Effects of Various Precipitants on Iron Removal from a Zinc Concentrate Pressure Leaching Solution

Claudio A Leiva,Claudio A Acuña,María E Gálvez,Gerardo E Fuentes,Jannan A Alcota

doi:10.3390/min12010084

Claudio A Leiva, Claudio A Acuña + Show 3 more

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https://doi.org/10.3390/min12010084

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Abstract

Autoclave leaching of zinc concentrate (Sphalerite) is an environmentally friendly process compared to roasting, which discharges pollutants into the atmosphere. Due to the amount of iron in the final product, a study is proposed to evaluate different reagents for eliminating iron from the autoclave outcome, minimizing Zn losses. The colloid formation, zinc losses, iron removal, phase separation stage characteristics (sedimentation and filtering), and reagent costs were used to evaluate six-iron precipitating reagents: CaO, Na2CO3, CaCO3, NaOH, MgO, and Ca(OH)2. CaO shows 99.5% iron removal and 87% zinc recovery. Although CaO was one of the reagents with significant zinc recovery, it presented operational difficulties in the filtration stage due to the high viscosity of the mixtures. Finally, Ca(OH)2 is the reagent recommended due to its ease of use, zinc yield recovery, electrowinning efficiency, and iron precipitate filtration rate. Zinc recovery was above 80%, while the iron concentration in the solution was below 50 ppm.

Highlights

It is well known that national and transnational mining companies, when commercializing their concentrates, lose the opportunity to recover elements of economic interest that are part of copper concentrates [1]
Many zinc concentrates produced in Bolivia and shipped through Antofagasta and Mejillones (Chile) are sold as concentrates, with zinc grades between 46% to 50% [2] and variable contents of silver, indium and germanium, with low gold grades
The saturation level of the solutions was controlled by oxidation with hydrogen peroxide and potassium permanganate

Summary

Introduction

It is well known that national and transnational mining companies, when commercializing their concentrates, lose the opportunity to recover elements of economic interest that are part of copper concentrates [1]. This situation occurs in the case of other polymetallic concentrates, such as zinc concentrates, whose elements of interest are not necessarily paid to the producer. A typical zinc concentrate contains 50–62% Zn, 0.3–2.5% Pb, variable contents of silver, indium, and germanium, with low concentrations of gold and other elements such as S, Fe and SiO2 [1]. To replace the roasting stage, a process is investigated to obtain zinc cathodes from concentrates, using the technology of autoclave leaching under pressure and temperature conditions [2]

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