Adsorption of Cd (II) from Aqueous Solutions by Raw and Modified Tea Residue Biochars

Abstract

In this study, tea residue was used as raw material for biochar to investigate the adsorption performance. Brunauer-Emmett-Teller (BET) analysis and Fourier transform infrared spectroscopy (FTIR) were used to determine the characteristics of adsorbents and to investigate the adsorption mechanism. The results showed that: (1) After modified with different concentration of KOH, the oxygen-containing functional groups and organic functional groups on the surface increased, specific surface area and pore structure amplified. Base modification provided ways for Cd (II) adsorption, such as ion exchange or cooperate with heavy metal, and provided more adsorption sites. (2) In the isothermal adsorption experiment, the Langmuir model could better match the adsorption behavior of biochars on Cd (II). 3 mol/L KOH modified biochar had the optimal adsorption effect. Under the condition of temperature was 45°C and pH was 6, the maximum saturated adsorption capacity can reach 120.028 mg/g, significantly higher than the unmodified biochar (G0 = 80.418 mg/g).