Characterisation of in-situ modified bacterial cellulose using 2-acetyl-1-pyrroline

Abstract

Bacterial cellulose (BC) is a biopolymer with high purity of cellulose andexcellent mechanical properties. Increased interest in the use of natural polymermakes BC as an excellent alternative for plant cellulose. Furthermore, themorphology and properties of BC can be easily altered by incorporation withadditives that are not specifically required for the growth of the bacteria infermentation media. This unique property of BC opens a new gate for developmentof new cellulose composites with desired properties by incorporation of selectivesuitable materials. In this research, bacterial cellulose-pyrroline (BC-P) compositeswere developed where BC was modified using in-situ technique. 2-acetyl-1-pyrroline from Pandanus amaryllifolius (pandan) was added into the fermentationmedium of BC at five different concentrations. The impact on the characteristics ofBC-P composites produced and their performance in hexavalent chromium (Cr (VI))removal from aqueous solution of Cr (VI) were studied. The results showed that theincrease of 2-acetyl-1-pyrroline concentration from 0 to 13 mg/L in the mediumresulted in the increase of wet weight from 18.41 g to 45.85 g and dry weight from1.31 g to 4.75 g. The physicochemical properties of BC-P composites producedwere studied. For microstructure study using field emission scanning electronmicroscopy analysis, all composites showed similar interwoven organized fibrilsnetwork. Small particles of pyrroline could be seen on the fibrils surface where theparticles number increased with the increase of 2-acetyl-1-pyrroline concentration.Mechanical testing revealed that high concentration of 2-acetyl-1-pyrroline gavebetter tensile strength of BC-P up to 48.20 MPa with crystanillity of 85.27%.Adsorption experiments with aqueous solution of Cr (VI) were carried out where theresults showed proportional removal of Cr (VI) from 58.65% to 83.06% withincrease of 2-acetyl-1-pyrroline concentration. Several factors were studied to obtainsuitable parameter for the adsoption process. In comparison to native BC, BC-Pcomposites had succesfully achieved up to 87% removal of Cr (VI) from aqueoussolution of Cr (VI). The most suitable conditions for the adsorption using BC-Pcomposites were at 180 min contact time with adsorbent dosage of 0.25 g, initial Cr(VI) concentration of 75 g/ml and pH 3. Mathematical modelling for adsorptionkinetics and isotherm were well correlated with the pseudo second-order (R2>0.96)and the Freundlich isotherm model (R2> 0.99), respectively. In conclusion, additionof 2-acetyl-1-pyrroline using in-situ technique was successfully proven to be able tomodify the characteristic of BC for producing new BC-P composites. Furthermore,the ability of BC-P composites as a biosorbent were proven by successfully achievedup to 87% efficiency of Cr (VI) ions removal from aqueous solution of Cr (VI).