Transformation behavior of hazardous jarosite into recyclable hematite in a solution with high concentrations of K+ and Na.

Iron in the leaching solution with high K+ and Na+ concentrations was usually precipitated as the typical hazardous and toxic jarosite residues. However, this method of treatment has been greatly restricted by increasingly strict environmental regulations. Here we propose that iron can be precipitated from the solution with high K+ and Na+ concentrations as recyclable hematite products by adjusting the concentration ratio of sodium and potassium ions in the solution. The transformation behavior of jarosite into hematite in high concentration potassium ion and sodium ion solution was explained based on collision theory. The results indicated that in instances where the concentration ratio of Na+/K+ is ≥ 4:1, the iron present in the solution can be effectively precipitated as a recyclable hematite product, as opposed to forming the conventional hazardous jarosite residue, even under conditions where the potassium ion concentration reaches levels as high as 4 g/L. On the other hand, thermodynamic and molecular dynamics simulations indicate that at a temperature of 185 °C, the decomposition transformation of Na-jarosite (32.64 kJ and 7.25 eV) is more energetically advantageous compared to that of K-jarosite (61.07 kJ and 15.31 eV). The results were verified by the leaching solution from smelting industry. The iron content in the residues is above 58%, the sulfur content is below 4%, the zinc content is below 1%, and the total iron concentration in the supernatant is about 4 g/L, reaching the production index of the smelting industry. The green, environmentally friendly, and recyclable separation of iron in a solution with high concentrations of potassium and sodium ions is achieved, which is of great significance for the treatment of iron-containing solution and wastewater in the chemical industry and metallurgy fields.

Selective separation of zinc and iron/carbon from blast furnace dust via a hydrometallurgical cooperative leaching method.

Blast furnace dust (BFD) contains ferrous and nonferrous metals and carbon, and is usually categorized as a typical secondary resource and hazardous waste produced by the iron-making process. The thermodynamic calculation and experimental investigation of the selective separation of zinc and iron/carbon from BFD via a NaCl-HCl-H2O system were carried out. Quantitative zinc and iron/carbon separation and recovery was achieved via a zinc-chloride (ZnCli2-i (i = 0, 1, 2, 3, 4)) cooperative leaching methodology using 3 mol/L NaCl at pH of 4, an L/S ratio of 4:1, a leaching temperature of 70 °C, a HCl concentration of 0.25 mol/L, and a leaching time of 2 h. Moreover, the total Cl- concentration used in for leaching was 2.09 mol (as concluded by the dosages of HCl and NaCl, and material). Results demonstrate that zinc was effectively leached from BFD, while the leaching of iron was hindered, in the acidic region. 93.2% of the zinc was extracted into a leaching solution containing 19.8 g/L zinc under the optimal conditions, and the ratio of the leaching agent to BFD was 300 mL to 75 g. The XRD and SEM-EDS analysis results of the residue reveal that ZnO and ZnS were leached, and the zinc-iron spinel (ZnFe2O4) was not leached and was present together with the iron oxide in the leaching residue. Iron and carbon in the leaching residue was enriched from 49.4% to 60.38%, and the iron and carbon were recovered as secondary resources that can be reused in the iron-making system.

Recovery of H2SO4 from an acid leach solution by diffusion dialysis.

Diffusion dialysis with a series of anion exchange membranes was used to recover H(2)SO(4) from an acid leach solution produced during the vanadium manufacturing process. The effects of sulfuric acid, FeSO(4) and VOSO(4) concentration, flow rate and flow rate ratio on the recovery of H(2)SO(4) were investigated. The results showed that sulfuric acid permeated well through the membranes used, while metal ions were efficiently rejected. The recovery of H(2)SO(4) increased as the sulfate concentration of the feed increased and the flow rate ratio of water to feed increased. More than 80% of the H(2)SO(4) could be recovered from the leach solution which contained 61.7 g/L free H(2)SO(4), 11.2 g/L Fe and 4.60 g/L V at a flow rate of 0.19x10(-3) m(3)/h m(2). V and Fe ion rejection were within 93-95 and 92-94%, respectively. A preliminary economic evaluation revealed that an investment in this process could be recovered within 27 months.