Abstract

Objective Sodium oxalate is a representative recalcitrant organic pollutant. To enhance its degradation performance， a hierarchically porous ceria-based copper catalyst is synthesized. The study investigated its catalytic ozonation mechanism， aiming to optimize ozone （O₃） mass transfer efficiency thereby accelerating O₃ decomposition into reactive oxygen species.

Methods A ceria-based copper catalyst was synthesized via spray-drying technique and salt-templated synthesis method， using NaCl as a salt template and phenolic resin （PF） as a shaping agent. Various samples were obtained by varying the NaCl and PF addition amounts under identical processing conditions. The micro-morphologies of all samples were characterized through X-ray diffraction （XRD） patterns， scanning electron microscopy （SEM） images， pore size distribution curves， and X-ray photoelectron spectroscopy （XPS） spectra. The degradation performance of various ceria-based copper catalyst samples for sodium oxalate in an aqueous solution was investigated， and the sample with the optimal degradation performance was identified. Using 5，5-dimethyl-1-pyrroline N-oxide （DMPO） as a trapping agent for hydroxyl radicals， the primary reactive species in the solution were detected by electron spin resonance （ESR）. The cycling stability of the optimal catalyst was studied through four repeated degradation experiments. Furthermore， the catalytic ozonation mechanism of the ceria-based copper catalysts was explored.

Results and Discussion Micro-morphological characterization of various samples indicated that catalyst particle size significantly increased with higher NaCl mass， whereas PF addition exhibited minimal influence on particle size. However， PF dosage substantially affected pore structure and specific surface area. Without PF addition， the salt template and metal oxides within the particles were insufficiently encapsulated， resulting in structural collapse after washing. Conversely， excessive PF led to an overly thick coating layer that impeded pore formation. With a NaCl-to-PF mass ratio of 1：1， the prepared sample Cu@CeO₂-NaCl-PF exhibited an average particle size of approximately 35.3 nm， mesopore size of 5 nm-45 nm， and macropore size of 3 000 nm- 5 000 nm. The specific surface area ， mesopore volume， macropore volume， and total pore volume reached 52.15 m²/g， 0.240 mL/g， 4.778 mL/g， and 5.115 mL/g， respectively. The mass fractions of Cu⁰-Cu⁺ and Ce³⁺ were 67.1% and 18.7%， respectively. The sample Cu@CeO₂-NaCl-PF demonstrated enhanced catalytic performance due to its larger specific surface area， multi-scale hierarchical porous structure， highly dispersed Cu active sites， and abundant low-valent metal ions. These structural advantages collectively promoted the gas-liquid-solid three-phase mass transfer， facilitating O₃ enrichment on the catalyst surface while significantly accelerating the conversion rate. At a degradation time of 45 min， complete degradation （100%） of oxalate was achieved by sample Cu@CeO₂-NaCl-PF. After the fourth cycle at a degradation time of 60 min， it maintained 95% degradation efficiency， with the residual concentrations of copper ions （comprising Cu⁰-Cu⁺ and Cu²⁺） in the solution measured at 0.23 mg/L ， 0.27 mg/L ， 0.34 mg/L ， and 0.37 mg/L sequentially across cycles， demonstrating exceptional recyclability at low leaching concentrations. Upon the addition of 1 mmol/L tert-butanol as a masking agent for hydroxyl radicals in the solution， the oxalate degradation rate of Cu@CeO₂-NaCl-PF at 60 min was reduced to 10%， confirming hydroxyl radicals as the primary reactive oxygen species responsible for oxalate degradation. In contrast， when 1 mmol/L CCl₄ was added as a masking agent for superoxide anions in the solution， its degradation rate exhibited only marginal reduction， indicating that superoxide anions were not directly involved in oxalate degradation. The sample Cu@CeO₂-NaCl-PF was demonstrated to accelerate O₃ decomposition， generating hydroxyl radicals.

Conclusion The catalyst Cu@CeO₂-NaCl-PF is characterized by a relatively large specific surface area， a multi-scale hierarchical porous structure， highly dispersed Cu active sites， and abundant low-valent metal ions. These features collectively enhance the gas-liquid-solid three-phase mass transfer and promote ozone enrichment on the catalyst surface， thus accelerating O₃ conversion efficiency. The catalyst Cu@CeO₂-NaCl-PF exhibits excellent cycling stability and remarkable capability in facilitating O₃ decomposition， generating hydroxyl radicals.

Get Citation: ZHANG Baoyi， GAO Xingmin， YAN Shen， et al. Preparation of ceria-based copper catalysts and their degradation performance for sodium oxalate［J］. China Powder Science and Technology， 2025， 31（5）： 1-12.

Received: 2025-03-12 .Revised: 2025-06-05, Online: 2025-06-26

Funding Project: 国家自然科学基金项目，编号：21906111；江苏省教育厅自然科学研究重大项目，编号：18KJA530004。

First Author: 张葆逸（1999—），男，硕士生，研究方向为催化剂制备。E-mail：20225209020@stu.suda.edu.cn。

Corresponding Author: 吴铎（1981—），男，教授，博士，博士生导师，江苏省“双创博士”引进人才，研究方向为吸入药物粉体制剂研发、 干细胞体外三维培养微载体创制、 废水深度处理催化剂材料及装备研发、 新型喷雾制粒装备设计与工艺优化等。E-mail：duo.wu@suda.edu.cn。

DOI：10.13732/j.issn.1008-5548.2025.05.009

CLC No: O643.36； TQ426.82； TB44       Type Code: A

Serial No: 1008-5548（2025）05-0001-12