Abstract
This study uses extracellular polymeric substance (EPS) secreted by bacteria Thiobacillus ferrooxidans and Thiobacillus thiooxidans to etch the copper. These two bacteria have the ability of etching metal. The etching mechanism is based on the metabolite (EPS) from growing bacteria. The EPS can oxidize metal by acquiring electron, and bacteria obtain the necessary energy in the course. Through the metabolism, one can machine the work piece. The factors influencing etching results include the pre-cultivation time, the concentration of ferric ion in the EPS solution of Thiobacillus ferrooxidans, the area of copper, and volume of solution. This study explores the correlation between these parameters and etching behavior. In this study, the EPS of Thiobacillus ferrooxidans reaches maximum material removal rate after culture of 3 days. At the beginning of etching, the rate of etching is very fast, but the copper removal amount is limited by the concentration of copper ion in the solution. It is suitable for the work piece with small amount of machining. The indicator of material removal rate is the concentration of ferrous ion during the etching process. The initial material removal rate of the EPS of thiobacillus thiooxidans is slow, but it is faster and faster. The total copper removal amount is more than thiobacillus ferrooxidans. It is suitable for large amount of machining. There is sulfur powder in the solution when etching copper, which increases the rate of machining and prevent the residue on copper sample.