Harvesting Nannochloropsis oculata by Chitosan and AlCl 3 -Induced Flocculation: Effects of Microalgal Condition on Floc
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Harvesting Nannochloropsis oculata by Chitosan and AlCl3-Induced Flocculation: Effects of Microalgal Condition on Flocculation Performance Quan Wang 1 & Kazuyuki Oshita 1 & Masaki Takaoka 1 Received: 29 June 2020 / Accepted: 1 October 2020 # Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Flocculation showed the potential for harvesting microalgae at a low cost. The inorganic flocculant (AlCl3) and organic flocculant (chitosan) are two representative and common flocculants, which were suited for different conditions (pH, salinity, and cell density). To investigate the effects of the three factors on the flocculation performance of the two flocculants, especially for the interaction effects among these factors, single-factor experiments and response surface methodology (RSM) were conducted. The results indicated that AlCl3 performed better under alkaline conditions, whereas chitosan showed better performance at acidic pH. Salinity had little influence on the flocculation efficiency (FE) of AlCl3. By contrast, increasing salinity reduced the FE of chitosan, especially above 8.4 g/L. As cell density increased, the optimal dosage of AlCl3 increased to a constant ~ 26 g/L. In contrast, the optimal dosage of chitosan continuously increased within the studied range. Also, RSM revealed significant interaction effects of [salinity][cell density] for AlCl3, due to which AlCl3 showed a good flocculation performance under either high cell density or high salinity conditions but poor with both high together. Significant interaction effects of [salinity][cell density] for chitosan was observed, and one of the two factors hence alleviated the negative influence from the other. Considering their performance under the different condition and the interaction effects, dual flocculation with AlCl3 + chitosan on multiplex conditions was evaluated, and the results indicated that higher FE with wider applicability could be achieved with lower dosages of the dual flocculant compared with utilization of the two flocculants individually under most of the conditions. Keywords Cell density . pH . Salinity . Microalgal biomass . Response surface methodology
Introduction Fossil fuel contributes to nearly 80% of global energy consumption, and its use results in the release of huge amounts of greenhouse gases into the atmosphere [1, 2]. To meet the growing energy demand with less CO2 discharge, various types of renewable energy have been explored, and biofuel, including biodiesel and bio-solid fuel produced from microalgae, has attracted a great deal of attention over the last Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12155-020-10201-z) contains supplementary material, which is available to authorized users. * Kazuyuki Oshita [email protected] 1
Department of Environmental Engineering, Graduate School of Engineering, Kyoto University, Cluster C, Kyoto Daigaku-Katsura, Nishikyo-ku, Kyoto 615-8540, Japan
few decades because of its rapid growth rate
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