimal conditions of photo-Fenton-like oxidation of RhB. The sample exhibited a high saturation magnetization of 28.6 emu/g. Additionally, the α/γ-Fe2O3 mixed-phase catalyst showed long-term stability during recycle experiments, with only a 5% decrease in activity.

Activation of peroxymonosulfate by Co-Mg-Fe layered doubled hydroxide for efficient degradation of Rhodamine B.

Reactive species serve as a key to remediate the contamination of refractory organic contaminants in advanced oxidation processes. In this study, a novel heterogeneous catalyst, CoMgFe-LDH layered doubled hydroxide (CoMgFe-LDH), was prepared for an efficient activation of peroxymonosulfate (PMS) to oxidize Rhodamine B (RhB). The characterization results showed that CoMgFe-LDH had a good crystallographic structure. Correspondingly, the CoMgFe-LDH/PMS process exhibited good capacity to remove RhB, which was equivalent to degradation performance as homogeneous Co(II)/PMS process. The RhB oxidation in the CoMgFe-LDH/PMS process was well described with pseudo-first-order kinetic model. Additionally, the oxidation process presented an excellent stability, and only 0.9% leaching rate was detected after six sequential reaction cycles at pH 5.0. The effects of initial pH, CoMgFe-LDH dosage, PMS concentration, RhB concentration, and inorganic anions on the RhB degradation were discussed in detail. Quenching experiments showed that sulfate radicals (SO4•-) acted as the dominant reactive species. Further, the removal of RhB from simulated wastewater was explored. The removal efficiency of RhB (90μM) could reach 94.3% with 0.8g/L of catalyst and 1.2mM of PMS addition at pH 5.0, which indicated the CoMgFe-LDH/PMS process was also effective in degrading RhB in wastewater.

Electrochemical Synthesis and Characterization of Poly(Rhodamine B) Coating on FTO

In this paper we describe the conditions of electrochemical synthesis of a homogeneous and highly adherent pink film of poly(Rhodamine B) (PRhB) on a conducting glass substrate, which facilitates and enables its optical characterization. The electrosynthesis was performed by cyclic voltammetry, galvanostatic and potentiostatic techniques in 0.1 M KCl as supporting electrolytes and 1 mM Rhodamine B (RhB) as monomer on fluorine doped tin oxide (FTO) samples. The anodic peak associated with the RhB oxidation appears at 0.977 V during the first scan and shifts to 1.059 V in the following cycles, indicating the increase in the electrical resistance of the polymer coating until it reaches the overpotential to overcome the resistance. Chronopotentiometry and chronoamperometry show that the PRhB is obtained at applied current densities and potentials higher than 10 μA cm-2 and 0.8 V, respectively and the polymer coating become thicker and darken with increasing the applied current and potential. Electrochemical methods show that the polymer growth is controlled by the maximum oxidation potential applied. The physico-chemical properties of generated PRhB film has been characterized by different microscopic and spectroscopic techniques such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and UV–visible spectrophotometry (UV-vis). The produced modified electrode would offer a promising candidate for future applications such as sensors and dye synthesized solar cell.

A metal-free voltammetric sensor for sensitive determination of Rhodamine B using carboxyl-functionalized carbon nanomaterials

Rhodamine B (RhB) is a synthetic xanthine dye that is harmful to environment and human health. Therefore, the development of low cost and efficient analytical techniques for RhB monitoring is very critical for environmental protection and food safety. Herein, a novel metal-free voltammetric sensor was constructed for sensitive detection of RhB using carboxyl-functionalized carbon nanomaterials. To understand the role of carboxyl functionalization in RhB electrooxidation, the electrochemical properties and voltammetric responses of carboxyl-functionalized multi-walled carbon nanotube (f-MWCNT), carboxyl-functionalized reduced graphene oxide (f-RGO), multi-walled carbon nanotube (MWCNT) and reduced graphene oxide (RGO) were compared. Amongst, the f-MWCNT/GCE exhibited the lowest charge transferred resistance and the largest electroactive surface area. The f-MWCNT/GCE showed extraordinary electrocatalytic activity for RhB oxidation, which is primarily attributed to the unique 3D structure and the carboxyl functionalization. The anodic peak current of RhB is linearly correlated to RhB concentration from 0.05 to 100 μM with a low limit of detection (LOD, 2.6 nM). In addition, the f-MWCNT/GCE achieved the selective identification and detection of RhB in presence of common metal ions and other red dyes, and retained a robust and stable voltammetric responses for at least a week. The f-MWCNT/GCE was successfully applied to detect RhB concentration in tomato sauce samples with good recovery.

Efficient reactive electrochemical carbon membranes for organic pollutants removal from aqueous solution: A study of multi-physics modeling and simulation approach

A novel application of three metal oxide catalysts CuOx, Fe2O3, and CoO onto coal-based carbon membrane (CM) in the enhancement of electrochemical removal of high concentration organic pollutants is presented. Their morphology, structure, and elemental composition were characterized. Analysis of their performance in the treatment of highly concentrated Rhodamine B (RhB), Rose Bengal, and phenol pollutants with respective concentrations of 600 mg/l, 637 mg/l, and 50 mg/l presented excellent removal efficiency (all >97 %). A study of the degradation mechanism of pollutants at the membrane surface was approached through multi-physics modeling and simulation of the reaction kinetics of complex indirect RhB oxidation chemistry occurring at the copper oxide membrane surface which involved oxidation of resistant intermediates. The results gave a degradation efficiency of 99.82 % after 60 s of reaction at the CM-CuOx surface which is very close to the experimental results. An understanding of the pollutants concentration distribution across the electrocatalytic filtration system was achieved through simulation of the transport, diffusion, and convection of degraded products through the membrane walls. No fouling was observed for RhB treatment and a new insight into the interactions between pollutants molecules and reactive membrane surfaces was brought by the mean of Monte-Carlo simulations of their adsorption mechanisms. Finally, a comparison with other Electrochemical Advanced Oxidation Processes (EAOPs), revealed that the membranes fabricated in this work possessed significant advantages both in terms of permeability and removal efficiency.

Porous ionic polymers as a photocatalyst: Self-assembly of donor-acceptor by regulating the valence state of photo-responsive groups

The world is on high alert against trace but extremely hazardous pollution of heavy metals and organic dyes in wastewater. Among various treatments, porous photocatalyst with dual functions of adsorptive enrichment and photodegradation are highly desirable yet challenging. Herein, we demonstrate a robust donor-acceptor (D-A) self-assembly by regulating the valence state of photo-responsive groups to construct porous ionic. The density function theory calculations reveal that the excitons induced on the neutral pyridine group (D) can be attracted by its neighboring cationic pyridinium one (A), thus the distinct charges separation and transfer enhancement can be realized in one PIP-based photocatalyst. Guided by this, a partially ionized pyridine-pyridinium (PB-PIPs) photocatalysts are fabricated, which show excellent adsorption capacity for the heavy metal Cr(VI) anion on pyridinium cations and rhodamine B (RhB) on the pyridine rings. Significantly, the target-adsorptions promote the accurate deliveries of excitons, that the simultaneous photocatalytic reduction of Cr(VI) and oxidation of RhB are achieved. The photodegradation performance of PB-PIPs under visible-light irradiation is superior to the state-of-the-art organic photocatalysts. Therefore, this convenient strategy of the valence state regulation provides a promising solution to the focus of synergistically visible-light harvesting, charges separating and transferring, and target-delivering in photocatalysis.

Flower-like hierarchical Sn3O4/montmorillonite nanostructure for the enhanced microwave-induced degradation of rhodamine B

A flower-like hierarchical nanostructure of Sn3O4/montmorillonite is first reported in this work. The nanomaterial was prepared by a one-pot hydrothermal synthesis method using tin chloride as the precursor, and the physicochemical characteristics of the material were examined by instrumental analyses. The prepared nanostructure was evaluated as a catalyst in the microwave-induced removal of rhodamine B (RhB). The influences of Sn content, oxidant, time of irradiation, and initial concentration of RhB were investigated. The results showed homogeneously dispersed Sn3O4 in a montmorillonite support with a cubic phase, and crystallite size smaller than to Sn3O4 was obtained. XPS investigation revealed the Sn3O4 phase, which is consistent with the band gap energy of 2.75 eV from UV-DRS measurements. The homogeneous distribution of the Sn3O4 nanoparticles influenced the increasing specific surface area of the nanocomposite compared to montmorillonite. The enhanced physicochemical properties significantly enhanced the catalytic activity in microwave induced RhB oxidation, with the degradation efficiency reaching 99.9% after 20 min of treatment. The kinetics of catalytic oxidation were best fitted to the pseudo-second-order equation and obeyed the Langmuir-Hinshelwood kinetics model. Furthermore, the catalytic oxidation condition optimization using a Box-Behnken Design revealed the contribution of oxidant, pH and catalyst dose as influencing factors for the efficiency.

Enhanced Photocatalytic Oxidation of RhB and MB Using Plasmonic Performance of Ag Deposited on Bi2WO6

Visible-light-driven heterostructure Ag/Bi2WO6 nanocomposites were prepared using a hydrothermal method followed by the photodeposition of Ag on Bi2WO6. A photocatalyst with a different molar ratio of Ag to Bi2WO6 (1:1, 1:2 and 2:1) was prepared. The catalytic performance of Ag/Bi2WO6 towards the photocatalytic oxidation of rhodamine B (RhB) and methylene blue (MB) was explored. Interestingly, the Ag/Bi2WO6 (1:2) catalyst exhibited superior performance; it oxidized 83% of RhB to Rh-110 and degraded 68% of MB in 90 min. This might be due to the optimum amount of Ag nanoparticles, which supported the rapid generation and transfer of separated charges from Bi2WO6 to Ag through the Schottky barrier. An excess of Ag on Bi2WO6 (1:1 and 2:1) blocked the active sites of the reaction and did not produce the desired result. The introduction of Ag on Bi2WO6 improved the electrical conductivity of the composite and lowered the recombination rate of charge carriers. Our work provides a cost-effective route for constructing high-performance catalysts for the degradation of toxic dyes.

ZIF-8 derived defect-rich nitrogen-doped carbon with enhanced catalytic activity for efficient non-radical activation of peroxydisulfate.

The non-radical oxidation processes of persulfate activation by carbon materials have shown great potential for industrial and saline wastewater treatment. Recently, metal-organic frameworks (MOFs) as an emerging precursor have been widely used for fabricating functional carbon materials. Herein, we reported ZIF-8 derived defect-rich nitrogen-doped carbon (ZCNs) via NaCl-assisted pyrolysis for efficient non-radical activation of peroxydisulfate to degrade rhodamine B (RB). All samples exhibited excellent catalytic activity, and ZCN-900 (pyrolyzed at 900°C) was found to be the most active, able to degrade 96% of RB quickly within 10min. Quenching tests and electron paramagnetic resonance (EPR) analyses suggested that the singlet oxygen (1O2) dominated the degradation process by a non-radical pathway. Furthermore, the effect of anions and water quality on RB oxidation were investigated, and ZCN-900/PDS system showed great resistance to the anions and natural organic matters (NOM). This work may provide a significant addition to MOF-based functional materials for environmental remediation based on the results above.

Highly dispersed and stable Fe species supported on active carbon for enhanced degradation of rhodamine B through peroxymonosulfate activation: Mechanism analysis, response surface modeling and kinetic study

Herein, highly dispersed Fe species supported on activated carbon (CA-Fe-C) was fabricated with the aid of citric acid, showing excellent catalytic performance and stability for the degradation of rhodamine B (RhB) through peroxymonosulfate (PMS) activation. The radical quenching study, electron paramagnetic resonance (EPR) measurement and PMS consumption analysis confirmed the RhB degradation mechanism involving reactive radical species attacking RhB and non-radical oxidation pathway. The main degradation intermediates were identified by LC-MS, and the possible RhB degradation pathways were deduced. A multivariate quadratic polynomial model was developed using the response surface methodology (RSM) to examine how the removal of RhB was influenced by several quantifiable factors, with the objective of optimizing RhB removal. The analysis of variance (ANOVA) was used to evaluate the adequacy and significance of the proposed model. The effects of solution pH values, initial concentration, inorganic anions, PMS dosage, catalyst dosage, and metal loading amount on RhB removal were investigated. The method of initial rates was employed to determine the intrinsic reaction rate law, and the reaction was identified to follow the Langmuir-Hinshelwood (L-H) kinetics model.

Key Considerations When Assessing Novel Fenton Catalysts: Iron Oxychloride (FeOCl) as a Case Study.

Iron oxychloride (FeOCl) has been reported to be a highly efficient heterogeneous Fenton catalyst over a wide pH range. In order to determine the true catalytic performance of FeOCl, we simultaneously quantified the adsorptive and oxidative removal of formate, oxalate, and rhodamine-B (RhB) and the formation of RhB oxidation products at both pH 4.0 and 7.0. FeOCl was found to be a poor Fenton catalyst at either pH, as gauged by the oxidation of formate, oxalate, and rhodamine B and the decomposition of H2O2, in comparison with ferrihydrite (Fhy), one of the most common Fe-containing Fenton catalysts. The adsorption of target contaminants to FeOCl and homogeneous Fenton processes, induced by dissolved iron, resulted in overevaluation of the catalytic performance of FeOCl, especially for (i) the use of strongly adsorbing target compounds, without consideration of the role of adsorption in their removal and (ii) exceedingly high concentrations of H2O2 to remove trace quantities of target contaminants. Overall, this study highlights that the systematic quantification of H2O2 decomposition, target compound adsorption, and oxidation as well as the concentrations of oxidized products formed are prerequisites for unequivocal elucidation of the catalytic nature and reaction mechanism of solid Fenton catalysts.

Hard-NaCl template-regulated LiCoO2 catalyst with enhanced activity for aqueous and gaseous organics elimination

Developing new and effective catalytic materials is of significant importance to the catalytic oxidation of multiphase organic pollutants. In the present work, lithium cobalt oxide (LiCoO2) was synthesized and modified via hard-NaCl template regulation for the oxidative elimination of organic dye, e.g. rhodamine B (RhB), and VOCs, e.g. benzene. Compared with the pristine sample, a medium-level NaCl addition offered a much more advanced reactivity towards RhB oxidation, with the elimination percentage rising from 31% to 60% after 20-min reaction for 50 mL 5 mg/L RhB and 4 g/L catalyst. As to benzene oxidation, the above NaCl-assisted catalyst manifested a giant step forward from the inertness of the unmodified sample, with 82%-86% of the ∼460 ppm inlet benzene being removed by the NaCl-LiCoO2 catalyst at 350 °C and 120 L/g/h in contrast to the 5% removal efficiency of the pristine sample. Characterization studies confirmed the fully developed mesoporous structure after NaCl removal, which facilitated the reactant diffusion as well as the accessibility of the catalytical sites, and the strengthened oxidativity of the NaCl-modified sample was ensured by its large number of surface adsorbed oxygen species. Besides, the C6H6-TPSR measurements gave a direct experimental evidence to the high activity of the oxygen species induced by NaCl modification. These favorable factors were all conducive to dye and VOCs oxidation.

Vanadium oxide‐supported copper ferrite nanoparticles: A reusable and highly efficient catalyst for rhodamine B degradation via activation of peroxymonosulfate

AbstractA magnetic vanadium oxide nanoparticles supported on spinel copper ferrite (CuFe2O4–VOx) are prepared, characterized, and examined for the peroxymonosulfate (PMS) activation to degrade Rhodamine B (RhB) in water solution. Interestingly, the results show that despite the inability of mixture of copper ferrite and vanadium oxides nanoparticles to the effective RhB decomposition, the prepared catalyst exhibits an excellent catalytic ability toward RhB oxidation. The influence of vital parameters, such as temperature, PMS concentration, catalyst loading, and initial pH are discussed comprehensively. The kinetic studies demonstrate that the pseudo‐first‐order model is well fitted for RhB degradation in CuFe2O4–VOx/PMS system and the activation energy is estimated at 19.60 kJ mol−1. Furthermore, it is found out that the concentration of leached metal ions in solution is negligible and PMS activation is done mainly on the surface of the catalyst. A probable mechanism of PMS activation over RhB degradation is proposed based on the results of free radical quenching studies and X‐ray photoelectron spectroscopy (XPS) analysis. Radical quenching experiments using various scavengers suggest SO4•−as a main reactive species in the degradation.

Improving Fenton-like oxidation of Rhodamin B using a new catalyst based on magnetic/iron-containing waste slag composite

Heterogeneous catalytic Fenton of Rhodamine B (RhB) was enhanced by magnetic waste iron slag composite (MIS) as a novel catalyst. The MIS was successfully enriched by an increase in mass rate of Fe element from 26.60% (in iron slag-IS) to 50.68% (in MIS-10). Besides, the textural properties of MIS-10 were remarkably improved in porous structure and BET specific surface area compared with IS. An almost complete degradation of RhB was obtained at the composite ratio between mixture of (Fe2+ and Fe3+) and IS of 10% (w/w), solution pH of 3, H2O2 of 1680 mg/L and catalyst dosage of 4000 mg/L for both IS/H2O2 and MIS-10/H2O2 systems within 120 min reaction time At this optimal operational condition, the decolorization and mineralization of RhB, respectively, reached 71.84% and 59.75% for IS/H2O2 system and 98.48% and 83.33% for MIS-10/H2O2 system. The first-order reaction rate constant (Kd) values of the pseudo-first-order kinetic followed the same sequence as COD removal. The Fe amount enriched in MIS-10’s constituent was proved the improving considerably reaction rate with H2O2 to generate continuously more hydroxyl (.OH) radicals which led to higher oxidation of RhB by MIS-10/H2O2 compared with IS/H2O2. The mechanisms of RhB enhanced degradation included adsorption, leaching iron through homogeneous Fenton reactions and heterogeneous Fenton reaction. The main mechanism of RhB oxidation by MIS-10/H2O2 system was through .OH which was produced by heterogeneous Fenton reaction due to the contribution of Fe elements enriched on the catalyst’s surface. The MIS-10 exhibited a high stability with very low iron leaching and maintained a high catalytic activity after 5 successive cycles, indicating MIS-10 is fully promising catalyst for Fenton oxidation of persistent organic compound from wastewater.

Co-carbonization of red mud and waste sawdust for functional application as Fenton catalyst: Evaluation of catalytic activity and mechanism

Synthesis of red mud/biochar (RMBC) composite was conducted by facile co-carbonization of red mud and waste sawdust. Multiple characterizations verify the reduction of ferric oxide and the formation of graphitic biochar with defects. Hydrogen peroxide activation by RMBC was investigated for Rhodamine B (RhB) oxidation. RMBC displays both adsorption and catalytic effects for RhB removal. Catalytic oxidation of RhB is effectively obtained at pH below 2.2. RhB oxidation is slightly improved with growing temperature. RhB oxidation in RMBC/H2O2 system obeys the pseudo first-order kinetic, and the low activation energy of 56 kJ/mol implies the effective hydrogen peroxide activation by RMBC. Associated with the determinations of radical and iron leaching, the dominant role of hydroxyl radical in solution is verified for RhB oxidation. The limitation of RMBC for heterogenous catalysis may be solved by the regulation of alkaline feature. RMBC processes special properties of red mud and biochar, and its application to wastewater treatment provides a green and sustainable approach obeying the “waste treating waste” concept.

Bimetal oxalate‐derived synthesis of laponite‐decorated CoFe2O4 porous nanostructures for activation of peroxymonopersulfate towards degradation of rhodamine B

AbstractBACKGROUNDAdvanced oxidation processes based on sulfate radical have been widely employed for oxidation degradation of organic contaminants. Catalytic activation of peroxymonopersulfate (PMS) with transition metal oxides holds great promise for the generation of sulfate radical. In this work, laponite‐decorated CoFe2O4 porous nanostructures have been prepared through the thermal decomposition of laponite/oxalates, and evaluated as a magnetic catalyst to activate PMS for the oxidation of rhodamine B (RhB).RESULTSThe decoration of porous CoFe2O4 microparticles with laponite was evidenced because of the presence of the vibration mode of SiO (at 1359 cm−1) in Fourier transform infrared spectra and the uniform distribution of Si and Mg elements from elemental mapping images. Decorating with laponite also resulted in an increase in amount of surface hydroxyl oxygen species, which facilitated the formation of CoOH complex for PMS activation. Furthermore, the enhanced activation of PMS with laponite‐decorated CoFe2O4 resulted in a faster removal (98.04%) of RhB as compared to undecorated CoFe2O4 (79.62%) within 56 min. Meanwhile, the rate constant increased from 0.0288 (CoFe2O4) to 0.0679 min−1 (laponite‐decorated CoFe2O4). The degradation rate of RhB progressively increased with reaction temperature and catalyst dosage. Scavenging and electron paramagnetic resonance tests manifested that the sulfate and superoxide radicals served as the major active species for the oxidation of RhB molecules.CONCLUSIONThe above results demonstrated positive effects of laponite on the textural property, surface chemical states and catalytic activity of porous CoFe2O4 microparticles. This study provides an insight into the promising role of laponite as an additive in improving PMS activation.