The removal of sulfate ions from natural waters, as well as from industrial effluents of different origins, is a problem, considering that most of the proposed processes are inefficient and have a high cost, mainly when reducing the sulfate ion concentration to values below 500 mg.L−1 is required. The flotation technique, combined with precipitation, has proven to be efficient for the removal of heavy metal ions. However, there is not enough research to confirm its efficiency for the removal of sulfate ions. This article presents the results of sulfate ion removal from synthetic solutions prepared in an acidic medium, applying the co-precipitation techniques with polyaluminum chloride (PAC) and solid/liquid separation by dissolved air flotation (DAF). The effect of the pH, the [PAC: sulfate ions] ratio, the effect of saturated water flow with air, and the flocculant and collector doses were studied. The achieved results confirm that it is possible to reduce the concentration of sulfate ions from 1 800 to 350 mg.L−1 (80% removal) from synthetic solutions by applying the flotation technique combined with precipitation.

The significant volume of copper smelting slags poses environmental challenges, particularly concerning soil and surface water contamination. However, these slags contain valuable elements such as copper and iron, the recovery of which can contribute to both environmental protection and the circular economy in Chile. This study analyzes, at both laboratory and industrial scales, the recovery of copper sulfides from the slags of the Hernán Videla Lira Smelter in Atacama, Chile. Physical, chemical, and mineralogical characterizations were performed, along with flotation tests (rougher and cleaner) to optimize the grinding degree, pH, reagents, and flotation times. The slag, with a copper grade of 0.71%, contains fayalite, magnetite, quartz, pyrite, and chalcopyrite. In the laboratory, the concentrate obtained in the rougher stage showed a copper grade of 3.7% with a recovery rate of 62.1%; in the cleaner stage, the grade increased to 24.4%, with a recovery rate of 71.7%. At the industrial level, the rougher–cleaner circuit produced concentrates with a copper grade of 27.9% and a recovery rate of 87.5% processing 1344 tons per day, thus demonstrating the viability of this methodology.

Iron concentration tailings contain many valuable minerals, including apatite, which is not currently being recovered despite its use to make fertilizers and chemicals. This article proposes a flotation circuit to recover apatite from tailings generated by mining in Chile, based on laboratory tests and using the “Split Factor” method. The iron tailings were characterized by granulometry, chemical and mineralogical analyses, zeta potential, and contact angle. The effect of the collector, frother, and dispersant dose, along with the number of flotation stages, on both the grade and recovery of P₂O₅ were studied. The results indicate that it is possible to produce concentrates with a P₂O₅ grade of 29.1% and 89.6% recovery in a flotation circuit that includes the rougher–scavenger–cleaner stages. To obtain these results, it is only necessary to condition the iron tailings with 400 gt⁻¹ of Atrac-2600, 400 gt⁻¹ of sodium silicate, 10 min of conditioning time, pH adjustment to 10, and a time for the rougher, cleaner, and scavenger stages set at 10, 7.6, and 6.8 min, respectively. A chemical interaction is suggested, where the collector is specifically adsorbed onto the apatite surface.

Chile es el mayor productor de cobre en el mundo, y este metal es obtenido principalmente a partir de los sulfuros de cobre, utilizando los procesos clásicos de flotación y pirometalúrgicos. En nuestro país existen siete fundiciones de cobre, las cuales generan grandes volúmenes de escoria. Este trabajo presenta los resultados obtenidos de recuperación de cobre contenido en escorias de horno de reverbero (HR) y de convertidor Teniente (CT) de la fundición Hernán Videla Lira, de Paipote mediante flotación. A través de pruebas de flotación rougher a escala de laboratorio se determinó que la granulometría, para ambos casos, corresponde a 70% menor a 74 µm, lográndose recuperaciones de 59,2% escoria HR y 86,8% para la escoria del CT, cuyas leyes de cobre en el concentrado fueron de 3,7% y 23,6% respectivamente. Las dosis de reactivos utilizados fueron 40 g/t de F-703 como colector y 30 g/t de H-70 como espumante. Los tiempos óptimos de flotación de las etapas rougher y cleaner, de ambas escorias, se determinaron mediante cinéticas de flotación. Finalmente se realizaron pruebas a nivel industrial con los resultados de laboratorio alcanzándose una ley de 18,2% de cobre (recuperación de 56,1%) para escoria HR, y para la escoria CT se obtiene una ley de 39,1% de cobre con una recuperación de 91,4%

Liquid effluents generated during mineral processing are usually contaminated with heavy metals and oxyanions, requiring an effective technique for their simultaneous removal. This study evaluated adsorption as a method to remove ions from an artificial acid effluent containing Cu²⁺, Zn²⁺, and ${\mathrm{S}\mathrm{O}}_4^{2-}$, using a mixture of activated carbon and barite as adsorbents. Adsorbent particles were prepared by grinding in a ring pulverizer for 120 s, using equal proportions of activated carbon and barite concentrate. The pH, contact time, and adsorbent particle mass were investigated. The results indicated that the adsorption efficiency depends on pH and adsorbent particle concentration: with increasing pH, the adsorption of Cu²⁺ and Zn²⁺ improves, while that of ${\mathrm{S}\mathrm{O}}_4^{2-}$ decreases. As the particle mass increases, the adsorption efficiency also increases. The maximum efficiency of simultaneous adsorption of ions of 55 ± 2.6% was achieved at pH 3 with an adsorbent particle concentration of 40 g·L⁻¹. The experimental data best fit the pseudo-1st-order kinetic model, suggesting that the limiting stage is external or internal diffusion and that the predominant adsorption mechanism is physisorption. Furthermore, the results were best fitted to the Freundlich isotherm, indicating heterogeneous and multilayer adsorption. In conclusion, the mixture of activated carbon and barite is presented as a potential adsorbent for acid effluent treatment with heavy metals and oxyanions.

The manufacture of barium sulfide or barium salts (BaS, BaCl₂, Ba (OH)₂, among others) requires high-purity barite ores (>90%). In this study, a new method to produce barium sulfide from low-grade barite ores (60% purity) is proposed. The method involves gravitational concentration of barite ore on a shaking table followed by mechanical activation of the barite concentrate with metallurgical coke in a ball mill. The mechanically activated mixture undergoes carbothermic reduction with an argon flow, resulting in the conversion of barite concentrate into barium sulfide. Gravitational concentration studies conducted using a shaking table demonstrated that, upon optimizing key operational parameters—namely, the wash-water flow rate, length, stroke frequency, the splitter positions of the concentrate, middlings, and tailings—a barite concentrate with a purity exceeding 95% BaSO₄ was successfully achieved. Mechanical activation of the barite/coal mixture lowered the initial temperature of the carbothermic reduction from 1100 K to 990 K, enabling complete conversion of barite to BaS, as confirmed by thermogravimetric curves and XRD analysis. Furthermore, the activation energy during the carbothermic reduction ranged from 300 to 500 kJ/mol, suggesting a complex reduction process of barite with metallurgical coke that is difficult to represent by a single reaction.