Search Results (19)

The conventional Fenton process generates large amounts of Fenton sludge during wastewater treatment. Achieving effective utilization of Fenton sludge and reducing its production remain pivotal challenges. In this study, Fenton sludge biochar catalysts (Cat) were prepared using Fenton sludge via pyrolysis. In addition, chemical oxygen demand (COD) from secondary effluent was removed by Fenton sludge biochar catalysts activated with H₂O₂/Fe(VI). Specifically, the removal efficiency of COD could reach 46.2% in the Cat−2/H₂O₂/Fe(VI) system under weakly alkaline conditions. The mechanistic analysis confirmed that high-valent iron, ^•OH, O₂^•−, and ¹O₂ all participate in the degradation process. Furthermore, a continuous-flow reactor was applied to treat secondary effluent, with COD decreasing from 65 mg/L to 36 mg/L. This study provides new insights into the resource utilization of Fenton sludge and the treatment of complex wastewater. Full article

Sediment improvers are important mediators of aquatic animals’ growth performance and the surrounding environmental quality. However, the physiological responses of crayfish (Procambarus clarkii) to different sediment improvers remain unclear. Here, we cultivated crayfish using two chemical (potassium monopersulfate and potassium ferrate) and two biological (purple nonsulfur photosynthetic bacteria and Bacillus subtilis) sediment improvers at low and high concentrations. After 42 days, we found that the addition of chemical sediment improvers was more effective in improving water quality than biological sediment improvers (e.g., more stable pH and lower nutrient concentrations). By contrast, the application of biological sediment improvers resulted in considerably enhanced final weight, weight gains, and survival rates. In all low-concentration groups, the activity of immune-related enzymes (e.g., superoxide dismutase and glutathione peroxidase) in the hemolymph and hepatopancreas considerably increased, whereas the malondialdehyde activity and mRNA expression of AMP genes (PcALF and PcCru) considerably decreased. Crayfish exposed to low concentrations of sediment improvers exhibited enhanced intestinal and hepatopancreatic integrity, with a thickened mucosal layer and increased density of epithelial cell granules. Additionally, the composition of the gut microbiota varied after the addition of different sediment improvers. In summary, our research indicated that different types of sediment improvers not only improved the farming environment but also had varying effects on crayfish. Therefore, an appropriate sediment improver based on specific aquaculture conditions is needed. Full article

Styrene production primarily relies on ethylbenzene dehydrogenation catalysts, with increasing performance demands as styrene units scale up. This paper presents the industrial application of the MacroCat-201S ethylbenzene dehydrogenation catalyst at the 350,000 tons/year styrene plant of Liaoning Bora LyondellBasell Petrochemical Co., Ltd. The catalyst, primarily composed of potassium ferrate, demonstrates excellent thermal stability and mechanical strength, ensuring long-term stable operation under low steam–oil ratios (1.0). Over a 36-month application period, the MacroCat-201S catalyst maintained high conversion rates and selectivity, with minimal catalyst deactivation. It also showed good crush resistance, and the reactor pressure drop remained low, indicating its potential for long-term efficient operation in styrene production. This paper further examines the influence of process parameters such as the steam–oil ratio and reaction temperature on catalyst performance and suggests strategies for optimizing catalyst usage in industrial applications. This study concludes that the MacroCat-201S catalyst significantly improves the reaction efficiency, reduces energy consumption, and shows promising potential for industrial use. Full article

Potassium ferrate(VI) (K₂FeO₄) as a particularly strong oxidant represents an effective and environmentally friendly waste water treatment material. When produced by anodic oxidation in highly alkaline aqueous solution, the K₂FeO₄ product is separated and sealed in inert plastic bags with the retention of some liquid phase with high pH. This method proved to be excellent for long-term storage at moderately low temperature (5 °C) for industrial applications. It is still imperative to check the ferrate(VI) content of the product whenever it is to be used. Fe-57 Mössbauer spectroscopy is an excellent tool for checking the ratio of ferrate(VI) to the degradation product iron(III) in a sample. For this purpose, normally the spectral areas of the corresponding subspectra are considered; however, this approximation neglects the possible differences in the corresponding Mössbauer–Lamb factors. In this work, we have successfully determined the Mössbauer–Lamb factors for the ferrate(VI) and for the most common iron(III) degradation products observed. We have found superparamagnetic behavior and low-temperature phase transformation for another iron(III) degradation product that made the determination of the Mössbauer–Lamb factors impossible in that case. The identities of a total of three different iron(III) degradation products have been confirmed. Full article

Industrial chlorinated solvents continue to be among the most significant issues in groundwater (GW) pollution worldwide. This study assesses the effectiveness of eight novel oxidation treatments, including persulfate (PS), ferrous sulfate, sulfidated nano-zero valent iron (S-nZVI), and potassium ferrate, along with their combinations, for the potential in situ remediation of GW polluted with chlorinated solvents (1,2-dichloroethylene, trichloroethylene, and tetrachloroethylene). Our bench-scale results reveal that the combined addition of PS and S-nZVI can effectively eliminate trichloroethylene (10 µg/L), achieving removal rates of up to 80% and 92% within 1 h, respectively, when using synthetic GW. In the case of real GW, this combination achieved removal rates of 69, 99, and 92% for cis-1,2-dichloroethylene, trichloroethylene, and tetrachloroethylene, respectively, within 24 h. Therefore, this proposed remediation solution resulted in a significant reduction in the environmental risk quotient, shifting it from a high-risk (1.1) to a low-risk (0.2) scenario. Furthermore, the absence of transformation products, such as vinyl chloride, suggests the suitability of employing this solution for the in situ remediation of GW polluted with chlorinated solvents. Full article

Doxycycline (DOX), a typical antibiotic, is harmful to aquatic ecosystems and human health. This study presents DOX removal by potassium ferrate (Fe(VI)) and montmorillonite and investigates the effect of Fe(VI) dosage, reaction time, initial pH value, montmorillonite dosage, adsorption pH, time and temperature on DOX removal. The results show that DOX removal increases when increasing the Fe(VI) dosage, with the optimal condition for DOX removal (~97%) by Fe(VI) observed under a molar ratio ([Fe(VI)]:[DOX]) of 30:1 at pH 7. The reaction of DOX with Fe(VI) obeyed second-order kinetics with a rate constant of 10.7 ± 0.45 M⁻¹ s⁻¹ at pH 7. The limited promotion (~4%) of DOX adsorption by montmorillonite was observed when the temperature increased and the pH decreased. Moreover, the synergetic effect of Fe(VI) and montmorillonite on DOX removal was obtained when comparing the various types of dosing sequences (Fe(VI) oxidation first and then adsorption; adsorption first and then Fe(VI) oxidation; simultaneous oxidation and adsorption). The best synergistic effect of DOX removal (97%) was observed under the simultaneous addition of Fe(VI) and montmorillonite, maintaining the Fe(VI) dosage (from 30:1 to 5:1). Five intermediates were detected during DOX degradation, and a plausible DOX degradation pathway was proposed. Full article

Sludge pyrolysis is a promising method for treating excess sludge as a by-product of municipal sewage plants, allowing for energy self-sufficiency and resource recovery. Before sludge pyrolysis begins, a few conditioning agents are added to the sludge that promote sludge dewatering. Potassium ferrate (K₂FeO₄) is applied as a conditioning agent with both cracking and flocculation effects, but the effects of K₂FeO₄ on the release characteristics of nitrogen, sulfur, and chlorine during sludge pyrolysis have not been elucidated. In this study, we analyzed the sludge pyrolysis characteristics and chemical state changes of N, S, and Cl contaminants in the dewatered sludge after K₂FeO₄ conditioning before and after pyrolysis. Further, the release characteristics of condensable/noncondensable gases during pyrolysis were assessed using thermogravimetric mass spectrometry (TG-MS) and pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS) analyses before and after conditioning. We found that potassium pertechnetate reduced the activation energy required for the sludge in the pyrolysis process. Noticeably this process made the sludge more susceptible to thermal decomposition leading to volatile production and also influenced the release of different contaminants generated by the pyrolysis process. Moreover, K₂FeO₄ promoted the release of C/H/O gases and reduced the release of N/S/Cl pollutant gases from the sludge. Overall, this study provides a theoretical basis for the selection of conditioning agents for the sludge conditioning and dewatering steps during the sludge pyrolysis process. Full article

Although the removal ability of potassium ferrate (K₂FeO₄) on aqueous heavy metals has been confirmed by many researchers, little information focuses on the difference between the individual and simultaneous treatment of elements from the same family of the periodic table. In this project, two heavy metals, arsenic (As) and antimony (Sb) were chosen as the target pollutants to investigate the removal ability of K₂FeO₄ and the influence of humic acid (HA) in simulated water and spiked lake water samples. The results showed that the removal efficiencies of both pollutants gradually increased along the Fe/As or Sb mass ratios. The maximum removal rate of As(III) reached 99.5% at a pH of 5.6 and a Fe/As mass ratio of 4.6 when the initial As(III) concentration was 0.5 mg/L; while the maximum was 99.61% for Sb(III) at a pH of 4.5 and Fe/Sb of 22.6 when the initial Sb(III) concentration was 0.5 mg/L. It was found that HA inhibited the removal of individual As or Sb slightly and the removal efficiency of Sb was significantly higher than that of As with or without the addition of K₂FeO₄. For the co-existence system of As and Sb, the removal of As was improved sharply after the addition of K₂FeO₄, higher than Sb; while the latter was slightly better than that of As without K₂FeO₄, probably due to the stronger complexing ability of HA and Sb. X-ray energy dispersive spectroscopy (EDS), X-ray diffractometer (XRD), and X-ray photoelectron spectroscopy (XPS) were used to characterize the precipitated products to reveal the potential removal mechanisms based on the experimental results. Full article

Potassium ferrate has strong oxidation in both acid and alkali environments, which has attracted extensive attention. However, the impact of the pH environment on this coupling process with the goal of resource recovery has not received attention. Under the goal of the efficient recovery of organic acid, the changes of solid–liquid characteristics of sludge after acid and alkaline ferrate pretreatment and during anaerobic digestion were discussed. The results showed that compared with blank control groups, after alkaline ferrate pretreatment, the volatile suspended solids (VSSs) decreased the most, reaching 28.19%. After being pretreated with alkaline ferrate, the sludge showed the maximum VFA accumulation (408.21 COD/g VSS) on the third day of digestion, which was 1.34 times higher than that of the acid ferrate pretreatment. Especially in an alkaline environment, there is no need to add additional alkaline substances to adjust the pH value, and the effect of sludge reduction and acid production is the best. Full article

Iron-manganese co-oxide film (MeO_x) has a high removal efficiency for ammonium (NH₄⁺) and manganese (Mn²⁺) in our previous studies, but it cannot effectively remove COD_Mn from water. In this study, the catalytic oxidation ability of MeO_x was enhanced by dosage with potassium ferrate (K₂FeO₄) to achieve the simultaneous removal of COD_Mn and NH₄⁺ from water in a pilot-scale experimental system. By adding 1.0 mg/L K₂FeO₄ to enhance the activity of MeO_x, the removal efficiencies of COD_Mn (20.0 mg/L) and NH₄⁺ (1.1 mg/L) were 92.5 ± 1.5% and 60.9 ± 1.4%, respectively, and the pollutants were consistently and efficiently removed for more than 90 days. The effects of the filtration rate, temperature and pH on the removal of COD_Mn were also explored, and excessive filtration rate (over 11 m/h), lower temperature (below 9.2 °C) and pH (below 6.20) caused a significant decrease in the removal efficiency of COD_Mn. The removal of COD_Mn was analyzed at different temperatures, which proved that the kinetics of COD_Mn oxidation was pseudo-first order. The mature sands (MeO_x) from column IV were taken at different times for microscopic characterization. Scanning electron microscope (SEM) showed that some substances were formed on the surface of MeO_x and the ratio of C and O elements increased significantly, and the ratio of Mn and Fe elements decreased significantly on the surface of MeO_x by electron energy dispersive spectrometer (EDS). However, the elemental composition of MeO_x would gradually recover to the initial state after the dosage of Mn²⁺. According to X-ray photoelectron spectroscopy (XPS) analysis, the substance attached to the surface of MeO_x was [(-(CH₂)₄O-)_n], which fell off the surface of MeO_x after adding Mn²⁺. Finally, the mechanism of K₂FeO₄-enhanced MeO_x for COD_Mn removal was proposed by the analysis of the oxidation process. Full article

Biomass materials are perceived as sustainable, carbon-rich precursors for the fabrication of carbon materials. In this study, we demonstrated the capacitance performance of biomass-derived carbon, produced by using golden shower tree seeds (GTs) as carbon precursors and potassium ferrate (K₂FeO₄) as the activation agent. The as-prepared porous carbon (GTPC) possessed an ultrahigh specific surface area (1915 m² g⁻¹) and abundant pores. They also exhibited superior electrochemical performance, owing to their well-constructed porous structure, high surface area, and optimized porous structure. Optimized activated carbon (GTPC-1) was used to assemble a symmetric solid-state supercapacitor device with poly(vinyl alcohol) (PVA)/H₂SO₄ as a solid-state gel electrolyte. The device exhibited a maximum areal energy density of 42.93 µWh cm⁻² at a power density of 520 µW cm⁻². Full article

The wastewater effluents from textile industries contain highly toxic metal complex dyes. For instance, azo dye has received significant attention owing to its toxicity and environmental stability. This study investigated the oxidation and coagulation processes to effectively remove azo dye from wastewater effluents. Potassium ferrate (K₂FeO₄) was selected as an oxidant because it has a high oxidation potential, is environmentally stable, and does not generate toxic byproducts. Moreover, it has a combination effect of coagulation and oxidation. Its performance was compared with a single oxidation process (using NaOCl) and a single coagulation process (using FeCl₃·6H₂O). Based on the jar test experiment, the optimized pH was estimated to be 3 and the optimal dosage was 56.4 mg/L for K₂FeO₄, and it removed nearly 100% of orange II azo dye (OD) and lissamine green B dye (LGB). However, its removal efficiency decreased when the pH increased to 12. In all processes, dye removal was completed in 5 min of the reaction. Overall, OD and LGB were effectively removed by K₂FeO₄, compared to the NaOCl and FeCl₃·6H₂O. This indicates that the combination of oxidation and coagulation of K₂FeO₄ outperformed the single treatment process without toxic byproduct production. Full article

The occurrence of environmental endocrine disrupting chemicals (EDCs) in aquatic environments has caused extensive concern. Graphene-like magnetic sawdust biochar was synthesized using potassium ferrate (K₂FeO₄) to make activated sawdust biochar and applied for the removal of 17-estradiol (E2). The characterization showed that the surface morphology of five graphene-like magnetic sawdust biochars prepared with different preparation conditions were quite different. The specific surface area and pore structure increased with the increment of K₂FeO₄ addition. The results have shown that graphene-like magnetic sawdust biochar (1:1/900 °C) had the best removal on E2. The experimental results indicated that pseudo-first-order kinetic model and the Langmuir model could describe the adsorption process well, in which the equilibrium adsorption capacity (q_e,1) of 1:1/900 °C were 59.18 mg·g⁻¹ obtained from pseudo-first-order kinetic model and the maximum adsorption capacity (q_max) of 1:1/900 °C were 133.45 mg·g⁻¹ obtained from Langmuir model at 298K. At the same time, lower temperatures, the presence of humic acid (HA), and the presence of NaCl could be regulated to change the adsorption reaction in order to remove E2. Adsorption capacity was decreased with the increase of solution pH because pH value not only changed the surface charge of graphene-like magnetic sawdust biochar, but also affected the E2 in the water. The possible adsorption mechanism for E2 adsorption on graphene-like magnetic sawdust biochar was multifaceted, involving chemical adsorption and physical absorption, such as H-bonding, π-π interactions, micropore filling effects, and electrostatic interaction. To sum up, graphene-like magnetic sawdust biochar was found to be a promising absorbent for E2 removal from water. Full article

Possible use of potassium ferrate (VI) (K₂FeO₄) for the treatment of landfill leachate (pH = 8.9, Chemical Oxygen Demand (COD) 770 mg O₂/L, Total Organic Carbon (TOC) 230 mg/L, Total Nitrogen (Total N) 120 mg/L, Total Phosphorus (Total P) 12 mg/L, Total Coli Count (TCC) 6.8 log CFU/mL (Colony-Forming Unit/mL), Most Probable Number (MPN) of fecal enterococci 4.0 log/100 mL, Total Proteolytic Count (TPC) 4.4 log CFU/mL) to remove COD was investigated. Central Composite Design (CCD) and Response Surface Methodology (RSM) were applied for modelling and optimizing the purification process. Conformity of experimental and predicted data (R² = 0.8477, R_adj² = 0.7462) were verified using Analysis of Variance (ANOVA). Application of K₂FeO₄ using CCD/RSM allowed to decrease COD, TOC, Total N, Total P, TCC, MPN of fecal enterococci and TPC by 76.2%, 82.6%, 68.3%, 91.6%, 99.0%, 95.8% and 99.3%, respectively, by using K₂FeO₄ 0.390 g/L, at pH = 2.3 within 25 min. Application of equivalent amount of iron (as FeSO₄ × 7H₂O and FeCl₃ × 6H₂O) under the same conditions allowed to diminish COD, TOC, Total N, Total P, TCC, MPN of fecal enterococci and TPC only by 38.1%, 37.0%, 20.8%, 95.8%, 94.4%, 58.2%, 90.8% and 41.6%, 45.7%, 29.2%, 95.8%, 92.1%, 58.2%, 90.0%, respectively. Thus, K₂FeO₄ could be applied as an environmentally friendly reagent for landfill leachate treatment. Full article

Porous graphitic biochar was synthesized by one-step treatment biomass using potassium ferrate (K₂FeO₄) as activator for both carbonization and graphitization processes. The modified biochar (Fe@BC) was applied for the removal of diclofenac sodium (DCF) in an aqueous solution. The as-prepared material possesses a well-developed micro/mesoporous and graphitic structure, which can strengthen its adsorption capacity towards DCF. The experimental results indicated that the maximum adsorption capacity (q_max) of Fe@BC for DCF obtained from Langmuir isotherm simulation was 123.45 mg·L⁻¹ and it was a remarkable value of DCF adsorption in comparison with that of other biomass-based adsorbents previously reported. Thermodynamic quality and effect of ionic strength studies demonstrated that the adsorption was a endothermic process, and higher environmental temperatures may be more favorable for the uptake of DCF onto Fe@BC surface; however, the presence of NaCl in the solution slightly obstructed DCF adsorption. Adsorption capacity was found to be decreased with the increase of solution pH. Additionally, the possible mechanism of the DCF adsorption process on Fe@BC may involve chemical adsorption with the presence of H-bonding and π–π interaction. With high adsorption capacity and reusability, Fe@BC was found to be a promising absorbent for DCF removal from water as well as for water purification applications. Full article