Cellulose extraction from Cladophora rupestris for extraction of nanomaterials

Abstract Cellulose from macroalgae is potential for the extraction of nanomaterials due to its availability and its great fraction in the biomass. Cladophora rupestris is a macroalgae and is a good material to which a cellulose may be extracted. The said macroalgae has no value-added products or uses yet. It has a lignocellulosic profile of: alpha-cellulose, 33.43 %; hemicellulose, 15.48%; holocellulose, 48.93; acid soluble lignin, 2.22%; acid insoluble lignin, 22.33%, extractives, 5.67% and total ash, 39.65%. Identifying the best method and conditions for the extraction of cellulose from the said material is a challenge that needs to be addressed. The process for the cellulose extraction considered variations on drying (oven, air, and sun drying), defatting (using solvents: methanol and hexane; and extraction time: 8 hrs and 4 days), solvent drying (oven and air drying), alkaline pre-treatment (0.1, 0.5, and 1M NaOH), fixed conditions on bleaching, bleached biomass oven drying. The biomass weight losses were monitored for some steps, attributing this on the removal of the lignin and extractives. The lignocellulosic profile of the crude cellulose extracted from the macroalgae using the best conditions was determined indicating an increased fraction of the cellulose components in the biomass and a transformation of the rigid biomass into a soft and paper-like texture. The functional groups present on the cellulose was determined. The extracted cellulose was used to produced cellulose nanofibril (CNF) with fiber diameter of the CNF ranges on 14.29 – 37.50 nm and crystallinity index of 92.48%. Attempts were done on extraction of cellulose nanocrystal (CNC) utilizing microwave-assisted acid hydrolysis (MAAH) and semi-batch acid hydrolysis (SBAH); and variation on the acid used (sulfuric acid, and oxalic acid), concentration of the acid, and the temperature conditions.