Green Process for Industrial Waste Transformation into Super-Oxidizing Materials Named Alkali Metal Ferrates (VI)

Abstract

The investigation presented here features the design of a cleaner and greener chemical process for the conversion of industrial wastes into super-oxidizing materials. The waste of interest is the iron sulfate heptahydrate (FeSO4·7H2O) mainly generated through the sulfate route used for titanium dioxide industrial production. The products of this transformation process are alkali ferrates (A2FeO4, A = Na, K) containing iron in its hexavalent state and considered as powerful oxidants characterized by properties useful for cleaning waters, wastewaters, and industrial effluents. The proposed process includes two steps: (i) The first step consisting of the pre-mixing of two solids (AOH with FeSO4·xH2O) in a rotary reactor allowing the coating of iron sulfate in the alkali hydroxides through solid–solid reactions; and (ii) the second step involves the synthesis of alkali ferrates in a fluidized bed by oxidation of the single solid obtained in the first step in diluted chlorine. The chemical synthesis of alkali ferrates can be carried out within a timeframe of a few minutes. The usage of a fluidized bed enhanced the energy and mass transfer allowing a quasi-complete control of the ferrate synthesis process. The alkali ferrate synthesis process described here possesses many characteristics aligned with the principles of the “green chemistry”.

Reactivity of Low-Grade Chromite Concentrates towards Chlorinating Atmospheres

“…By analogy, the ability of chlorine to oxidize iron (II,III) into iron(VI) in high alkali medium by gas-solid and solid-solid reactions was also demonstrated in recent investigations [ 41 , 42 , 43 , 44 , 45 , 46 ].…”

Ferrous Industrial Wastes—Valuable Resources for Water and Wastewater Decontamination

“…The main challenge was the lack of data in recent years regarding ferrous waste potential applications; thus, the research was extended to 1992. If agri-food wastes (e.g., biomass are well-known for their efficient applications in environmental remediation, especially for water decontamination and compost use [ 25 , 26 , 27 , 28 ], iron as the main component of ferrous waste was still partially reused; today, the main challenge is the transition from the linear concept of disposal to the circular concept of secondary products conversion into raw materials [ 1 , 29 , 30 ]. The use of wastes with iron content as raw materials integrated into the circular economy concept was intensively studied for the sintering process, pig iron production, ferroalloys or other steel products, or pigment and cement industry [ 31 ].…”

Thermochemical Route for Extraction and Recycling of Critical, Strategic and High-Value Elements from By-Products and End-of-Life Materials, Part II: Processing in Presence of Halogenated Atmosphere

“…Furthermore, the preliminary thermal treatment of an e-waste sample containing brominated substances was also performed. This study was performed in the frame our research program focusing mostly on the treatment of low-grade raw materials and solid residues by a thermo-chemical route [ 23 , 24 , 25 , 26 , 27 , 28 ] and on the valorization of certain iron bearing wastes via chemical synthesis of new and green materials [ 29 , 30 , 31 , 32 , 33 , 34 ].…”