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Wastewater Treatment with Green Chemical Ferrate: An Eco-Sustainable Option
Published in Prabhat Kumar Rai, Phytoremediation of Emerging Contaminants in Wetlands, 2018
The superior performance of potassium ferrate(VI) as an oxidant/disinfectant for environmental remediation has been demonstrated in various research (Jiang, 2007). Nonetheless, some challenges have existed regarding the implementation of ferrate(VI) technology in full-scale treatment of wastewater and sewage sludge owing to either the instability property of ferrate(VI) solution or the high preparation cost of solid ferrate(VI) (Jiang, 2007). The treatment efficiencies of Fe(VI) and FeCl3 were compared by Stanford et al. (2010). Removal of phosphorus reached 40% with a Fe(VI) dose as low as 0.01 mg/L compared with 25% removal with 10 mg/L of Fe(III). For lower doses (<1 mg/L as Fe), Fe(VI) achieved removal of suspended solids (SS) and COD between 60% and 80%. In contrast, Fe(III) did not perform well in the control sample where no iron chemical was dosed. The ferrate solution was found to be stable for a maximum of 50 min, beyond which Fe(VI) was reduced to less oxidant species. This provided the maximum allowable storage time of the electrochemically produced ferrate(VI) solution. Results demonstrated that low addition of ferrate(VI) should lead to good removal of P, biological oxygen demand (BOD), COD, and SS from wastewater compared with ferric addition (Stanford et al., 2010; Jiang, 2013).
Oxidative Flotation Separation of Chalcopyrite and Pyrite Using K2FeO4 in Seawater
Published in Mineral Processing and Extractive Metallurgy Review, 2022
Yubiao Li, Wanqing Duan, Wanqing Li, Xu Yang, Wen Chen
Various oxidants with properties of high selectivity and low environmental pollution have been used to depress pyrite from other sulfide minerals (Moimane, Plackowski, and Peng 2020). However, the high usage of oxidizer increases the operation cost. Therefore, it is necessary to develop a low-cost and highly efficient strategy to separate pyrite. Potassium ferrate (K2FeO4, Fe(VI)), with many excellent properties such as high stability, easy preparation, strong oxidizing capacity, good selectivity, and nontoxic, is usually regarded as an environmentally friendly and powerful oxidant at a wide pH range. Recently, Liao et al. (2020) applied K2FeO4 as a clean and efficient depressant for selective separation of chalcopyrite and molybdenite at pH ranging from 4 to 9. They found that hydrophilic substances were formed on chalcopyrite surface not molybdenite surface due to the selective oxidation of K2FeO4, which increased the difference of both floatabilities, thereby achieving selective separation of chalcopyrite and molybdenite. However, the oxidation mechanism of K2FeO4 on chalcopyrite/pyrite is still unclear during the flotation process and needs to be investigated systematically.
Moderate potassium ferrate dosage enhances methane production from the anaerobic digestion of waste activated sludge
Published in Environmental Technology, 2022
Yongqi Sun, Mengyu Zhang, Ting Song, Suyun Xu, Liwen Luo, Jonathan Wong, Xuefeng Zhu, Hongbo Liu
Potassium ferrate (PF) is considered as a green oxidant reagent with powerful oxidization, high selectivity, and non-toxic chemical substance; thus, it has been widely used in the treatment of wastewater and WAS [17]. Its redox potentials of +2.20 V in acidic solutions and +0.72 V in basic solutions [18,19]. In the PF process, the strong oxidation of Fe (VI) can effectively lyse sludge extracellular polymeric substances (EPS) and microbial cells, releasing abundant organic matter into the liquid phase of sludge [20]. The final reduction product, iron hydroxide, is an environmentally friendly material that can help further remove contaminants and improve the dehydration of WAS [21,22]. The study of Ye et al [2] showed that when PF dosage was 0.81 g/g, TS decreased by 31% and the ratio of soluble chemical oxygen demand (SCOD) to total chemical oxygen demand (TCOD) increased to 0.32. It was proved that PF could decompose WAS and increase its solubility.
Properties and mechanism of Cr(VI) adsorption and reduction by K2FeO4 in presence of Mn(II)
Published in Environmental Technology, 2022
Liang Xu, Fenglian Fu, Peijing Yu, Guangzhao Sun
Several technologies were developed to remove Cr(VI) from contaminated water bodies, including electrodialysis method [9]. membrane filtration [10], photocatalysis [11], reduction [12] and adsorption [8,13]. Among these methods, the relatively efficient approach for removing Cr(VI) was adsorption with reduction. Potassium ferrate (K2FeO4) was an environmental friendly agent and had received attention for its many functions, including oxidation, disinfection and subsequent coagulation [14]. Compared with the other commonly used oxidants such as permanganate and ozone, ferrate(VI) exhibited the strongest oxidizing potential of +2.2 V at acidic pH in water/wastewater treatment [15,16]. Moreover, its reduction products were ferric nanoparticles, excellent adsorbents/coagulants with γ-Fe2O3 (core)/γ-FeOOH (shell) nanoparticles structure [17,18], and ferric nanoparticles had been proven to effectively remove high Cr(VI) concentrations [19–21]. Meanwhile, in order to enhance Cr(VI) removal and reduce the toxicity of adsorbed Cr(VI), divalent manganese (Mn(II)) was also selected. Because Mn(II) could interact with γ-Fe2O3 to form γ-Fe2O3-Mn(II) complex that had dual adsorption/reduction properties, it could improve the removal of hazardous species [22,23]. Simultaneously, Mn(III/IV) (oxy)hydroxides (MnOx) formed by oxidation of Mn(II) acting an adsorbent had been proven to remove toxic metal ions, including As(III), As(V), and Cr(VI) [24,25].