Mg(NO3)2·6H2O-Assisted in situ-Fabrication of Tea Residual Biochar for Ultra-Fast and High Adsorption of Rhodamine B

Abstract

In this work, porous biochar (MN-TRB750) was fabricated via direct pyrolysis of tea residue (TR) and Mg(NO3)2·6H2O (MN). The as-synthesized MN-TRB750 reached a specific surface area of 839.54 m2·g-1 and an average pore size of 3.75 nm with multi-level pore architecture. MN decreased TR's carbonization temperature and promoted the aromatics extent, pore structure for the frizzly flake-like biochar. Rhodamine B (RhB) was chosen as the adsorbate to explore the removal performance of organic dyes in this study. The results indicated that the maximum adsorption capacity of RhB on MN-TRB750 at 20 ℃ is up to 809.0 mg·g-1 with isotherms fitted well to Freundlich and Dubinin-Radushkevic models. The adsorption kinetics followed pseudo-second-order and Elovich models with an equilibrium adsorption capacity of 757.6 mg·g-1 as the initial concentration of RhB is 260 mg·L-1. High pore filling, hydrogen bond, π-π interaction determined the adsorption of RhB onto MN-TRB850 through a multi-active center and exothermic chemical sorption process.