**3.3 Hydroxyethyl cellulose (HEC)**

Hydroxyethylcellulose (HEC) (**Figure 4**) has been introduced a polysaccharide derivative with gel thickening, emulsifying, bubble-forming, water-retaining and stabilizing properties. It is a white, yellowish-white or grayish-white, odorless and tasteless, hygroscopic powder [23, 24].

**Figure 3.**

*Structure of sodium carboxymethylcellulose (repeating unit of glucose) shows the d-glucose units are linked through* β*-1, 4 bonds. ----O represents the continuation of the polymeric chain.*

#### **Figure 4.**

*Structure of hydroxyethylcellulose (repeating unit of glucose) shows the d-glucose units are linked through* β*-1, 4 bonds. ----O represents the continuation of the polymeric chain.*

Hydroxyethylcellulose (HEC) and its hydrophobically modified derivatives have been widely used in many industrial areas such as pharmaceuticals, cosmetics, textiles, paint and mineral industries including in oil extraction, coating, medication, food, and polymer polymerization. This was non-toxic and inexpensive. Despite this, only a few reports on HEC as a sulphide depressant have been published. The function of hydroxyethyl cellulose (HEC) in the flotation separation of chalcopyrite and galena has been investigated, and the explanation for this has been explained. In the presence of H2O2, a small amount of HEC can depress galena flotation but had only a negligible effect on chalcopyrite flotation. HEC was adsorbed on galena surfaces primarily through chemical reactions with oxidation products formed on the surface, and the addition of H2O2 can significantly improve HEC adsorption by producing further oxidation products. As a result, its research would be used as a galena depressant in the flotation separation of chalcopyrite and galena, as well as to propose a method for separating copper/lead sulphide minerals. Furthermore, HEC can be used as the stabilizer of beer foam [25–30].
