Effective harvesting of microalgae by coagulation–flotation

Xia, Ling; Li, Yinta; Huang, Rong; Song, Shaoxian

doi:10.1098/rsos.170867

Cited by 41 publications

(23 citation statements)

References 41 publications

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“…For high viscosity oils, the most viable solution is the transesterification of algae oil to its related fatty ester ("biodiesel"). Singh and Patidar [9], Xia et al [10] and Laamanen et al [11] have established that foam flotation as a microalgae harvesting technique offers better harvesting characteristics compared to other techniques and has significant added value beyond energy-efficient biomass recovery. Research efforts have concentrated on improving the techniques of microalgae harvesting, methods of oil extraction and the reaction conditions.…”

Section: Introductionmentioning

confidence: 99%

Biodiesel Production through Acid Catalyst In Situ Reactive Extraction of Chlorella vulgaris Foamate

et al. 2022

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A method of biodiesel production from the freshwater microalgae Chlorella vulgaris based on the conversion of the dewatered algal biomass from a foam column (“foamate”) was investigated. The foam column collected and concentrated the microalgae. The foam was generated by passing air through a pool of algae, to which a collector/surfactant cetyltrimethylammonium bromide (CTAB) had been added. To produce biodiesel, the resultant “foamate” was esterified in situ using sulfuric acid and methanol. The effect of reaction temperature (30–70 °C), reaction time (30–120 min) and methanol/oil molar ratio (100–1000), were examined in a single-stage extraction–transesterification experiment on biodiesel yield at concentration of the catalyst H2SO4/oil molar ratio of (8.5/1). The thermodynamics and kinetics of transesterification of the microalgae oil were also investigated. The maximum biodiesel yield (96 ± 0.2%) was obtained at a reaction temperature of 70 °C, a reaction time of 90 min and methanol/oil molar ratio of 1000/1. Reaction kinetic parameters were determined that fitted the experimental data at all temperatures. A reversible reaction with first order forward and second order backward kinetics were found to be a good match for the experimental results. The kinetic model fitted experiments well under various temperatures and methanol/oil mole ratios. Under the most suitable conditions of reaction temperature, reaction time and methanol/oil molar ratio, the apparent activation energy was found to be 18.7 kJ/mol and pre-exponential factor 51.4 min−1. The activation entropy (ΔS), change in Gibbs free energy (ΔG) and variation in activation enthalpy (ΔH) revealed that the transesterification reaction is endergonic and unspontaneous, while the endothermic nature of the reaction was confirmed by the positive value (16.6 kJ/mol) of the ΔH. The thermodynamic information and kinetic model reported here will provide valuable insight into the understanding of the in situ transesterification process from algae foamate to biodiesel.

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Section: Introductionmentioning

confidence: 99%

Biodiesel Production through Acid Catalyst In Situ Reactive Extraction of Chlorella vulgaris Foamate

et al. 2022

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“…Another study optimized the flotation technology by combining coagulation and flotation to obtain almost 100% biomass recovery. However, the cost of operation was still not favorable [ 9 ].…”

Section: Introductionmentioning

confidence: 99%

A review on chemical mechanism of microalgae flocculation via polymers

Pugazhendhi

Shobana²,

Bakonyi

et al. 2019

Biotechnology Reports

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“…It relies on the hydrophobic surface chemistry and when air bubbles are passed through the sample that bind to these surfaces brings about separation of cells into a foam at the surface. Enhanced flotation recovery of >98% has recently been reported by the combined use of Al 3+ as a coagulant combined with cetyltrimethylammonium bromide (CTAB) [54]. Economic assessment of these methods is ongoing.…”

Section: Froth Flotationmentioning

confidence: 99%

Key Targets for Improving Algal Biofuel Production

et al. 2021

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A number of technological challenges need to be overcome if algae are to be utilized for commercial fuel production. Current economic assessment is largely based on laboratory scale up or commercial systems geared to the production of high value products, since no industrial scale plant exits that are dedicated to algal biofuel. For macroalgae (‘seaweeds’), the most promising processes are anaerobic digestion for biomethane production and fermentation for bioethanol, the latter with levels exceeding those from sugar cane. Currently, both processes could be enhanced by increasing the rate of degradation of the complex polysaccharide cell walls to generate fermentable sugars using specifically tailored hydrolytic enzymes. For microalgal biofuel production, open raceway ponds are more cost-effective than photobioreactors, with CO2 and harvesting/dewatering costs estimated to be ~50% and up to 15% of total costs, respectively. These costs need to be reduced by an order of magnitude if algal biodiesel is to compete with petroleum. Improved economics could be achieved by using a low-cost water supply supplemented with high glucose and nutrients from food grade industrial wastewater and using more efficient flocculation methods and CO2 from power plants. Solar radiation of not <3000 h·yr−1 favours production sites 30° north or south of the equator and should use marginal land with flat topography near oceans. Possible geographical sites are discussed. In terms of biomass conversion, advances in wet technologies such as hydrothermal liquefaction, anaerobic digestion, and transesterification for algal biodiesel are presented and how these can be integrated into a biorefinery are discussed.

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Effective harvesting of microalgae by coagulation–flotation

Cited by 41 publications

References 41 publications

Biodiesel Production through Acid Catalyst In Situ Reactive Extraction of Chlorella vulgaris Foamate

Biodiesel Production through Acid Catalyst In Situ Reactive Extraction of Chlorella vulgaris Foamate

A review on chemical mechanism of microalgae flocculation via polymers

Key Targets for Improving Algal Biofuel Production

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