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Utilization of plentiful fine-disseminated iron oxide ores resources attracted increasing attention in these years due to the depletion of easy-dressing iron ore reserves. In this paper, an improved Fe recovery method from the refractory fine-grained iron ores was proposed, and iron can be stepwise recovered by microwave-assisted reduction roasting with the addition of Na2SO4, followed by acid leaching of roasted ore and then magnetic separation of leached ore. Experimental and mechanism analysis results indicated that during the roasting process, 70.38% of Na2SO4 would react with fine-disseminated kaolinite in raw ore to form acid-soluble NaAlSiO4, achieving the crude extraction of ore samples by acid leaching. Moreover, the images of SEM showed that the addition of Na2SO4 during the roasting process can also promote the aggregation and growth of iron-rich particles, promoting the iron-rich particles' liberation in milling and resulting in a further dramatic improvement in Fe grade and Fe recovery ratio of iron concentrate by magnetic separation. The iron concentrate contained 56.91% Fe, 9.48% Mn, 3.11% Al, and 1.64% Si with a recovery of 83.52%, indeed up to the iron ores quality requirement of the steel and iron industry. This technology can also provide an inspiring idea for utilizing and processing other similar raw materials. [ABSTRACT FROM AUTHOR]

To tackle the challenge of bauxite residue (BR), generated during the alumina production, as well as to recover some of its metal content, three combinatory H2-based processes were utilized. Firstly, Greek BR was mixed with NaOH to produce water soluble Na-aluminates and was roasted under pure H2 gas in order to reduce the Fe+3 content. Then the first process combined water leaching and magnetic separation, the second water leaching and melting and the last included wet magnetic separation. The water media resulted in the dissolution of Na-aluminate phases and the production of Al, Na-ion rich leachates. From these, pregnant leaching solutions recovery of Al was 78%, 84% and for the third case it reached 91%. Concerning Na recovery, it could reach 94%. Both melting process and magnetic separation aimed for Fe recovery from the material. The former case however still needs to be optimized, here its concept is introduced. The magnetic fraction, after the dry magnetic separation, varied in Fe content from 31.57 wt.% to 38.50 wt.%, while after the wet magnetic separation it reached 31.85 wt.%.

Copper is commonly produced by hydrometallurgical processes. The production of this metal results in the formation of emissions (unwanted solids, liquids and gases). In this paper, an effluent from a Cu producer company is valorized by means of Fe and Cu recovery. In the current process, an effluent from the secondary solvent extraction (secondary raffinate) was sent to neutralization plant to be discharged. In this paper a modification of the process is proposed. The secondary raffinate was contacted with TP207 resin for Fe 3 + and Cu recovery. Metals were eluted from the resins using another real effluent (primary raffinate, effluent from the primary solvent extraction) from the same plant. Experiments for the uptake and elution were carried out in batch and in columns. The effect of pH, resin dosing, and temperature onto metals retention are analyzed. Retention efficiencies (loading capacities) were 50.1% (8.1 mg·g − 1 ) for Cu and 54.8% (23.2 mg·g − 1 ) for Fe 3 + under the optimal operational conditions (pH = 0.45 and T = 65 °C). These values were confirmed in column tests. It is possible to recover Fe 3 + and Cu from the secondary raffinate, leaving most of Fe 2 + and other elements in solution. The experimental affinities that TP207 showed are: Cu > Fe 3 + > Fe 2 + > Zn. The elution of Fe and Cu was quantitatively achieved with concentrated H 2 SO 4 solution. When acidified primary raffinate was used as eluting solution, an enriched solution containing 14.3 g Cu·L − 1 , 20.3 g Fe 2 + ·L − 1 , and 18.6 de g Fe 3 + ·L − 1 was obtained. This enriched primary raffinate can be reintroduced in the process as leaching solution. So, after the modification of the process, using secondary raffinate as loading solution and acidified primary raffinate as eluting solution, the ion-exchange stage could substitute the external FeSO 4 addition. In addition, 30–80 kg Cu·h − 1 are reintroduced in the process. [ABSTRACT FROM AUTHOR]

The nitrogen and sulphur oxide (NO x and SO 2) emissions are causing a serious threat to the existence of life on earth, requiring their effective removal for a sustainable future. Among various approaches, catalytic or electrochemical reduction of air pollutants (NO x) has gained much attention due to its high efficiency and the possibility of converting these gases into valuable products. However, the required catalysts are generally synthesized from lab-grade chemicals, which may not be a sustainable approach. Herein, a sustainable approach is presented to synthesize an efficient iron-based catalyst directly from industrial/lake wastewater (WW) for NO x -reduction. According to the theoretical calculations and experimental results, Fe-ions could be readily recovered from wastewater because it has the best adsorption efficiency among all other co-existing metals (Ni2+, Cd2+, Co2+, Cu2+, and Cr6+). The subsequent experimental investigations confirmed the preferential Fe adsorption from different WW streams to develop Fe 3 O 4 @EDTA-Fe composite, whereby Fe 3 O 4 could be used due to its high recycling ability, and ethylenediaminetetraacetic acid (EDTA) acted as a chelating agent to adsorb Fe-metal from effluents. The Fe 3 O 4 @EDTA-Fe exhibited high efficiency (≥87%) for NO x reduction even in the presence of high-degree oxygen contents (10–12%). Moreover, Fe 3 O 4 -EDTA-Fe showed excellent long-term stability for 24 h and maintained more than 80% NO x reduction. The fabricated catalyst has a great potential for executing a dual role simultaneously for Fe-recovery and NO x removal, promoting the circular economy concept and providing a potentially sustainable remediation approach for large-scale applications. [Display omitted] • Wastewater effluents are utilized as alternative Fe source for sustainable catalyst synthesis. •Etched Fe 3 O 4 -L-Fe has best selectivity for Fe recovery by theoretical and experimental results. •Characterization tools confirmed synthesis of Fe 3 O 4 -L-Fe with abundant active sites. •Etched Fe 3 O 4 -L-Fe outperformed other composites (e.g., Fe 3 O 4 -L-M) in NO x removal. •Etched Fe 3 O 4 -L-Fe showed good stability and maintained >80% NO x removal after 24 h. [ABSTRACT FROM AUTHOR]

E-waste has become one of the greatest sources of environmental pollution. Bioleaching is known as a new, simple, and environmentally friendly technology for metal recovery requiring low energy input, unskilled labor operations, moderate conditions, and low costs. Acidithiobacillus ferrooxidans is a famous and puissant mesophilic bacterium applied extensively to recover metals from ores and different industrial and municipal wastes. It is necessary to identify the parameters affecting consumers E-waste recycling. Separating and recovering different types of E-waste is impossible for small recycling units. There should be a specific combination of E-waste, enabling the extraction of the maximum amount of precious metals. The main objective of the present study is finding the optimal combination of the most important printed circuit boards (PCBs) to maximize recovery of Cu, Ni, and Fe (as the most gold inhibitor metals) using adapted A. ferooxidans. The polymers and low-density materials were separated using the shaking table method to reach a concentrated sample. A. ferooxidans was adapted to the 15 g/l of the defined samples within 177 d. The D-optimal method was adopted to find the optimum E-waste combination. Pulp density, inoculum size, temperature, and stirring rate were fixed at 15 g/l, 10% (w/w), 30 °C , and 130 rpm in all experiments. The optimal percentages of computer PCBs plus CPUs, mobile phone PCBs, TV PCBs, copy machine PCBs, and fax PCBs were determined as 21.5%, 43.5%, 3%, 13.5%, and 18.5%. The application of this optimal E-waste composition resulted in 100% Cu and Fe extraction and 54% Ni recovery. It was concluded that increasing the concentration of a definite metal in PCB mixtures improves the recovery efficiency of that metal. Increasing Cu concentration in the bioleaching solution decreases Fe recovery. Significant amount of Cu and Fe in all samples reduces Ni recovery. • Finding the best combination of E-waste to recover the maximum amount of Fe, Ni and Cu. • Mixture design is conducted to find the optimal E-waste composition. • Under optimal combination 100% of Cu and Fe, and 54% of Ni were recovered. • Cu, Ni and Fe are the most important metals that inhibit gold recovery. [ABSTRACT FROM AUTHOR]