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In recent years, the rapid economic development in Taiwan has resulted in greater complexity in handling industrial hazardous waste. The main aim of this paper was to present a trend analysis of the online reported amounts of industrial hazardous waste from the official database over the past decade (2010–2020). In addition, this study focused on the environmental policies and regulatory measures for the mandatory material resources from industrial hazardous waste according to the promulgation of the revised Waste Management Act. It was found that the annual reported amounts of industrial hazardous waste ranged from 1200 thousand metric tons to 1600 thousand metric tons, reflecting a balanced relationship between the industrial production and waste management. Based on the principles of resource recycling and circular economy, some case studies for specific types of industrial hazardous waste (including spent acid etchant, spent pickling liquid, and spent dimethyl formamide-contained liquid) were compiled to echo the government efforts in sustainable material management. In Taiwan, recycling amounts in 2020 were recorded up to 92,800, 130,460, and 54,266 metric tons, respectively. It was suggested to be a successful circular economy model in the printed circuit boards, steel/iron processing, and synthetic leather industries. In order to effectively reduce the environmental loadings and conserve material resources from industrial hazardous waste, some recommendations were also addressed to provide for the policy makers, environmental engineers and process manager. Full article

Potassium ferrate (K₂FeO₄) is a multi-functional green reagent for water treatment with considerable combined effectiveness in oxidization, disinfection, coagulation, sterilization, adsorption, and deodorization, producing environment friendly Fe(III) end-products during the reactions. This study uses a simple method to lower Fe(VI) preparation cost by recycling iron from a spent steel pickling liquid as an iron source for preparing potassium ferrate with a wet oxidation method. The recycled iron is in powder form of ferrous (93%) and ferric chlorides (7%), as determined by X-ray Absorption Near Edge Spectrum (XANES) simulation. The synthesis method involves three steps, namely, oxidation of ferrous/ferric ions to form ferrate with NaOCl under alkaline conditions, substitution of sodium with potassium to form potassium ferrate, and continuously washing impurities with various organic solvents off the in-house ferrate. Characterization of the in-house product with various instruments, such as scanning electron microscopy (SEM), ultraviolet-visible (UV-Vis), X-ray diffraction (XRD), and X-ray absorption spectroscopy (XAS), proves that product quality and purity are comparative to a commercialized one. Methylene blue (MB) de-colorization tests with in-house potassium ferrate shows that, within 30 min, almost all MB molecules are de-colorized at a Fe/carbon mole ratio of 2/1. Full article