Heterogeneous persulfate activation by nano-sized Mn3O4 to degrade furfural from wastewater

Ultra-fast and ultra-efficient phenol removal from aqueous solution using a nano biocarbon adsorbent by RSM-CCD method: parameters, isotherm, kinetic, ANOVA

The purpose of this research is to investigate the ability of peanut shell activated carbon (PSAC) to adsorb phenol from aqueous solutions. Phenolic wastewater in various industries and their release to the environment are environmental problems. Among the various separation methods, adsorption is an accepted method because of its efficiency, simplicity, cost-effectiveness, and possibility to use different adsorbent materials to achieve maximum adsorption efficiency. Response surface methodology (RSM) was used to minimize the required experiments, modeling, finding the optimal point, and variance analysis. Among the studied variables, pH, adsorbent dosage, and initial concentration are important. The results show that it is possible to completely remove at 300 ppm of phenol concentration and 5 min. Characterization of PSAC was done using Fourier transform infrared spectroscopy spectrum (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer-Emmet-Teller (BET), and size analysis. By examining the isotherm models, it was found that the adsorption follows the Langmuir model. The maximum adsorption capacity was 250 mg g-1 based on the Langmuir model. The three combined features of complete removal, ultra-fast adsorption, and high adsorption capacity are the unique features of this nano biocarbon for phenol removal.

Remediation of wastewater by biosynthesized manganese oxide nanoparticles and its effects on development of wheat seedlings

Introduction

Nanoparticles play a vital role in environmental remediation on a global scale. In recent years, there has been an increasing demand to utilize nanoparticles in wastewater treatment due to their remarkable physiochemical properties.

Methods

In the current study, manganese oxide nanoparticles (MnO-NPs) were synthesized from the Bacillus flexus strain and characterized by UV/Vis spectroscopy, X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy.

Results

The objective of this study was to evaluate the potential of biosynthesized MnO-NPs to treat wastewater. Results showed the photocatalytic degradation and adsorption potential of MnO-NPs for chemical oxygen demand, sulfate, and phosphate were 79%, 64%, and 64.5%, respectively, depicting the potential of MnO-NPs to effectively reduce pollutants in wastewater. The treated wastewater was further utilized for the cultivation of wheat seedlings through a pot experiment. It was observed that the application of treated wastewater showed a significant increase in growth, physiological, and antioxidant attributes. However, the application of treated wastewater led to a significant decrease in oxidative stress by 40%.

Discussion

It can be concluded that the application of MnO-NPs is a promising choice to treat wastewater as it has the potential to enhance the growth, physiological, and antioxidant activities of wheat seedlings.

Persulfate-assisted heterogeneous photocatalytic degradation of furfural from aqueous solutions using TiO2-ZnO/biochar composite

This study evaluated the performance of TiO2-ZnO/biochar as activator of persulfate (PS) for degradation of furfural. After the successful synthesis of the catalyst, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) methods were used to investigate the properties of TiO2-ZnO/biochar. The findings of this research suggests that under optimal conditions (pH = 3, catalyst dosage = 1 g/L, persulfate concentration = 1.2 mM, and furfural concentration = 10 mg/L), the PS/Catalysts/UV system can remove 96 % of furfural within 15 min. Under ideal conditions, the experimental results fit well with the first-order kinetic model (R2 > 0.95), and the rate constant (Kobs) was derived as 0.195 min-1. The quenching experiments provided further insights that confirmed the participation of SO4°- and OH° radicals in the degradation process. Nevertheless, the evidence strongly supports the idea that SO4°- plays a more prominent and dominant role as the primary radical species responsible for furfural degradation. Based on the obtained results, it can be concluded that the PS/Catalysts/UV system has an appropriate ability to remove furfural from aqueous solutions, which suggests promising perspectives for its practical application in pollutant treatment scenarios.

Sustainable wastewater treatment by RO and hybrid organic polyamide membrane nanofiltration system for clean environment

One of the environmental pollution is happened by the discharge of industrial wastewater that needs to be adequately filtered. Given that the effluent from the leather industry contains high levels of chromium, heavy metals, lipids, and Sulphur, it is one of the wastewater disposals that are most damaging. This experimental study focuses on reverse osmosis and hybrid organic polyimide membrane for nanofiltration for sustainable wastewater treatment. In the RO and organic polyamide Nano-porous membranes, a thin film of polyamide membrane was used for efficient filtration. Taguchi analysis optimized process parameters such as pressure, temperature, pH, and volume reduction factor. The outcome shows an 89% reduction in total wastewater hardness, an 88% reduction in sulfate, and an 89% efficiency reduction in COD. As a result, the proposed technology significantly increased filtration efficiency.

Adsorptive removal of acid red 18 dye from aqueous solution using hexadecyl-trimethyl ammonium chloride modified nano-pumice

Discharging untreated dye-containing wastewater gives rise to environmental pollution. The present study investigated the removal efficiency and adsorption mechanism of Acid Red 18 (AR18) utilizing hexadecyl-trimethyl ammonium chloride (HDTMA.Cl) modified Nano-pumice (HMNP), which is a novel adsorbent for AR18 removal. The HDTMA.Cl is characterized by XRD, XRF, FESEM, TEM, BET and FTIR analysis. pH, contact time, initial concentration of dye and adsorbent dose were the four different parameters for investigating their effects on the adsorption process. Response surface methodology-central composite design was used to model and improve the study to reduce expenses and the number of experiments. According to the findings, at the ideal conditions (pH = 4.5, sorbent dosage = 2.375 g/l, AR18 concentration = 25 mg/l, and contact time = 70 min), the maximum removal effectiveness was 99%. The Langmuir (R2 = 0.996) and pseudo-second-order (R2 = 0.999) models were obeyed by the adsorption isotherm and kinetic, respectively. The nature of HMNP was discovered to be spontaneous, and thermodynamic investigations revealed that the AR18 adsorption process is endothermic. By tracking the adsorption capacity of the adsorbent for five cycles under ideal conditions, the reusability of HMNP was examined, which showed a reduction in HMNP's adsorption effectiveness from 99 to 85% after five consecutive recycles.

Mn3O4 Catalysts for Advanced Oxidation of Phenolic Contaminants in Aqueous Solutions

Water-soluble organic pollutants, such as phenolic compounds, have been exposed to environments globally. They have a significant impact on groundwater and surface water quality. In this work, different Mn3O4 catalysts were prepared for metal oxide activation of peroxymonosulfate (PMS) to remove the phenolic compound from the water environment. The as-prepared catalysts were characterized using thermogravimetric-differential thermal analysis (TG-DTA), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area analysis. Furthermore, the effect of temperature and reusability of the as-prepared Mn3O4 catalysts is also investigated. The Mn3O4 nanoparticles (NPs) catalyst reveals an excellent performance for activating PMS to remove phenol compounds. Mn3O4 NPs exhibits 96.057% efficiency in removing 25 ppm within 60 min. The kinetic analysis shows that Mn3O4 NPs fitted into pseudo-first order kinetic model and exhibited relatively low energy activation of 42.6 kJ/mol. The reusability test of Mn3O4 NPs displays exceptional stability with 84.29% efficiency after three-sequential cycles. The as-prepared Mn3O4 NPs is proven suitable for phenolic remediation in aqueous solutions.

Surface facet Fe2O3-based visible light photocatalytic activation of persulfate for the removal of RR120 dye: nonlinear modeling and optimization

Photocatalytic activation of persulfate (PS) is recently emerged as an energy-efficient and environmentally sustainable approach for pollutants degradation, which enables to leverage the strengths of low-cost solar energy and heterogeneous catalysis. Herein, we investigated the photocatalytic decomposition of reactive red 120 (RR120) dye using PS-activated Fe₂O₃ nanoparticles and elucidated the effect of their facets, α-Fe₂O₃ (001), β-Fe₂O₃ (100), and γ-Fe₂O₃ (111). β-Fe₂O₃ not only boosted the charge carrier separation but also provided more active sites for PS activation resulting in 6- and 3.5-fold higher photocatalytic activities compared to α-Fe₂O₃ and γ-Fe₂O₃, respectively. Response surface methodology and artificial neural network coupled with genetic algorithm models were utilized to optimize and foresee Fe₂O₃/PS system under visible light. Almost 100% color removal and 82% organic removal were observed under the optimum conditions at 20 mg/L RR120, 22 mg/L β-Fe₂O₃, 18 mg/L PS, and pH: 3. Scavenger test indicated that both sulfate and hydroxyl radicals are responsible for the observed RR120 removal. Although cell viability test indicated that cytotoxicity of wastewater is not significantly reduced after treatment. All the results proposed that β-Fe₂O₃/PS at relatively low doses has a great potential to decompose and mineralize recalcitrant dyes in wastewater under invisible light.

Degradation of sulfadiazine in aqueous media by peroxymonosulfate activated with biochar-supported ZnFe2O4 in combination with visible light in an internal loop-lift reactor

Solid waste resource utilization and the treatment of wastewater are two important aspects in environmental protection. Here, biochar (BC) derived from municipal sewage sludge has been combined with ZnFe₂O₄ to form the photocatalyst ZnFe₂O₄/biochar (ZnFe/BC), and it was used to degrade sulfadiazine (SDZ) in the presence of peroxymonosulfate (PMS) under visible (Vis) light irradiation in an internal loop-airlift reactor (ALR). The surface morphology and structure of ZnFe/BC have been characterized by X-ray diffraction (XRD), scanning electron microscopy equipped with an attachment for energy-dispersive spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS). ZnFe/BC displays outstanding photocatalytic performance and reusability. After four reuse cycles of ZnFe/BC in the Vis/ZnFe/BC/PMS system, the SDZ degradation rate and efficiency still reached 0.082 min⁻¹ and 99.05%, respectively. Reactive species in this system included free radicals SO₄˙⁻, ˙OH, and ˙O₂⁻, as well as non-radicals ¹O₂, e⁻, and h⁺, as established from the results of chemical quenching experiments and electron paramagnetic resonance (EPR) analyses. Moreover, a mechanism of action of the Vis/ZnFe/BC/PMS system for SDZ degradation was proposed. The acute toxicity of the reaction solution towards Photobacterium phosphoreum T3 spp. in the Vis/ZnFe/BC/PMS process increased during the first 40 min and then decreased, illustrating that Vis/ZnFe/BC/PMS provided an effective and safe method for the removal of SDZ.

Solid waste resource utilization and the treatment of wastewater are two important aspects in environmental protection.

A Review of Manganese(III) (Oxyhydr)Oxides Use in Advanced Oxidation Processes

The key role of trivalent manganese (Mn(III)) species in promoting sulfate radical-based advanced oxidation processes (SR-AOPs) has recently attracted increasing attention. This review provides a comprehensive summary of Mn(III) (oxyhydr)oxide-based catalysts used to activate peroxymonosulfate (PMS) and peroxydisulfate (PDS) in water. The crystal structures of different Mn(III) (oxyhydr)oxides (such as α-Mn₂O₃, γ-MnOOH, and Mn₃O₄) are first introduced. Then the impact of the catalyst structure and composition on the activation mechanisms are discussed, as well as the effects of solution pH and inorganic ions. In the Mn(III) (oxyhydr)oxide activated SR-AOPs systems, the activation mechanisms of PMS and PDS are different. For example, both radical (such as sulfate and hydroxyl radical) and non-radical (singlet oxygen) were generated by Mn(III) (oxyhydr)oxide activated PMS. In comparison, the activation of PDS by α-Mn₂O₃ and γ-MnOOH preferred to form the singlet oxygen and catalyst surface activated complex to remove the organic pollutants. Finally, research gaps are discussed to suggest future directions in context of applying radical-based advanced oxidation in wastewater treatment processes.

Electrocatalytic degradation of diuron herbicide using three-dimensional carbon felt/β-PbO2 anode as a highly porous electrode: Influencing factors and degradation mechanisms

Traditional planar PbO₂ anodes have been used extensively for the electrocatalytic degradation process. However, by using porous PbO₂ anodes that have a three-dimensional architecture, the efficiency of the process can be significantly upgraded. In the current study, carbon felt (CF) with a highly porous structure and a conventional planar graphite sheet (G) were used as electrode substrate for PbO₂ anodes. Both CF/β-PbO₂ and G/β-PbO₂ anodes were prepared by the anodic deposition method. The main properties of the electrodes were characterized by XRD, EDX-mapping, FESEM, and BET-BJH techniques. The electrocatalytic degradation of diuron using three-dimensional porous CF/β-PbO₂ anode was modeled and optimized by a rotatable central composite design. After optimizing the process, the ability of porous CF/β-PbO₂ and planar G/β-PbO₂ anodes to degrade and mineralize diuron was compared. The electrocatalytic degradation of the diuron was well described by a quadratic model (R² > 0.99). Under optimal conditions, the kinetics of diuron removal using CF/β-PbO₂ anode was 3 times faster than the G/β-PbO₂ anode. The energy consumed for the complete mineralization of diuron using CF/β-PbO₂ anode was 2077 kWh kg^-1 TOC. However, the G/β-PbO₂ anode removed only 65% of the TOC by consuming 54% more energy. The CF/β-PbO₂ had more stability (115 vs. 91 h), larger surface area (1.6287 vs. 0.8565 m² g^-1), and higher oxygen evolution potential (1.89 vs. 1.84 V) compared to the G/β-PbO₂. In the proposed pathways for diuron degradation, the aromatic ring and groups of carbonyl, dimethyl urea, and amide were the main targets for HO^• radical attacks.

Removal of acetaminophen through direct electron transfer by reactive Mn2O3: Efficiency, mechanism and pathway

Mn₂O₃ with certain oxidative reactivity, was fabricated via sol-gel method and applied for the removal of acetaminophen (APAP). The mechanism of APAP oxidation was revealed in depth through electrochemical tests and X-ray photoelectron spectroscopy (XPS). Moreover, the selective abatement of various organic contaminants contained different functional groups by Mn₂O₃ was investigated through linear free energy relationship (LFER) estimated with peak potentials (E_op) of these organic contaminants. Under acidic condition, APAP could be effectively eliminated by Mn₂O₃. The open circuit potential (OCP) and zeta potential tests illustrate that the oxidative reactivity of Mn₂O₃ is associated to the surface acid-base behavior of Mn₂O₃ and its surface charge situation. The XPS experiments and Mn leaching results imply that Mn(III) could capture electron from APAP and release Mn²⁺ to aqueous phase. The intermediates could be ascribed to fragmentation of acetamido radicals and phenoxy radicals, both of which were formed through electron transfer from APAP to Mn₂O₃. The reactive Mn₂O₃ shows selective oxidation of different contaminants in the electron transfer process. LFER analysis indicates good negative linear correlation between lnk₁ and E_op of various pollutants. The efficiency of Mn₂O₃ in the elimination of APAP and selective oxidation of different contaminants suggest some new insights for transformation of APAP and other electron-rich pollutants in the environments.

Diuron degradation using three-dimensional electro-peroxone (3D/E-peroxone) process in the presence of TiO2/GAC: Application for real wastewater and optimization using RSM-CCD and ANN-GA approaches

The present study investigates the efficiency of a three-dimensional electro-peroxone (3D/E-peroxone) reactor filled with TiO₂-GAC in removing diuron from aqueous solution and in the remediation of real pesticide wastewater. The behavior of the system in terms of the effect of independent variables on diuron was investigated and optimized by RSM-CCD and ANN-GA methods. Both approaches proved to have a very good performance in the modeling of the process and determined the optimum condition of the independent variables as follows: initial pH = 10, applied current = 500 mA, supporting electrolyte = 0.07 M, ozone concentration = 10 mg L^-1, and reaction time = 10 min. The 3D/E-peroxone process achieved a synergistic effect in diuron abatement and reduced significantly energy consumption, as compared to its individual components. H₂O₂ concentration generated in the electrolysis system was notably increased in the presence of TiO₂-GAC microparticles. The BOD₅/COD ratio of the real pesticide wastewater increased from 0.049 to 0.571 within 90 min treatment. Giving to the considerable enhancement of the biodegradability of the wastewater, this study strongly suggests that the 3D/E-peroxone process can be considered as a promising pretreatment step before a biological treatment process to produce intermediates which are more easily degradable by microorganisms.

Heterogeneous catalytic oxidation degradation of BPAF by peroxymonosulfate active with manganic manganous oxide: Mineralization, mechanism and degradation pathways

In this study, the catalytic ability and mechanisms involved in activating peroxymonosulfate (PMS) with Mn₃O₄ and the degradation pathways of bisphenol-AF (BPAF) removal was investigated. SO₄^-• and ·OH which were explored by and scavenging tests were the major reactive radicals in the Mn₃O₄/PMS system. A simple simulation algorithm was also used to calculate the relative concentrations of SO₄^-• ([SO₄^-•]) and ·OH ([·OH]) which were 8.39 × 10 ^-15 M and 6.96 × 10 ^-13 M, respectively. The mechanism for the electron transfer between the Mn (II) and Mn (III) species was discussed. Three degradation pathways of BPAF were determined by the GC/MS and LC/MS technology, including chemical mechanism of oxidation, hydroxylation, electron transfer, polymerization, and ring-cleavage. In addition, the results suggested that the Mn₃O₄/PMS system had an efficient total organic carbon (TOC) removal rate and excellent environmental adaptability, the removal rate of TOC being as high as 73.2% in the control condition. Furthermore, the reuse experiments and the comparison on the structural and componential changes of Mn₃O₄ powder before and after reaction demonstrated that the Mn₃O₄ catalyst possessed excellent stability and reusability. Finally, a maximum BPAF degradation of approximately 90.0% was achieved on the optimal conditions for 500 mg/L Mn₃O₄ dosage, 4 mM PMS concentration, 7.0 ± 0.2 initial pH, and 5 mg/L BPAF concentration respectively. And the effect of the coexisting anions and natural environmental water quality were also considered. This study demonstrated the Mn₃O₄/PMS system can be considered as a green approach for the removal of environmental reluctant pollutants.

Tetracycline Removal by Activating Persulfate with Diatomite Loading of Fe and Ce

Persulfate (PS)-based oxidation technology is efficient in removing refractory organics from water. A novel diatomite (DIA) support Fe and Ce composite (Fe-Ce/DIA) was prepared for activating persulfate to degrade tetracycline in water. The Fe and Ce were uniformly loaded on DIA, and the total pore size of Fe-Ce/DIA was 6.99 × 10⁻² cm³/g, and the average pore size was 12.06 nm. Fe-Ce/DIA presented a good catalytic activity and 80% tetracycline was removed under the persulfate system. The Fe-Ce/DIA also had photocatalytic activity, and the corresponding tetracycline removal efficiency was 86% under UV irradiation. Fe-Ce/DIA exhibited less iron dissolution rate compared with Fe-DIA. The tetracycline degradation rate was enhanced when the temperature increased. The optimal tetracycline removal efficiency was obtained when the conditions were of persulfate 10 mM, Fe-Ce/DIA dosage 0.02 g/L, and tetracycline concentration 50 mg/L. In addition, Fe-Ce/DIA showed a wide pH application and good reusability and stability.