In recent years, the excess discharge of ammonia nitrogen from wastewater into surface water has been regulated by more stringent standard. The air stripping method is successfully used to treatment of high-concentration ammonia nitrogen; however, alkali will be added to keep pH more than 10, which is costly and not environment-friendly operation. In this study, an advanced air stripping (AAS) based on foam separation of removing ammonia nitrogen in low concentration from aqueous solution at low pH was proposed. The effect of conditions such as air flow rate, temperature, SDS dosage, coexisting ionic strength, pH, and initial ammonia nitrogen concentration on the removal efficiency was studied. The advanced air stripping exhibited favorable removal efficiency for NH₄⁺-N in low concentration from aqueous solution (20 mg·L⁻¹) with a broad range of low pH 3.0–9.0. Besides, for strongly alkaline (pH=11.0) solution, the advanced air stripping can alleviate the decrease of pH to some extent and keep ammonia nitrogen stripping out continuously based on equilibrium shift between NH₄⁺ and NH₃. A microcalorimeter was applied to demonstrate the interaction between the negatively charged hydrophilic groups of SDS and NH₄⁺ ions, helping to understand the mechanisms more clearly. The simple operation and the satisfactory removal efficiency could imply that the advanced air stripping is a promising technology for minimizing low-concentration NH₄⁺-N.

Graphical abstract

中文翻译：

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通过先进的气提从低pH值的水溶液中去除低浓度的氨氮

近年来，更严格的标准对废水中氨氮向地表水中的过量排放进行了规定。气提法已成功用于高浓度氨氮的处理。但是，将添加碱以保持pH值大于10，这是昂贵的操作，而且不环保。在这项研究中，提出了一种基于泡沫分离技术的先进的空气汽提法（AAS），该技术从低pH值水溶液中去除低浓度的氨氮。研究了空气流速，温度，SDS用量，共存离子强度，pH和初始氨氮浓度等条件对去除效率的影响。先进的气提工艺对NH ₄ ^+具有良好的去除效率-N来自水溶液（20 mg·L ^-1）的低浓度，pH范围很低，为3.0-9.0。此外，对于强碱性（pH = 11.0）溶液，先进的气提可以在一定程度上缓解pH值的降低，并基于NH ₄ ⁺和NH _3的平衡迁移，使氨氮的汽提连续不断地进行。应用微量热计来证明SDS的带负电荷的亲水基团与NH ₄ ⁺离子之间的相互作用，有助于更清楚地了解机理。简单的操作和令人满意的去除效率可能意味着先进的气提是将低浓度NH ₄ ⁺最小化的有前途的技术。-N。

图形概要