Biosorption of Cr(VI) onto Auricularia auricula dreg biochar modified by cationic surfactant: Characteristics and mechanism

To efficiently remove Cr(VI) from aqueous solution, the cationic surfactant Cetyltrimethyl Ammonium Bromide (CTAB) was used to modify the Auricularia auricula dreg biochar (AADB), and the adsorption characteristics and mechanism of modified AADB (MAADB) were investigated as compared with those of AADB. The analyses by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), Fourier transform infrared (FTIR), X-ray diffraction (XRD) and other physiochemical methods demonstrated that the cationic surfactant modification enhanced the adsorption capacity of biochar for Cr(VI) by providing hydrophilic and hydrophobic groups, such as hydroxide, phosphate, carbonate and carboxyl. According to the single factor experiments, the appropriate adsorption of Cr(VI) onto MAADB occurred at adsorbent dosage of 3 g/L, pH 2.0, Cr(VI) initial concentration of 20 mg/L, 25 °C, contact time of 120 min. CTAB modification improved the adsorption rate and quantity for Cr(VI) by 6.4% and 8.0%, respectively. The adsorption process was well described by the Langmuir isotherm and the pseudo-second order equation. After three biosorption-desorption cycles, the final regeneration efficiency of MAADB was 54%.