A new reactor design for harvesting algae through electrocoagulation-flotation in a continuous mode

Microalgae biomass, as a promising alternative feedstock, can be refined into biodiesel, pharmaceutical, and food productions. However, the harvesting process for quality biomass still remains a main bottleneck due to its high energy demand. In this study, a novel technique integrating alkali-induced flocculation and electrolysis, named salt-bridge electroflocculation (SBEF) with non-sacrificial carbon electrodes is developed to promote recovery efficiency and cost savings. The results show that the energy consumption decreased to 1.50 Wh/g biomass with a high harvesting efficiency of 90.4% under 300 mA in 45 min. The mean particle size of algae flocs increased 3.85-fold from 2.75 to 10.59 µm, which was convenient to the follow-up processing. Another major advantage of this method is that the salt-bridge firmly prevented cells being destroyed by the anode’s oxidation and did not bring any external contaminants to algal biomass and flocculated medium, which conquered the technical defects in electro-flocculation. The proposed SBEF technology could be used as a low cost process for efficient microalgae harvest with high quality biomass.

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“…The electrical energy consumption (in Wh/g biomass) of the SBEF process was calculated as Eq. 3 (Parmentier et al, 2020):…”

Section: Algae Analytical Methodsmentioning

confidence: 99%

A Novel Salt-Bridge Electroflocculation Technology for Harvesting Microalgae

Hou

Liu

et al. 2022

Front. Bioeng. Biotechnol.

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“…In flocculation methods, chemical compounds such as sodium hydroxide (NaOH), magnesium sulfate (MgSO 4 ), magnesium chloride (MgCl 2 ), calcium chloride (CaCl 2 ), sodium alginate (NaC 6 H 7 O 6 ), tannin, and other polymers can be used (Table 2). However, these can be combined to optimize the processes in the recovery of larger volumes of biomass [43,45,49]. In recent years, combined methods such as sedimentation-flocculation-coagulation, flocculationcentrifugation, and electrocoagulation-flotation have been used and show promise concerning cost and energy efficiency [43][44][45][46]49,50].…”

Section: Recent Advances In Harvesting Algae and Pretreatments For Th...mentioning

confidence: 99%

“…However, these can be combined to optimize the processes in the recovery of larger volumes of biomass [43,45,49]. In recent years, combined methods such as sedimentation-flocculation-coagulation, flocculationcentrifugation, and electrocoagulation-flotation have been used and show promise concerning cost and energy efficiency [43][44][45][46]49,50]. Moreover, natural (including EPS) and synthetic flocculating agents are applied in microalgal recovery [42,51].…”

Section: Recent Advances In Harvesting Algae and Pretreatments For Th...mentioning

confidence: 99%

Recent Advances of Microalgae Exopolysaccharides for Application as Bioflocculants

et al. 2022

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Microalgae are used in flocculation processes because biopolymers are released into the culture medium. Microalgal cell growth under specific conditions (temperature, pH, luminosity, nutrients, and salinity) provides the production and release of exopolysaccharides (EPS). These biopolymers can be recovered from the medium for application as bioflocculants or used directly in cultivation as microalgae autoflocculants. The optimization of nutritional parameters, the control of process conditions, and the possibility of scaling up allow the production and industrial application of microalgal EPS. Therefore, this review addresses the potential use of EPS produced by microalgae in bioflocculation. The recovery, determination, and quantification techniques for these biopolymers are also addressed. Moreover, other technological applications of EPS are highlighted.

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“…Electrocoagulation requires "sacrificial" reactive metal electrodes, which react with the medium to produce positively charged ions and induce coagulation by inactivating repulsive negative charges on the surface of microalgal cells [47]. These cations interact with hydroxyl radicals produced by the electric field to generate metal hydroxides, which adsorb to the cell surface and assist in forming flocs, which are finally lifted to the surface via hydrogen gas bubbles (created by H2O electrolysis) [48] or inducing the cells to move across the medium and aggregate on the cathode (positively-charged electrode) [40]. Compared with chemical coagulation, electrocoagulation has the environmental benefit of requiring no harsh chemical additives [47], and can outperform centrifugation in terms of biomass recovery [40]; however, the cost of single-use electrodes combined with the energy requirement can disqualify it from most large-scale applications on both environmental and economic grounds [49].…”

Section: Electrocoagulationmentioning

confidence: 99%