Department of Civil Engineering, Universidade Federal de Viçosa, Av. P.H. Rolfs, s/n, 36570-900 Viçosa, MG, Brazil.
Department of Civil Engineering, Universidade Federal de Viçosa, Av. P.H. Rolfs, s/n, 36570-900 Viçosa, MG, Brazil.
J Environ Manage. 2018 Apr 1;211:154-163. doi: 10.1016/j.jenvman.2018.01.033. Epub 2018 Feb 4.
The objective of this study was to evaluate ADMI color removal from a biologically treated textile mill effluent by heterogeneous photocatalysis with UV-visible irradiation (UV-vis) using a novel catalyst composed of TiO supported on hydrotalcite and doped with iron oxide (HT/Fe/TiO). Simulated biological treatment of solutions of the dyes (50 mg/L) used in the greatest amounts at the mill where the textile effluent was collected resulted in no color removal in reactive dye solutions and about 50% color removal in vat dye solutions, after 96 h, indicating that the secondary effluent still contained a large proportion of anionic reactive dyes. Photocatalytic treatments were carried out with TiO and HT/Fe/TiO of Fe:Ti molar ratios of 0.25, 0.5, 0.75 and 1, with varying catalyst doses (0-3 mg/L), initial pH values (4-10) and UV-vis times (0-6 h). The highest ADMI color removal with unmodified TiO was found at a dose of 2 g/L and pH 4, an impractical pH value for industrial application. The most efficient composite was HT/Fe/TiO 1 at pH 10, also at a dose of 2 g/L, which provided more complete ADMI color removal, from 303 to 9 ADMI color units (96%), than unmodified TiO, from 303 to 37 ADMI color units (88%), under the same conditions. Hydroxyl radicals were responsible for the color reduction, since when 2-propanol, an OH scavenger, was added color removal was very low. For this reason, the HT/Fe/TiO 1 composite performed better at pH 10, because the higher concentration of hydroxide ions present at higher pH favored hydroxyl radical formation. COD reductions were relatively low and similar, approximately 20% for both catalysts after 6 h under UV-vis, because of the low initial COD (78 mg/L). Secondary effluent toxicity to Daphnia similis (EC = 70.7%) was reduced by photocatalysis with TiO (EC = 95.0%) and the HT/Fe/TiO 1 composite (EC = 78.6%). HT/Fe/TiO 1 was reused five times and still lowered secondary effluent ADMI color below local discharge limits. Benefits of the HT/Fe/TiO 1 catalyst compared to TiO include its lower bandgap energy (2.34 eV vs 3.25 eV), higher ADMI color removal and its magnetic nature that facilitated its recovery and would reduce treatment costs.
本研究的目的是通过使用负载在水滑石上并掺杂氧化铁的 TiO2（HT/Fe/TiO）的非均相光催化作用，在 UV-可见辐射（UV-vis）下评估 ADMI 从经过生物处理的纺织厂废水中的去除情况。模拟对从收集纺织厂废水的工厂中使用的最大量的染料（50mg/L）的溶液进行的生物处理，在反应性染料溶液中没有去除颜色，而在还原染料溶液中约去除 50%的颜色，在 96 小时后，表明二级出水仍含有大量的阴离子反应性染料。使用 TiO2 和 HT/Fe/TiO2（Fe:Ti 摩尔比为 0.25、0.5、0.75 和 1）进行光催化处理，催化剂剂量（0-3mg/L）、初始 pH 值（4-10）和 UV-vis 时间（0-6 小时）均有所不同。在剂量为 2g/L 和 pH 4 时，未改性的 TiO2 对 ADMI 颜色的去除率最高，但对于工业应用来说，该 pH 值不切实际。最有效的复合材料是 HT/Fe/TiO2-1，在 pH 为 10 时，剂量也为 2g/L，与未改性的 TiO2 相比，提供了更完全的 ADMI 颜色去除，从 303 个 ADMI 颜色单位减少到 9 个 ADMI 颜色单位（96%），而未改性的 TiO2 则从 303 个 ADMI 颜色单位减少到 37 个 ADMI 颜色单位（88%），在相同条件下。羟基自由基是导致颜色减少的原因，因为当添加羟基自由基清除剂 2-丙醇时，颜色去除率非常低。出于这个原因，HT/Fe/TiO2-1 复合材料在 pH 为 10 时表现更好，因为较高的 pH 值会导致更高浓度的氢氧根离子形成，从而有利于羟基自由基的形成。COD 去除率相对较低且相似，在 UV-vis 照射 6 小时后，两种催化剂的 COD 去除率均约为 20%，因为初始 COD（78mg/L）较低。用 TiO2（EC=95.0%）和 HT/Fe/TiO2-1 复合材料（EC=78.6%）进行光催化处理后，降低了对大型蚤（Daphnia similis）的二级出水毒性（EC=70.7%）。HT/Fe/TiO2-1 已重复使用五次，仍将二级出水的 ADMI 颜色降低到当地排放标准以下。与 TiO2 相比，HT/Fe/TiO2-1 催化剂的优势包括其较低的带隙能（2.34eV 与 3.25eV）、更高的 ADMI 颜色去除率和其磁性，这有利于其回收并降低处理成本。
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