Waste water from chemical industries contains heavy metals, organic and inorganic materials, fertiliser, petrochemicals, and many other additives that highly impact natural water bodies and must be prevented from entering into the water cycle; otherwise, deadly impact on the aquatic Ecosystem. Various processes are available to treat water like adsorption, aeration, sedimentation, screening, disinfection, chemical oxidation etc.(Li et al. 2011; Osman 2014; Chaitali Gohatre 2016; Colla et al. 2016; EH et al. 2018).
Industrial wastewater contains oil and grease, and these are considered threatening to aquatic animals, marine animals, and human beings. Therefore, before discharge to the main water stream, the oil and grease present in the industrial wastewater need to separate. Among various forms of oil, the oil which is present as a separate layer or presents as a bulk quantity can be separated easily by following the methodology described in the literature (Hassler 2011; Li et al. 2014; Xue et al. 2014; Razali et al. 2015). However, the emulsified form of the oil is very difficult to separate efficiently. Therefore, an attempt has been made to separate the emulsified oil from the industrial wastewater up to 99% (S. Liubartsevaa et al. 2015; Xiong et al. 2015).
In the effluent, the emulsified oil forms a physical hydro-bonding with the nearest water molecules. The discussed attachment is physical attachment, defined by the attractive force between the emulsified oil and the water. For the removal of emulsified oil in the effluent stream, the physical hydro-bonding needs to break. The detachment mentioned above is performed by using additives which creates a strong electrostatic force between the additive and the oil. The described mechanism is depicted with the help of the following schematic. (Fig. 1)
Stage 1: Oil and water interaction in the effluent.
Stage 2: Oil and water separation in the effluent
After separating emulsified oil, the density of oil increases compared to water due to the attachment of strong metallic ions with the oil molecules. Furthermore, for the agglomeration of separated oil droplets, strong interactions among the oil droplets are required, and this is done by adjusting the pH. After that, due to gravity, the flocs settle, and an effluent stream free from oil and grease is obtained (Lin et al. 2007; Choi et al. 2009; King et al. 2015; S. Liubartsevaa et al. 2015).
In the current work, using the above-discussed mechanism, the emulsified form of the oil is tried to remove very efficiently, and the proposed process has not been disclosed in the literature, and the obtained separation efficiency is also much higher than the reported value. Furthermore, the additive consumption rate is comparatively lower than the data reported in the literature (GUPTA, Vinod Kumar, ALI, Imran, SALEH, Tawfik A.; Gu and Li 1998; Teduka and Nishioka 2014; Zhu et al. 2016; Wu et al. 2018).
It is a highly effective process for removing colloidal, soluble, and suspended particles as well as other types of pollutants such as organic compounds, colour, micro pollutants, fat, and oils, by aggregating macro and micro particulates into larger ones and then sedimenting them(EH et al. 2018). This process helps to reduce the organic matter, pH, turbidity, alkalinity, oil concentration and increase the dissolved oxygen level.