Degradation mechanism of octadecylamine and 4-dodecylmorpholine in Salk Lake Brine under UV light

More than 80 % of the potash fertilizer globally is produced by the froth flotation process. Octadecylamine (ODA) and 4-dodecylmorpholine (DMP), the most commonly used flotation collectors, are discharged into salt lakes, posing a hazard to human health and environmental safety. This study investigated ODA and DMP degradation processes under ultraviolet radiation. The experimental results showed that the degradation efficiency of ODA and DMP of 10 ppm reached 100 % within 60 min of UV irradiation in the brine. In contrast, complete degradation in pure water required 80 and 90 min for ODA and DMP, respectively. Notably, salt ions significantly accelerated the degradation of these organic amines compared to pure water. The nitrogen element in both compounds was ultimately converted into ammonium (NH₄⁺). Total organic carbon (TOC) measurements and gas chromatography-mass spectrometry (GC-MS) analyses revealed that the degradation process initiated with the cleavage of C-N bonds, followed by the breakdown of carbon chains. Based on GC-MS data, potential degradation pathways and mechanisms for ODA and DMP were proposed. The possible degradation pathways and mechanisms of ODA and DMP were proposed following GC-MS analyses. Field experiments and the detection of organic compounds in actual brines further validated the photodegradation reactions and mechanisms of the organic amines. This work guides the use of flotation agents and pollution control to produce potassium salts in salt lakes and aids in understanding the degradation processes of organic amines in natural environments.