Effect of different flocculants on the flocculation performance of microalgae, Chaetoceros calcitrans, cells. Afr J Biotechnol 8:5971-5978

AFRICAN JOURNAL OF BIOTECHNOLOGY (Impact Factor: 0.57). 11/2009; 8(21):5971-5978.


The possibility of using flocculation technique for the separation of microalgae, Chaetoceros calcitrans, biomass from the culture broth was investigated. The flocculation experiments were conducted in 500 mL beaker using culture broth obtained from 10 L photobioreactor. The harvesting efficiency of 90 and 60% was obtained in flocculation without flocculants conducted for 10 days at 27°C (in light and dark) and 4°C (dark), respectively. Harvesting efficiency higher than 90% with short settling time was achieved by adjusting the culture pH to 10.2 using either sodium hydroxide (NaOH) or potassium hydroxide (KOH). Improved cell viability (> 80%) and settling time with a slight improvement of flocculation efficiency was achieved by the addition of polyelectrolytes flocculant (Magnafloc® LT 27 and LT 25). However, the flocculants were only functioned when the pH of the microalgae culture was pre-adjusted to a certain value that promotes cells entrapment and surface charge neutralization prior to flocculation process. The flocculation efficiency and cell viability obtained in flocculation with Magnafloc® (LT 25 and LT 27) was comparable to that obtained in flocculation with chitosan. When chitosan and Magnafloc® (LT 25 and LT 27) were used as flocculants, the highest flocculation efficiency of C. calcitrans cells was observed at pH 8 and 10.2, respectively. Substantial increased in sedimentation rate was observed with increasing flocculants dosage though the flocculation efficiency and cell viability were not significantly varied. © 2009 Academic Journals. Cited By (since 1996): 2, Export Date: 14 June 2011, Source: Scopus

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    • "The very perspective approach to microalgae recovery is by using industrial coagulants and flocculants, agents that are used for fresh water (Harith et al., 2009) or wastewater treatment (Jiang, 2015). These agents have different uses according to their roles. "
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    ABSTRACT: The effects of coagulant (FeCl3·6H2O), various flocculants based on polyacrylamide (PAA), polyethylenoxide (PEO) and flocculated biomass as ballast agent, dosage and sedimental time on flocculation efficiency of harvesting Chlorella vulgaris GKV1 cultivated in a laboratory were investigated. The results of this work indicated that the flocculation efficiency achieved about 90% after 5min of sedimentation when adding of coagulant and flocculant mixture (FeCl3 50mg/l+PEO based Sibfloc-718 7.5mg/l) or flocculant with ballast agent (Sibfloc-718 7.5mg/l+10% flocculated biomass). PAA and PEO showed good flocculation efficiency at dosage of 0.025 and 0.015g/l, respectively without pH adjustment. Finally, the most suitable flocculation method was discussed in this paper. Copyright © 2015 Elsevier Ltd. All rights reserved.
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    • "The incubation time was 30 min in all experiments anionic flocculants only after algal surface charge neutralization by pH adjustments. The application of flocculant LT25 and LT 27 at a pH of 10.2 with the microalgae Chaetoceros calcitrans resulted in flocculation efficiencies above 90 % (Harith et al. 2009). The increase of pH before flocculation might improve FE, but negatively affect media recycling and thereby cost-effectiveness. "
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    ABSTRACT: Although microalgae show a great potential in the biotechnology sector, high production costs have limited industrial applications. Biomass harvest is one of the major bottlenecks in microalgae cultivation due to high energy inputs which are needed to separate the cells from the surrounding media. Chemical flocculation is considered to be a reliable resource to improve cost-effectiveness in the downstreaming processing. Flocculation efficiency is dependent on several factors such as the polymer type and charge as well as on the microalgae species. In the present study, 15 polyelectrolytes were tested for their potential to harvest algal biomass. Cationic, anionic and nonionic flocculants were tested in different amounts at varying incubation times to determine the adequate conditions needed. By testing the three chlorophytes, Chlorella sp., Scenedesmus acuminatus and Chlamydomonas reinhardtii, the influence of different sizes, morphologies and motilities of the flocculation efficiency was verified. Furthermore, the biocompatibility of an efficient flocculant was tested in a recycling experiment over a period of 8 weeks.
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    • "Conventionally, flocculants are classified as very low, low, medium, high, or very high molecular weight and are also characterized based on their ionic nature as cationic, anionic or non-ionic [7]. These polymers have proven to be efficient and economically viable for the flocculation of the diatom Chaetoceros calcitrans [8]. However, there is a need for studies to evaluate the efficiency of flocculants applied to other microalgae species with greater commercial interest and especially to marine species due to the problems caused by saltwater during the flocculation process. "
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    ABSTRACT: The harvesting of microalgae is currently one of the bottlenecks hindering the commercial production of microalgae-based biofuels and products. The objective of this study was to determine the best flocculant and its optimum concentration in order to harvest the marine microalga Conticribra weissflogii (previously Thalassiosira weissflogii) for further use in the production of biofuels or bioelements. Experiments were conducted with cultures in the logarithmic and stationary growth phases. The low-charge FLOPAM® FO 4240 SH was the most effective at concentrations of 2 and 4 mg m−3 in the LOG phase cultures, with flocculation efficiencies >90%. Smaller flocculation efficiencies were observed for cells in the stationary growth phase, most likely due to the production of dissolved organic carbon by the microalga. The highest microalgae density generated higher flocculation rates, whereas the pH and salinity negatively impacted flocculant efficiency.
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