K₂FeO₄-Modified Biochar And Its Adsorption Capability

Due to its special structural properties,biochar has great potential in remediation of wastewater.Magnetic biochar has attracted great attention due to its easy separation by a magnetic and been widely applied for removal of heavy metals and organic dyes from aqueous solution.In this thesis,K2FeO4 was employed to engineer areca leaf and pomelo peel biochars,and oxygen-containing-group-rich nonmagnetic and magnetic biochars rich were prepared through pyrolysis,respectively.The adsorption capabilities of engineered areca leaf and pomelo peel biochars toward methylene blue and Cr(VI)were investigated in aqueous solution.The biochars were characterized by FTIR,XPS,XRD,SEM,TEM,organic element analysis.In addition,the adsorption kinetics and thermodynamics of both biochars were tested,and the adsorption mechanisms were illuminated.The main results of the research are as follows:(1)A K2FeO4-catalyzed oxidative pyrolysis was developed for enhancing the adsorption capability of areca leaf biochar toward methylene blue at low temperature.The modified biochar pyrolyzed at 200℃ displayed much higher adsorption capacity than pristine biochar due to the introduction of surface oxygen-containing groups.In addition,high adsorption capability was observed over a wide pH range for the modified biochar and nearly neutral pH was obtained after adsorptions.Mechanistic studies revealed that the adsorption of the pristine biochar was mainly determined by hydrogen bonding and electrostatic interaction.Whereas,the adsorption of the K2FeO4-modified biochar was attributed to cation exchange besides hydrogen bonding and electrostatic interactions.(2)A magnetic biochar was prepared through K2FeO4-promoted pyrolysis of pomelo peel for adsorption of hexavalent chromium.Oxygen-containing groups and single phase γ-Fe2O3 were simultaneously generated on the biochar pyrolyzed at 300℃.The magnetic biochar exhibited 209.64 mg/g maximum adsorption capability at 45℃,surpassed the magnetic biochars reported in the literature.Moreover,a good magnetism was obtained,thereby the magnetic biochar can be easily separated from aqueous solution by a magnet.Both γ-Fe2O3 and biochar matrix were contributed to adsorption of Cr(VI)by reduction,electrostatic interaction and complexation.This provide was attractive method for preparation of highly adsorptive magnetic biochar in one-step operation without extra modifier.