Tuning the adsorption and mechanical properties of sustainable cellulose films from sunflower pith for different applications

This study demonstrates a sustainable strategy to tailor high-performance cellulose films from sunflower pith-an agricultural byproduct with low lignin content, hierarchical porosity, and inherent pectin richness for diverse applications. By exploiting these natural attributes, high-pressure homogenization alone produced native films (NF-H) with balanced mechanical strength (47.89 MPa tensile strength) and exceptional adsorption capacities (91.70 % methylene blue removal; 45.80 mg/g Cu²⁺ adsorption), rivaling commercial activated carbon. Alkali pretreatment (1 % NaOH) increased the tensile strength of cellulose films to 93.56 MPa by removing the non-cellulose component, but significantly reduced their adsorption capacity (38.44 % methylene blue removal; 4.27 mg/g Cu²⁺ adsorption), respectively, due to pectin loss. A micro/nanofibril composite approach (MCF:TOCNF =1:1) was capable of further improving the mechanical performance of cellulose films (118.54 MPa, 147.53 % increase over NF-H). Nevertheless, the dense structure of these composite films hindered the accessibility of active sites, resulting in lower adsorption capacities. This tunable system allows property optimization: high-adsorption films for wastewater treatment or high-strength films for structural uses. The work highlights sunflower pith as a low-energy, chemical-free feedstock, offering a scalable platform to convert agricultural waste into functional materials tailored for specific applications. • Cellulose films made by homogenization showed 91.70 % dye removal, 45.80 mg/g Cu²⁺ adsorption, and 47.89 MPa tensile strength. • Alkali pretreatment (1 % NaOH) improved tensile strength to 93.56 MPa, but reduced adsorption due to pectin loss. • Composite films (MCF:TOCNF = 1:1) achieved 118.54 MPa tensile strength, showing 147 % improvement over untreated films. • A low-energy, chemical-free process for tailoring cellulose films from sunflower pith for multiple applications.