REMOVAL OF CADMIUM FROM DILUTE-SOLUTIONS BY FLOTATION

Cadmium constitutes a priority pollutant existing in waste streams fro m metal plating and various other industries. The removal of this toxi c metal employing the dissolved air flotation technique was investigat ed in laboratory batch experiments; the mechanism of precipitate flota tion as the respective hydroxide was followed. Main examined parameter s include: recycle ratio, pH of the solution, concentrations of added surfactant (sodium dodecyl sulphate), frother (ethanol) and cadmium. P romising results have been obtained, at the pH range between 10 and 11 approximately, showing the significance of flotation as a separation process in water and wastewater treatment for dilute solutions (around 10 mg/l of metal). Under the optimum conditions removal of cadmium wa s near to 100%, while the remaining concentration in the solution afte r flotation was less than 0.10 mg/l. A comparison was also attempted b etween two flotation techniques applying different bubble generation m ethods, i.e. dissolved air and dispersed air flotation. These experime nts run in parallel and under the same conditions.