Initial Rhodamine B Concentration Research Articles

Coconut Shell Carbon Preparation for Rhodamine B Adsorption and Mechanism Study.

Phosphoric acid is used as a chemical activator to prepare coconut shell carbon (PCSC), and for investigating rhodamine B (RhB) adsorption performance. The optimal conditions for the preparation of PCSC (calcined temperature, phosphoric acid concentration), and the influence of adsorption conditions (concentration, pH, etc.) on RhB and the recovery performance of optimal carbon are investigated. Experimental results show that when the amount of PCSC (600 °C, 2 h) is 0.2 g, the initial RhB concentration is 10 mg/L, pH = 6, and the adsorption time is 30 min, it can have 95.84% RhB adsorption efficiency. Liquid ultraviolet spectroscopy also supports this adsorption performance. Characterization data showed that hydroxyl and ester groups, aromatic structures, and PO43- existed on the surface of PCSC, and the amount decreased with increasing calcined temperature. PCSC has a BET (N2) surface area of 408.59 m2/g and has a micropore distribution, EDS-detected P content is 3.91%. SEM showed that the PCSC formed micropores which could better adsorb RhB. The kinetic and thermodynamic analysis of the adsorption of RhB by PCSC showed that the adsorption process was in accord with quasi-secondary kinetic equations and ΔGθ was between -1.65 and -18.75 kJ/mol. The adsorption was a physical adsorption and a spontaneous endothermic reaction, and the obtained PCSC sorption isotherms were classified as Langmuir-type. The RhB adsorption mechanism on PCSC includes pore diffusion, hydrogen bonding, and π-π conjugation. The PCSC prepared by H3PO4 modification has superior adsorption and recycling performance for RhB, providing a reference for the preparation of other biomass carbon materials for the treatment of dye wastewater.

A highly efficient Co-based catalyst for peroxymonosulfate activation for rapid degradation of RhB over a wide pH range

Cobalt-based materials have been demonstrated to be effective heterogeneous catalysts for peroxymonosulfate activation in degrading many refractory organic pollutants. In this study, a new cobalt-based catalyst was prepared using cobalt chloride hexahydrate (CoCl2·6H2O) as the Co2+ source, 2,3-pyrazine dicarboxylic acid and 3,6-DI-4-pyridyl-1,2,4,5-tetrazine (4-PYTZ) as ligands. This catalyst was employed as a peroxymonosulfate activator for the degradation of Rhodamine B(RhB). The results indicated that the prepared Co-based catalyst can effectively degrade RhB dye in aqueous solution by activating peroxymonosulfate (PMS). Specifically, when the initial concentration of RhB was 20 mg/L, its degradation rate exceeded 98 % within merely 9 min. The factors influencing the activation of PMS by the Co-based catalyst were examined, including PMS concentration, reaction temperature, solution pH, and the concentration of organic pollutants. Stability and reusability tests demonstrated that the prepared catalyst exhibited good stability, with the degradation rate of RhB remaining above 97 % after four repetitive experiments. Free radical quenching experiments and electron paramagnetic resonance (EPR) analyses revealed that sulfate radicals (SO4−) and hydroxyl radicals (OH) are the primary reactive radicals accountable for the degradation process. Additionally, it displayed excellent adaptability over a wide pH range, particularly within the pH levels ranging from 5 to 9. This study demonstrates that the prepared Co-based catalyst can serve as a stable and effective option for degrading organic dyes in wastewater treatment applications.

Removal of Rhodamine-B dye from Aqueous Solutions Using Alkaline-Modified Activated Carbon from Cocoa Pod Husk.

Rhodamine-B (RhB) dye in wastewater poses health and environmental risks due to respiratory and eye infections, neurotoxicity, and carcinogenicity, necessitating proper disposal for risk mitigation. This study investigates RhB removal from water using NaOH-modified activated carbon derived from cocoa pod husk (CPHAC). Employing a face-centered central composite design, operational variables were optimized to achieve maximum RhB dye removal efficiency. The study reveals a removal efficiency of 98.87 ± 0.84% under optimized conditions: adsorbent dose of 1.34g, contact time of 71.59min, and an initial RhB concentration of 6.61 ppm. The Freundlich isotherm model demonstrated a good fit, suggesting that RhB removal is governed by heterogeneity and multilayer adsorption. Kinetic experiments revealed that adsorption follows a pseudo-second-order model, indicating likely irreversible adsorption with dye molecules forming chemical bonds on CPHAC's surface. Overall, this study demonstrates the effectiveness of CPHAC as an efficient adsorbent for RhB removal from water.

Green synthesis of silver nanoparticles from southern Eucalyptus globulus: Potent antioxidants and photocatalysts for rhodamine B dye degradation

Nanotechnology and nanoscience provide innovative foundations for delivering a wide range of new and enhanced technologies to the modern world. To break down Rhodamine B (RhB) dye solutions, this work describes the creation of silver nanoparticles (Ag-NPs) using the aqueous leaf extract of Eucalyptus globulus (E. globulus). The biosynthesized Ag-NPs were studied using UV–vis spectroscopy and SEM in conjunction with EDX, TEM, FTIR, HPLC and XRD. Stable Ag-NPs were synthesized using E. globulus, as evidenced by the absorption peaks at 431 nm seen in the UV–vis spectrum analysis. Spherical-shaped particles were visible in the SEM images, and the metallic form of the synthesised Ag-NPs was verified by EDX. The initial concentration of RhB, reaction duration, temperatures, and pH were all adjusted to optimise the photocatalytic degradation of RhB using Ag-NPs. The results indicated that photocatalytic effectiveness increased with rising pH. After 80 min at room temperature, the degradation reached 91.20 % at pH 12. The antioxidant EC50 results demonstrate that Ag-NPs exhibited a higher level of protective antioxidants (20.15 ± 0.3 µg/mL for DPPH and 10.24 ± 0.2 µg/mL for ABTS) compared to the E. globulus leaf extracts.

Visible light responsive SiO2/g-C3N4/BiOBr/Bi heterojunction photocatalyst for degradation of rhodamine B

For the purpose of alleviating the negative influence of rhodamine B (RhB) abuse on the environment, it is imperative to design a green and efficient photocatalyst for tackling organic dye-contaminated wastewater. Herein, a novel SiO2/g-C3N4/BiOBr/Bi (denoted as Si/CN/BiOB/Bi) photocatalyst with enhanced photodegradation activity has been successfully created. The influence of variable parameters including Bi doping amount, initial concentration of RhB, photocatalyst dosage, and reaction temperature on the photocatalytic performance of Si/CN/BiOB/Bi under visible light illumination are analyzed in detail. Results indicated that the degradation rate constant of RhB over Si/CN/BiOB/Bi-0.5 is 25.1, 18.1, and 2.2 times higher than that of CN, Si/CN, and Si/CN/BiOB, respectively. The Si/CN/BiOB/Bi-0.5 photocatalyst displayed high photocatalytic performance after 5 recycled runs. The improved photocatalytic performance can be attributed to the novel morphology as well as the excellent synergetic effects of Si/CN, BiOBr, and Bi, which enables the catalysts to accelerate the separation of photogenerated carriers. In brief, a new Si/CN/BiOB/Bi photocatalyst has a great application perspective for the purification of RhB wastewater.

Separation performance of cationic and anionic dyes from water using polyvinylidene fluoride-based ultrafiltration membrane incorporating polyethylene glycol

Membrane separation shows high performance in the dye’s removal at nanofiltration conditions. Pinpointing the problems accompanying using high pressure in the nanofiltration process sparks increased interest among investigators to tackle this important point. This work tackles the problem of using the nanofiltration process to remove intermediate molecular weight dyes by decorating new functionalized membranes working at ultrafiltration conditions. Flat sheet ultrafiltration membranes were successfully prepared by the phase inversion technique from polymeric solutions containing 16, 18, and 20 wt% of polyvinylidene fluoride (PVDF) and N, N-dimethyl formamide as a solvent. The prepared membranes were tested using rhodamine B (RhB) dye as a model pollutant at different transmembrane pressures of 1, 2, 3, and 4 bar. Optimistic permeability, permeate flux, and dye removal were obtained using 18 wt% of PVDF. This membrane was developed with different polyethylene glycol (PEG) contents of 3, 6, and 9 wt% to improve the hydrophilicity and permeability of the membrane surface at low pressure. The morphology analysis, elemental composition, and surface functional groups of the pure and modified membranes were examined. The effect of dye concentration and pH of the feed solution on the permeate flux and RhB removal was studied using an 18 wt% PVDF membrane containing 6 wt% of PEG. The results showed that incorporating 6 wt% of PEG in the 18 wt% PVDF casting solution reduced the CA from 78.85° for pure PVDF to 62.08° and enhanced the permeability from 7.16 L/m2.h for pure PVDF to 74.72 L/m2.h at 1 bar and initial RhB concentration of 10 mg/L. While RhB dye removal slightly decreased from 93.08 % for pure PVDF to 91.26 %. The results showcased the potential efficiency of the (6 wt%)PEG/(18 wt%)PVDF membrane for dye separation from water. Also, molecular weight cut-off was evaluated using RhB as a cationic dye, acid orange 10, and congo red as anionic dyes and it was 478 Da.

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.