RESEARCH ARTICLE Bioleaching of copper from pre and post thermally activated low grade chalcopyrite contained ball mill spillage Sandeep PANDA (✉) 1,2 , Nilotpala PRADHAN 1 , Umaballav MOHAPATRA 2 , Sandeep K. PANDA 3 , Swagat S. RATH 1 , Danda S. RAO 1 , Bansi D. NAYAK 1 , Lala B. SUKLA 1 , Barada K. MISHRA 1 1 CSIR-Institute of Minerals and Materials Technology, Bhubaneswar 751013, India 2 Department of Botany, North Orissa University, Baripada 757003, India 3 Regional Center of Central Tuber Crops Research Institute, Bhubaneswar 751019, India © Higher Education Press and Springer-Verlag Berlin Heidelberg 2013 Abstract Bioleaching of a low grade chalcopyrite (ball mill spillage material) was tested for copper recovery in shake flasks. The original samples (as received) were thermally activated (600°C, 30 min) to notice the change in physico-chemical and mineralogical characteristics of the host rock and subsequently its effect on copper recovery. A mixed culture of acidophilic chemolithotrophic bacterial consortium predominantly entailing Acidithiobacillus fer- rooxidans strain was used for bioleaching studies and optimization of process parameters of both original and thermally activated samples. Mineralogical characteriza- tion studies indicated the presence of chalcopyrite, pyrite in the silicate matrix of the granitic rock. Field emission scanning electron microscopy coupled with Energy dispersive spectroscopy (FESEM-EDS) and X-ray Fluor- escence (XRF) analysis indicated mostly SiO 2 . With pH 2, pulp density 10% w/v, inoculum 10% v/v, temperature 30°C, 150 r$min –1 , 49% copper could be recovered in 30 days from the finest particle size ( – 1 + 0.75 mm) of the original spillage sample. Under similar conditions 95% copper could be recovered from the thermally activated sample with the same size fraction in 10 days. The study revealed that thermal activation leads to volume expansion in the rock with the development of cracks, micro and macro pores on its surface, thereby enabling bacterial solution to penetrate more easily into the body, facilitating enhanced copper dissolution. Keywords ball mill spillage, thermal activation, bioleach- ing, copper 1 Introduction Different kind of wastes such as the low grade/run-off mine ores, concentrator plant disposed tailings etc., are generated at the mining site as a result of extensive mining activity during processing of ores and concentrates for metal production. These wastes add no value to the mining industry because of the economical aspects involved in their processing through conventional routes of metal recovery and hence they are dumped in huge stockpiles. On the other hand, these wastes are a serious concern to the mining industries due to their abundance, presence of metal values and environmental issues associated with them. Over the past few years, due to the depletion of high grade and oxide ores, the low grade ores have been inviting attention of a great deal of researchers and industrialists for recovering respective metals at a competitive price. Presently the increase in copper prices has made the exploitation of remaining copper reserves and utilization of copper bearing wastes, even more attractive. Chalcopyrite (CuFeS 2 ) is an abundantly occurring copper mineral in nature which accounts for about 70% of the total copper reserves [1] but is relatively recalcitrant to hydrometallur- gical processing because of its special crystal structure and electrochemistry in contrast to many other copper minerals [2]. One of the most promising biotechnological strategies developed to optimize copper dissolution from low grade ores involves utilization of acidophilic microorganisms as biologic catalysts, through a process termed as bioleaching (Mineral Biotechnology). Thus mining wastes have a greater generation in the mineral processing field and hence are processed through bio-hydrometallurgical routes for metal recovery [3–5]. This process has got many advantages over conventional process of extraction which includes its simplicity, low cost and insignificant environ- mental pollution [3,6]. Currently, bioleaching of chalco- Received February 27, 2012; accepted December 21, 2012 E-mail: panda.sandeep84@gmail.com Front. Environ. Sci. Eng. 2013, 7(2): 281–293 DOI 10.1007/s11783-013-0484-5