Lab-scale to blueprint: A thermo-mechanistic framework for Cr(VI) capture through Pb-oxides embedded nitrocellulose nanofibers

Renewable NC/PbO/Pb 3 O 4 nanofibers engineered for Cr(VI) waste treatment; • Dual-oxide valence synergy enhances interfacial stability and Pb O site density; • Rapid uptake and high time-point adsorption capacity (754 mg g −1 ) in representative realistic concentration; • Thermo-mechanistic modeling links kinetics to matrix-filler energetics; • Pb leaching ≤7.9 μg L −1 ; safe operation verified across regeneration cycles. Electrospun nitrocellulose (NC) nanofibers embedded with dual lead oxides (PbO/Pb 3 O 4 ; 2.5 wt% each oxide) were developed as a reusable adsorbent for hexavalent Chromium [Cr(VI)] capture while enabling a “blueprint-style” thermo-mechanistic performance profiling. SEM confirmed uniform nanofibers with an average diameter of 111.1 nm, and FTIR verified oxide incorporation through characteristic Pb-O/Pb-O-Pb vibrations in the low-wavenumber region. N 2 physisorption indicated a slight but steady rise in accessible porosity after oxide embedding. Surface area (BET) increased from 1.34 to 1.83 m 2  g −1 , and total pore volume from 0.055 to 0.0687 cm 3  g −1 . This change aligns with particle decoration or embedding that enhances interfacial voids without forming microporosity. Under dilute optimization conditions (C 0  = 5–30 mg L −1 ), the composite achieved 98% Cr(VI) removal at pH 3, an adsorbent dosage of 0.03 g, and a contact time of 25 min. To verify performance under representative high-strength industrial loading, kinetics were further evaluated at the controlled Cr(VI) solution prepared at the measured barium chromate production-line concentration (C 0  = 470 mg L −1 ), yielding rapid uptake with q t $q_t$ = 754 mg g −1 at 25 min. Equilibrium modeling followed Langmuir behavior ( q m $q_m$ = 367.5 ± 18.4 mg g −1 , K L  = 4.33 ± 0.68 L mg −1 , R 2  = 0.98; R L  = 0.044–0.0076), with more favorable apparent Langmuir-derived free-energy descriptors for the composite than for neat NC (ΔG°:-1.57 ± 0.45 to −3.62 ± 0.39 kJ mol −1 ), while kinetics were best described by the pseudo-second-order model (R 2  = 0.99; q e $q_e$ = 441.7 ± 12.6 mg g −1 ). The nanofiber retained 70.1 ± 2.1% of its adsorption capacity after 25 adsorption-desorption cycles, and Pb leaching remained low (2.8–7.9 μg L −1 ; 0.006–0.017% of embedded Pb), well below relevant guideline/action thresholds. A Comparative Performance Index (CPI) integrating capacity, affinity, and energy criteria demonstrated consistent performance under varied operating conditions. This thermo-mechanistic framework links laboratory adsorption descriptors with early process-screening criteria, providing a basis for subsequent continuous-flow validation. Download: Download high-res image (270KB) Download: Download full-size image