生物炭光催化氧化–吸附协同脱除养殖循环水氨氮研究

Synergistic Removal of Ammonia Nitrogen from Recirculating Aquaculture Water by Biochar Photocatalytic Oxidation – Adsorption

摘要:

通过正交试验研究环境参数对生物炭光催化脱除养殖环境水中氨氮影响规律,借助对照与捕获试验解析了光照、曝气、添加生物炭条件下的脱氨差异,结合反应前后生物炭结构特征阐明光催化脱氨所涉氮迁移路径与脱氨机制。结果表明,氨氮脱除效果受控于其初始浓度、反应温度和时间,其中初始浓度为主控因素。当氨氮初始质量浓度9mg/L、生物炭添加量5g/L、温度45℃、pH值6、反应时间140 min时,氨氮去除率最高可达63.2% ,生物炭最大脱氨量为1.14mg/g。氨氮脱除过程中光照、曝气和添加生物炭之间存在协同作用,且在低浓度氨氮去除时表现得尤为显著,脱除的氨氮中52. 6%被氧化为硝态氮,仅2.8%被氧化为亚硝态氮,剩余44.6%均被生物炭吸附,表明生物炭光催化脱氨受到光催化氧化和吸附两种机制共同作用,且氧化产物以硝态氮为主。其中光催化氧化依托h?(光生空穴)、·O?2 (超氧自由基)、·OH(羟基自由基)3种中间产物实现。生物炭对NH+4的吸附能够促进h+和·O?2对氨氮的氧化,但h+却会阻碍生物炭与NH+4的接触。此外,·OH的形成亦有助于生物炭对NH+4的吸附。光催化氧化和吸附作用的互促为养殖循环水绿色高效脱氨提供了新思路。

Abstract:

The influence of environmental parameters on biochar photocatalytic ammonia nitrogen removal was studied through orthogonal experiments. Control and capture experiments were conducted to analyze the differences in ammonia nitrogen removal process under varying conditions of illumination, aeration, and biochar addition. Combined with the structural characteristics of biochar before and after reaction, the nitrogen migration pathway and ammonia removal mechanism involved in photocatalytic ammonia removal were clarified. The results showed that removal effects of ammonia nitrogen were controlled by the ammonia nitrogen concentration, reaction temperature and time, and the ammonia nitrogen concentration was the main controlling factor. When the initial concentration of ammonia nitrogen was 9mg/L, the biochar dosage was 5g/L, the reaction temperature was 45℃, the pH value was 6, and the reaction time was 140 min, the removal rate of ammonia nitrogen could reach up to 63.2% and the maximum ammonia nitrogen removal capacity per unit mass of biochar was 1.14mg/g. There was a synergistic effect between light, aeration and biochar addition during ammonia nitrogen removal, which was especially significant in the removal of low concentration ammonia nitrogen. Of the removed ammonia nitrogen, 52.6% was oxidized to nitrate nitrogen, only 2.8% was oxidized to nitrite nitrogen, and the remaining 44. 6% was adsorbed by biochar. These results indicated that the photocatalytic removal of ammonia nitrogen by biochar involved both photocatalytic oxidation and adsorption, with nitrate nitrogen being the main oxidation product. During the photocatalytic oxidation process, ammonia nitrogen was oxidized by h?,·O?2, and·OH. The adsorption of ammonia nitrogen by biochar led to the alteration of charge distribution on the surface of biochar, which promoted the oxidation of ammonia nitrogen by h? and·O?2. However, the presence of h? would hinder the contact between biochar and NH?4, and the formation of·OH contributed to the adsorption of NH?4 by biochar. The mutual promotion of photocatalytic oxidation and adsorption could provide a potential approach for green and efficient nitrogen removal in recirculating aquaculture water.