Metal-doped(Cu,Zn)Fe2O4 from integral utilization of toxic Zn-containing electric arc furnace dust: An environment-friendly heterogeneous Fenton-like catalyst

Pure metal-doped(Cu,Zn)Fe2O4 was synthesized from Zn-containing electric arc furnace dust(EAFD)by solid-state reaction using copper salt as additive.The effects of pretreated EAFD-to-Cu2(OH)2CO3·6H2O mass ratio,calcination time,and calcination temperature on the structure and catalytic ability were systematically studied.Under the optimum conditions,the decolorization efficiency and total organic carbon(TOC)removal efficiency of the as-prepared ferrite for treating a Rhodamine B solution were approximately 90.0%and 45.0%,respectively,and the decolorization efficiency remained 83.0%after five recycles,suggesting that the as-prepared(Cu,Zn)Fe2O4 was an efficient heterogeneous Fenton-like catalyst with high stability.The high catalytic activity mainly depended on the synergistic effect of iron and copper ions occupying octahedral positions.More importantly,the toxicity characteristic leaching procedure(TCLP)analysis illustrated that the toxic Zncontaining EAFD was transformed into harmless(Cu,Zn)Fe2O4 and that the concentrations of toxic ions in the degraded solution were all lower than the national emission standard(GB/31574-2015),further confirming that the as obtained sample is an environment-friendly heterogeneous Fenton-like catalyst.

A novel hydrothermal method for zinc extraction and separation from zinc ferrite and electric arc furnace dust

A novel hydrothermal process was developed to extract zinc from pure zinc ferrite（ZnFe2O4） nanopowder and zinc-containing electric arc furnace（EAF） dust using hexahydrated ferric chloride（FeCl3-6H2O） as a decomposing agent.The effects of solid FeCl3-6H2O to ZnFe2O4 ratio by mass（RF/Z）,hydrothermal reaction temperature,and time on zinc extraction were systematically investigated.In the results,when the hydrothermal reaction is conducted at 150℃ for 2 h with RF/Z of 15：20,the efficiency of zinc extraction from ZnFe2O4 reaches97.2%,and the concentration of ferric ions（Fe^3＋） in the leaching solution is nearly zero,indicating a high selectivity for zinc.In addition,the zinc extraction efficiency from the EAF dust reaches 94.5%in the case of the hydrothermal reaction performed at 200℃ for 10 h with the solid FeCl3-6H2O to EAF dust ratio by mass（RF/EAF dust） of 15：10.Zinc and iron separation is achieved by adjusting the pH value of the leaching solution according to the different precipitation pH values of metal hydroxides.

New pyrometallurgical process of EAF dust treatment with CaO addition

The non-carbothermic zinc pyrometallurgical processing of electric arc furnace(EAF) dust was investigated on a laboratory scale. The main objective of this process was to convert highly stable zinc ferrite(Zn Fe2O4), which accounts for more than half of total zinc in the EAF dust, into Zn O and Ca2Fe2O5 by Ca O addition. The EAF dust was mixed with Ca O powder in various ratios, pressed into pellets, and heated in a muffle furnace in air at temperatures ranging from 700 to 1100°C for a predetermined holding time. All Zn Fe2O4 was transformed into Zn O and Ca2Fe2O5 at a minimum temperature of 900°C within 1 h when sufficient Ca O to achieve a Ca/Fe molar ratio of 1.1 was added. However, at higher temperatures, excess Ca O beyond the stoichiometric ratio was required because it was consumed by reactions leading to the formation of compounds other than Zn Fe2O4. The evaporation of halides and heavy metals in the EAF dust was also studied. These components could be preferentially volatilized into the gas phase at 1100°C when Ca O was added.