Introduction: Methylene blue (MB) and Cu²⁺ threaten human health and aquatic ecosystems, with MB causing cardiotoxicity at 3.5 mg/kg and Cu²⁺ exceeding EPA's 1.3 mg/L limit. However, MB is extensively used in textile dyeing due to its strong color affinity and stability, while Cu²⁺ finds widespread applications in electroplating, mining, and electronics. Huangshui (HS), a major liquid by-product of Baijiu production in China, is rich in polysaccharides but is typically discarded as waste. This study aims to addresses this waste by developing Huangshui polysaccharide (cHSP) to enhance biobased hydrogels for more effective wastewater purification.
Methods: cHSP was immobilized in SA-FFO matrices. Hydrogels were characterized by FTIR, SEM-EDS, XRD, VSM, and TGA. Adsorption performance for MB/Cu²⁺ was assessed under varied conditions (0~460 min, pH 2.0~10, 10~200 mg/L, and 298~328 K).
Results: FTIR/XRD confirmed functional groups (O-H, COO⁻, and Fe-O) and Fe₃O₄ crystallinity. SEM revealed enhanced porosity in SA-FFO-cHSP. TGA showed that the thermal stability of Mag-SA-cHSP was higher than Mag-SA. The zeta potential showed that the potential charge of SA-FFO-cHSP (-13.7~-27.5 mV) was lower than SA-FFO (-9.49~-25.05 mV) at pH 2-6. SA-FFO-cHSP achieved 87.43 mg/g (MB) and 67.89 mg/g (Cu²⁺). Adsorption kinetics of hydrogels for MB or Cu2+ showed distinct behaviors: MB uptake followed pseudo-second-order kinetics, whereas Cu²⁺ adsorption obeyed the Elovich model. Regeneration studies confirmed excellent reusability of hydrogels for MB (87–99% capacity retention) and good reusability for Cu²⁺ (66–69% retention) after four cycles.
Conclusions: cHSP-enhanced SA-FFO hydrogels demonstrate high-efficiency dual adsorption (MB/Cu²⁺) and reusability, enabling sustainable wastewater treatment via waste HS valorization. Future work should address complex pollutant systems and hydrogel degradation pathways.
