School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, 200240, China.
Environ Sci Pollut Res Int. 2021 Jul;28(26):35113-35125. doi: 10.1007/s11356-021-13164-6. Epub 2021 Mar 4.
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 NH-N in low concentration from aqueous solution (20 mg·L) 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 NH and NH. A microcalorimeter was applied to demonstrate the interaction between the negatively charged hydrophilic groups of SDS and NH 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 NH-N.
近年来，由于污水中氨氮的过度排放已受到更严格标准的限制。空气汽提法已成功地用于处理高浓度氨氮，但需要添加碱以保持 pH 值大于 10，这不仅成本高，而且操作不环保。本研究提出了一种基于泡沫分离的先进空气汽提（AAS）方法，用于去除低 pH 值下低浓度氨氮。考察了空气流量、温度、SDS 用量、共存离子强度、pH 值和初始氨氮浓度等条件对去除效率的影响。先进的空气汽提法对低浓度氨氮（20mg·L）具有良好的去除效果，适用的 pH 值范围较宽，为 3.0-9.0。此外，对于强碱性（pH=11.0）溶液，先进的空气汽提法可以在一定程度上缓解 pH 值的下降，并基于 NH 和 NH 之间的平衡转移，使氨氮不断被汽提出来。微量量热计用于证明 SDS 的带负电荷的亲水基团与 NH 离子之间的相互作用，有助于更清楚地了解其机制。该方法操作简单，去除效率高，这意味着先进的空气汽提法是一种很有前途的技术，可以最大限度地减少低浓度 NH-N 的排放。
