Application of magnetic humic soil composite material based on multi-frequency driving technology for the selective removal of cesium ions from water

The rapid development of the nuclear power industry has led to the generation of a large amount of radioactive wastewater. Among radioactive pollutants, cesium-137 (137Cs) is the main pollutant with a half-life of 30.2 years. The humus soil of aged garbage has a loose and porous structure and a large specific surface area, which provided an ideal carrier environment for the loading and dispersion of PB NPs, enhancing the stability and surface activity of nanoparticles, and improving their adsorption performance. Therefore, this study developed three magnetic composite adsorbents (PB1/Fe3O4/AARH, PB2/Fe3O4/AARH and PB3/Fe3O4/AARH) based on multi frequency driving technology to compare the adsorption and separation performance of magnetic aged waste biochar with different PB growth frequencies for cesium under different conditions. Key parameters such as temperature, time, pH value, and dissolved organic matter were optimized using response surface methodology to determine the optimal treatment conditions for the three adsorbents in Cs containing wastewater. The results showed that compared with the surface state of aged garbage biochar grown only once with PB, the iron content in PB3/Fe3O4/AARH increased by 37.92 %, and the specific surface area increased by 40.656 m2/g. At an initial concentration of 60 mg/L, under the adsorption conditions of pH 7, time 12 h, and temperature 328 K, the maximum adsorption capacity of PB3/Fe3O4/AARH was 61.09 mg/g. In addition, the adsorption isotherms of Cs by PB3/Fe3O4/AARH followed the Freundlich model, and the adsorption kinetics followed the second-order kinetic model. The adsorption of Cs conformed to the intraparticle diffusion model, and the adsorption process was endothermic. The adsorption mechanism of Cs by PB3/Fe3O4/AARH mainly involved ion exchange and metal complexation. PB3/Fe3O4/AARH, as a novel adsorbent, releases cyanide concentrations significantly lower than the World Health Organization's standard of 0.07 mg/L. At the same time, it can recover radioactive Cs from water through magnetic separation technology, reducing secondary pollution and providing a potential adsorption method for Cs removal.