Carbon Material with High Specific Surface Area Improves Complex Copper Ores’ Bioleaching Efficiency by Mixed Moderate Thermophiles

Xiaodong Hao,Hongwei Liu,Xueduan Liu,Guanzhou Qiu,Aijia Chen,Yili Liang,Ping Zhu,Huaqun Yin

doi:10.3390/min8070301

Abstract

The catalysis of carbon materials with different specific surface areas (SSA) (2, 400, 800 and 1200 m2/g) on complex copper ores bioleaching by moderately mixed thermophiles was investigated. The copper extractions increased with the rise in SSA of carbon materials. A recovery of 98.8% copper in the presence of 1200 m2/g activated carbon was achieved, and improved by 30.7% and 76.4% compared with biotic control and chemical leaching. Moreover, the addition of 1200 m2/g activated carbon adsorbed large amount of bacteria, accelerated the oxidation rate of ferrous iron and maintained the solution redox potential at relatively low values, and significantly increased the dissolution of primary copper sulfide (62.7%) compared to biotic control (6.0%). Microbial community succession revealed that activated carbon changed the microbial community composition dramatically. The S. thermosulfidooxidans ST strain gained a competitive advantage and dominated the microbial community through the whole bioleaching process. The promoting effect of carbon material with higher SSA on copper extraction was mainly attributed to better galvanic interaction, biofilm formation, direct contact and lower redox potential.

Highlights

Due to the continuous decrease of valuable copper minerals, the beneficiation and utilization of complex and low-grade copper ores that used to be considered as wastes needs a relook
The electrical conductivity of graphite (0.6 S/m) was much higher than the other three activated carbons (0.1 S/m) (Table 1), but the copper extractions were significantly enhanced by activated carbons instead of graphite, which suggested that specific surface areas (SSA) was the key factor affecting Cu leaching efficiency
The copper extractions improved with the increase in SSA of carbon materials both in chemical leaching and bioleaching experiments

Summary

Introduction

Due to the continuous decrease of valuable copper minerals, the beneficiation and utilization of complex and low-grade copper ores that used to be considered as wastes needs a relook. Bioleaching has become a preponderant technology for copper extraction from complex copper ores on account of its advantages in high processing capacity, low-cost production and eco-friendly for nature. Primary copper sulfide (chalcopyrite) including chalcopyrite-bearing mineral is refractory to be dissolved due to the formation of a passivation layer, stable structural configuration and higher lattice energy [1,2,3]. Increasing the bioleaching efficiency and ultimate copper extractions from complex copper sources is the most urgent problem affecting the economy of copper mining. The addition of modifier is beneficial to increasing the copper recovery rate. It has been documented that some catalytic agents (e.g., Ag+ , polyethylene glycol and Cl− )

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