Iron-Based Adsorbents Derived from Groundwater Deferrization Sludge for Spent Oil Removal from Aqueous Media

High Resolution Image Download MS PowerPoint Slide The paper presents the results of the synthesis and study of iron oxide-based sorbents (Fe x O y -NPs) obtained from iron removal station sludge by exothermic combustion in solution using glycine, urea, citric acid, and urotropine as reducing agents. X-ray phase analysis revealed that the phase composition depends on the nature of the reducing agent and temperature: at 300–500 °C, the magnetite content reached 97–99% for citric acid and urea, whereas when using glycine, the Fe 3 O 4 fraction did not exceed 30%. The point of zero charge values shifted to the alkaline region with increasing synthesis temperature, reaching 8.8 at 700 °C. The specific surface area for methylene blue was up to 186 m 2 /g, but the calculated values exceeded the BET data by 3.5–4 times due to multilayer sorption on the functionalized surface, which is consistent with the FTIR spectra. The oil sorption capacity (OSC) of the synthesized sorbents reached 6.1 g/g (glycine, 500 °C), which is comparable to or exceeds the indicators of a number of natural and commercial sorbents. After five sorption-regeneration cycles at 800 °C, the OSC decreased by only 15.7%, confirming the stability of the material. The constructed polynomial and machine learning models (CatBoost, XGBoost) provided high accuracy of OSC prediction ( R 2 = 1.0), which demonstrates the promise of machine learning for optimizing synthesis conditions.