The simultaneous removal of oil and heavy metals from industrial wastewater by joint precipitation and air flotation

Abstract

AbstractA joint precipitation and air flotation system was used to simultaneously remove oil and heavy metals from an industrial wastewater. The wastewaters were subjected to hydroxide treatment and chemical collectors simultaneously. The flotation tests were run for 4 min. For the particular wastewaters studied, the optimal pH and air injection rate was 9.18 and 12,150 cm3/min, respectively. Three different chemical collectors were investigated (WOF‐67, Nalco‐7182, and Jayfloc‐806*); the optimal collector dosage was typically in the range of 2–5 mg/L (depending on the particular chemical collector and heavy metal of concern). Removals of the heavy metals and oil typically exceeded 85%; oil removals are great as 96.2% were achieved. Removal of the heavy metals and oil probably occurred through a coprecipitation‐adsorption mechanism. Removals of the various heavy metals compared favorably between the individual removal and simultaneous removal (of heavy metals and oil) studies. By appropriate choice of the chemical collector, its dosage, pH and air injection rate, the selectivity for individual metal species can be affected.