Key Role of Persistent Free Radicals in Hydrogen Peroxide Activation by Biochar: Implications to Organic Contaminant Degradation
Key Role of Persistent Free Radicals in Hydrogen Peroxide Activation by Biochar: Implications to Organic Contaminant Degradation
复制标题
DOI：
10.1021/es4048126
复制
发表时间：
2014-02-04
影响因子：
11.4
通讯作者：
Zhou, Dongmei
中科院分区：
文献类型：
--
作者：
Fang, Guodong;Gao, Juan;Zhou, Dongmei
本文研究了以松针、小麦和玉米秸秆为原料的生物炭对过氧化氢(H_2O_2)的活化作用，并对其降解2-氯联苯进行了研究。研究发现，生物炭能有效地活化过氧化氢，产生羟基自由基((OH)-O-中心点)来降解2-CB。并通过电子顺磁共振(EPR)和水杨酸(SA)捕集技术对其活化机理进行了探讨。结果表明，生物炭含有持久性自由基(PFRs)，通常为1018个不成对自旋/克。在生物炭中加入H_2O_2后，捕获的[(OH)-O-中心点]浓度较高，PFRs浓度下降幅度较大，说明PFRs是形成(OH)-O-中心点的主要原因。这一假说得到了PFRs浓度与捕获量[(OH)-O-中心点]以及2-CB降解的k(Obs)之间的线性关系的支持。当包括在不同温度下热解的所有生物炭时，PFRs浓度与捕获量[(OH)-O-中心点]的相关系数(R-2)为0.723，与k(OBS)的相关系数为0.668。对于用不同有机溶剂(甲醇、正己烷、二氯甲烷和甲苯)洗涤的同一生物炭，相关系数显著增加到0.818-0.907。生物炭单电子转移是生物炭活化过氧化氢的一种可能机制，这一结果得到了自由基猝灭研究的支持。这一研究结果为生物炭的研究提供了一条新的途径，并深入了解了炭质材料(如活性碳和石墨)活化H_2O_2的机理。
We investigated the activation of hydrogen peroxide (H2O2) by biochars (produced from pine needles, wheat, and maize straw) for 2-chlorobiphenyl (2-CB) degradation in the present study. It was found that H2O2 can be effectively activated by biochar, which produces hydroxyl radical ((OH)-O-center dot) to degrade 2-CB. Furthermore, the activation mechanism was elucidated by electron paramagnetic resonance (EPR) and salicylic acid (SA) trapping techniques. The results showed that biochar contains persistent free radicals (PFRs), typically 1018 unpaired spins/gram. Higher trapped [(OH)-O-center dot] concentrations were observed with larger decreases in PFRs concentration, when H2O2 was added to biochar, indicating that PFRs were the main contributor to the formation of (OH)-O-center dot. This hypothesis was supported by the linear correlations between PFRs concentration and trapped [(OH)-O-center dot], as well as k(obs) of 2-CB degradation. The correlation coefficients (R-2) were 0.723 and 0.668 for PFRs concentration vs trapped [(OH)-O-center dot], and PFRs concentration vs k(obs)., respectively, when all biochars pyrolyzed at different temperatures were included. For the same biochar washed by different organic solvents (methanol, hexane, dichloromethane, and toluene), the correlation coefficients markedly increased to 0.818-0.907. Single-electron transfer from PFRs to H2O2 was a possible mechanism for H2O2 activation by biochars, which was supported by free radical quenching studies. The findings of this study provide a new pathway for biochar implication and insight into the mechanism of H2O2 activation by carbonaceous materials (e.g., activated carbon and graphite).