Analysis of reasons for decline of bioleaching efficiency of spent Zn–Mn batteries at high pulp densities and exploration measure for improving performance

• Published in: Bioresource technology 2012-05, Vol.112, p.186-192
• Main Authors: Xin, Baoping, Jiang, Wenfeng, Li, Xin, Zhang, Kai, Liu, Changhao, Wang, Renqing, Wang, Yutao
• Format: Article
• Language: English
• Subjects: Bacteria; Bacteria - growth & development; Bacteria - metabolism; Bacterial leaching; Batteries; Biodegradation, Environmental; Bioleaching; Colony Count, Microbial; Density; Efficiency decline; Electric Power Supplies; Environmental Restoration and Remediation - methods; Environmental Restoration and Remediation - standards; Extraction; High pulp density; Hydrogen-Ion Concentration; Kinetics; Manganese; Manganese - isolation & purification; Media; Oxygen; Recovery of Zn and Mn; Spectrometry, X-Ray Emission; Spent Zn–Mn batteries; Time Factors; X-Ray Diffraction; Zinc; Zinc - isolation & purification
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2012.02.133

► Bioleaching was used for extraction of valuable Zn and Mn from the spent batteries at high pulp densities. ► Bioleaching dynamics of both Zn and Mn under different pulp densities were compared. ► Reasons for decrease of bioleaching efficiency at high pulp densities were unveiled. ► Feasible measures for improving efficiency at high pulp density of 4% were proposed. ► Extraction yields of 100% for Zn and 89% for Mn at 4% of pulp density were attained. The reasons for decline of bioleaching efficiency of Zn and Mn from spent batteries at high pulp densities were analyzed; the measures for improving bioleaching efficiency were investigated. The results showed that extraction efficiency of Zn dropped from 100% at 1% of pulp density to 29.9% at 8% of pulp density, with Mn from 94% to only 2.5%. It was almost the linear reduction of the activity of the sulfur-oxidizing bacteria with increase of pulp density that witnessed declined bioleaching efficiency of Zn; it was the complete inactivation of the iron-oxidizing bacteria at 2% of pulp density or higher that witnessed declined bioleaching dose of Mn. By means of reducing initial pH value of leaching media, increasing concentration of energy matters and exogenous acid adjustment of media during bioleaching, the maximum extraction efficiency of almost 100% for Zn and 89% for Mn at 4% of pulp density was attained, respectively.