Introduction In the wastewater treatment by flotation technique, nanoparticles may act as surfactant molecules, being incorporated into surfactant-stabilised foams for several years. The gas flotation process is divided... [ view full abstract ]
Introduction
In the wastewater treatment by flotation technique, nanoparticles may act as surfactant molecules, being incorporated into surfactant-stabilised foams for several years.
The gas flotation process is divided in four main stages: generation of gas bubbles inside the liquid, occurrence of contact between gas bubbles and pollutants, adherence of pollutants to gas bubbles and the actual flotation of aggregates to the surface of the liquid where they form a foam that needs to be removed. A fifth stage can be added to this division, namely the use of surfactants to help the formation and stability foams formed by the gas-particle/oil aggregates. The paper is focused on the use of oxide nanoparticles as surfactants in the fifth stage of the flotation process to help the formation and stability of foams in wastewater treatments by air flotation.
Methods
In this study, we investigate the application of nanomaterials as froth stabiliser in flotation and the experiments consisted in testing of two oxide nanomaterials for the removal of oil pollutant from wastewater.
Prior to the flotation experiments, CuFe2O4 and Fe3O4 nanomaterials were prepared by coprecipitation method.
The experiments were done on a synthetic wastewater containing a concentration of oil of 25% in the presence and in the absence of Fe3O4 and CuFe2O4 nanomaterials. Dissolved air flotation system contained also 5% of anionic surfactants and 5 % of amphoteric surfactants.
Results and discussion
Before testing their application in wastewater treatment by flotation, both oxides nanomaterials were structural and morphological characterized by XRD (Fig. 1a and b) and TEM analyses (Fig 2 a and b). In order to evaluate their potential of application in oil removal from wastewater by flotation were studied the following parameters such as: treatment efficiency [%] and the stability of froth.
The preliminary study of the influence of using Fe3O4 or CuFe2O4 nanomaterials in the wastewater treatment by flotation revealed that the main advantages were observed the increasing the stability of the foam containing the oil pollutant and the decreasing of the time needed for wastewater treatment.
For both ferrite nanoparicles (CuFe2O4 and Fe3O4) tested the wastewater treatment efficiency was 100 %.
