Construction of mineral-carbon nanosheet using waste activated sludge and bentonite for boosting dye adsorption

Waste activated sludge (WAS) produced in the industrial process is major pollutants, which has gained extensive attention. Appropriate treatment and resource utilization are of great significance to the economy development and environment protection. Herein, a novel strategy using WAS coupled with bentonite (BT) to synthesize mineral-carbon nanosheets (MCN) to enhance dye adsorption was proposed. The results demonstrated BT promoted the pyrolysis of WAS, thereby forming a sheet-like structure and construction of C-O-Si/C-O-Al sites on the surface. This composite exhibited enhance adsorption performance for dye methylene blue (MB) with a kinetic (0.000314 mg/(g/min)) and equilibrium adsorption capacity (90 mg/g), compared with those of activated carbon (0.000423 mg/(g/min)) and 25.6 mg/g). Spectroscopic tests indicated that C-O-Si/C-O-Al sites were dominate sites and the sheet-like structure could expose these sites, thus increasing the adsorption performance. This study demonstrates that WAS is an effective low-cost raw material for carbon adsorbent, offering a sustainable strategy for resource utilization of WAS and environmental remediation, achieving the goal of "treating waste with waste".