A Facilely Synthesized Tourmaline–Biochar Composite for Enhanced Removal of Cr (VI) from Aqueous Solution

Abstract

Hexavalent chromium (Cr (VI)), an anthropogenic heavy metal pollutant, is harmful to human beings, due to its carcinogenicity. In this study, a tourmaline–biochar composite (TMBC) was synthesized to remove Cr (VI) from an aqueous solution. The effects of different ratios (TM:BC) and pyrolysis temperatures on TMBC adsorption performance were compared. The TMBC samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and scanning electron microscope–energy-dispersive spectrometry (SEM-EDS). The kinetics and thermodynamics were analyzed to investigate the sorption mechanism. The results showed that the proper pyrolysis temperature was 650 °C, and the ratio of TM:BC was 1:3. SEM results showed the TM was well attached to the BC which assisted tourmaline dispersion. The adsorption kinetics were well fitted by the pseudo-second-order model, indicating that the sorption was related to chemical absorption. Langmuir adsorption isotherms suggested monolayer adsorption between the Cr (VI) and the TMBC, and the maximum adsorption capacity of the TMBC for Cr (VI) was 43.64 mg/g, which was more than twice the amount for the pristine TM (17.84 mg/g). The automatic polarization of water caused by tourmaline was the unique adsorption property of the TMBC. Therefore, TMBCs can be used as an economic adsorbent in the remediation of heavy metal pollution.