Abstract:
In common practice, a battery-manufacturing plant in this case study manages lead ions in its wastewater by chemical precipitation. Due to a large amount of wastewater per day, it is by far not in time by the chemical precipitation to reduce lead ions from the total volume below the nation permissible quality of 0.2 mg/l. To handle this restriction, the wastewater after chemical precipitation, which contains lead ions about 1-2 mg/l, is reused in the process. It is of great concern to avoid lead exposure in the workplace, we proposed the application of hollow fiber supported liquid membrane. The wastewater before chemical precipitation containing lead ions of 7.5 mg/l was used as feed solution. A suitable extractant was selected by solvent extraction. The pH of feed solution, concentration of the extractant, types and concentration of stripping solutions, types of organic solvents and flow rates of feed and stripping solutions were investigated. Feed and stripping solutions were circulated counter-currently. By using 0.12 M D2EHPA in kerosene, pH of feed solution of 3.0, 0.25 M HNO3 and equal flow rates of feed and stripping solutions of 100 ml/min, the highest percentages of extraction and stripping of 99% and 97% were achieved at 90 minutes. The residual amount of lead ions was found to be 0.045 mg/l. In addition, it is found that mass transfer coefficient of lead ions in aqueous feed (ki) and that of the complex species of lead ions and the extractant in liquid membrane phase (km) were 4.980 x 10-4 and 1.089 x 10-5 cm/s, respectively indicating that the diffusion of the complex species via liquid membrane was the mass transfer controlling step. Finally, at known initial concentration, the separation time with respect to the concentration of lead ions to meet industrial wastewater regulation can be predicted by the mathematical model.