Removal of emulsified oil from wastewater using froth flotation

Abstract

Froth flotation is a surfactant-based separation process which is applicable for removing oil from water. Ortho-dichlorobenzene (ODCB) which is commonly used in many industrial applications was used as the oil for studying the removal efficiency by batch froth flotation. Mixtures of sodium dodecyl sulphate (SDS) and nonylphenol ethoxylate (NP(EO)₁₀ or Teric 10) were used for studies of microemulsion formation of ODCB. It was found that small amounts of NaCl added to mixed surfactants could improve microemulsion formation. However, precipitation and liquid crystal that limit the solubilization capacity of solution appeared at high NaCl concentration. The mixed surfactants concentrations of 3 and 5 % by weight of mixed surfactants were selected for froth flotation experiment. The prepared solutions i.e. water and middle phase (w-m), water and oil phase (w-o) and water, middle and oil phase (w-m-o) were transferred to a flotation column to determine oil removal efficiency. The results showed that ODCB removal in the w-m-o system was much higher than the w-o and w-m systems. The effect of NaCl in the w-m-o system was studied and showed that adding 0.5 by weight of NaCl increased ODCB removal but adding more than 1.0 by weight of NaCl decreased ODCB removal. The effect of volume of each phase was also studied. The results showed that when volume of oil phase decreased and volume of water phase increased in the w-o system, ODCB removal decreased. When volume of middle phase increased and volume of water phase decreased in the w-m system, ODCB removal increased.