Preparation Of Biomass Carbon Materials And Their Application In Treatment Of Dye Wastewater

With the rapid development of printing and dyeing industry,the pollution of water on Earth is more serious.According to the characteristics of high COD and low light transmission,the treatment of dye wastewater has become an important task in the field of environmental protection.The preparation of biomass carbon materials and the application in the removal of organic dyes are an important way to protect water resources.In this paper,carbon materials were prepared from biomass as carbon source for the removal of methylene blue?MB?in printing and dyeing wastewater.The results are as follows:?1?The porous carbon materials was prepared by the hydrothermal and high temperature calcination method with corn stalks as carbon source.Porous carbon was characterized by merans of XRD,SEM,XPS and BET,etc.The results show that porous carbon morphology is porous with lamellar structure with specific surface area of 679.2378 m2/g.The adsorption properties of methylene blue were studied by using porous carbon as adsorbent.The effects of the amount of adsorbent,pH,temperature and reaction time on the adsorption properties were investigated.The results showed that the removal rate was 99.2%under optimal conditions:the amount of adsorbent was 0.25 mg/g,the initial concentration of MB was 50 mg/L,the pH was 6.7,the temperature was 318 K,and the adsorption time was 40 min.The adsorption of MB by porous carbon was consistent with quasi-second-order kinetic model.Thermodynamic data show that this adsorption is spontaneous,the endothermic physical adsorption process.After 5 cycles of adsorption,the removal rate was 93%,indicating that the porous carbon has a good cycle of renewable properties.?2?Carbon quantum dots?CQDs?were prepared by hydrothermal method using corn stalks as carbon source.CQDs ware characterized by means of FTIR,TEM,and XPS,etc.The average size of carbon dots is 2.4 nm,and it has good water dispersibility.The surface contains many oxygen-containing groups such as OH,C=O,and C-O-C,etc.The degradation effect of MB was studied by using CQDs as Fenton-like catalyst.It was investigated that the effects of the amount of catalyst,the initial concentration of MB and the amount of H2O2 on the degradation rate of MB.The results showed that the removal rate was 93.6%under the optimal conditions:the amount of H2O2 was 6.68 g/L,the concentration of CQDs was 3.24 g/L,the initial concentration of MB was 10 mg/L,the reaction time was 180 min.The kinetic response of CQDs to MB is in accordance with the quasi-first order kinetic model.?3?The graphite carbonitride materials were prepared by calcination of urea and melamine as raw materials.The SEM results showed that the graphite-type carbon nitride?g-C₃N₄?prepared with urea as the raw material had a better morphology of lamellar.The?g-C₃N₄/CQDs?composites were prepared by combining graphite carbonitride with carbon quantum dots.The degradation effect of MB was studied by using g-C₃N₄/CQDs as Fenton-like catalyst.The degradation rate of MB by g-C₃N₄/CQDs composite was 91.2%by using ultrasonic-Fenton-like technology,while that of g-C₃N₄ is 15.5%.It was investigated that the effects of the amount of catalyst,pH,the initial concentration of MB and the amount of H2O2 on the degradation rate of MB.The results showed that the removal rate which was 97.1%of MB was the best when the amount of H2O2 was 0.3388 g/L,the concentration of g-C₃N₄/CQDs was 0.66 g/L,the initial concentration of MB was 10 mg/L.The kinetic response of g-C₃N₄/CQDs to MB is in accordance with the quasi-first order kinetic model.The degradation rate of the catalyst was 90%after 4 cycles,indicating that the g-C₃N₄/CQDs composites had better recycle performance.