Nascent-state manganese dioxide (NSMD) and ferric hydroxide (NSFH) are the main intermediates formed during potassium permanganate and Fenton oxidation processes, respectively, which play an important role in the removal of organic contaminants. This study investigates the removal efficiency in 38 synthetic dye wastewaters by NSMD and NSFH. Results showed that the average removal rates (R_exp) of dyes by NSMD and NSFH were 83.58 ± 5.96% and 43.11 ± 4.17%, respectively. SEM, FT-IR, TGA, XRD and BET analyses revealed that NSMD had a larger specific surface area and more abundant surface hydroxyl groups, resulting in a stronger adsorption capacity than that of NSFH. Besides, the degradation of dyes by NSMD was a combination of adsorption and oxidation; NSFH involved only in the adsorption effect, and thus NSMD had higher removal efficiency than that of NSFH. Additionally, to better illustrate the internal factors that affect the removal efficiency, correlation analyses between R_exp and 28 molecular descriptors, as well as quantitative structure–activity relationship (QSAR) model analysis using R_exp as dependent variables and molecular descriptors as independent variables, were conducted. The optimal QSAR models for NSMD and NSFH systems were R_pre = 1.829–0.460BO_x + 0.017μ − 1.248q(CH⁺)_x + 0.024E_LUMO and R_pre = −0.949 + 0.001MM − 0.017μ + 4.674f(0)_x − 0.072E_HOMO − 0.413q(C⁻)_n + 0.034N_N, respectively, which suggested that the maximum value of bond order (BO_x) representing oxidation capacity and the relative molecular mass (MM) representing adsorption capacity are the dominant factors affecting the dye removal of NSMD and NSFH, respectively. These findings not only reveal the differences and characteristics of dye removal using NSMD and NSFH, but also provide a rapid way to evaluate the removal efficiency of the two systems.

中文翻译：

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酸性条件下新生二氧化锰与氢氧化铁去除废水中染料的对比研究

初生态二氧化锰 (NSMD) 和氢氧化铁 (NSFH) 分别是高锰酸钾和芬顿氧化过程中形成的主要中间体，在去除有机污染物方面起着重要作用。本研究调查了 NSMD 和 NSFH 对 38 种合成染料废水的去除效率。结果表明，平均去除率 ( R _exp) NSMD 和 NSFH 的染料分别为 83.58 ± 5.96% 和 43.11 ± 4.17%。SEM、FT-IR、TGA、XRD和BET分析表明NSMD具有更大的比表面积和更丰富的表面羟基，导致比NSFH更强的吸附能力。此外，NSMD对染料的降解是吸附和氧化的结合；NSFH仅参与吸附作用，因此NSMD的去除效率高于NSFH。此外，为了更好地说明影响去除效率的内部因素，R _exp与 28 个分子描述符之间的相关性分析，以及使用R _{exp 的}定量构效关系 (QSAR) 模型分析进行因变量和分子描述符作为自变量。NSMD 和 NSFH 系统的最佳 QSAR 模型是R _pre = 1.829–0.460BO _x + 0.017 μ − 1.248 q (CH ⁺ ) _x + 0.024 E _LUMO和R _pre = −0.949 + 0.001MM − 0.017 μ + f ( 4.674) ) _x − 0.072 E _HOMO − 0.413 q (C ⁻ ) _n + 0.034 N _N，这表明键阶（BO_x ) 代表氧化能力和相对分子质量 (MM) 代表吸附能力分别是影响 NSMD 和 NSFH 染料去除的主要因素。这些发现不仅揭示了使用 NSMD 和 NSFH 去除染料的差异和特征，而且为评估两种系统的去除效率提供了一种快速的方法。