Controllable synthesis of porous silicate@carbon heterogeneous composite from Coal Gangue waste as eco-friendly superior scavenger of dyes

Abstract

Converting naturally abundant Coal Gangue (CG) waste into new materials with special functions or excellent performance has always been desirable. Here, the new porous heterogeneous silicate@carbon composites with high specific surface area of 650.96 m 2 /g (52.88 times of CG), excellent adsorption and removal ability to cationic dyes were synthesized by a controllable one-pot reconstitution reaction process of calcined CG. The optimal composite adsorbent composed of 10.179% Mg and 0.35% carbon can adsorb 269.86 mg/g of Methylene blue (MB) and 504.91 mg/g of Basic Red 14 (BR), which are 29.2 and 28.6 times higher than that of original CG and calcined CG, respectively. The MB and BR dyes in 200 mg/L of the initial dye solution can be removed almost completely after adsorption with 2 g/L of the composite adsorbent, which is significantly superior to raw CG and calcined CG. The dynamic column adsorption curves indicate the adsorption equilibrium was attained at C / C 0 values of 0.78 (for MB adsorption) and 0.75 (for BR adsorption). The used adsorbent can be regenerated and reused for multiple cycles, and the removal efficiency of the adsorbent towards dye is still higher than 90% after 5 regenerations. The adsorption isotherms and adsorption kinetics were studied and the adsorption mechanism was explored. This study demonstrates a feasible way to achieve a sustainable cycle "from waste to environmental purification materials". • Coal Gangue (CG) was converted to synthesize new porous silicate composite adsorbent. • The specific surface area of the adsorbent (650.96 m 2 /g) reaches 52.88 folds of CG. • The adsorbent adsorb 269.86 mg/g of MB and 504.91 mg/g of ABR dye (over 28.6 folds of CG). • Dyes in 200 mg/L of initial solution were almost completely removed by the adsorbent. • The adsorbent shows excellent dye removal efficiency in a dynamic adsorption process.