Effect of acid treatments on thermal properties of bacterial cellulose produced from cassava liquid waste

Abstract

Bacterial cellulose, BC is a natural compound that produced by bacteria Acetobacter xylinum in static or agitated cultures. BC has excellent properties such as excellent mechanical properties, high crystallinity, high purity, high water holding capacity and high permeability for water vapour and gases. Based on this unique and extraordinary properties, BC has the potential to be used in a wide range of applications, including food packaging, biomedical products, electronics, and energy. Nata de cassava (NdC) is a type of BC produced from cassava liquid waste that is fermented with the help of bacteria Acetobacter xylinum in static culture. The acid treatment using various concentration of phosphoric acid, H3PO4 (20 – 60 mmol) on the NdC samples was done to improve the BC thermal stability. This research aims to study the effects of acid treatments on the thermal properties of NdC. FTIR has confirmed the successful of acid treatments on the samples, while thermogravimetric analysis (TGA) was carried out to determine thermal stability of the NdC membrane. Thermal decomposition occurs primarily in two stages: the first occurs at a rapid rate of decomposition, while the second occurs more slowly. The last step shows that by increasing the acid concentration, resulted in increase of membrane residue where the higher (60 mmol) concentration of phosphorous-contained membrane exhibited a low degradation, reduced by 72.69% of its mass at 600 °C, in comparison to pure NdC which reduced by 91.39% of its mass. The main reason in improvement of char residue is that the treatment of cellulose with H3PO4 has released the ester form so that the phosphorous radicals (PO and POO) can be easily released during the thermal decomposition of this compound. It indicates that by treating the NdC samples with H3PO4 resulted in less weight degradation and improve the thermal stability of bacterial cellulose. In conclusion, the acid treatment on the NdC has successfully improved the thermal properties, thus it has potential to be applied as a conducting membrane in fuel cell application.