Mine tailing storage represents an important environmental issue. The generation and dispersal of dust from mine tailings can contaminate air and surrounding soils. In addition, metals and soluble salts present in these wastes could pollute groundwater and surface water. The recovery of metals from mine tailings can contribute to minimize the environmental risk and to achieve a circular economy model. The main objective of the present work is to study the use of two carbon-based materials, a commercial activated carbon (AC) and a commercial charcoal (VC) in the leaching of zinc and copper from low-grade tailing waste. Experimental results obtained show that it is possible to achieve the recovery of more than 87 wt% of Zn after 6 h of leaching with different sulfuric acid solutions. The addition of carbon-based materials increases the extraction of Zn at high sulfuric acid concentrations (1 M) from 89% to 99%. The addition of VC significantly increases the extraction of Cu in leaching solution with high sulfuric acid concentration (1 M), from 41 to 61%. Future research will be necessary to optimize the properties of carbon-based materials and their recovery after leaching experiments in order to assess their potential for industrial application.

Excessive amounts of sodium cations (Na⁺) in water is an important limiting factor to reuse poor quality water in agriculture or industry, and recently, much attention has been paid to developing cost-effective and easily available water desalination technology that is not limited to natural resources. Biochar seems to be a promising solution for reducing high loads of inorganic contaminant from water and soil solution, and due to the high availability of biomass in agriculture and forestry, its production for these purposes may become beneficial. In the present research, wheat straw, sunflower husk, and pine-chip biochars produced at 250, 450 and 550 °C under simple torrefaction/pyrolysis conditions were chemically modified with ethanol or HCl to determine the effect of these activations on Na sorption capacity from aqueous solution. Biochar sorption property measurements, such as specific surface area, cation exchange capacity, content of base cations in exchangeable forms, and structural changes of biochar surface, were performed by FTIR and EPR spectrometry to study the effect of material chemical activation. The sorption capacity of biochars and activated carbons was investigated by performing batch sorption experiments, and adsorption isotherms were tested with Langmuir’s and Freundlich’s models. The results showed that biochar activation had significant effects on the sorption characteristics of Na⁺, increasing its capacity (even 10-folds) and inducing the mechanism of ion exchange between biochar and saline solution, especially when ethanol activation was applied. The findings of this study show that biochar produced through torrefaction with ethanol activation requires lower energy demand and carbon footprint and, therefore, is a promising method for studying material applications for environmental and industrial purposes.

Chalcopyrite, the main ore of copper, is refractory in sulfuric media with slow dissolution. The most commonly employed hydrometallurgical process for the oxidation of chalcopyrite and copper extraction is the sulfuric acid ferric sulfate system The main objective of the present work is to study the use of cheap carbon-based materials in the leaching of copper and zinc from a sulfide complex mineral from Iberian Pyrite Belt (IPB). The addition effect of commercial charcoal (VC) and two magnetic biochars (BM and HM) that were obtained by pyrolysis of biomass wastes was compared to that of commercial activated carbon (AC). The experimental results performed in this work have shown that the presence of carbon-based materials significantly influences the kinetics of chalcopyrite leaching in the sulfuric acid ferric sulfate media at 90 °C. The amount of copper and zinc extracted from IPB without the addition of carbon-based material was 63 and 72%, respectively. The highest amount of extracted zinc (>90%) was obtained with the addition of VC and AC in IPB/carbon-based material ratio of 1/0.25 w/w. Moreover, it is possible to recover more than 80% of copper with the addition of VC in a ratio 1/0.25 w/w. Moreover, an optimization of the properties of the carbon-based material for its potential application as catalyst in the leaching of metals from sulfide is necessary.