The treatment of low-concentration ammonium (e.g., <50 mg L⁻¹) in highly acidic wastewaters through traditional biological nitrification, physical separation, or chemical stripping remains a huge challenge. Herein, we report that photocatalytic ammonium oxidation using bismuth oxychloride (BiOCl) can successfully occur in Cl⁻-laden solutions within a pH range of 1.0-6.0. All reactions follow pseudo-zero-order kinetics (with rate constants of 0.27-0.32 mg L⁻¹ min⁻¹ at pH 2.0-6.0 and 0.14 mg L⁻¹ min⁻¹ at pH 1.0), indicating the saturation of reactive species by the reactants. The interlayer is self-oxidized by the valence band holes (VB h⁺), resulting in the formation of Cl^• and subsequently HClO, which is excited upon UV irradiation to provoke consecutive photoreactions for chlorine radical generation. Compared to the free chlorine, HO^•, Cl^•, and Cl₂^•−, the ClO^• produced using the UV/BiOCl system plays a predominant role in oxidizing ammonium under acidic conditions. BiOCl exhibits good stability because of the compensation of Cl⁻ from solution and maintains high activity under different conditions (i.e., different cations and co-existing anions, temperatures, and initial substrate concentrations). The successful removal of ammonium from real wastewater using the UV/BiOCl system suggests that this is a promising method for treating diluted ammonium under highly acidic conditions.

通过传统的生物硝化、物理分离或化学汽提处理高酸性废水中的低浓度铵（例如，<50 mg L ^-1）仍然是一个巨大的挑战。在此，我们报告了使用氯氧化铋 (BiOCl) 的光催化铵氧化可以在1.0-6.0 的 pH 值范围内成功地发生在含 Cl ^{- 的}溶液中。所有的反应遵循伪零级动力学（具有0.27-0.32毫克的L速率常数^-1分钟^-1，在pH 2.0-6.0和0.14毫克的L ^-1分钟^-1，在pH 1.0），表明反应性物质的由饱和反应物。中间层被价带空穴自氧化 (VB h ⁺)，导致形成 Cl ^•和随后的 HClO，后者在紫外线照射下被激发以引发连续的光反应以产生氯自由基。与游离氯、HO ^•、Cl ^•和Cl ₂ ^{• - 相比}，使用UV/BiOCl 系统产生的ClO ^•在酸性条件下氧化铵中起主要作用。由于 Cl ^-的补偿，BiOCl 表现出良好的稳定性并在不同条件下（即不同的阳离子和共存的阴离子、温度和初始底物浓度）保持高活性。使用 UV/BiOCl 系统从实际废水中成功去除铵表明这是一种在高酸性条件下处理稀释铵的有前途的方法。