Adsorption of cationic dyes from aqueous solution onto modified nanocellulose reinforced porous bio based polyurethane hybrid composites

In this study polyurethane (PU) based porous composites were synthesized by using the biobased polyol derived from chaulmoogra and grape seed oils. These polyols were used for the preparation of porous PU composites using methylene diphenyl diisocyanate as hard segment and polyethylene glycol (PEG6000) as soft segment with 1,4-diazabicyclo[2, 2, 2]octane (DABCO) as catalyst. Swelling ratio of the PU were analyzed by using water, salt, acid and base buffers. Nanocellulose prepared from moringa olifera seed pods were modified (aminated, carboxylated and phosphorylated) and were added as fillers (1, 3, and 5 weight %) to obtain porous polyurethane composites. The prepared samples were also characterized by using XRD, SEM, FT-IR, along with other physical and chemical methods. The SEM results show the nanofibrillation of cellulose and closed cell porosity in polyurethane. The strength of nanocellulose filled polyurethane composites (mNC-PU) increased with the increase in the mNC-content. Using the obtained mNC as filler, porous polyurethane composite with good adsorption capacity were prepared, and were used for the adsorption of Indigo carmine (IC), Rhodamine-B(Rh-D) and mixed (binary) dye system. The experimental process parameters optimization was carried out using Box Behnken Design. The predicted and the experimental percentage of dye removal were found to be in good agreement with a maximum of experimental percentage dye removal being in the range of 85 to 94 % for both IC dye and Rh-D dye individually and from mixed dye system. The coefficient of determination value and adjusted coefficient of determination value indicated that the model had significant fit. An increase in pH was found to increase the sorption capacities of the porous polyurethane towards the dyes. Maximum adsorption was found in the higher pH range of 9–12.