Study On Harvesting Behaviors Based On Algal Surface Features

Recently,consumption of energy increasing with the global economy grow up rapidly.Conventional fossil fuel cannot reach the normal demand for maintaining human society in the future,therefore exploiting sustainable and clean energy instead of fossil fuel has become a significant direction.Consequently,manufacturing the biofuel by microalgae has drawn lots of attention and become a promoting energy industry.However,one severe problem to use microalgae in commercial-scale manufacture is its high cost,especially in the harvesting period,which occupied 20~30% of the whole investment.This article took chlorella as an example,focused on the surfaces characters such as hydrophbicity,tension,contract angles,etc.Employing flocculation and flotation to explore main factors affected the harvesting recovery by single factor and orthogonal experiments.The main conclusion of this thesis are as follows:(1)Hydrophobicity was a significant factor influenced the recovery of microalgae flotation.The hydrophobicity raised substantially after adding surfactants.Surface tension of Chlorella was improved by applying surfactants and flocculation.Chlorella was a kind of hydrophilic microalgae by surface energy calculating and the energy barrier had a higher energy barrier under acidic condition.(2)Al2(SO4)3,FeCl3 and Ca(OH)2 had a great harvesting performance of Chlorella,Al2(SO4)3,and FeCl3 were the best.(3)The cationic surfactants(C16TAB,C14TAB),anionic surfactant(Rhamnolipid),nonionic surfactant(Tea Saponin)can increase the hydrophobicity of Chlorella,the C16 TAB and C14 TAB had a better effect.(4)Orthogonal experiments were employed to determine the optimum condition of microalgae harvesting.Results showed that the flocculation recovery rate of Chlorella could reach to 94.22% when the dosage of Al2(SO4)3 was 1.1g/L,pH was 8,dilution ratio was 4;the flotation recovery rate of Chlorella could reach to 96.09% when the dosage of C16 TAB was 80mg/L,pH was 9,airflow rate was 160L/h.(5)In the flocculation and flotation method,pH is a significant factor influencing harvest recovery of Chlorella.The experiments result indicated the higher recovery was obtained under alkaline condition.(6)The pseudo-first-order kinetic model was an appropriate method to describe the adsorption kinetics data of both surfactants C16 TAB and Saponin onto Chlorella vulgaris.Physical adsorption may the dominant direction in the adsorption process.(7)Freundlich model could be used properly to describe the isothermal process f both surfactants C16 TAB and Saponin onto Chlorella vulgaris and the adsorption configuration of C16 TAB and Saponin was multi-layer structure and spontaneous.The thermodynamic parameters of C16 TAB and Saponin and infrared characterization of Chlorella further indicated that hydrogen bond was possibly essence of the adsorption process.