Initial Rhodamine B Concentration Research Articles

Co2+-adsorbed chitosan-grafted-poly(acrylic acid) hydrogel as peroxymonosulfate activator for effective dye degradation

In this work, chitosan-grafted-poly(acrylic acid) (CS-g-PAA) was synthesized for use as a Co2+ adsorbent and circularly utilized as a peroxymonosulfate (PMS) activator in the degradation of rhodamine B (RhB) dye. CS-g-PAA demonstrated 3.7 times higher adsorption capacity toward Co2+ than pristine chitosan. The impact of the adsorption conditions was evaluated. The pseudo-second-order kinetic model and the Langmuir isotherm model best described the adsorption process. Under optimum conditions, the adsorption capacity of CS-g-PAA for Co2+ was 212 mg/g. The Co2+-adsorbed CS-g-PAA hydrogel was further utilized in the RhB degradation process. The effects of catalyst dosage, initial RhB concentration, pH, and the coexistence of anions on the degradation of RhB were studied. The hydrogel catalyst could remove 98 % of RhB within 5 min, at a degradation rate of 0.624 per min. Electron paramagnetic resonance (EPR) analysis and the radical scavenger experiment suggested that SO4•−, HO•, 1O2, and O2•− were involved in the degradation. Furthermore, when tested in various water systems, high degradation efficiencies of 98 % were attained after 20 min. The hydrogel catalyst performed excellent degradation over ten cycles without any chemical recovery processes. Moreover, high degradation efficiencies were observed between 95 % and 98 % when tested with other dyes.

Construction of Co-doped Fe2O3/carbonized melamine foam heterogeneous catalyst for enhanced degradation of organic pollutants through peroxymonosulfate activation

Co-doped Fe2O3/carbonized melamine foam heterogeneous catalyst (CMF/Co-Fe2O3) was prepared by hydrothermal method. Rhodamine B (RhB) degradation was employed as a model test for evaluating peroxymonosulfate (PMS) activation. The degradation efficiency of RhB can reach 97 % in the catalyst dosage (50 mg/L), PMS concentration (100 mg/L), pH = 7 and RhB initial concentration (10 mg/L) after 60 min reaction. The reaction rate constant is 10 times higher than that of CMF/Fe2O3 and the activation ability of PMS is greatly improved. The degradation efficiency of RhB can be inhibited by increasing the initial mass concentration of RhB and pH value. The effect of temperature on the degradation rate of RhB conforms to the Arrhenius model, and the degradation process is a surface reaction controlled process. The results of free radical capture experiments and electron paramagnetic resonance (EPR) experiments showed that SO4¯ was the main active free radical for RhB degradation. After four cycles, the degradation efficiency of RhB still maintains 80 % with CMF/10 %Co-Fe2O3 catalyst. The heterogeneous catalyst exhibited potential application in the field of degradation of dye wastewater due to its excellent cycling stability.

Utilization of palm leaves powder for removal of Rhodamine-B from an aqueous solution

In this research, adsorption of Rhodamine-B (RhB) from an aqueous solution onto palm leaves powder at room temperature was reported. The adsorption capacity of palm leaves powder was increased with initial concentration of RhB, and contact time while declined with temperature, pH, and mass of palm leaves powder. Results of adsorption kinetics study represented that RhB adsorption fitted to pseudo-second-order model because the value of correlation coefficient (R2 = 0.995) was close to unity. Adsorption isotherm illustrations indicated that RhB adsorption obeyed Langmuir isotherm model with correlation coefficient (R2 = 0.999) close to unity. Results of thermodynamics investigation indicated that RhB adsorption onto palm leaves powder was an exothermic process because the value of change in enthalpy (ΔH°= −16.95 KJ/mol) was negative. Moreover, the positive value of Gibb’s free energy represented that RhB adsorption onto palm leaves powder was a non-spontaneous process. In addition, the regeneration of palm leaves powder was also conducted.

The adsorption properties and mechanisms of magnetic carbon-silicon composites in situ prepared from coal gasification fine slag.

A novel magnetic carbon-silicon composite (Fe-HH-CGFS) was prepared from solid waste coal gasification fine slag (CGFS) by a two-step acid leaching and one-step chemical co-precipitation process, which was optimized using a 3-factor, 3-level Box-Behnken design and then analyzed for correlation. Fe-HH-CGFS was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), thermal gravimetric analysis (TGA), and vibrating sample magnetometer (VSM) measurements. The results demonstrated that Fe-HH-CGFS had a reverse spinel structure with an average particle size of 5.14 nm, exhibiting a microporous/mesoporous structure with a specific surface area (SSA) of 196.84 m2 g-1 and pore volume of 0.346 cm3 g-1. Furthermore, Fe-HH-CGFS could achieve 97.59% removal efficiency of rhodamine B (RhB) under the optimal conditions: an initial concentration of RhB of 100 mg L-1, an adsorption time of 60 min, and a dosage of Fe-HH-CGFS of 1.0 g L-1. The pseudo-second-order model and the Langmuir isotherm satisfactorily described the adsorption behavior. The results indicated that the RhB removal process was a single-molecule layer endothermic adsorption, which is dominated by chemical adsorption reactions. This work is expected to provide an alternative route for the high-value utilization of CGFS and offer a valuable insight for the recycling of other solid wastes, aligning with the green development concept of "treating wastes with wastes".

Natural bamboo powder and coffee ground as low-cost green adsorbents for the removal of rhodamine B and their recycling performance

Bamboo and coffee, which are abundant and inexpensive, have been used as green adsorbents for the adsorption of industrial dye rhodamine B (RB). Bamboo and coffee are natural sources of cellulose, hemicellulose, and lignin, making them promising green materials for industrial dye removal. The effects of various adsorption conditions, such as contact time, temperature, dose of bamboo powder (BP), coffee ground (CG), initial concentration of RB, and pH values of RB solution, were measured. Consequently, the kinetics of RB adsorption onto bamboo and coffee was in accordance with the pseudo-second-order model, with an activation energy of 29.51 kJ mol−1 for bamboo and 27.46 kJ mol−1 for coffee. The Langmuir model is well fitted to the whole adsorption period at different temperatures, in which the increase in the tested temperature has improved the adsorption capacity (i.e., BP: 6.76 mg g−1/30 °C, 6.96 mg g−1/40 °C, 7.64 mg g−1/50 °C and CG: 6.53 mg g−1/30 °C, 6.80 mg g−1/40 °C, 7.51 mg g−1/50 °C). Moreover, the spontaneous nature of the adsorption was based on the negative Gibbs free energy values obtained (i.e., from − 11.09 to − 14.30 kJ mol−1 [BP] and from − 10.34 to − 13.07 kJ mol−1 [CG]). These revealed that RB adsorption occurred at physical and chemical adsorption states. In addition, the recycling capability of adsorbents was determined in five cycles. Therefore, these materials are promising candidates for low-cost adsorbents.

Synthesis and characterization of nanocomposites containing Buchholzia coriacea pod decorated with multi-walled carbon nanotubes for remediation of rhodamine B dye from aqueous solution

A novel nanocomposite (WKM) was synthesized by crosslinking Buchholzia coriacea pod (WK) and f-MWCNTs for the efficient adsorption of rhodamine B (RhB) from wastewater. The uptake of RhB onto WK and WKM was influenced by initial pH, adsorbent dose, the temperature of the adsorptive system, contact time and initial RhB concentration. Optimum experimental conditions of 100 min agitation time, 0.05 g dosage, solution pH 3.0 and 100 mg dm−3 initial concentration were obtained. The uptake of RhB onto WK and WKM was well expressed by Freundlich isotherm and a monolayer maximum uptake capacity of 67.82 mg g−1 and 87.58 mg g−1 was determined for WK and WKM, respectively. The adsorption of RhB onto WKM and WK followed the Elovich and pseudo-first-order kinetic models, respectively. Thermodynamic parameters such as ∆G°, ∆H° and ∆S° reveal that the uptake of RhB onto WK and WKM was spontaneous and endothermic. Meanwhile, WKM demonstrated excellent reusability. Hence, this study presents a nanocomposite (WKM) with robust potential for RhB removal.

Exploring a chemical input free advanced oxidation process based on nanobubble technology to treat organic micropollutants

Advanced oxidation processes (AOPs) are increasingly applied in water and wastewater treatment, but their energy consumption and chemical use may hinder their further implementation in a changing world. This study investigated the feasibility and mechanisms involved in a chemical-free nanobubble-based AOP for treating organic micropollutants in both synthetic and real water matrices. The removal efficiency of the model micropollutant Rhodamine B (RhB) by oxygen nanobubble AOP (98%) was significantly higher than for air (73%) and nitrogen nanobubbles (69%). The treatment performance was not significantly affected by pH (3–10) and the presence of ions (Ca2+, Mg2+, HCO3−, and Cl−). Although a higher initial concentration of RhB (10 mg/L) led to a slower treatment process when compared to lower initial concentrations (0.1 and 1 mg/L), the final removal performance reached a similar level (∼98%) between 100 and 500 min. The coexistence of organic matter (humic acid, HA) resulted in a much lower reduction (70%) in the RhB removal rate. Both qualitative and quantitative analysis of reactive oxygen species (ROSs) using fluorescent probe, electron spin resonance, and quenching experiments demonstrated that the contributions of ROSs in RhB degradation followed the order: hydroxyl radical (•OH) > superoxide radical (•O2−) > singlet oxygen (1O2). The cascade degradation reactions for RhB were identified which involve N-de-ethylation, hydroxylation, chromophore cleavage, opening-ring and final mineralisation processes. Moreover, the treatment of real water samples spiked with RhB, including natural lake water and secondary effluent from a sewage works, still showed considerable removals of the dye (75.3%–90.8%), supporting its practical feasibility. Overall, the results benefit future research and application of chemical free nanobubble-based AOP for water and wastewater treatment.

Interface engineering of a magnetic 2D-C3N4/Fe2O3/NiFe-LDH heterostructure for efficient photocatalytic degradation of methylene blue and rhodamine B dyes under visible light

Double layer hydroxide (LDH) as a photocatalyst has potential features in water pollution control. In the present study, the iron (III) oxide /two-dimensional carbon nitride/nickel‑iron LDH (Fe2O3/2D-C3N4/NiFe-LDH) composite was synthesized by pyrolysis and co-precipitation process from waste iron rusts as one of the cheap precursors along with NiFe-LDH and g-C3N4. The photocatalytic activities of magnetic Fe2O3/2D-C3N4/NiFe-LDH as stable photocatalyst for degradation of methylene blue (MB) and rhodamine B (RhB) as cationic dyes was studied and then the characteristics of the resulting materials, including morphology, structure, crystal phase, optical and electronic properties, were clearly investigated using different techniques. The fabricated Fe2O3/2D-C3N4/NiFe-LDH provide greatly improved photocatalytic performance for dye degradation compared to the sole Fe2O3 and Fe2O3/g-C3N4.The maximum elimination efficiency of MB and RhB are 91.2% and 88.5% respectively. 80% COD photodegradation was achieved under optimal conditions including catalyst loading (0.36 g/L), initial pH (9.0), LED irradiation time (60 min), and initial concentration of MB (10 mg/L) and RhB (9 mg/L). The obtained photocatalyst was effectively recovered using an applied magnetic field. Based on the reusability study, the fabricated photocatalyst was chemically stable and corrosion resistant.

Z-scheme MnO2/Mn3O4 heterojunctions with efficient peroxymonosulfate activation for organic pollutant removal

The exploration of efficient heterogeneous catalysts for persistent organic pollutant removal is extremely attractive. In the present work, MnO2/Mn3O4 photo-Fenton catalysts were designed by a facile hydrothermal route to activate peroxymonosulfate (PMS) under visible light irradiation for organic pollutant degradation. The optimized MnO2/Mn3O4 heterojunction shows excellent Rhodamine B (RhB) removal efficiency, whose apparent kinetic constant is 11.9 and 5.36 times as high as the MnO2 and Mn3O4. Meanwhile, there is a neglectable attenuation in catalytic performance after 5 recycling runs. Based on the active species trapping experiments, the non-radical process contributes more than the radical process during RhB degradation. Moreover, factors including the dosage of PMS, initial RhB concentration, initial pH, the presence of various anions, different organic pollutants, and water sources are investigated. Systematical characterizations reveal that the enlarged specific surface areas and the efficient charge separation aroused from the Z-scheme mechanism are attributed to the enhanced photo-Fenton performance. The present work contributes to the construction of the Mn-based photo-Fenton catalyst with efficient PMS activation capacity for environmental remediation.

Advance oxidation processes of Rhodamine B under O3/UV using spent bleaching earth-ZnO composite: Performance in kinetics

Spent bleaching earth and ZnO composite (SBE/ZnO) was prepared as the catalyst for the advanced oxidation processes (AOPs) of rhodamine B (RB) under O3/UV. The photocatalytic ozonation process of RB was conducted at an ozone flow rate of 1 L/min by adjusting the variation of initial RB concentration, catalyst dosage, and reaction time. The RB removal efficiency of 96.7% was reached within 36 min at optimal operational conditions (initial concentration of 100 mg/L and catalyst dosage of 1.5 g). The kinetical analysis at this condition showed that the photocatalytic ozonation process of RB followed a pseudo-first-order reaction with a rate constant of 0.0975 min-1. Meanwhile, the effect of operational variables was evaluated using response surface methodology (RSM) and resulted in an optimized model for RB Removal following equation: RB Removal = 84.95 - 6.24A + 5.81B + 22.45C + 3.07AB + 13.14AC - 6.72BC + 0.1174A2 + 7.86B2 - 8.90C2, where A is the initial concentration of RB, B is catalyst dose and C is reaction time, with a high coefficient of determination R2 = 0.9432.

Efficient degradation of dye wastewater by catalytic ozonation reactive ceramic membrane with facile spraying of nano Ti[sbnd]Mn oxides: A pilot scale attempt

The traditional treatments of dye wastewater exist obvious drawbacks of low efficiency but high energy consumption. To solve this problem, based on the concept of combining degradation and separation, an integrated process of TiMn oxides catalytic ozonation and ceramic membranes (CM) was proposed to degrade dye wastewater in this paper. Specifically, TiO2/MnO2 hybrid catalysts were loaded on the surface of CM with a spraying printing method to prepare a reactive ceramic membrane (TiO2/MnO2-CM). The degradation efficiency and permeate flux of the TiO2/MnO2-CM + O3 system on Rhodamine B (RhB) were investigated. The SEM results illustrated that the catalyst was successfully loaded on the surface of CM. Additionally, the degradation efficiency of RhB was 100 % in 40 min under the conditions of catalyst spray layers 12, ozone concentration 2.5 g/cm3, and initial concentration of RhB 20 mg/L, and the permeate flux of TiO2/γ-MnO2-CM was as high as 125.399 kg/ (m2·h). Supplementarily, the study revealed that TiO2/γ-MnO2-CM could increase the concentration of ozone in water and catalyze ozone to produce more hydroxyl radicals (•OH), and the concentration of dissolved ozone was 0.7545 mg/L, •OH 68.16 μmol/L respectively. Eventually, the catalytic ozonation TiO2/γ-MnO2-CM device was scaled up, which treated 96 L RhB with a degradation efficiency of 100 % in 50 min. The work gives a solid foundation and scientific value for the industrial application of reactive CM in water or wastewater treatment.

Highly-efficient removal of Rhodamine B using a flow-through electrocatalytic filtration system: Characteristics, efficiency and mechanism

The objective of this research is to develop an effective electrocatalytic filtration system using Ti/SnO2-Sb membrane anodes for eliminating Rhodamine B (RhB) from wasteater. Compared to Ti/SnO2-Sb plate anode, the prepared Ti/SnO2-Sb membrane anodes featured smaller particle size, bigger electrocatalytic active surface area, lower charge transfer resistance, and higher potential for oxygen evolution. The electrocatalytic filtration system obtained RhB removal of 90.29% with EE/O of 5.51 kWh m−3 after 90 min of electrolysis when initial pH value was 5, current density was 10 mA cm−2, initial RhB concentration was 50 mg L−1, and membrane flux was 2.17 m3 (m2·h)−1, respectively. The flow-through electrocatalytic filtration system was found to be limited by kinetics under a high membrane flux and dominated by an indirect radical oxidation. Finally, the possible RhB degradation pathways were proposed based on the detected intermediates and density functional theory calculations.

Co3O4 decoration on iron-contained biochar composite fabricated by co-pyrolysis of red mud and spent coffee ground: A synergistic hybrid for Rhodamine B degradation via peroxymonosulfate activation

In this study, a composite was prepared by co-pyrolysis of red mud (RM) and spent coffee grounds (SCG). Then, cobalt was incorporated in the as-prepared RM/biochar composite (RMBC) and employed as the heterogeneous activator of peroxymonosulfate (PMS) for Rhodamine B (RhB) degradation. A temperature-programmed reaction and X-ray diffraction (XRD) measurements disclosed that the hematite (Fe2O3) phase in RM experienced a step-wise reduction to magnetite (Fe3O4) and Fe0 with increasing temperature during the co-pyrolysis of RM and SCG. The RMBC exhibited low performance for PMS activation to degrade RhB. However, incorporating 1.5 wt% Co can drastically improve the catalytic performance. The influence of initial pH, catalyst dosage, initial RhB concentrations, and temperature on the degradation efficiency was investigated. The quenching experiments combined with electron paramagnetic resonance analysis proved that the ·OH and SO•−4radicals, and 1O2 no-radical were the main reactive species for RhB degradation in the Co3O4/RMBC/PMS system.

A sustainable route for production of graphene oxide-contained nanostructured carbons from rice husk waste and its application in wastewater treatment

Agricultural biomass, such as rice husk (RH), is a renewable source of bioenergy. However, a large amount of RH ash (RHA) is generated after the thermal conversion of RH. The main component of RHA is silica (>85 wt%). This study used recyclable RHA as a mesoporous SBA-15 template source. Next, ordered mesoporous carbon/ graphene oxide (RH-CMK-3/GO) composites were synthesized through the direct carbonization of GO, sucrose, and an SBA-15 template. Experimental data demonstrated that GO was successfully conjugated on the surface of CMK-3. The RH-CMK-3/GO exhibited a highly ordered mesostructure, which was not affected by the incorporation of GO. Compared with bare RH-CMK-3, the RH-CMK-3/GO had an enhanced surface area and pore volume. The composite exhibited a highest pore volume of 1.143 cm 3/g, a surface area of 1138 m2/g, and a pore diameter of 3.68 nm. The RH-CMK-3/GO revealed a higher ability for the adsorption of rhodamine B (RhB) than did the SBA-15, SBA-15/GO, and pure CMK-3 materials. The removal of RhB increased with increases in the composite dosage, solution pH and temperature, and carbonization temperature and time and a decrease in the initial RhB concentration. Moreover, the RH-CMK-3/GO exhibited a highest removal efficiency of 100%. The thermodynamics, kinetics, and isotherm adsorption data for the RH-CMK-3/GO composite exhibited satisfactory fitting for the endothermic, pseudo-second-order, and Langmuir models, respectively. Moreover, the composite exhibited good reusability. These results suggest that RHA can be effective for the fabrication of valuable mesoporous carbon nanocomposites and the elimination of organic contaminants from wastewater.

Development of MOF-MXene composite for the removal of dyes and antibiotic

Metal-organic framework composites have gained great attention in the adsorptive remediation of environmental pollutants because of their unique features such as tunable pore size and modification of their framework. The main objective of this study was to fabricate UiO-66/MXene (Ti3AlC2) composite through solvothermal method and newly synthesized adsorbent was characterized by utilizing powder X-Ray diffraction analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. Exceptional adsorption properties of UiO-66/MXene composite were verified by adsorption of two model dyes i.e., methylene blue (MB), rhodamine B (RhB), and antibiotic i.e., tetracycline (OTC). Adsorption process was studied by applying different optimization parameters such as pH, contact time, adsorbent dose, and initial concentration of MB, RhB, and OTC. Results showed that UiO-66/MXene composite have best adsorption performance with removal rate of 98 % for MB, 97 % for RhB, and 99 % for OTC. Four kinetic models e.g., pseudo-first order, pseudo-second order, intraparticle diffusion and Elovich models were applied, and results showed that kinetic process was well described by pseudo-second-order kinetic model for dyes and antibiotic. Maximum adsorption capacity (qm) of UiO-66/MXene composite was achieved up to 312, 285, and 476 mg/g for MB, RhB, and OTC respectively. Four different isotherm models are used such as Langmuir, Freundlich, Dubinin–Kaganer–Radushkevich (DKR), and Temkin, the study shows that the Langmuir isotherm model describes well for the adsorption of MB, RhB, and OTC. Thermodynamic studies suggested that the process of adsorption was spontaneous and endothermic for dyes and antibiotic. The results recommend that the successful synthesis of UiO-66/MXene composite offers beneficial visions in the development of MOF composites as adsorbents for water refining.

Study on the mechanism of high effective mineralization of Rhodamine B in three dimensional electrochemical system with γ-Fe2O3@CNTs particle electrodes

Three-dimensional electrochemical reactor (3DER) is an efficient technology for the treatment of printing and dyeing wastewater. The particle electrode between anode and cathode is the core unit of 3DER, which determines the treatment efficiency of wastewater. However, the deactivation of the particle electrode caused by the coverage of the catalytic sites seriously hindered the continuous operation of 3DER. In this work, γ-Fe2O3@CNTs particle electrode was prepared by immersion calcination, and its performance was evaluated by degradation of Rhodamine B (RhB) wastewater in 3DER. The study showed that in γ-Fe2O3@CNTs/Mn@FNE-3DER, the removal rate of RhB reached the best of 99.16% within 7 min under the conditions of γ-Fe2O3@CNTs dosage of 1.00 g·L-1, initial RhB concentration of 100 mg·L-1, pH 7.0, and current density of 20 mA·cm−2. The superior catalytic activity of the system is mainly due to the charge transfer channel in γ-Fe2O3@CNTs structure, which improves the mass transfer efficiency of electrons. According to LC-MS analysis, the degradation process of RhB can be divided into five stages: deethylation, chromophore cracking, debenzylation and deamination, ring opening and mineralization. Hydroxyl radicals play an important role in this process. After the reaction, most RhB is converted into CO2 and H2O. In addition, the study also showed that the Fe3+/Fe2+ circulating system formed between the anode and cathode was the important reason for the high degradation efficiency of RhB. After five cycles of experiments, the degradation efficiency of 92.55% was still maintained, indicating that the particle electrode has significant stability and reusability in the catalytic process. To sum up, the excellent performance of γ-Fe2O3@CNTs particle electrode in three-dimensional electrochemical system provides a promising idea for the actual treatment of printing and dyeing wastewater.

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.

Synthesis of 2D/2D direct Z-scheme WO3/Bi5O7I heterojunctions for decomposition and detoxification of organic compounds under simulated sunlight

For this study, a WO3/Bi5O7I direct Z-scheme heterojunction material was successfully synthesized via a solvothermal-calcination method. The WO3/Bi5O7I heterostructure enhanced the absorption of light and accelerated the separation of charge carriers. Under simulated sunlight irradiation, the removal rate of rhodamine B (RhB) reached 99.6% over the optimal WB14 composite (mass ratio of WO3: Bi5O7I was 14%), which was 2.53 and 30 times that of pristine Bi5O7I and WO3, respectively. Experimental parameters including the WB14 dosage, initial RhB concentration, solution pH, and water sources were explored. Meanwhile, the WB14 exhibited excellent stability and reusability under simulated sunlight. The degradation pathway of RhB was speculated and the toxicity of intermediates was evaluated using the ECOSAR program. Moreover, tetracycline (TC) was employed as a common antibiotic to verify the universality of the catalysts. Capturing experiments and electron paramagnetic resonance (EPR) tests revealed that h+ served as the main active species in the photocatalysis, while OH and O2– played secondary roles. Finally, the formation of Z-scheme heterojunctions between the Bi5O7I and WO3 was inferred based on charge carrier migration and reactive species in the photocatalytic system. This study provides insights into the design of Z-scheme heterojunctions, which is helpful toward the development of Z-scheme heterojunction concepts.

Efficient activation of peroxymonosulfate via Cu2+/Cu+ cycle enhanced by hydroxylamine for the degradation of Rhodamine B.

The application of Cu2+/peroxymonosulfate (PMS) process for the elimination of refractory pollutants in industrial wastewater is limited by the slow transformation from Cu2+ to Cu+. In this research, hydroxylamine (HA) was employed to improve the degradation capacity of the Cu2+/PMS process. Rhodamine B (RhB) was selected as the target compound to indicate the performance of HA/Cu2+/PMS process. Compared with the Cu2+/PMS process, the reduction of Cu2+ to Cu+ was effectively promoted by HA in the HA/Cu2+/PMS process, which increased the decomposition rate of PMS by 29.2%, correspondingly, promoted the removal rate of RhB by 77.6%. The degradation of RhB followed pseudo-second-order kinetics in the proposed process. The active species analysis subsequently indicated hydroxyl radicals (·OH) and sulfate radicals (SO4·-) played important roles for degrading RhB with ·OH as the dominant active radical. The effects including initial pH, RhB concentration, PMS concentration, and Cu2+ concentration on the degradation of RhB were further investigated and discussed in detail. Additionally, the HA/Cu2+/PMS process exhibited effective RhB removal in simulated wastewater. From the perspective of waste utilization (Cu2+) and the remediation of organic contamination, the work would provide a valuable and promising process.

A Novel Metal-Containing Mesoporous Silica Composite for the Decolorization of Rhodamine B: Effect of Metal Content on Structure and Performance.

A series of novel MnxFey@SiO2 (x,y = 1-20%) nanocomposites were synthesized for the first time via the sol-gel/combustion method with different content of precursors (Mn and Fe acetate salts). The effect of precursor content and ratio on physicochemical properties were observed by various characterization methods. Moreover, Rhodamine B (RhB) was chosen as the target pollutant to test the performance of these nanocomposites under a photocatalytic Fenton-like reaction. The results showed that the nanocomposite morphology improved by increasing Fe and Mn content. In this study, interesting behavior was observed in BET results which were different from the fact that increasing metal content can decrease the surface area. This study revealed that one metal could be more critical in controlling the properties than another. Moreover, the precursor ratio appears to have a more tangible effect on the surface area than the effect of precursor content. Among all synthesized nanocomposites, Mn1Fe5@SiO2 showed the highest surface area of 654.95 m2/g. At optimum batch conditions (temp = 25 °C, catalyst dosage = 1 g L-1, H2O2 = 75 mmolL-1, and initial RhB concentration = 50 mg L-1), complete removal (simultaneous adsorption/degradation) occurred using Mn1Fe5@SiO2 at neutral pH. This study showed that the designed nanomaterial could be used as a dual functional adsorbent/photocatalyst in different environmental applications.