Effect of temperature on removal of copper from electroplating industrial sludge via biosolubilization: kinetics and thermodynamics studies

The industrial sludge with heavy metal poses a severe threat to the environment and human health when it is disposed to a landfill site without proper treatment. In this work, the removal of Cu from electroplating industrial sludge by biosolubilization was studies using adapted Acidithiobacillus ferrooxidans as the bacterial agent with due importance for investigating the effect of temperature. The experiments were carried out in 250 mL Erlenmeyer flasks with 5% (w/v) sludge and at the different temperatures between 27 and 39C. Experimental results showed that the temperature had great impact on biosolubilization, and the ideal temperature was found to be 36C. The pseudo-first-order kinetic model was used to determine the rate-constant values of Cu solubilization at different temperatures. Using the shrinking core model analysis, the rate-controlling step was identified. In addition, the activation energy, Gibbs free energy, and change in enthalpy and entropy were calculated for the biosolubilization process.