Insight Into the Effect of NaClO on Structure, Crystallinity and Thermal Behavior of Almond Shell‐Based TEMPO Cellulose Nanofibers

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.