自由基调控型电化学体系的构筑及其脱氯羟基化阿特拉津机理研究

Dechlorination and hydroxylation of atrazine to nontoxic hydroxyatrazine is generally considered as an efficient detoxification method to remediate atrazine-contaminated water. However, •OH-based advanced oxidation processes could not hydroxylate atrazine into nontoxic hydroxyatrazine as •OH primary attacked the side chain of atrazine to generate the toxic dealkylation intermediates such as CEAT, CIAT, and CAAT. In this project, Oxalic acid was added into the electrochemical advanced oxidation processes (EAOPs) using boron doped diamond (BDD) anode to adjust the types and quantities of active species. The addition of oxalic acid would facilitate the generation of •CO2- and •O2- which could alter the degradation pathway of atrazine in EAOPs, avoiding generation of toxic dealkylation intermediates and promoting the hydroxylation of atrazine to nontoxic hydroxyatrazine. The active species types and their concentration, formation mechanism and disappearance in BDD/oxalic acid system will be investigated systematically, and the characteristics of atrazine degradation and mechanism of the interaction of different active species and atrazine in BDD/oxalic acid system were subsequently studied. The mechanism of dechloriantion and hydroxylation for atrazine in BDD/oxalic acid will be studied in detail with help of theoretical calculation and advanced techniques. The effect of environmental factors on dechlorination-hydroxylation of atrazine will also be discussed. This project could provide theoretical and technical support for the development of green, facile and effective strategy to remediate s-triazine herbicide contamination.

阿特拉津脱氯羟基化能实现阿特拉津污染水体的无毒化治理，有效地解决以阿特拉津为代表的三嗪环类除草剂水污染问题。但在高级氧化体系中，羟基自由基主要进攻阿特拉津的侧链脱烷基生成有毒的含氯产物。本项目通过在以硼掺杂金刚石电极为阳极的电化学高级氧化体系中加入草酸，调控体系活性物种种类，诱导亲核物种二氧化碳自由基和超氧自由基生成，优化阿特拉津的降解路径，避免生成有毒的含氯产物，促进阿特拉津脱氯羟基化生成无毒的ATR-OH。本项目将系统研究BDD/草酸体系中活性物种的种类、浓度及其形成机制和消亡规律；研究阿特拉津在BDD/草酸体系中的降解特性以及各种活性物在阿特拉津脱氯羟基化过程中的作用；借助理论计算和先进的表征手段深入分析阿特拉津在体系中发生C-Cl键断裂和羟基插入的反应机制；探讨环境因素对阿特拉津脱氯羟基化影响。本项目将为发展绿色、高效的三嗪类除草剂污染治理技术提供理论和技术支持。

阿特拉津是一种高效，价格低廉的三嗪类除草剂，被广泛应用于农业生产中。但因其毒性大对水生生物甚至人类的健康安全造成极大危害。目前，基于生成•OH的高级氧化技术通常被视为治理阿特拉津污染的有效手段。而阿特拉津降解过程中的毒性与脱氯程度密切相关，•OH主要进攻阿特拉津的侧链生成累积毒性更强的含氯脱烷基产物。本研究系统性地探究了阿特拉津易脱烷基降解，难脱氯脱毒的根本原因，并针对性地提出了亲核取代的方法（如：UV/H2O, 酸化硫代硫酸盐）生成高活性的亲核取代物种，定向进攻阿特拉津的C-Cl键，实现阿特拉津高选择性脱氯，生成无毒的羟基化产物。该方法突破了阿特拉津降解过程中“易降解”、“难脱毒”的瓶颈性问题。基于上述研究成果，针对含阿特拉津的三嗪环农药废水显碱性（pH ≥ 11.0）的特点，本研究还首次提出了在碱性条件下实现三嗪津类除草剂阿特拉津脱氯的方法。首先通过碱催化绿色化学试剂双氧水脱质子产生大量HO2-，HO2-与废水中残存的阿特拉津发生亲核取代反应生成三嗪过氧化物，三嗪过氧化物进一步与HO2-发生还原反应生成无毒的2-羟基阿特拉津。碱性双氧水技术对其他典型的三嗪类除草剂（如西玛津、扑灭津、特丁津）也具有显著的脱氯脱毒效果。该治理方法具有绿色，成本低廉，操作简便、处理效率高、不产生二次污染以及抗干扰能力强等优点，具有较强的应用前景。