# Microalgal Biomass Generation via Electroflotation: A Cost-Effective Dewaring Technology
## 5 Electroflotation-Facilitated Dewatering for Microalgal Biomass Generation
### Factors Affecting the Performance of Electroflotation-Based Microalgal Dewatering Process
#### 5.2.2 Electrode Characteristics  
For an efficient electroflotation system, attention must be accorded to the electrode-related characteristics such as the material of construction, polished state of the surface, electrode number, and configuration, geometry, and size [77]. The electrodes are the major site of reactions and can be classified as either anode, where oxidation reactions occur, or cathode, where reduction reactions occur as shown in Figure 2. It is, thus, important that the selected electrode is effective and cheap [81]. Diverse materials such as aluminum (Al), iron (Fe), zinc (Zn), copper (Cu) as anodes and stainless steel, carbon/graphite (C), titanium (Ti) alloys like iridium oxide/titanium dioxide (IrO\({}_{2}\)/TiO\({}_{2}\)), titanium/iridium oxide (Ti/IrO\({}_{2}\)), and titanium/rubidium oxide (Ti/RbO\({}_{2}\)) as cathodes have been used and each affected bubble characteristics and the performance of the electroflotation process differently as mentioned in Table 6. Many studies have found that under similar experimental conditions, using Al as an anode outperforms Fe in terms of quantity of dewatered and harvested microalgae. For instance, [PERSON] et al. (2011) investigated the use of either Al or Fe as anode in combination with Ti alloy (IrO\({}_{2}\)/TiO\({}_{2}\)) as the cathode and found that Al was more efficient than Fe as an electrode in both freshwater (_Chlorella vulgaris_) and marine microalgae (_Phaeodactylum tricornutum_) dewatering processes [73]. These observations were ascribed to reasons such as conductivity and floc formation from the destabilization of negatively charged microalgae via charge neutralization, that occurs more efficiently for Al than Fe. Since the cathodes are inert, they are the major site for bubble generation via H\({}_{2}\) production in electroflotation. However, extensive research that performs bubble size measurements arising from electrolysis using different electrode materials has been undertaken in diverse fields other than in microalgae dewatering and generations [67]. Regardless of this fact, the operating principles are the same and as such key findings in those studies will be drawn on to make a case in this instance. Consequently, [PERSON] et al. (1991) generated bubbles of different sizes with platinum (Pt) and stainless-steel plates and found that the latter yielded the finest bubble sizes (diameter: 22-34 um) [82]. Moreover, the least measured bubble size generated by electroflotation process is 17 um and was obtained for both H\({}_{2}\) (with either platinum (Pt) or Fe electrode) [74] and O\({}_{2}\) (with graphite electrode) [83]. Studies have shown a connection between the diameter of the microbubbles and the polished state, either smooth or roughness of the electrode surface; where the current increases led to smaller bubble generation for the rough surface and vice versa for the smooth surface [84]. A similar relationship between the quantity of microbubbles generated and the size of the electrode surface has also been reported [85]. For instance, lesser electrolysis time was required to achieve over 90% microalgae recovery efficiency with No. 30 mesh (diameter = 0.6 mm) than with No. 10 mesh (diameter = 2 mm) stainless-steel cathode [68]. The authors reasoned that more microbubble generation coupled with faster detachment from the smaller sized electrode surface led to an increase in hydrogen and microalgae cells collisions thus yielding better microalgae removal efficiencies [68]. Though electrode configuration effect on electroflotation has been extensively studied in other fields, it has received less attention in microalgae dewatering applications [86]; although it can alter the distribution of microbubbles. For microalgae dewatering using electroflotation, both batch and continuous laboratory-scale setups have largely been undertaken with vertically placed electrode plate configurations (Table 6) [73; 78; 79]. A perforated-plate type electrode has been used [17].