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Effects of pH, inorganic anions, and surfactants on the photocatalytic degradation of aqueous ammonia in graywater.

机译：pH，无机阴离子和表面活性剂对灰水中氨水的光催化降解的影响。

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摘要

Global water consumption has been increasing due to population growth. Accordingly, water recycling is a good strategy to compensate for the increased water demand. The overall objective of this study was to investigate the feasibility of using titanium dioxide (TiO2)-photocatalysis to recycle graywater in a simplified model system. We evaluated effects of three major parameters, including pH, inorganic anions, and surfactants, on the photocatalytic degradation of aqueous ammonia (NH4+ /NH3) in graywater in a bench scale reactor. Our results show that higher initial rates of NH4+/NH3 photocatalytic oxidation were obtained in higher pH solutions, and the initial rates were proportional to the initial concentrations of neutral NH3, and not total NH3 (i.e., [NH4 +] + [NH3]). We conducted experiments on the effects of four inorganic anions (Cl-, SO42-, H2PO4-/HPO42-, and HCO3-/CO32-) on NH 4+/NH3 degradation at pH ∼9 and ∼10 and nitrite (NO2-) oxidation over the pH range of 4-11. Cl-, SO42-, and HCO3 - had no effect on NH4+/NH3 and NO2- photocatalytic oxidation at pH ∼9 and ∼10, whereas CO32- slowed NH4+/NH 3 but not NO2- photocatalytic oxidation at pH ∼11. While HPO42- enhanced NH4 +/NH3 photocatalytic oxidation at pH ∼9 and ∼10, H2PO4-/HPO42- inhibited NO2- oxidation at low to neutral pH values. Photocatalytic oxidation of NH4+/NH3 to NO2- is the rate-limiting step in the complete oxidation of NH4+/NH3 to NO3 - in the presence of common wastewater anions at pH > 9. As for surfactants, their degradation rates were faster than that of NH4+/NH 3 at pH ∼10.1. Surfactant significantly slowed the initial rates of NH4+/NH3 degradation, with the detrimental effect increasing in the order sodium dodecylbenzene sulfonate (SDBS) cetylpyridinium chloride (CPC) nonylphenol polyethoxylate (10) (NP10). Adsorption of surfactants could not explain the slower initial rates of NH 4+/NH3 photocatalytic degradation in the presence of 2 x 10-5 M surfactants. We concluded that formation of hydroxyl radical (˙OH) scavengers, including formate and carbonate, from the photocatalytic degradation of surfactants was the main reason for decreasing initial rates of NH4+/NH3 degradation. Our results show that TiO2 photocatalysis can remove both carbonaceous and nitrogenous biological oxygen demand (CBOD and NBOD), which has implications in graywater recycling.;Key words: Aqueous ammonia, Titanium dioxide, pH, Inorganic anions, Surfactants, Hydroxyl radicals, Graywater
机译：由于人口增长，全球用水量一直在增加。因此，水的再循环是补偿增加的水需求的好策略。这项研究的总体目标是研究在简化的模型系统中使用二氧化钛（TiO2）-光催化再循环灰水的可行性。我们评估了三个主要参数（包括pH，无机阴离子和表面活性剂）对台式反应器中灰水中氨水（NH4 + / NH3）的光催化降解的影响。我们的结果表明，在较高pH的溶液中可获得较高的NH4 + / NH3光催化氧化初始速率，且初始速率与中性NH3的初始浓度成正比，而不与总NH3的浓度成正比（即[NH4 +] + [NH3]） 。我们进行了实验，研究了四种无机阴离子（Cl-，SO42-，H2PO4- / HPO42-和HCO3- / CO32-）在pH约9和约10时对NH 4 + / NH3降解以及亚硝酸盐（NO2-）的影响。在4-11的pH范围内发生氧化。 Cl-，SO42-和HCO3-在pH约为9和〜10时对NH4 + / NH3和NO2-光催化氧化没有影响，而CO32-在pH约为11时减慢了NH4 + / NH 3，但对NO2-光催化氧化没有影响。虽然HPO42-在pH值约为9和10时增强了NH4 + / NH3的光催化氧化，但H2PO4- / HPO42-在低至中性pH值时抑制了NO2-氧化。在pH> 9的常见废水阴离子存在下，将NH 4 + / NH 3光催化氧化为NO 2-是将NH 4 + / NH 3完全氧化为NO 3的限速步骤。 NH4 + / NH 3的pH值约为10.1。表面活性剂显着减慢了NH4 + / NH3的初始降解速率，其有害作用以十二烷基苯磺酸钠（SDBS）<十六烷基氯化吡啶鎓（CPC）<壬基酚聚乙氧基化物（10）（NP10）的顺序增加。表面活性剂的吸附不能解释在2 x 10-5 M表面活性剂存在下NH 4 + / NH3光催化降解的初始速率较慢。我们得出结论，由表面活性剂的光催化降解形成包括甲酸酯和碳酸酯在内的羟基自由基（＜OH）清除剂是降低NH 4 + / NH 3降解初始速率的主要原因。我们的结果表明，TiO2光催化能够去除碳和氮生物需氧量（CBOD和NBOD），这对灰水的回收利用具有重要意义;关键词：氨水，二氧化钛，pH，无机阴离子，表面活性剂，羟自由基，灰水

著录项

  • 作者

    Zhu, Xingdong.;

  • 作者单位

    The University of Oklahoma.;

  • 授予单位 The University of Oklahoma.;
  • 学科 Engineering Environmental.
  • 学位 Ph.D.
  • 年度 2007
  • 页码 152 p.
  • 总页数 152
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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