Detection of strontium species and Sr(OH)₂ NPs formation via double oxidation effect on coal oxide: Preparation and characterization of new coal oxide and its mixture

We introduce an approach double oxidizing process for obtaining water-soluble coal oxide (CObt) and its new mixture for low-cost Sr detection performance. CObt demonstrated a good carbon-based Sr detector with a tunable optical property under various pH conditions. The interaction of CObt with Sr metal cation (0.12 mol/L) indicated a turn-ON photoluminescence (PL) response signal in acidic and basic conditions. The CObt may combine with maghemite (gamma-Fe2O3) to create a new mixture, and by forming a mixture we can recover adsorbed Sr by using magnet. The Sr adsorption behavior was also captured using Transmission Electron Microscope (TEM) image, and strontium hydroxide (Sr(OH)(2)) formation was observed. We observed Sr2+ adsorption performance on the CObt and its mixture up to 40 % of the initial concentration of SrCl2. The presence of maghemite (gamma-Fe2O3) in the mixture makes the Sr separation more easily for practical separation. In addition, the formation of Sr(OH)(2) (larger size) was identified in basic conditions, and the result also demonstrated a different phenomenon from acidic conditions. The energy dispersive X-ray spectroscopy (EDS) analysis revealed that Sr and Cl are strongly detected in acidic conditions. Additionally, the interaction time (>24 h) must be considered as an essential factor in the mechanism of Sr(OH)(2) formation.