Modification Of Graphite Phase Carbon Nitride And Its Photocatalytic Reduction Of Hexavalent Chromium In Water

With the development of the printing and dyeing industry,the widespread use of dyes has led to the discharge of dye wastewater into natural water.Dye-containing industrial wastewater has complex composition,high mass concentration and is not easy to degrade.In this paper,the characteristics of g-C3N4 alginate microspheres and the application status of carbon nanotubes were analyzed by summarization and research.It was found to have a high specific surface area,a rich pore structure and strong adsorption.Through the synergy between them,such as surface chemistry and other properties,the performance of the composite is superior to any single material.Compared with other treatment methods,the adsorption method has the characteristics of simple process,strong operability and no secondary pollution.Photocatalytic technology is applied to dye wastewater due to its high efficiency,economy and environmental protection.There are three main processes for reducing dye wastewater by photocatalytic technology.First,the semiconductor material absorbs light energy to excite photoelectrons to generate electron-hole pairs,and then photoelectrons transition from valence band to conduction band.Finally,photoelectrons on the conduction band remove dye wastewater.Graphite-type carbon nitride(g-C3N4),a novel semiconductor non-metallic material,has good chemical stability and thermal stability,low cost,non-toxicity,small optical band gap value(2.7 eV),visible light response.And other characteristics,and is widely used in the field of photocatalysis.When we study the mechanism of dye wastewater removal efficiency of g-C3N4,we found that single g-C3N4 has a small specific surface area and high photoelectron and hole recombination rate,so it does not achieve the desired effect,and carbon nanotubes are unique in structure and excellent.The mechanical properties were first discovered during the preparation process.Electrical and chemical properties,showing a wide range of applications,attracting many scientists in the field of materials,physics,electronics and chemistry are very concerned about it and become a new international material field.Research frontiers and hot spots.At present,the research on the characteristics and preparation methods of carbon nanotubes has made great progress,with emphasis on mass production and application.In the field research,the combination of carbon nanotubes and g-C3N4 reduced the recombination efficiency of photoelectrons and holes,and improved the removal rate of materials and printing and dyeing wastewater,which greatly accelerated the reaction rate.The following studies were carried out in combination with the above:(1)synthesizing g-C3N4 and CNTs semiconductor materials,and further synthesizing Ca@alginic acid microspheres loaded g-C3N4 and carbon nanotube composite materials,and performing SEM on the morphology,structure and chemical properties of these three materials respectively.Characterization of XRD,TGA,FI-IR,EDS,ESR,TEM,PL,etc.The results show that the composite has good ductility and a certain microporous structure.The adsorption of methylene blue is mainly s-triazine ring.(2)Using a high temperature thermal polymerization method,melamine was selected as a precursor to prepare a pale yellow bulk g-C3N4.The g-C3N4 was ground and sieved,and the surface-repaired carbon nanotubes were added to recombine the carbon nanotubes at different reaction times and different amounts of carbon nanotubes.The effects of photocatalytic removal of methylene blue on the quality of the composite materials were investigated.The study showed that the photocatalytic degradation of MB was carried out by using different materials of AGS.The degradation effect of AGS loading g-C3N4/CNTs was much higher than that of AGS loading single g-C3N4 or CNTs,and when the ratio of g-C3N4 to CNTs was 1:I The effect is the best.The most economical and environmentally friendly treatment efficiency of the composite material is 0.5g.The treatment of 200mL of 50mg·L-1 MB has high photocatalytic efficiency after 7 cycles of experiments.(3)Ca@alginic acid microsphere-loaded g-C3N4 and carbon nanotube composite materials are effectively used as adsorbents.The effects of temperature,pH,reaction time and initial concentration of MB on the removal of MB by Ca@alginic acid microspheres loaded with g-C3N4 and carbon nanotube composites were investigated.The results show that the maximum adsorption capacity is at pH 13,and the best-fit kinetic model is a pseudo second-order kinetic model.The maximum adsorption temperature was 20°C.The maximum adsorption capacity of MB was 119.05 mg·g-1 by Langmuir isotherm adsorption equation.The photodegradation kinetics of the composites followed the second-order kinetics.It has been studied that the regeneration and reuse of adsorption-photocatalysts have also been carried out for up to seven cycles,but due to the influence of microorganisms,the cyclic adsorption effect is not good.