Fecha de publicación: -- Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE This study used almond shells as the raw material. After removing impurities via chemical treatment, almond shell nanocellulose (TOCNFs) was prepared using TEMPO-mediated oxidation combined with ultrasonic treatment. The influence of sodium hypochlorite on the structure, crystallinity, and thermal behavior of almond shell-based TEMPO cellulose nanofibers was investigated in detail. This study demonstrates a feasible approach for fabricating nanocellulose from almond shells, highlighting the potential for the valorization of agricultural by-products into biomass-based nanomaterials.

ABSTRACT
Agricultural waste almond shells (AS) served as raw materials for the synthesis of cellulose nanofibers (TOCNFs) through chemical pretreatment, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation, and ultrasonic treatment. The influence of NaClO dosage on the properties of the resultant nanocellulose was investigated. FTIR spectra confirmed that the chemical treatments effectively removed non-cellulosic components, increasing the relative cellulose content from 58.73% ± 0.42% to 73.93% ± 2.00%. XRD patterns revealed that all samples retained cellulose I crystal structures, with a maximum crystallinity of 86.23%. The carboxyl content was positively correlated with the amount of NaClO added. With an increase in NaClO dosage, the carboxyl content of TOCNFs increased continuously, reaching a maximum of 1.85 ± 0.02 mmol/g at a NaClO dosage of 20 mmol/g. The zeta potential analysis indicated that TOCNFs displayed superior colloidal dispersion stability. TEM and SEM images further confirmed the successful preparation of TOCNFs, with an average diameter of 3.23 ± 0.74 nm at a NaClO dosage of 15 mmol/g. Thermogravimetric analysis revealed that TEMPO oxidation slightly reduced the thermal stability of cellulose owing to surface functionalization. This study demonstrates a feasible approach for fabricating nanocellulose from almond shells, highlighting the potential for the valorization of agricultural by-products into biomass-based nanomaterials.