Potassium Ferrate Research Articles

Application of Potassium Ferrate(VI) in the Treatment of Selected Water and Wastewater Pollutants – Short Review

Abstract The paper presents the application of potassium ferrate(VI) (K2FeO4 ) for the removal of selected pollutants from water and wastewater. The research results on the degradation of endocrine disrupting compounds (EDCs), decomposition of surfactants (SPCs), personal care products (PCPs), pharmaceuticals and their metabolites have been reviewed. Due to K2FeO4 strong oxidizing and coagulating properties, high stability, non–toxic by–products and non–selectivity it is sometimes called “environmentally friendly oxidant”. Due to this reasons K2FeO4 can be a multi–purpose water and wastewater treatment chemical and an alternative to advanced oxidation processes (AOPs).

Efficient Removal of Diclofenac from Aqueous Solution by Potassium Ferrate-Activated Porous Graphitic Biochar: Ambient Condition Influences and Adsorption Mechanism.

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 (qmax) 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.

Biomass-derived highly porous nitrogen-doped graphene orderly supported NiMn2O4 nanocrystals as efficient electrode materials for asymmetric supercapacitors

Herein, three-dimensional N-doped porous graphene materials (3DPNG) are successfully synthesized by potassium ferrate (K2FeO4) activation and graphitization using biomass-loofah as carbon source and dicyandiamide as nitrogen source. Furthermore, the mesoporous structure and defects on the surface of 3DPNG can regulate the in-situ growth of NiMn2O4 nanocrystals formation NiMn2O4/3DPNG composite and achieve conductive networks effectively, which not only make electrolyte ions contact with internal NiMn2O4 nanoparticles, but also provide a good electron transport path for electrochemical reaction. Detailed electrochemical characterization indicate that the NiMn2O4/3DPNG electrode exhibits a specific capacitance as high as 1308.2 F g−1 at a current density of 1 A g−1, demonstrates good rate characteristics of 77.9% when current density increased to 15 A g−1. The calculation of contribution rate of pseudocapacitance demonstrate that the behavior of electrode is combining diffusion property and pseudocapacitive property. Besides, a asymmetric supercapacitor (ASC) is assembled using NiMn2O4/3DPNG as positive electrode, 3DPNG as negative electrode, which displays excellent cyclic stability (91.6% retention after 10,000 cycles) and high energy density (45.25 Wh kg−1 at the power density of 11380 W kg−1), implying the great potential application of biomass-derived carbon materials in supercapacitors.

Enhanced dark fermentative hydrogen production from waste activated sludge by combining potassium ferrate with alkaline pretreatment

Alkaline pretreatment was demonstrated to be effective in the enhancement of hydrogen production. However, the sludge solubilization rate of alkaline pretreatment is still limited. This study reports a new strategy of K2FeO4 + pH 9.5 for sludge mesophilic anaerobic fermentation. Experimental results showed that the combination of K2FeO4/pH 9.5 pretreatment had a greater hydrogen yield than the individual K2FeO4 and pH 9.5. The maximum hydrogen yield was 19.2 mL per gram volatile suspended solids (VSS) under the optimal condition (0.02 g per gram total suspended solids K2FeO4 + pH 9.5). Kinetic analysis showed that the highest hydrogen production potential of 19.9 mL/g VSS was obtained in the combined reactor, which well fitted the first-order kinetic model (R2 = 0.9925). Besides, the fermentation type was mainly acetic and butyric in the combined reactor, which contributed to hydrogen production. Further analyses showed that the combined pretreatment reduced hydrogen sulfide yield, providing an environmentally friendly method to sludge treatment.

Taguchi Method and Response Surface Methodology in the Treatment of Highly Contaminated Tannery Wastewater Using Commercial Potassium Ferrate.

The potential implementation of Envifer®, a commercial product containing potassium ferrate (40.1% K2FeO4), for the purification of highly contaminated tannery wastewater from leather dyeing processes was proposed. The employment of the Taguchi method for optimization of experiments allowed the discoloration (98.4%), chemical oxygen demand (77.2%), total organic carbon (75.7%), and suspended solids (96.9%) values to be lowered using 1.200 g/L K2FeO4 at pH 3 within 9 min. The application of the central composite design (CCD) and the response surface methodology (RSM) with the use of 1.400 g/L K2FeO4 at pH 4.5 diminished the discoloration, the chemical oxygen demand, the total organic carbon, and suspended solids within 9 min. The Taguchi method is suitable for the initial implementation, while the RSM is superior for the extended optimization of wastewater treatment processes.

Comparison of different disinfection processes for controlling disinfection by-product formation in rainwater

With increasing shortage of clean water, rainwater has been considered as a precious alternative drinking water source. The processes applied to rainwater treatment are responsible for the safety of drinking water. Therefore, we systematically compared different disinfection processes to evaluate the control of disinfection by-product (DBP) formation and integrated cyto- and genotoxicity of the treated rainwater for the first time. The evaluated disinfection processes included chlorination and chloramination, pre-oxidation by potassium permanganate (KMnO4) and potassium ferrate (K2FeO4), ultraviolet/hydrogen peroxide (UV/H2O2), and ultraviolet/persulfate (UV/PS) processes. The results revealed that chloramination was effective for controlling the formation of carbonaceous DBPs (C-DBPs), but not nitrogenous DBPs (N-DBPs). Compared to KMnO4 pre-oxidation, better reduction of almost all DBPs was observed during K2FeO4 pre-oxidation. According to the calculation of cytotoxicity index (CTI) and genotoxicity index (GTI), cyto- and genotoxicity of the samples decreased obviously at the dosage of ≥ 2.0 mg/L KMnO4 and K2FeO4. The control of the cyto- and genotoxicity of the formed DBPs from the two UV-related AOPs was more effective at the dosage of ≥ 1.0 mM PS and ≥ 5.0 mM H2O2. Moreover, UV/PS was much more powerful to alter the structure of DBP precursors in rainwater.

Enhanced solubilization and biochemical methane potential of waste activated sludge by combined free nitrous acid and potassium ferrate pretreatment

The increasing production of waste activated sludge (WAS) from wastewater treatment plants presents an inherent environmental burden. In this study, Free nitrous acid combined with potassium ferrate (FNA + PF) pretreatment was used to enhance solubilization and biochemical methane potential of WAS. Results indicated that the maximum removal rates of total suspended solid by PF, FNA, and PF + FNA pretreatment were 21.84%, 38.09%, and 56.17%, respectively. The biochemical methane potential of WAS without pretreatment reached 61.22 L CH4/kg VSS added while this value increased to 147.07 L CH4/kg VSS added after FNA + PF pretreatment (0.06 g/g TSS NaNO2 and 0.25 g/g TSS K2FeO4). Shotgun metagenomic analysis revealed that FNA + PF pretreatment could increase the diversity and stability of microbial communities by shifting methanogenic pathways from strictly acetoclastic to acetoclastic/hydrogenotrophic, thereby enhancing methane production. This study suggested that FNA + PF pretreatment is a promising technology to reduce WAS and enhance methane production by pretreated WAS during anaerobic digestion.

Treatment of Polysilicon Production Wastewater by Ferrate(VI) Microcapsule Oxidation and Biological Aerated Biofilter

Polysilicon production wastewater (PPW) is characterized by complex composition, high chemical oxygen demand (COD) concentration and poor biodegradability. An integrated process comprising of ferrate(VI) oxidation and biological aerated biofilter (BAF) was developed at lab scale for treating PPW with an initial COD of 3630 mg/L, biochemical oxygen demand (BOD5) of 350 mg/L, suspended solids (SS) of 440 mg/L, and turbidity of 430 nephelometric turbidity units (NTU). Firstly, the potassium ferrate(VI) (K2FeO4) microcapsules were synthesized by using the phase separation method in cyclohexane, and ethylcellulose was used as the microcapsule wall materials (WM). The stability could be enhanced greatly when ferrate(VI) was encapsulated in the microcapsules with a mass ratio of K2FeO4:WM of 1:4 in the air compared with pure K2FeO4. The microcapsules exhibited sustained release behaviour and higher oxidation efficiency than pure K2FeO4. The microcapsules were used to pretreat PPW. Under the oxidation conditions of pH 6.0, microcapsule dosage 5.0 g/L and reaction time 70 min, the removal efficiency of COD, suspended solids (SS) and turbidity reached 55.1%, 61.3% and 74.2%, respectively. Subsequently, the oxidation effluent was subjected to BAF treatment. Under a hydraulic residence time of 48 h and a gas:water ratio of 6:1, the final effluent values of COD, SS and turbidity were 308 mg/L, 35 mg/L and 28 NTU, respectively, corresponding to total removal of 91.5%, 92.0% and 93.5%, respectively. Thus, this work demonstrates the feasible and potential application of encapsulated ferrate(VI) samples in the degradation of various toxic effluents.

Oxidation of Capecitabine - anticancer drug by potassium ferrate (VI) in alkaline medium: A kinetic and mechanistic approach.

Oxidation of Capecitabine - anticancer drug by potassium ferrate (VI) in alkaline medium: A kinetic and mechanistic approach.

Removal of Microcystis aeruginosa and control of algal organic matters by potassium ferrate(VI) pre-oxidation enhanced Fe(II) coagulation

The problem of cyanobacteria blooms during potable water production has generated wide concern. Ferrate(VI) serving as a pre-oxidation tactic was first applied to enhance conventional Fe(II) coagulation for Microcystis aeruginosa-laden water treatment at lab scale. Results demonstrated that ferrate(VI) pre-oxidation could successfully destabilize algae cells through destroying the protective organic layer. The residual ferrate(VI) together with post-added Fe(II) could provoke a comproportionation reaction, where large amounts of Fe hydrolyzates [Fe(OH)3] are formed. The in-situ Fe(OH)3 with abundant reactive surface is responsible for the promotion of flocs growth by facilitating the clustering and cross-linking of algal organic matters (AOM) and cyanobacteria cells, simultaneously resulting in satisfactory reductions in OD680, turbidity and UV254. Overdose of ferrate(VI) could cause severe cell destruction along with the release of intracellular organic matter (IOM), which may impair the water quality by increasing the concentration of dissolved organic carbon (DOC) and the disinfection by-products formation potential (DBPFP). Meanwhile, considering the Fe residual in settled water, the optimal ferrate(VI) dose (20 µM) and Fe(II) dose (80 µM) were proposed. Besides, the synergistic effect of both the degradation by ferrate(VI) and the adsorption by in-situ Fe(OH)3 contributed to the removal of DOC and Microcystin-LR. This study suggests that ferrate(VI) might be a potential candidate for pre-treatment to assist Fe(II) coagulation when addressing algae-laden water.

Formation of potassium ferrate in a membrane-less electrolysis process of water decomposition

Formation of potassium ferrate in a membrane-less electrolysis process of water decomposition

Uncommon chemical species in PM2.5 and PM10 and its potential use as industrial and vehicular markers for source apportionment studies

Chemical characterization of PM2.5 and PM10 is important to identify potential compounds that induce biological responses that translate into cardio-respiratory health problems. This study shows the reliability of the use of crystalline phases, identified in samples from receptor sites, as source markers, helping researchers to infer the main sources of air pollution, even without the use of receptor models. PM2.5 and PM10 samples were collected at two sites in an urban industrialized region located at southeast of Brazil and analyzed by Synchrotron X-ray Diffraction to identify crystalline compounds. Results show 5 PM10 and PM2.5 species not previously reported in the literature. We propose reaction mechanisms for these species and identify specific sources for each crystalline phase found: BaTiO3 was found in PM10 receptor samples and proved to be a vehicular marker formed during brake action; maghemite (γ-Fe2O3), pyracmonite [(NH4)3Fe(SO4)3], ammonium perchlorate (NH3OHClO4) and potassium ferrate (K2Fe2O4) were found in PM2.5 proved to be markers of industrial activities. The crystalline phases found in PM samples from receptor sites and the mechanisms of reactions showed the reliability of the use of crystalline phases as source markers in the identification of potential sources of air pollution without misinterpretation of the likely source.

TCT-792 Meta-Analysis of Radial Hemostasis Trials Using Patent Hemostasis and a Potassium Ferrate Hemostatic Disc

Incorporating a potassium ferrate hemostatic disc (StatSeal Advanced, Biolife, Sarasota, Florida) as an adjunct to a hemostasis band has been shown to reduce time to hemostasis (TTH) with low rates of radial artery occlusion (RAO). Hematoma rates, however, have been variable across previous trials.

Removal of Acid Red 27, Reactive Black 5 and Acid Green 16 from Aqueous Solutions using Potassium Ferrate(VI)

The article presents the possibility of using potassium ferrate(VI) (K2FeO4) to remove dyes (Acid Red 27, Reactive Black 5, Acid Green 16) belonging to the single azo, double azo and triarylmethane classes from aqueous solutions with an initial concentration of 100 mg/l (Chemical Oxygen Demand (COD) values for AR27, RB5 and AG16 sulutions were 172, 156 and 198 mg O2/l, respectively). For the most favorable values of oxidation parameters of AR27 and RB5 (pH 7, K2FeO4 concentration, 180 and 240 mg/l, respectively, reaction time 10 min), visual discolouration of the aqueous solutions investigated and a decrease in COD values of 83.7% and 81.4%, respectively, were achieved. In the case of AG 16 dye, in the most favorable conditions of the oxidation process (pH 3, K2FeO4, concentration 300 mg/l, 15 min), visual discolouration and a decrease in the COD value of 83.8% were also obtained. The probable reasons for the higher resistance of AG16 to oxidation using K2FeO4 compared to AR27 and RB5 were also explained, based on the analysis of the structure and type of bonds present in the molecule AG 16.

Potassium Ferrate(VI) as a Highly Efficient and Environmentally Friendly Chemiluminescence Reagent in Acidic Solution.

Herein we report that the reactions of potassium ferrate (VI) with a number of reductants can produce strong chemiluminescence (CL) in acidic aqueous solution. The CL Spectra were registered and compared with the classical KMnO4 and NaClO-H2O2 CL systems. The characteristic emission peaks at 1268 and 1050 nm were observed, which are consistent to the spectrum obtained from the NaClO-H2O2 system. Additional emission bands at 680 nm further confirmed the formation of singlet oxygen dimers. The high CL intensity and the chemically green nature of K2FeO4, prompt us to further develop it as a novel CL reagent. Sensitive response and wide calibration ranges were obtained for dopamine, ascorbic acid, and ethanol. The linear range for the determination of three analytes were 50 nM to 50 μM for dopamine (LOD: 20 nM), 5.0 μM to 1.0 mM for ascorbic acid (LOD: 2.21 μM), and 0.5 μM to 1.0 mM for ethanol (LOD: 0.30 μM). Thus, K2FeO4 has a great potential for the postcolumn detection of those UV featureless compounds.

Removal of nonylphenol and nonylphenol monoethoxylate from water and anaerobically digested sewage sludge by Ferrate(VI)

Nonylphenol (NP) and nonylphenol monoethoxylate (NP1EO) have toxic and persistent characteristics, and are incompletely degraded in conventional wastewater treatment processes. These compounds are present in sewage sludge that can be reused as fertilizers or soil conditioners. Accordingly, NP and NP1EO should be properly removed before being discharged in the environment. In this study, potassium ferrate (K2FeO4) containing hexavalent iron (Fe(VI)) was used as an environment-friendly oxidizing agent to mediate NP and NP1EO degradation. The aim of this study was to investigate the effects of pH and Fe(VI) dosage on the degradation of NP and NP1EO in water and anaerobically digested sewage sludge samples. In water samples, under conditions examined in this study, maximum removal efficiencies for NP and NP1EO were 98% and 92%, respectively. For digested sewage sludge samples, the maximum removal efficiencies of NP and NP1EO were 58% and 96%, respectively. The results demonstrated that Fe(VI) can potentially degrade NP and NP1EO in water and digested sewage sludge samples. However, organic matter as a matrix in the sludge sample would inhibit the degradation of NP and NP1EO by Fe(VI). The pH values before and after adding K2FeO4 to the samples had an obvious influence on the removal of NP and NP1EO.

Catalytic degradation of estrogen by persulfate activated with iron-doped graphitic biochar: Process variables effects and matrix effects

Advanced oxidation processes (AOPs) based on sulfate radicals (SO4∙-) is being actively investigated as an effective technology for aqueous organic pollutants degradation. In this work, a novel iron-doped graphitic biochar (Fe@GBC), which was synthesized by one-step method using biomass-derived biochar as precursor and potassium ferrate (K2FeO4) as activator, was applied to activate persulfate (PS) for the degradation of 17β-estradiol (E2). The characterizations indicated that Fe@GBC was successfully doped with iron particles and possessed a porous graphitic carbon structure. In order to evaluate the applicability of Fe@GBC, the effects of various reaction parameters, such as initial pH, catalyst dosage, PS concentration, as well as the reusability and stability of Fe@GBC were systematically investigated. With the synergistic effect of doped iron particles and porous graphitic carbon structure, Fe@GBC exhibited a high activity for PS activation and great degradation capacity to E2 (almost 100% degradation efficiency within 90 min). Through radical quenching experiments and electron spin resonance (ESR) analysis, it found that both SO4∙- and OH∙ were responsible for the degradation of E2, while SO4∙- played a dominant role. Moreover, Fe@GBC/PS also exhibited good degradation performance in complex water matrices. Overall, the facile one-step synthetic strategy and superior performance make Fe@GBC an alternative catalyst for persulfate activation and aqueous pollutants degradation.

Impacts of Potassium Ferrate(VI) on the Growth, Protein, and Enzyme of the Microcystis aeruginosa

As potassium ferrate(VI) is an important kind of water treatment agent which has a high efficiency in algal removal, its effects on the cell substance are rarely discussed. The changing of the protein and enzyme was analyzed here to deeply understand the oxidation of Fe on the protein in the algae. The result of the research showed the inactivation on growth and the biochemical process of the algal cell were all inhibited by Fe, including the function of the photosynthesis system. During the process, SOD (superoxide dismutase), CAT (catalase), POD (peroxidase), and GST (glutathione S-transferase) played cooperative roles to prevent the injury on the cells from destructive oxidation stress. The lipid peroxidation strengthened the defense system. The damage was intensified with the increase of ferrate concentration.

Treatment of Real Textile Wastewater by Using Potassium Ferrate(VI) and Fe(III)/H2O2. Application of Aliivibrio Fischeri and Brachionus plicatilis Tests for Toxicity Assessment

The paper presents the possibility of applying combined chemical oxidation processes using potassium ferrate(VI) (K2FeO4) and Fe(III)/H2O2 for the treatment of real wastewater from the textile industry characterised by an increased content of organic substances (COD = 1920 mg O2/L). The use of both processes under optimal conditions included the use of the RSM method (Response Surface Methodology) in order to make it possible to decrease the COD of the wastewater by 75.4% (final COD = 472 mg O2/L). The toxicity of wastewater treated under the most favourable conditions, determined using two test organisms (Aliivibrio fischeri and Brachionus plicatilis), decreased by 33 and 45%, respectively. In some cases the method described can be used on a larger scale.

Effect of different co-treatments of waste activated sludge on biogas production and shaping microbial community in subsequent anaerobic digestion

Different pretreatment approaches enhance hydrolysis and biogas production of waste activated sludge (WAS). However, the best WAS pretreatment method may vary for different purposes. The aim of this study was to compare different combined treatments using potassium ferrate, alkali, and ultrasonication treatment in terms of hydrolysis, biogas production, and microbial community structure during subsequent anaerobic digestion. The soluble chemical oxygen demand (SCOD) increased sharply during sludge pretreatment. Co-treatment with potassium ferrate and ultrasonication (PF + ULT) provided the highest concentration of SCOD (10,206 mg/L) and volatile fatty acids (VFAs) (9160 mg/L). Maximum cumulative methane production, 752.6 mL during 21 days of subsequent anaerobic digestion, was achieved for alkali and ultrasonication (ALK + ULT) co-treated sludge, a 39.3% improvement compared with raw sludge. Our results indicate that PF + ULT and ALK + ULT co-treatments are suitable for methanogenesis in subsequent anaerobic digestion. Co-treatment typically improves biogas production and sludge hydrolysis relative to a single pretreatment. Illumina sequencing of 16S rRNA genes showed that sludge subjected to ALK pretreatment and ALK + ULT co-treatment contained the same predominant populations, and the community structure of PF was similar to PF + ULT. Principal coordinate analysis (PCoA) based on weighted UniFrac distance indicated differences in the microbial communities of the pretreated and raw sludges. The predominant archaeal populations were Methanomassiliicoccus and Methanobacterium in the ALK + ULT and ALK pretreated sludges, and the majority were Methanomassiliicoccus (76.82%) in PF + ULT co-treated sludge, indicating that different pretreatment methods could substantially shape archaeal communities of pretreated sludge. These results reveal that sludge pretreatment not only impacts sludge hydrolysis and biogas production, but also significantly influences the microbial community in subsequent anaerobic digestion.