Flotation technique is widely used to recover fine mineral particles, de-inking of recycled paper and to separate oil from water [20]. The recovery of particles (diameter: 1–10 µm) is inversely proportional to the bubble size. In conventional methods to generate bubbles such as agitated and sparged columns is too large [21]. Smaller and homogeneous gas bubbles of hydrogen and oxygen can be produced at the electrodes surface under the applied electric current in electroflotation process. Moreover, the concentration of gas bubbles can be controlled by varying the current density. Increased current density promotes collision among the bubbles, particles and oil drops which in turn affect the concentration of bubbles [22]. Electrode material and pH are the most significant parameters to control the bubble size and their distribution. It is reported that smallest hydrogen bubbles can be obtained at neutral pH; whereas oxygen bubbles size increases with pH [23]. Electroflotation is very efficient for separating oil from water or oil emulsions, textile and heavy metal as it is shown in Table 2.
Some researchers combined both electrocoagulation and electroflotation processes into a single system to treat various types of wastewater. Electrocoagulation occurs at the anodic side, where aluminum or iron anode dissolves to produce coagulant ions of Al3+ or Fe2+; while hydrogen evolves at the cathode side thus inducing the flotation process [24]. Current density is the most important parameter in such combined system since the dissolution of anode, generation of bubbles and size of the bubbles increase with increasing the current density [25]. Electrolyte conductivity, electrode arrangement and pH are the other influencing parameters of the combined system. Some experimental results of such combined system for treating textile and heavy metal containing wastewater and river water is tabulated in Table 2.
Flotation technique is widely used to recover fine mineral particles, de-inking of recycled paper and to separate oil from water [20]. The recovery of particles (diameter: 1–10 µm) is inversely proportional to the bubble size. In conventional methods to generate bubbles such as agitated and sparged columns is too large [21]. Smaller and homogeneous gas bubbles of hydrogen and oxygen can be produced at the electrodes surface under the applied electric current in electroflotation process. Moreover, the concentration of gas bubbles can be controlled by varying the current density. Increased current density promotes collision among the bubbles, particles and oil drops which in turn affect the concentration of bubbles [22]. Electrode material and pH are the most significant parameters to control the bubble size and their distribution. It is reported that smallest hydrogen bubbles can be obtained at neutral pH; whereas oxygen bubbles size increases with pH [23]. Electroflotation is very efficient for separating oil from water or oil emulsions, textile and heavy metal as it is shown in Table 2.Some researchers combined both electrocoagulation and electroflotation processes into a single system to treat various types of wastewater. Electrocoagulation occurs at the anodic side, where aluminum or iron anode dissolves to produce coagulant ions of Al3+ or Fe2+; while hydrogen evolves at the cathode side thus inducing the flotation process [24]. Current density is the most important parameter in such combined system since the dissolution of anode, generation of bubbles and size of the bubbles increase with increasing the current density [25]. Electrolyte conductivity, electrode arrangement and pH are the other influencing parameters of the combined system. Some experimental results of such combined system for treating textile and heavy metal containing wastewater and river water is tabulated in Table 2.
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