Zn bio extraction from a zinc rich paint sludge by indigenous Pseudomonas aeruginosa

Abstract

Paint sludge is considered hazardous waste due to its heavy metals and high organic compounds. Incineration and landfilling are the methods of disposing of sludge collected from the paint spray of an automotive factory in Iran. Pseudomonas aeruginosa was isolated from water-based paint sludge using Bushnell-Haas medium and identified by chemical and molecular methods. A two-step bioleaching experiment using the Response surface methodology was used to investigated P. aeruginosa to mobilize the contaminant zinc metal from the paint sludge. Variables included temperatures from 32 to 37 °C, the rotation speed of shaker from 120 to 180 rpm, particle sizes from 1 to 3 mm, and bacteria were adapted to a pulp density of 7 g/L. When the bioleaching process was optimized at pH 7, temperature 32 °C, particle size 3 mm, and 180 rpm, the concentration of zinc decreased to 28.71%. A decrease in zinc of 27% was confirmed by repeating the experiment three times. The ANOVA test confirmed the most effective parameters were temperature and particle size. The most efficient process to remove zinc was achieved as a result of the effect between temperature and pH.

Keywords:

• Automotive industry
• paint sludge
• bioleaching
• Pseudomonas aeruginosa
• RSM
• CCD

Acknowledgments

The authors acknowledge their gratitude to the Iranian Research Institute for Science and Technology (IROST), Iran Mineral Processing Research Center (IMPRC), and the Piraye Zist Caspian Company for help in conducting the study.

Conflict of interest

The authors declared no conflict of interest.