Biochar pyrolyzed from MgAl-layered double hydroxides pre-coated ramie biomass (Boehmeria nivea (L.) Gaud.): Characterization and application for crystal violet removal

• DOI: 10.1016/j.jenvman.2016.08.070
• Publication Date: 2016-09-09T12:35:22Z
• Authors: Xiao-fei Tan; Yun-guo Liu; Yan-ling Gu; Shao-bo Liu; Guang-ming Zeng; Xiaoxi Cai; Xin-jiang Hu; Hui Wang; Si-mian Liu; Lu-hua Jiang
• Keywords: Magnesium Hydroxide; Photoelectron Spectroscopy; Temperature; Aluminum Hydroxide; 02 engineering and technology; Hydrogen-Ion Concentration; Wastewater; Boehmeria; 6. Clean water; Water Purification; 12. Responsible consumption; Solutions; Kinetics; Charcoal; Microscopy, Electron, Scanning; Thermodynamics; Gentian Violet; Adsorption; Biomass; 0210 nano-technology; Groundwater; Water Pollutants, Chemical

A novel biochar/MgAl-layered double hydroxides composite (CB-LDH) was prepared for the removal of crystal violet from aqueous solution by pyrolyzing MgAl-LDH pre-coated ramie stem (Boehmeria nivea (L.) Gaud.). Pyrolysis played dual role for both converting biomass into biochar and calcining MgAl-LDH during the pyrolysis process. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray analysis (EDS), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and zeta potential analysis were used to characterize the CB-LDH. The results of characterization suggested that the calcined LDH was successfully synthesized and coated on biochar. The resulted CB-LDH had higher total pore volume and more functional groups than the pristine biochar. Adsorption experimental data fitted well with the pseudo-second order kinetics model and the Freundlich isotherm model. The rate-controlled step was controlled by film-diffusion initially and then followed by intra-particle diffusion. Thermodynamic analysis showed that the adsorption of crystal violet was a spontaneous and endothermic process. The higher pH and temperature of the solution enhanced the adsorption performance. CB-LDH could also have excellent ability for the removal of crystal violet from the actual industrial wastewater and groundwater with high ionic strength. LDH adsorption, electrostatic attraction, pore-filling, π-π interaction and hydrogen bond might be the main mechanisms for crystal violet adsorption on CB-LDH. The results of this study indicated that CB-LDH is a sustainable and green adsorbent with high performance for crystal violet contaminated wastewater treatment and groundwater remediation.