Abstract
Low-cost porous ceramic microspheres from waste gangue were prepared by simple spray drying and subsequent calcination. Effects of calcination temperature on phase and microstructure evolution, specific surface area, pore structure, and dye adsorption mechanism of the microspheres were investigated systematically. Results showed that the microspheres were spherical, with some mesopores both on the surface and inside the spheres. The phase kept kaolinite after calcined at 800 and 900°C and transformed into mullite at 1000°C. The microspheres calcined at 800°C showed larger adsorption capacity and removal efficiency than those calcined at higher temperatures. Methylene blue (MB) and basic fuchsin (BF) removal efficiency reached 100% and 99.9% with the microsphere dosage of 20 g/L, respectively, which was comparable to that of other low-cost waste adsorbents used to remove dyes in the literature. Adsorption kinetics data followed the pseudo-second-order kinetic model, and the isotherm data fit the Langmuir isotherm model. The adsorption process was attributed to multiple adsorption mechanisms including physical adsorption, hydrogen bonding, and electrostatic interactions between dyes and gangue microspheres. The low-cost porous microspheres with excellent cyclic regeneration properties are promising absorbent for dyes in wastewater filtration and adsorption treatment.
Highlights
Ceramic microspheres have attracted a lot of attention for various applications due to their small size (0.01– 1.0 mm), light weight, low heat conductivity, and high dispersion [1,2,3,4]
We described novel low-cost porous microspheres from gangue using spray drying method and thereafter systematically characterized the effects of calcination temperature on initial products using phase evolution, pore structure, micrographs, functional groups, and adsorption properties of Methylene blue (MB) and basic fuchsin (BF) solutions
The Thermal gravimetric (TG) curve of the green gangue microspheres showed that the major mass loss before 1100 °C was ~13 wt%, which was due to the evaporation of free water, decomposition of minerals, and combustion of carbon and organic matters [13,17]
Summary
Ceramic microspheres have attracted a lot of attention for various applications due to their small size (0.01– 1.0 mm), light weight, low heat conductivity, and high dispersion [1,2,3,4]. The spray drying method was applied to fabricate glass foams and hollow sphere ceramics, which was considered to be prospective, low-cost, and widely used in industrial applications. Qiu and Cheng [21] modified the coal gangue with sodium tetraborate (Na2B4O7·10H2O) during calcination process to improve its removal efficiency of Mn2+, which was due to the increase of pore volume (from 0.021 to 0.067 cm3/g) and specific surface area (from 9.29 to 20.05 m2/g) for raw coal gangue. We described novel low-cost porous microspheres from gangue using spray drying method and thereafter systematically characterized the effects of calcination temperature on initial products using phase evolution, pore structure, micrographs, functional groups, and adsorption properties of MB and BF solutions
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