The absolute radical quantum yield (Φ𝛷$\mathit{\Phi }$) is a critical parameter to evaluate the efficiency of radical-based processes in engineered water treatment. However, measuring Φ𝛷$\mathit{\Phi }$ is fraught with challenges, as current quantification methods lack selectivity, specificity, and anti-interference capabilities, resulting in significant error propagation. Herein, we report a direct and reliable time-resolved technique to determine Φ𝛷$\mathit{\Phi }$ at pH 7.0 for commonly used radical precursors in advanced oxidation processes. For H₂O₂ and peroxydisulfate (PDS), the values of Φ𝛷$\mathit{\Phi }$_•OH and ΦSO•−4${\mathrm{\Phi }}_{{\mathrm{SO}}_4^{•-}}$ at 266 nm were measured to be 1.10 ± 0.01 and 1.46 ± 0.05, respectively. For peroxymonosulfate (PMS), we developed a new approach to determine ΦPMS•OH${\mathrm{\Phi }}_{•\mathrm{OH}}^{\mathrm{PMS}}$ with terephthalic acid as a trap-and-trigger probe in the nonsteady state system. For the first time, the ΦPMS•OH${\mathrm{\Phi }}_{•\mathrm{OH}}^{\mathrm{PMS}}$ value was measured to be 0.56 by the direct method, which is stoichiometrically equal to ΦPMSSO•−4${\mathrm{\Phi }}_{{\mathrm{SO}}_4^{•-}}^{\mathrm{PMS}}$ (0.57 ± 0.02). Additionally, radical formation mechanisms were elucidated by density functional theory (DFT) calculations. The theoretical results showed that the highest occupied molecular orbitals of the radical precursors are O–O antibonding orbitals, facilitating the destabilization of the peroxy bond for radical formation. Electronic structures of these precursors were compared, aiming to rationalize the tendency of the Φ$\mathit{\Phi }$ values we observed. Overall, this time-resolved technique with specific probes can be used as a reliable tool to determine Φ$\mathit{\Phi }$, serving as a scientific basis for the accurate performance evaluation of diverse radical-based treatment processes.

中文翻译：

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直接测定基于羟基和硫酸盐自由基的处理过程中的绝对自由基量子产率


绝对自由基量子产率 (Φ𝛷$\mathit{\Phi }$
）是评估工程水处理中基于自由基的工艺效率的关键参数。然而，测量 Φ𝛷$\mathit{\Phi }$
由于当前的量化方法缺乏选择性、特异性和抗干扰能力，导致显着的误差传播，因此充满挑战。在这里，我们报告了一种直接可靠的时间分辨技术来确定 Φ𝛷$\mathit{\Phi }$
pH 7.0，用于高级氧化过程中常用的自由基前体。对于 H ₂ O ₂ 和过二硫酸盐 (PDS)，Φ 的值𝛷$\mathit{\Phi }$
在266 nm处测量 _•OH 和ΦSO•−4分别为1.10±0.01和1.46±0.05。对于过一硫酸盐（PMS），我们开发了一种在非稳态系统中用对苯二甲酸作为捕获和触发探针测定ΦPMS·OH的新方法。首次用直接法测得ΦPMS•OH值为0.56，化学计量等于ΦPMSSO•−4（0.57±0.02）。此外，通过密度泛函理论（DFT）计算阐明了自由基形成机制。理论结果表明，自由基前体的最高占据分子轨道是O-O反键轨道，有利于自由基形成的过氧键的不稳定。比较了这些前体的电子结构，旨在合理化我们观察到的 Φ 值的趋势。总体而言，这种具有特定探针的时间分辨技术可以用作确定 Φ 的可靠工具，为各种基于自由基的治疗过程的准确性能评估提供科学基础。