Xiang Hu,Liping Zhang,Yiyun An,Weiwei Wang,Huitong Li,Zeyu Lian
Manganese and ammonia nitrogen pollution are widespread in the water of northern Chinese mines, exacerbating regional water scarcity and potential ecological issues. This study aimed to remova dissolved manganese(II) and ammonia nitrogen from mine water using a natural zeolite (NZ) modified with sodium hexametaphosphate impregnation (SHMP-NZ) and loaded with 3D manganese(III)/(IV) oxide nanosheets (SHMP-NZ/MnO x ). The influence of factors such as pH value, dissolved oxygen, and coexisting ions on adsorption was investigated. The capacity of NZ to removing ammonium was determined by SHMP impregnation, while the capability to remove manganese was determined by 3D manganese(III)/(IV) oxide nanosheets . Compared to NZ, SHMP-NZ/MnO x exhibited an increased efficiency of 39.93% and 41.54% in the simultaneously removing low-concentration manganese(II) and ammonia nitrogen, respectively. Adsorption processes of manganese and ammonia nitrogen onto NZ and SHMP-NZ/MnO x followed the Elovich and pseudo second order kinetic models, respectively. Both materials exhibited stages of external diffusion, internal diffusion, and reaction equilibrium during adsorption. The maximum adsorption capacities of SHMP-NZ/MnO x for manganese(II) and ammonia nitrogen were 10.12 mg/g and 26.24 mg/g, representing improvements of 72.7% and 113.2%, respectively, compared to NZ. The primary mechanism for ammonia nitrogen removal by SHMP-NZ/MnO x was based on ion exchange, while manganese(II) removal was mediated by Mn 3+ /Mn 4+ species. A regeneration study over five cycles indicated that SHMP-NZ/MnO x possessed promising reusability potential.
Smuggling has caused serious adverse effects on the global market and national security, among which drug smuggling is increasingly rampant. Thus, the development of high-tech security strategies has become an urgent challenge for customs supervision. Recently, lanthanide ions (Ln 3+ ) doped upconversion nanoparticles (UCNPs) have opened up new ways for security and anti-fake applications due to their unique optical properties under near-infrared excitation. Here, we propose a novel upconversion microcrystal composed of hexagonal phase NaYF 4 :Ln 3+ capped by sodium hexametaphosphate (SHMP), successfully used in customs supervision. The addition of SHMP can not only regulate the morphology of microcrystals, but also significantly improve the luminescence properties of UC. The absolute quantum yield is up to 7% at the low power density of 30 W∙cm −2 , above most currently reported levels. Without adding any organic additives, the precise control of particle phase and morphology (e.g., microrod, hexagonal prism and hollow sphere) would be achieved by adjusting the doping ratio of SHMP/Ln 3+ . As the reaction time extends, the morphology of NaYF 4 :Ln 3+ changes from ellipsoid to microrod, while cubic phase transforms into hexagonal phase. Under the excitation of 980 nm laser, the green upconversion emission of hexagonal NaYF 4 :Ln 3+ microrods is significantly strengthened, which is more powerful than other observed particles with other shapes. This strong upconversion emission that depends on morphology and phase has huge application potential in security anti-counterfeiting and photonic devices .
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