Utilization of microalgae in green context: Adsorptive removal of ionic contaminants from aqueous media and production of microalgal bioplastics

Microalgae are known for their remarkable growth rates and adaptation capabilities. In this study, microalgae were used as environmentally friendly materials for two different applications. The first part is focused on removal of dyes from aqueous media using microalgae as adsorbents. Nile blue, methylene blue, eriochrome black t, and congo red are used as model charged contaminants. Seven microalgae species were used either immobilized in hydrogels or in free forms. Two of best cationic dye adsorbing species, Chlorella and Scenedesmus were selected for further experiments. Effects of growth period and Ca2+ deprivation on dye removal was studied. In kinetic experiments employing Chlorella, pseudo-first order, pseudo-second order and intraparticle diffusion models were employed for the interpretation of resulting data. Langmuir, Freundlich and Temkin models were used to fit resulting adsorption isotherms. Moreover, FT-IR analysis was conducted on these microalgae before and after dye adsorption. In the second part, a type of cyanobacteria Spirulina-based biodegradable plastic films were prepared in different formulations by casting method. Films were characterized by tensile tests and zeta potential measurements. Spirulina was used in Spirulina/PVA blends in the absence or presence of several concentrations of microbial Transglutaminase as crosslinker. Spirulina was also tested as the single matrix with several concentrations of plasticizer and the enzyme. Additionally, proteins were extracted from Spirulina and films were prepared using this extract, modified or not modified with microbial Transglutaminase.