Bacterial-mediated recovery of copper from low-grade copper sulphide using acid-processed rice straw.

Bacteria community and copper recovery in presence of acid-processed rice straw (ARW) were explored during low-grade copper sulphide bioleaching. The results indicated a strongly promoting response of appropriate-quality ARW with improved bacteria concentration and enhanced copper recovery. The highest bacteria concentration reached 9.54 × 107 cells·mL-1 with an increase by 69.15%. And a maximum of 95.32% copper leaching rate with a relatively low Fe3+ concentration (329.00 mg·L-1) was obtained in presence of 1.0 g powdered ARW compared to only 83.40% in its absence. That is due to less development of passivation layer formed by Fe3+ hydrolysis, which is contributed by reducing ARW. 16S rDNA analysis illustrated the dominant leaching bacteria (Acidithiobacillus ferrooxidans) was influenced significantly, whose proportion reached 40.38% to the total bacteria when the ARW was added compared to 15.92% in its absence. And Stenotrophomonas accounted for the highest proportion of the bacteria community throughout bioleaching process.