Porous carbon prepared from lotus leaves as potential adsorbent for efficient removal of rhodamine B

Abstract

Lotus leaf porous carbon (LLPC) prepared from waste lotus leaves has a large specific surface area (2440 m2 g-1), and is used for the adsorption of rhodamine B (RhB) from wastewater in this study. The effects of different parameters such as LLPC dose, initial pH of wastewater, adsorption time, initial RhB concentration, and temperature on adsorption have been systematically explored. Notably, 100% removal efficiency of RhB (60 ppm) is obtained at a low LLPC concentration of 0.125 g l-1. The adsorption equilibrium with a maximum theoretical adsorption capacity of 718.9 mg g-1 at 313 K is described by the Langmuir isotherm. The results for removal efficiency as a function of time are consistent with the pseudo second-order kinetic model and the adsorption process is dominated by chemisorption. Thermodynamic studies confirm that RhB absorption by LLPC is spontaneous at 313 K. The experiments conducted to determine the adsorption mechanism show that intraparticle diffusion is not the only rate-limiting step during adsorption, and the boundary effect becomes more dominant with an increase in adsorption time. The excellent RhB adsorption performance of LLPC and adsorption mechanism afford novel insights into this process for the application of biomass materials in wastewater treatment.