Bioleaching of Zn from sphalerite using Leptospirillum ferriphilum isolate: effect of temperature and kinetic aspects

Venkatesa Prabhu Sundramurthy,Baskar Rajoo,Natesan Rajendran Srinivasan,Rajan Kavitha

doi:10.1186/s13765-020-00528-8

Abstract

Biological methods for leaching of nonferrous and noble metals from its sulfide ores are widely applied at industrial enterprises of different countries. This process is based on the use of the oxidative activity of acidophilic microorganisms. Since all bio systems are quite sensitive to the temperature, bacterial leaching process also significantly effects. In the present study, the impact of temperature on bacterial leaching of Zn from its sulphide ore, sphalerite, was investigated using ore adapted iron oxidizing bacteria. The bacteria were isolated from mine drainage samples and subjected to gene sequencing. The acquired nucleotide sequence revealed that the isolate was Leptospirillum ferriphilum. The nucleotide sequence of L. ferriphilum isolate was submitted to National Center for Biotechnology Information (NCBI) and accession number KF743135 was assigned. Using the isolate, the Zn leaching data were collected in the 298–318 K temperature range. The results showed that leaching of Zn increases with temperature until optimum temperature of 313 K and achieves highest leaching efficiency of 96.96% within 20 days. Since bioleaching of minerals have become increasingly applied in different mining industries, there is immense important to analyze mechanistically-based kinetics for the design, optimization, operation, and control of biochemical processes. The kinetic study showed that the rate of Zn leaching was maximized at the optimum temperature. Further, the leaching data were analyzed using shrinking core model which revealed that the rate of leaching was inhibited by diffusion through product layer. Reaction kinetics is also to be contrasted with thermodynamics. Using Arrhenius law of thermodynamics, it was found that activation energy for Zn bioleaching reaction was 39.557 kJ mol−1. Such investigations will be necessitated for designing and implanting the ideal bioleaching system for metal bio-mining industries.

Highlights

Zn is the fourth most broadly used metal in the world after iron, aluminum, and copper
The results showed that the highest zinc recovery, 98.5%, was obtained during 25 days with pulp density 50 (g/L)
Three different types of zinc sulphides, marmatite, sphalerite and Zn is separated from sphalerite (ZnS), were studied for comparative bioleaching of Zn using A. ferrooxidans and a moderately thermoacidophilic iron-oxidizing bacterium by Shi et al [13]. They observed that the bioleaching of marmatite concentrate was advantageous over that of the sphalerite and synthetic ZnS which clears that Zn extraction could be influenced by mineral properties

Summary

Introduction

Zn is the fourth most broadly used metal in the world after iron, aluminum, and copper. Three different types of zinc sulphides, marmatite, sphalerite and ZnS (synthetically prepared), were studied for comparative bioleaching of Zn using A. ferrooxidans and a moderately thermoacidophilic iron-oxidizing bacterium by Shi et al [13]. They observed that the bioleaching of marmatite concentrate was advantageous over that of the sphalerite and synthetic ZnS which clears that Zn extraction could be influenced by mineral properties.

Results

Conclusion