Levofloxacin (LEV), a widely used fluoroquinolone antibiotic, is highly resistant to microbial biodegradation and poses serious threats to aquatic ecosystems and human health. Conventional treatment methods face challenges in achieving efficient and sustainable removal. In a study published in ENG. Chem. Eng. , researchers at Tiangong University report a composite sponge material that integrates adsorption and photocatalytic degradation for effective LEV removal.
The ZnCuCCS sponge was fabricated via hydrothermal xanthate decomposition and in situ deposition. Cellulose and chitosan were first converted to soluble xanthates, which upon hydrothermal treatment released S²⁻ anions that reacted with Zn²⁺ and Cu²⁺ ions to form ZnS, CuS, and Zn₁₋ₓCuₓS nanoparticles. Na₂SO₄·10H₂O was used as a porogen to create a well developed porous structure. The resulting sponge exhibits a porosity of 88.37 % and recovers its original shape after 80 % compression, with 76.2 % stress retention after 30 cycles, confirming excellent mechanical robustness.
XRD and HRTEM confirmed the successful formation of ZnS (0.326 nm interplanar spacing, (111) plane) and CuS (0.271 nm, (006) plane), with Cu²⁺ doping into the ZnS lattice to form Zn₁₋ₓCuₓS. XPS revealed characteristic peaks for Zn 2p (1021.28 and 1044.38 eV), Cu 2p (932.88 and 952.48 eV), and S 2p (161.38 and 162.88 eV), confirming the presence of Zn²⁺, Cu²⁺, and S²⁻.
The ZnCuCCS composite exhibits a narrow bandgap of 1.31 eV, significantly lower than that of undoped ZnCCS (3.05 eV), enabling enhanced visible light absorption. Photoluminescence spectroscopy showed a red shift from 508 to 554 nm upon Cu doping, indicating suppressed charge carrier recombination. Electrochemical impedance spectroscopy revealed lower charge transfer resistance, and transient photocurrent measurements confirmed improved charge separation efficiency.
In LEV removal tests, the stepwise adsorption–photodegradation model achieved 80.1 % removal after 180 min, outperforming the simultaneous model (71.3 %). The optimal CeX: ChX mass ratio was 8:2 (65 % adsorption), while the optimal Zn: Cu molar ratio was 3:7, achieving a total removal efficiency of 90.12 %. Active species scavenging experiments identified h⁺ and O₂⁻ as the dominant species, with ESR confirming their generation under light irradiation. The proposed mechanism involves LEV adsorption onto the sponge surface via electrostatic interactions, followed by photocatalytic degradation driven by the immobilized semiconductor nanoparticles.
Reusability tests showed that ZnCuCCS maintained a removal efficiency of 72.9 % after five cycles, with a 17.2 % decline attributed to minor structural damage and residual active site occupation. In a simulated continuous flow system using lake water, the material achieved 90.08 % degradation efficiency after 100 min, confirming its practical applicability under environmentally relevant conditions.
This work provides a facile and robust strategy for fabricating polysaccharide based composite sponges with superior adsorption–photocatalytic performance, offering a promising solution for antibiotic-contaminated wastewater treatment.
ENGINEERING Chemical Engineering
Experimental study
Not applicable
Synergistic adsorption-photocatalytic degradation of levofloxacin using Zn1−xCuxS-modified cellulose/chitosan sponge
17-Apr-2026