Cellulose nanofibrils (CNFs) were surface functionalized with hexamethylenediamine (HMDA) and, further, integrated with native CNFs in various weight mass ratios to fabricate water-stable films by the solvent casting method, to be used for the removal of tri-chromatic and anionic black reactive dye with the highest bleeding effect in the very first minutes of textile laundering, and in a weight mass compared to a commercial color-catcher sheet (Delta Pronatura (DP)). The effects of CNF-HMDA content on film bath absorption, surface potential and contact angle properties, as well as dye removal kinetics from different laundering baths (A – without and B – with a detergent) in up to 140 min were studied at 20C versus 60C and using different dye concentrations (0.1–1 g/L). It was found that bath absorption is decreased significantly (up to 60%) by increasing the CNF-HMDA content in the films, as compared to using a DP color-catcher sheet, due to a morphologically denser structure with surface-positioned hydrophobic ethylene moieties of HMDA, as well as reducing electrostatic attraction groups of CNF and HMDA. Such a surface interacts kinetically faster with anionic and hydrophobic dye molecules already at 20C, reaching up to 37–80% removal of all dye colorants in the first 20 min. In contrast, the dye removal efficacy of the DP color-catcher sheet is due to it interacting with a cationic polymer being released from the surface, which is better only for a bluish color, and at 60C, while being between 30% and 48%, as its release is hindered and reduced by the deposition of surfactants from the detergent.
COBISS.SI-ID: 21205526
Water stable, flexible and ecological acceptance composite films were prepared by the solvent casting process using native, dealuminated (treated with HCl to affect the surface chemistry and pore structure) and/or surface modified (coated with a cationic surfactant PDADM of different molecular weights) H-ZSM-5 type zeolite of different shapes (spherical vs. rod) and Si/Al ratios (P26 vs. P371) as adsorbents and cellulose nanofibrils (CNFs) as a networking matrix (in a weight ratio of 4:1). The films were tested for removal of the black anionic reactive dye with the highest bleeding effect at the first rinsing cycle of textile laundering. The effects of zeolite structure and surface chemistry on films dye’ removal kinetics from a standardised rinsing bath were investigated for up to 140 min at room temperature and using 0.1 g/l of dye concentration, depending on the film-to-bath weight-to-volume ratios (from 1:10 to 1:1000), thus simulating different rinsing conditions. The results show that up to 80% of the dye was removed in the first 20 min in the lowest weight-to-volume ratio (1:10), fitting the Langmuir isotherm, and the process followed the pseudo-second order kinetic, yielding a multi-layer adsorption mechanism with a monolayer capacity of 11 mg/g and 21 vs. 30 mg/g by films prepared from native or HCl-treated and PDADMA100 vs. PDADMA400 coated P371 zeolites, respectively. Such efficacy was due to the more densely and fully surface-covered longitudinal P371 with PDADM400, given the huge electrostatic attraction sites for dye molecules, compared to the partly interpenetrated PDADM into relatively larger pore-sized (450 nm vs. 220 nm) of P26. The filtration performance of the films was also examined, be used for the removal of the dye from the rinsing bath, released from the washing drum. An ultra-high flux rate (11.000 kL/m2 h MPa) with 45% of dye removal efficacy and capacity of 24 mg/g wss provided by films prepared from spherical and aggregated P26PDADMA-400, showing its high potential also as a filter membrane.
COBISS.SI-ID: 21623062
Water-stable and eco-friendly membranes were fabricated from carboxymethyl cellulose (CMC) acting as anionic adsorbent and cellulose nanofibrils (CNFs) as strengthening filler by solvent- and unidirectional freeze-casting processes, both supported with simultaneous citric acid (CA) mediated cross-linking. Spectroscopic, thermogravimetric and potentiometric titration techniques were applied to evaluate the efficacy of the cross-linking as well as to quantify the processing-dependant surface charge. In addition, the CMC/CNF assembling and membrane porosity were identified microscopically as the combinatorial effect of components ratio and the applied fabrication technique. Finally, the membrane’s cationic dyes adsorption capacity and kinetic were evaluated depending on the dyes ionization constants, solution pH, and the contact time using batch equilibrium experiment, and further evaluated for filtration performance at optimal pH. The resulting, freeze-casted membranes demonstrate anisotropic to isotropic and highly ()?90%) porous structures with gradient pore sizes (from few nm up to 200 µm range). This provides relatively high and stable flux rates (150–190 kL/m2 h MPa) with ~?100% cationic dye adsorption, fast dynamic (8.536–5.446 kg/g min) and capacity (1828–1398 g/kg), which highlight their potential in dead-end filtration technologies without need for additional separation step. The similar dye adsorption capacity was assessed for denser and nano-porous ((?50 nm) solvent-casted membranes, however, with much lower and time-declining flux rates (100–10 L/m2 h MPa), demonstrating their potential usage in spiral wound-cross-flow modules. Both types of membranes anyhow showed high dye removal capacity (? 90%) even after 4th (solvent-casted) and 50th (freeze-casted) reusing cycle, present a high-value alternative to commercial activated carbons or other bio-nano-absorbents.
COBISS.SI-ID: 21917206