Study On Adsorption Performance Of Modified Sugarcane Bagasse For Simulating Cr⁶⁺Containing Wastewater

The main purpose of this study was to prepare adsorbents with high specific surface area,large pore volume,and characteristic functional groups such as oxygen-containing functional groups,nitrogen-containing functional groups,sulfur-containing functional groups or phosphorus-containing functional groups to remove Cr(?)in simulated wastewater.Three kinds of bagasse-based adsorbent materials were prepared by using bagasse as raw materials.The adsorption effects of three kinds of modified bagasse on Cr(?)were investigated under different pH,adsorbent dosage,adsorption time and initial concentration of wastewater.And the adsorption process was evaluated by adsorption isotherm model and adsorption kinetic equation.Three kinds of adsorbent materials were characterized by scanning electron microscopy(SEM),Fourier transform infrared spectroscopy(FTIR),specific surface area and pore(BET)to explore the adsorption mechanism.The main results of the experiment were as follows:The first type of adsorbents was three different acid modified bagasse.The maximum adsorption capacity of oxalic acid modified bagasse(OMB)to Cr(?)reached 3.432mg/g,the maximum adsorption capacity of phosphate modified bagasse(PMB)to Cr(?)reached 3.622mg/g,and the maximum adsorption capacity of bagasse(XMB)to Cr(?)reached 3.532 mg/g.The pore volume and specific surface area of acid-modified bagasse were increased by about three times compared with unmodified bagasse.The second type of adsorbents was bagasse char which were pyrolyzed under different atmospheres.The maximum adsorption capacity of bagasse pyrolyzed in nitrogen(NB)to Cr(?)was 4.573mg/g,the maximum adsorption capacity of bagasse pyrolyzed in air(AB)to Cr(?)was 3.509mg/g,and the maximum adsorption capacity of bagasse pyrolyzed in vacuum(VB)to Cr(?)was 3.338 mg/g.The specific surface area of this kind of bagasse carbon was 100~300 times that of the unmodified bagasse,and the pore volume was 30~100 times that of the unmodified bagasse.The third type of adsorbent was bagasse hydrothermal carbon prepared by using different acid as medium.The maximum adsorption capacity of bagasse hydrothermal carbon using oxalic acid as medium(OBC)to Cr(?)was 6.752mg/g,the maximum adsorption capacity of bagasse hydrothermal carbon using phosphoric acid as medium(PBC)to Cr(?)was 7.758mg/g.The maximum adsorption capacity of bagasse hydrothermal carbon using sulfuric acid as medium(SBC)to Cr(?)was 6.266 mg/g.Compared with unmodified bagasse,the bagasse hydrothermal carbon had an increase in pore volume of about 20 times and specific surface area of about 100 times.The adsorption of Cr(?)by the three types of bagasse-based adsorbents were all better fitted by the pseudo-second-order kinetic equation and the Langmuir isotherm adsorption model,indicating that the adsorption process were all mainly single-layer adsorption,and mainly chemical adsorption.Through the modification,the three types of bagasse-based adsorbents have corresponding oxygen-containing functional groups,nitrogen-containing functional groups,phosphorus-containing functional groups or sulfur-containing functional groups,which played an important role in the process of combining hexavalent chromium,mainly electrostatic adsorption,redox and complexation.