Synergy of flocculation and flotation for microalgae harvesting using aluminium electrolysis

Shi, Wenqing; Zhu, Lin; Chen, Qiuwen; Ji, Lu; Pan, Gang; Hu, Liang; Qian, Yi

doi:10.1016/j.biortech.2017.02.084

Cited by 40 publications

(16 citation statements)

References 43 publications

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“…Optimal conditions for electrochemical harvesting of C. vulgaris were reported to be aluminum electrodes, 60 min treatment with 2.9 mA/cm 2 of current density, pH 4, stirring speed of 250 rpm, and an inter-electrode distance of 1 cm. Compared with the cases for aluminum, the algae harvesting performance using iron electrodes was generally lower due to the low current efficiency [129,135]. The flocculation capability of iron hydroxide formed from the iron electrode was also lower than that of the aluminum hydroxide formed from an aluminum electrode [136].…”

Section: Sacrificial Electrodementioning

confidence: 94%

“…This was clearly observed when the current density was increased from 2.2 to 6.7 mA/cm 2 during ECF processing of C. vulgaris with considerably decrease in processing time from 7 to 4 min. The energy consumption under the reduced current density was estimated to be 2.94 × 10 −4 kWh/g biomass [129]. Fayad et al [127] compared aluminum and iron electrodes in batch mode harvesting of C. vulgaris.…”

Section: Sacrificial Electrodementioning

confidence: 99%

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Flocculation Harvesting Techniques for Microalgae: A Review

et al. 2019

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Microalgae have been considered as one of the most promising biomass feedstocks for various industrial applications such as biofuels, animal/aquaculture feeds, food supplements, nutraceuticals, and pharmaceuticals. Several biotechnological challenges associated with algae cultivation, including the small size and negative surface charge of algal cells as well as the dilution of its cultures, need to be circumvented, which increases the cost and labor. Therefore, efficient biomass recovery or harvesting of diverse algal species represents a critical bottleneck for large-scale algal biorefinery process. Among different algae harvesting techniques (e.g., centrifugation, gravity sedimentation, screening, filtration, and air flotation), the flocculation-based processes have acquired much attention due to their promising efficiency and scalability. This review covers the basics and recent research trends of various flocculation techniques, such as auto-flocculation, bio-flocculation, chemical flocculation, particle-based flocculation, and electrochemical flocculation, and also discusses their advantages and disadvantages. The challenges and prospects for the development of eco-friendly and economical algae harvesting processes have also been outlined here.

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Section: Sacrificial Electrodementioning

confidence: 94%

Section: Sacrificial Electrodementioning

confidence: 99%

Flocculation Harvesting Techniques for Microalgae: A Review

et al. 2019

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“…5B) due to the use of non-sacrificial electrodes, which differs with the decrease of phosphate concentration by electrolysis using Fe/Al electrodes. 41,42 Hence, nutrient bioavailability increase and other parameter stability (Fig. 5B, Table S2) make medium reusable for microalgae continuous culture.…”

Section: Recommendations For Future Applicationsmentioning

confidence: 99%

Sustainable Harvesting of Microalgae by Coupling Chitosan Flocculation and Electro-Floatation

Zhu¹,

Xu²,

Guo³

et al. 2020

Preprint

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<a></a>In this study, we proposed a new method for edible microalgae harvesting by coupling chitosan flocculation and electro-floatation using carbon electrodes, and tested it at different operation conditions. The surface charge of microalgae cells was measured to explore the underlying mechanisms. The responses of growth medium to microalgae harvesting were also investigated to evaluate the feasibility of sustainable utilization of culture medium. (1) Microalgae harvesting efficiencyThe microalgae harvesting efficiency of the proposed method were tested using Chlorella vulgaris (C. vulgaris). C. vulgariscells (FACHB-24) were purchased from the Institute of Hydrobiology, Chinese Academy of Sciences, and cultured in the BG11 medium, which consists of 500 mg L-1 Bicin, 100 mg L-1 KNO3, 100 mg L-1 b-C3H7O6PNa2, 50 mg L-1 NaNO3, 50 mg L-1Ca(NO3)2•4H2O, 50 mg L-1 MgCl2•6H2O, 40 mg L-1 Na2SO4, 20 mg L-1 H3BO3, 5 mg L-1 Na2EDTA, 5 mg L-1 MnCl2•4H2O, 5 mg L-1 CoCl2•6H2O and 0.8 mg L-1 Na2MoO4•2H2O, 0.5 mg L-1 FeCl3•6H2O and 0.5 mg L-1 ZnCl2. The batch cultures were conducted in an illuminating incubator (LRH-250-G, Guangdong Medical Apparatus Co., Ltd., China) with continuous cool white fluorescent light of 2500 ± 500 lux on a 12 h light and 12 h darkness regime at the temperature of 30 ± 1°C.The microalgae harvesting efficiency system consists of a flat stir paddle <a></a><a></a>(Zhongrun Water Industry Technology Development Co., Ltd., China) for mixing during chitosan flocculation and two round carbon electrode plates (Jinjia Metal Co., Ltd., China) for electro-floatation. The carbon electrode plate has a surface area of 55.4 cm2 and a thickness of 0.2 cm, which was horizontally installed at the bottom with a gap of 2 cm between the two plates. There are 85 small round holes on each carbon electrode plate to allow gas bubbles freely pass it during electrolysis, such that the effective surface area was 38.7 cm2. The electric current was supplied by a direct current power supply (DF1730SL5A, Ningbo Zhongce Dftek Electronics Co., Ltd., China). C. vulgaris culture at the exponential growth phase was used in the microalgae harvesting test. The initial cell concentration was set to 3.63 × 1010 cells L-1. 0.5 L of readily prepared C. vulgaris solution was transferred to the harvesting cell. Water-soluble chitosan was purchased from Qingdao Yunzhou Bioengineering Co. Ltd., China. Prior to the test, a chitosan stock solution (2 g L-1) was prepared as follows: 1 g chitosan was added to 0.5 L distilled water and completely diluted by stirring. After chitosan was added, the microalgae solution was stirred at 200 rpm for 2 min and 40 rpm for another 10 min; electro-floatation was started in the last 5 min during chitosan flocculation. The microalgae solution was allowed to stand for 10 min, and then water samples were carefully collected from an outlet 2 cm above the carbon electrode plate to enumerate the cell number using an Axioskop 2 mot plus microscope (Carl ZEISS, Germany). The microalgae harvesting efficiency was calculated as (initial cell concentration-sample cell concentration)/initial cell concentration × 100%. In the test, the chitosan dosage was set to 0, 2, 4, 6, 8, 10, 12 and 15 mg L-1, and the current density was set to 0, 0.2, 0.4 and 0.6 A. All the tests were conducted in triplicate at the raw microalgae solution pH of 8.6.(2) Surface charges of chitosan, microalgae cells and microalgae flocsThe surface charges of chitosan, microalgae cells and microalgae flocs were characterized using a Zetasizer 2000 (Malvern Co. United Kingdom). (3) Sustainable utilization of microalgae culture mediumBefore and after microalgae harvesting, medium nutrients (phosphate, ammonium and nitrate) were measured according to Chinese Monitoring Analysis Method of Water and Wastewater; medium pH and temperature were measured using a Yellow Springs Instruments (Yellow Springs, Ohio, USA)(4) Cost evaluationThe cost of microalgae harvesting was estimated by summing flocculants and energy costs per unit of harvested microalgae biomass. The chitosan and electric power are 0.03 USD g-1 and 0.08 USD (kWh)-1, respectively.

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“…However, yeast, pollen or chlorella are industry products or popular tonic food with relative limited yield and high prices. In contrast, harvesting HABs is becoming feasible as cost-effective technologies developed 28 and HABs is conventionally treated as hazardous waste with little values. Therefore, the use of cyanobacteria as the raw material for the production of hollow porous microspheres is preferable in terms of cost.…”

Section: Introductionmentioning

confidence: 99%

From harmful Microcystis blooms to multi-functional core-double-shell microsphere bio-hydrochar materials

Pan

2017

Sci Rep

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Harmful algal blooms (HABs) induced by eutrophication is becoming a serious global environmental problem affecting public health and aquatic ecological sustainability. A novel strategy for the utilization of biomass from HABs was developed by converting the algae cells into hollow mesoporous bio-hydrochar microspheres via hydrothermal carbonization method. The hollow microspheres were used as microreactors and carriers for constructing CaO2 core-mesoporous shell-CaO2 shell microspheres (OCRMs). The CaO2 shells could quickly increase dissolved oxygen to extremely anaerobic water in the initial 40 min until the CaO2 shells were consumed. The mesoporous shells continued to act as regulators restricting the release of oxygen from CaO2 cores. The oxygen-release time using OCRMs was 7 times longer than when directly using CaO2. More interestingly, OCRMs presented a high phosphate removal efficiency (95.6%) and prevented the pH of the solution from rising to high levels in comparison with directly adding CaO2 due to the OH− controlled-release effect of OCRMs. The distinct core-double-shell micro/nanostructure endowed the OCRMs with triple functions for oxygen controlled-release, phosphorus removal and less impact on water pH. The study is to explore the possibility to prepare smarter bio-hydrochar materials by utilizing algal blooms.

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Synergy of flocculation and flotation for microalgae harvesting using aluminium electrolysis

Cited by 40 publications

References 43 publications

Flocculation Harvesting Techniques for Microalgae: A Review

Flocculation Harvesting Techniques for Microalgae: A Review

Sustainable Harvesting of Microalgae by Coupling Chitosan Flocculation and Electro-Floatation

From harmful Microcystis blooms to multi-functional core-double-shell microsphere bio-hydrochar materials

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