Preparation of dialdehyde cellulose cross-linked gelatin composites and study on removal of tannic acid from wastewater

Abstract

Gelatin (GE), known for its non-toxicity and abundant functional groups, enables effective tannic acid (TA) adsorption. However, its high hygroscopicity and poor mechanical strength limit its practical application. In this study, a series of cross-linked composites (DACG) were synthesized from GE and dialdehyde cellulose (DAC) at various mass ratios of 1:0.3-1:1.4. Among these, DACG1-3 (ratios 1:1, 1:0.8, and 1:0.7) formed a solid gel, with over 80 % yield and 95 % degree of substitution, and were selected for further study. FTIR confirmed Schiff base (C=N) formation between DAC and GE. SEM, TGA, and XRD revealed that DACG exhibited an irregular sheet structure, enhanced thermal stability, and altered crystallinity. DACG1-3 achieved up to 90 % TA removal under optimal conditions (pH <5.5, 0.35 g/L adsorbent, 30 °C), reaching equilibrium within 24 h. DACG1 maintained over 60 % TA removal efficiency after 3 adsorption-desorption cycles. The TA adsorption mechanism of DACG1-3 was investigated by adsorption isotherm fitting, FTIR, and XPS. The Langmuir linear adsorption model (R² > 0.996) was well described the adsorption of TA by DACG1-3, indicating that the adsorption mainly occurred in a monolayer, with the fitted maximum adsorption capacity (Q_m) of 410.71 ± 2.50 mg/g for DACG1. FTIR and XPS proved that DACG adsorbed TA by hydrogen bonds. Additionally, DACG1-3 exhibited antibacterial activities against Staphylococcus Aureus, Escherichia Coli, Bacillus Subtilis, and Staphylococcus Aureus. This work presents a recyclable, biocompatible, and multifunctional adsorbent with strong potential for integrated wastewater treatment and microbial control.

Keywords: 2,3-Dialdehyde cellulose; Adsorption; Gelatin; Tannic acid; Wastewater.