Electroflotation extraction of carbon material powders in the presence of metal ions

Abstract

Emitted or insufficiently purified waste water from the most of enterprises, as well as production wastes of minerals development in mining plants, water from mines and pits are considered as the main sources of contamination of water basins. Inorganic and organic compounds, nonferrous metals ions are presented in waste water of electroplating-chemical production; they should be extracted using the modern methods. Sorption extraction of harmful components from waste water with various compositions has especial interest owing to its acceptability and absence of secondary contaminations. Activated coals (AC) are widely used in different scientific branches as carbon sorbents; among other applications, they are used in technological processes of adsorption purification, separation, extraction and concentration of various substances in gaseous and liquid media [1–5]. Waste water processing by carbon sorbent directly in the volume of processed liquid is one of the efficient methods of water purification [6–10]. However, use of this method is complicated due to the problems of consequent carbon sorbent separation from purified water. Analysis of technical literary sources displayed that sedimentation and filtration, mainly combined with coagulation and flocculation, are the main methods for carbon material separation from purified water; sediment tanks, tissue filters and membrane systems are used rarely. Retention is the most simple method for separation of fine-comminuted active coal from liquid phase. However, it is used very rarely due to its large duration (more than two hours). Forming of large and dense flakes during additional introduction of flocculants and coagulants in solution has a serious influence on particles deposition in the process of sedimentation [11]. Coagulant concentration in purification plants at large production facilities can reach in this case the range from 1 g/m3 [8] to 10 g/m3 [7, 12]. The effect of coagulant nature on the process efficiency is noted in the work [13]. Filtration is also used for coal separation from purified liquid. This method has several disadvantages, such as necessity of often replacement and regeneration of filtering materials, selection of filters for different sizes of particles. It is known from the technical literature that flotation method can be used for extraction of carbon materials, i.e. using various organic additives [14, 15]. However, it was established that extraction of carbon material via flotation is restricted sue to application of high coagulant concentrations or organic additives; at the same time, extraction degree of activated coal particles does not reach high values. Electroflotation extraction of carbon material powders in the presence of metal ions