Electrocoagulation–flotation (ECF) for microalgae harvesting – A review

Visigalli, Simone; Barberis, Maria Giulia; Turolla, Andrea; Canziani, Roberto; Berden-Zrimec, Maja; Reinhardt, Robert M.; Ficara, Elena

doi:10.1016/j.seppur.2021.118684

Cited by 61 publications

(17 citation statements)

References 95 publications

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“…The cell damage happened when the microalgae cells remained in the pellet for a longer time with the compressive forces applied [63,64]. On the other hand, in microalgae harvesting operations through flocculants, it is possible to contaminate the harvested biomass as well as the processed water [65][66][67]. Coagulation-flocculation may reach a separation efficiency of 86-100% by utilizing the aluminum sulphate with the concentration from 20 to 180 mg Al L −1 [68,69] or ferric chloride with the concentration between 140-400 mg Fe L −1 [69,70].…”

Section: Suspended Microalgal Cultivationmentioning

confidence: 99%

“…Coagulation-flocculation may reach a separation efficiency of 86-100% by utilizing the aluminum sulphate with the concentration from 20 to 180 mg Al L −1 [68,69] or ferric chloride with the concentration between 140-400 mg Fe L −1 [69,70]. However, the inevitable release of the chemicals flowing through the processed water is the limitation, causing the harvested biomass to be contaminated as well as inhibiting photosynthesis and microalgae growth due to the residual chemicals [65][66][67]. In fact, the harvesting process will reduce the possibility of the water recycling to be used as the growth medium and its direct release into the environment [65,66].…”

Section: Suspended Microalgal Cultivationmentioning

confidence: 99%

“…However, the inevitable release of the chemicals flowing through the processed water is the limitation, causing the harvested biomass to be contaminated as well as inhibiting photosynthesis and microalgae growth due to the residual chemicals [65][66][67]. In fact, the harvesting process will reduce the possibility of the water recycling to be used as the growth medium and its direct release into the environment [65,66]. Moreover, Leong et al [71] proposed in their studies that a single processing unit involving the harvesting, cell disruption, and extraction of microalgae products based on Liquid Biphasic systems (LBs) are quite promising, especially for the microalgae bio-refinement and improving the techno-economic feasibility of microalgae cultivation.…”

Section: Suspended Microalgal Cultivationmentioning

confidence: 99%

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Assuaging Microalgal Harvesting Woes via Attached Growth: A Critical Review to Produce Sustainable Microalgal Feedstock

et al. 2021

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Third-generation biofuels that are derived from microalgal biomass have gained momentum as a way forward in the sustainable production of biodiesel. Such efforts are propelled by the intention to reduce our dependence on fossil fuels as the primary source of energy. Accordingly, growing microalgal biomass in the form of suspended cultivation has been a conventional technique for the past few decades. To overcome the inevitable harvesting shortcomings arising from the excessive energy and time needed to separate the planktonic microalgal cells from water medium, researchers have started to explore attached microalgal cultivation systems. This cultivation mode permits the ease of harvesting mature microalgal biomass, circumventing the need to employ complex harvesting techniques to single out the cells, and is economically attractive. However, the main bottleneck associated with attached microalgal growth is low biomass production due to the difficulties the microalgal cells have in forming attachment and populating thereafter. In this regard, the current review encompasses the novel techniques adopted to promote attached microalgal growth. The physicochemical effects such as the pH of the culture medium, hydrophobicity, as well as the substratum surface properties and abiotic factors that can determine the fate of exponential growth of attached microalgal cells, are critically reviewed. This review aims to unveil the benefits of an attached microalgal cultivation system as a promising harvesting technique to produce sustainable biodiesel for lasting applications.

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Section: Suspended Microalgal Cultivationmentioning

confidence: 99%

Section: Suspended Microalgal Cultivationmentioning

confidence: 99%

Section: Suspended Microalgal Cultivationmentioning

confidence: 99%

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Assuaging Microalgal Harvesting Woes via Attached Growth: A Critical Review to Produce Sustainable Microalgal Feedstock

et al. 2021

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“…Aside from increased efficiency and control over the flocculation process [10], Mollah et al [11] reported the following as benefits of electrocoagulation over the conventional chemical coagulation process: less sludge, total dissolved solids (TDS), and chemical residual in the effluent; larger and more stable flocs; easy collection of flocs; less maintenance; and minimal risk of secondary pollution. It is owing to these benefits that electrocoagulation as a method of harvesting microalgae is gaining popularity in the biomass production industry.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Pb, Mg, Al, Zn, and Cu as Electrode Materials in the Electrocoagulation of Microalgae

Phiri

Pak

et al. 2021

Processes

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Apart from the conventionally used iron (Fe) and aluminum (Al) electrodes in microalgae harvesting, experiments were designed to examine the viability of lead (Pb), magnesium (Mg), zinc (Zn), and copper (Cu) as electrode materials in the harvesting of microalgae. The effect of voltage on the flocculation efficiency (FE) of the electrode materials was examined and compared. By dividing the optimal FE values by their corresponding periods, a simple yet practical approach was used to rank the electrode materials. From highest to lowest flocculation efficiency, the results were as follows: Cu, Zn, Mg, Al, and Pb at 10 V; Mg, Zn, Cu, Al, and Pb at 20 V; and Mg, Zn, Al, Cu, and Pb at 30 V. Important factors such as temperature, periodic FE, consumption of electrode material, pH, and metallic concentrations in the effluent were evaluated. The temperature increase proposed to have been affected by electric resistance drop and anodic corrosion, between 1.7 °C and 3.3 °C, 5 °C and 8.9 °C, and 10.5 °C and 18.4 °C was recorded at 10 V, 20 V, and 30 V respectively. Except for the supernatants of the experiments from Al electrodes, which remained relatively unaffected by voltage and time, the pH of all the other supernatants increased with time and voltage. The effluents recorded metallic concentrations between 0.513 mg/L and 43.8 mg/L for Pb, 7.02 mg/L and 20.5 mg/L for Mg, 1.34 mg/L and 9.09 mg/L for Al, 0.079 mg/L and 0.089 mg/L for Zn, and 0.252 mg/L and 0.434 mg/L for Cu electrodes.

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“…After bioremediation, the algal biomass must be separated from the treated effluent and ideally valorized as raw material for fuels and/or specialty chemicals. Separation of the algal biomass has been studied using membrane technology [6], electrocoagulation [7,8], radiofrequency [9], and coagulation with polymers [10], but these techniques involve complex equipment and additional costs that are compatible only with large scale systems with the subsequent valorization of the algal biomass in multiple applications. A possible alternative is the decantation of the sedimented biomass, in the form of an algal sludge that can be further dried or mixed with other biomass feedstocks to be used in energy or material applications.…”

Section: Introductionmentioning

confidence: 99%

Optimization of Biochar Production by Co-Torrefaction of Microalgae and Lignocellulosic Biomass Using Response Surface Methodology

Viegas

Nobre²,

Correia

et al. 2021

Energies

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Co-torrefaction of microalgae and lignocellulosic biomass was evaluated as a method to process microalgae sludge produced from various effluents and to obtain biochars with suitable properties for energy or material valorization. The influence of four independent variables on biochar yield and properties was evaluated by a set of experiments defined by response surface methodology (RSM). The biochars were characterized for proximate and ultimate composition, HHV, and methylene blue adsorption capacity. HHV of the biochars was positively correlated with carbonization temperature, residence time, and lignocellulosic biomass content in the feed. Co-torrefaction conditions that led to a higher yield of biochar (76.5%) with good calorific value (17.4 MJ Kg−1) were 250 °C, 60 min of residence time, 5% feed moisture, and 50% lignocellulosic biomass. The energy efficiency of the process was higher for lower temperatures (92.6%) but decreased abruptly with the increase of the moisture content of the feed mixture (16.9 to 57.3% for 70% moisture). Biochars produced using algal biomass grown in contaminated effluents presented high ash content and low calorific value. Dye removal efficiency by the produced biochars was tested, reaching 95% methylene blue adsorption capacity for the biochars produced with the least severe torrefaction conditions.

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Electrocoagulation–flotation (ECF) for microalgae harvesting – A review

Cited by 61 publications

References 95 publications

Assuaging Microalgal Harvesting Woes via Attached Growth: A Critical Review to Produce Sustainable Microalgal Feedstock

Assuaging Microalgal Harvesting Woes via Attached Growth: A Critical Review to Produce Sustainable Microalgal Feedstock

Evaluation of Pb, Mg, Al, Zn, and Cu as Electrode Materials in the Electrocoagulation of Microalgae

Optimization of Biochar Production by Co-Torrefaction of Microalgae and Lignocellulosic Biomass Using Response Surface Methodology

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