Key Takeaways & Executive Findings
- •• • The optimal Cu:Ce ratio of 1:1 in Cu–CeOx/TiO2 lowered the thermal remediation temperature for naphthalene-contaminated soil from 250 °C to 211.5 °C, a reduction of 38.5 °C, directly cutting energy consumption and preserving soil structure. • • At identical temperatures, the catalyst-enhanced group achieved an average 19.49% higher naphthalene removal rate compared to the non-catalyst control, demonstrating significant catalytic activity enhancement. • • Material characterization confirmed that Cu and Ce doping induced crystal defects in TiO2, increasing oxygen vacancies and hydroxyl radical generation, which are critical for oxidative degradation of naphthalene at lower temperatures. • • The catalyst promoted stepwise degradation of naphthalene into alcohols, carboxylic acids, and aldehydes, ultimately mineralizing to H2O and CO2, with fewer by-products than the control, indicating a cleaner remediation pathway.
Abstract
Traditional soil thermal remediation requires high temperatures (>300 °C), which can damage soil structure, increase energy consumption, and elevate carbon emissions. This study developed a Cu–CeOx/TiO2 trimetallic catalyst to enable low-temperature thermal remediation of naphthalene-contaminated soil. Using nano-TiO2 as a support, catalysts with varying Cu/Ce ratios were prepared via impregnation-calcination. Material characterization (XRD, TEM, XPS, etc.) revealed that Cu and Ce incorporation induced crystal defects in TiO2, enhancing lattice oxygen activity and electron mobility, thereby generating more oxygen vacancies and hydroxyl radicals. Performance evaluation using a TGA-GC-FTIR-MS platform showed that the catalyst with Cu:Ce = 1:1 achieved the best remediation efficiency, reducing the thermal remediation temperature from 250 °C to 211.5 °C and increasing the removal rate by an average of 19.49% compared to the non-catalyst group at the same temperature. The catalyst facilitated stepwise degradation of naphthalene into smaller organic molecules (alcohols, carboxylic acids, aldehydes) and ultimately into H2O and CO2. This work demonstrates that Cu–CeOx/TiO2 significantly lowers the energy demand of thermal remediation, offering a promising approach for low-carbon remediation of organic-contaminated soils.
1. Introduction
Conventional thermal desorption for organic-contaminated soil remediation typically operates above 300 °C, a threshold that compromises soil physicochemical properties, destroys organic matter, and incurs prohibitive energy costs and carbon emissions. While catalytic approaches have been explored to lower operating temperatures, prior systems often relied on noble metals or complex engineering, limiting scalability and economic viability. The central bottleneck remains achieving sufficient catalytic activity at mild temperatures without degrading soil quality.
This study addresses that gap by engineering a Cu–CeOx/TiO2 trimetallic catalyst that leverages the synergistic effects of copper and cerium oxides on a high-surface-area titania support. The catalyst's design promotes oxygen vacancy formation and electron transfer, enabling efficient naphthalene oxidation at temperatures as low as 211.5 °C. By integrating material characterization with thermal analysis, the work provides a mechanistic understanding of the catalytic pathway, offering a practical route to low-carbon, energy-efficient soil remediation.
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XUAN Yuning, YU Jintao, ZHANG Changbo, MA Xiaoyu, TANG Xiaoyong, CAO Xinyu, XU Haitao, LYU Shuguang, LIU Yuhao (2026). Low-Temperature Thermal Remediation of Naphthalene-Contaminated Soil Using Cu–CeOx/TiO2 Trimetallic Catalysts. Chinese Journal of Environmental Engineering. https://doi.org/10.12030/j.cjee.202508081
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Frequently Asked Questions
What is the optimal Cu:Ce ratio in the Cu–CeOx/TiO2 catalyst, and how does it affect the thermal remediation temperature?
The optimal Cu:Ce molar ratio is 1:1. This formulation reduced the required thermal remediation temperature from 250 °C to 211.5 °C, a 15.4% decrease, while achieving a 19.49% higher removal rate compared to the non-catalyst control at the same temperature.
How does the Cu–CeOx/TiO2 catalyst enhance naphthalene degradation at low temperatures?
The catalyst introduces crystal defects in TiO2, increasing oxygen vacancies and hydroxyl radical generation. These reactive species facilitate the stepwise oxidation of naphthalene into smaller intermediates (alcohols, carboxylic acids, aldehydes) and ultimately into CO2 and H2O, as confirmed by TGA-GC-FTIR-MS analysis.
What are the potential scalability and cost implications of using Cu–CeOx/TiO2 for full-scale soil remediation?
The catalyst uses earth-abundant metals (Cu, Ce) and TiO2, which are relatively inexpensive compared to noble-metal catalysts. The synthesis method (impregnation-calcination) is straightforward and amenable to scale-up. However, detailed cost-benefit analyses and pilot-scale trials are needed to assess economic viability against conventional thermal desorption.
Does the catalyst affect soil properties after remediation?
The study indicates that the lower operating temperature (211.5 °C) helps preserve soil structure and organic matter compared to conventional high-temperature (>300 °C) processes. However, long-term impacts on soil microbial communities and nutrient content require further investigation.
What is the degradation pathway of naphthalene in the presence of the catalyst?
The catalyst promotes stepwise degradation: naphthalene is first oxidized to oxygenated intermediates such as alcohols, carboxylic acids, and aldehydes, which are further broken down into smaller molecules and ultimately mineralized to CO2 and H2O. This pathway was verified by identifying intermediate fragments in the mass spectra during thermal desorption.
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