Sodium Hydroxide-Activated Persulfate Remediation of Sites Contaminated with Moderate Concentrations of Aniline and Analysis of the Microbial Community Characteristics

With the widespread application of aniline, its improper discharge in industrial production and accidental leaks during production and transportation have led to contamination of soil and groundwater environments. Persulfate advanced oxidation technology shows great potential for remediating organic compound pollution. This study focused on a specific aniline-contaminated site to identify oxidants and activators, optimize their ratios, and investigate the effects of relevant factors on oxidative remediation. It also examined changes in the microbial communities at the site before and after contamination, as well as before and after oxidative remediation. We found that the removal efficiency of aniline was most significant when the molar ratio of the optimal oxidant (sodium peroxydisulfate (Na2S2O8)) to the optimal activator (sodium hydroxide (NaOH)) was 1:1. When the initial aniline concentration in the soil reached 1000 mg/kg, it was necessary to increase the amount of the oxidant appropriately to maintain efficient removal. Environmental temperature and the content of organic matter in the soil had a relatively minor impact on the oxidation reaction. Following oxidation, the soil ammonia nitrogen content decreased, whereas nitrate and nitrite concentrations increased, with a significant rise in nitrate levels and substantial production of sulfate ion. Moreover, after aniline contamination, the microbial diversity in the soil of the site decreased, and the abundance of the genus Hydrogenophilus significantly increased. It is noteworthy that following oxidation treatment, the soil microbial community demonstrated a rapid trajectory of functional and structural recovery. Within five days of oxidant application, the community composition shifted from being predominantly composed of aniline-degrading taxa to closely resembling the original site in both community structure and inferred functional potential.