Cellulose Nanofibrils and Nanocrystals Valorized from Pistachio Hull Possess Unique Chemo-structural and Rheological Properties Depending Upon Solvent System: Potencies of Green Techniques and Genetic Algorithm

This study aimed to produce cellulose nanoparticles from pistachio hull via four different protocols. First, microcellulose was produced by consecutive purification protocols then sulfuric acid (C), microwave-assisted sulfuric acid (MW), hydrotropic solvent (HS), and deep-eutectic solvent (DES) extraction systems were implemented. The effectiveness of process parameters was scrutinized by response surface methodology. Genetic programming and genetic algorithm, the most promising evolutionary-learning strategies, were also recruited to fit models and find optimum points, respectively. The nanoparticles produced at optimum conditions were characterized, and structural, morphological, and chemical properties were compared by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM) and zeta-potential analyses. HS and DES resulted in higher yields (up to 79.9 and 90.6%, respectively), while C and MW provided higher crystallinity indexes (61.1 and 62.2%, respectively). The highest viscosity values were obtained by DES. All nanocellulose samples exhibited elastic properties according to storage modulus (Gʹ) and loss modulus (Gʺ) data at varying frequencies. Still, DES-treated nanocellulose suspension showed the highest Gʹ and Gʺ values which indicate adequate nanofibrillation. The underutilized industrial by-product could be a new raw material for producing either cellulose nanocrystals or nanofibrils.