Study On The Preparation Of Mesoporous TiO₂ Controlled-release Materials And Its Release And Remediation Of Tetracycline In Groundwater

The remediation of organic pollutants in groundwater has been a challenging task in environmental management due to the cumulative nature of these pollutants and the unique characteristics of the groundwater environment.Persulfate-based chemical oxidation controlled-release materials（CRMs）are an emerging in-situ remediation technique that has immense potential for remediating organic pollutants in groundwater.It offers sustainable remediation capabilities and addresses the problem of low oxidant utilization in traditional in-situ remediation technologies.This paper describes the construction of an advanced oxidation system that combines asymmetric mesoporous TiO₂ and persulfate with controlled-release technology to develop an efficient catalytic and environmentally friendly CRMs.The preparation of CRMs and long-term release performance were optimized by regulating the catalyst activity and the material ratio.The remediation performance and degradation mechanism of the CRMs in a simulated groundwater environment were investigated through the degradation of tetracycline（TC）.The study’s primary research contents and results are as follows:（1）An efficient and environmentally friendly asymmetric mesoporous TiO₂ catalyst was prepared using a soft template method,and persulfate（PDS）was successfully activated for degradation of TC under light avoidance conditions.The asymmetric mesoporous structure provided the catalyst with a large amount of Ti³⁺and a large specific surface area,thereby enhancing the adsorption and degradation of TC under dark conditions.The activation and degradation mechanism of the system was analyzed by combining free radical quenching experiments,ESR measurements,and high-performance liquid chromatography-mass spectrometry（HPLC-MS）.The results indicated that the catalytic degradation of asymmetric mesoporous TiO₂ with a calcination time of one hour was optimal,and the activation of persulfate generated sulfate radicals（SO₄^-·）and hydroxyl radicals（·OH）,which cooperatively degraded TC.This study provides valuable insights into the development of efficient and eco-friendly catalysts for the degradation of organic pollutants.（2）In this study,a Fenton-like system was constructed using asymmetric mesoporous TiO₂and PDS to constrcut the CRMs via a paraffin binder mixing and shaping method for groundwater remediation.The ratio between different materials was adjusted to optimize the preparation and release performance of the CRMs.The CRMs with the preferred ratio was selected as paraffin wax:quartz sand:sodium persulfate:asymmetric mesoporous TiO₂=3:12:2:0.6.The susceptible sites of TC were determined using the Fukui index,and the pathways of TC degradation by the CRMs were inferred by analyzing the HPLC-MS data.The mechanism of TC degradation by the CRMs was consistent with the powder system,involving the joint oxidative decomposition of TC molecules by SO₄^-·and·OH.The CRMs exhibited excellent properties for soil and groundwater remediation.（3）Based on the performance of the CRMs formulated,the study further explores their high efficiency in groundwater remediation.In static water environments,the controlled-release system exhibits a degradation effect on TC comparable to that of the powder system.Additionally,increasing the temperature or acidic conditions can promote TC degradation by the CRMs.The mesoporous TiO₂/PDS system is influenced by inorganic anions,with Cl^-causing the most interference with the CRMs.In dynamic water environments,the CRMs has distinct advantages over traditional chemical injection remediation,as it can sustainably degrade TC.Moreover,the CRMs is highly adaptable,demonstrating strong stability and the ability to accommodate different initial TC concentrations.The high permeability groundwater medium and low water flow rate are conducive to the degradation of TC by the CRMs.Two different matrices of CRMs were successfully prepared by resourceizing magnesium slag and CaAl-LDH.Overall,this study highlights the potential of the CRMs in groundwater remediation and provides insights into their performance under various environmental conditions.To achieve in-situ remediation of organic contaminants,such as antibiotics,in groundwater,an efficient,catalytic,and environmentally friendly CRMs was developed.The CRMs demonstrates sustained effectiveness in contaminated groundwater remediation,improving oxidant utilization,and avoiding secondary pollution of the environment.These positive results suggest promising prospects for practical applications and provide a novel approach in the field of in-situ groundwater remediation.