Experimental design and optimization of process parameters for nanocellulose extraction from pineapple leaves using central composite design

• The cellulose content of Pineapple leaf is 66.36%. • The yield of nanocellulose is affected by extraction time, acid concentration, temperature, and acid-to-feedstock ratio. • The thermogravimetry result shows that the thermal stability of nanocellulose extracted by hydrochloric acid is better than that of sulfuric acid. The yield of nanocellulose is affected by different parameters, including acid concentration, reaction time, temperature, and the acid-to-fiber ratio. This work aims to extract nanocellulose from pineapple leaves and optimize the process parameters using a central composite design. The chemical composition of pineapple leaf waste was determined using standard methods, and the obtained results were 66.36±0.31%, 19.84±0.13%, 7.8±0.14%, and 13.23±0.4% for cellulose, hemicellulose, lignin, and extractives, respectively. The extraction was done by alkali treatment, delignification, and hydrochloric acid hydrolysis. The time, temperature, acid concentration, and the ratio of acid to feedstock were studied by response surface methodology. The optimum yield was 76.2% at 42.5 minutes, 60.5 ℃, 4 M, and 1 to 20 g/ml for reaction time, temperature, acid concentration, and feedstock to acid solution ratio respectively. The functional group, particle size distribution, crystallinity, and thermal stability were determined using Fourier-Transform Infrared Spectroscopy (FTIR), Dynamic Light Scattering (DLS), X-ray Diffraction (XRD), and Thermogravimetry Analysis (TGA) respectively. The average particle size was found to be 23.87 nm with a polydispersity index of 0.7. The FTIR results confirm the significant reduction or complete removal of lignin, hemicellulose, and other amorphous parts found in pineapple leaf. The Crystallinity Index (CI) of pineapple leaf is 40.6%, cellulose is 60.7% and nanocellulose is 80.4% respectively. The thermogravimetry analysis shows the thermal stability of the nanocellulose is better than that of pineapple leaf.