Preparation And Adsorption Catalytic Mechanism Of Silica-zeolite/ Nano-TiO₂ Composite Functional Material Based On Advanced Treatment Of Cyanide-containing Wastewater

Cyanide as an excellent complexing agent is widely used in production processes such as electroplating and metallurgy.Especially in the gold smelting industry,the amount of cyanide is huge,and the wastewater containing high concentration of cyanide,copper,zinc and other heavy metal ions is discharged.Cyanide is a highly toxic substance and has a very low lethal dose to organisms,which seriously threatens the life safety of humans and animals.At present,the methods for treating cyanide-containing wastewater are more,but all of them have some defects,which hinder their application in practice.Therefore,exploring an efficient and clean method to treat cyanide-containing wastewater is of great significance to the development of environmental protection and gold smelting industries!Photocatalytic oxidation technology has been widely concerned because of its high efficiency in degradation of organic matter and simple reaction conditions.Photocatalyst nano Ti O₂ has become a research hotspot due to its strong photocatalytic activity,high stability and non-toxic,and has been widely used to deal with environmental pollution problems.However,the application of Ti O₂ particles is limited due to its easy agglomeration,wide band gap（3.2 e V）,and easy recombination of generated photogenerated electron-holes.Based on the analysis and discussion of the existing treatment methods of cyanide-containing wastewater,this paper proposed a method for efficiently and cleanly removing of CN^-,Cu²⁺and Zn²⁺from cyanide-containing wastewater by silica zeolite supported modified nano-Ti O₂ material under ultraviolet light irradiation.The performance of Ti O₂ is improved by doping metallic elements（Mn,Fe）or nonmetallic elements（N）with silica zeolite loaded with high specific surface area and uniform pore size.Si-based nano-Ti O₂ and elemental doped Si-based nano-Ti O₂ powder materials prepared by the sol-gel method are used as the photocatalyst,and the high-pressure mercury lamp is used as the light source.The main research results of this paper are as follows:（1）The silicon-based nano-Ti O₂ is prepared,and the scanning electron microscope（SEM）and BET show that the nano-Ti O₂ is uniformly supported on the surface of the silicon-based carrier.The specific surface of the material was 146.6±2.4m²/g,which was 7 times that of pure Ti O₂.The photocatalytic results show that:1)After 1 h of stirring in the dark,2 h of light,and standing for 5 h,the cyanide and copper ion removal efficiency of silicon-based nano-Ti O2 materials are 95.5%and 80%,respectively.2)The photocatalytic degradation of CN^-by nano-Ti O₂ conforms to the pseudo-first-order kinetic model,the silicon-based nano-Ti O₂ has higher adsorption catalytic performance,and the reaction rate constant is increased by 2.83 times.3)After the catalysis,the p H value of the solution is about 7,there is no volatilization of HCN during the photocatalysis process,and the degradation of cyanide is entirely due to the contribution of photocatalysis.（2）The effects of single doping and co-doping of metallic elements（Mn,Fe）and non-metallic element（N）on the photocatalytic degradation of cyanide-containing wastewater by nano-Ti O₂ are studied.1)The materials are characterized by scanning electron microscopy/energy spectroscopy with EDS（SEM/EDS）,X-ray diffraction（XRD）,Brunner-Emmet-Teller（BET）,ultraviolet spectrum（UV-Vis）,thermal gravimetric（TGA）,X-ray photoelectron spectroscopy（XPS）and X-ray fluorescence spectrometry（XRF）.The results show that the doped elements Mn,Fe and N are uniformly dispersed;Ti O₂ is anatase type,and element doping does not change the crystal phase structure of the material;Metal element（Mn,Fe）doping can increase the specific surface area of the material,while non-metallic element（N）doping can reduce the specific surface area of the material.2)The experimental results show that the silicon-based nano-Ti O₂ co-doped with Mn-N has the best photocatalytic performance,and the best doping amount is 0.05%Mn and 7%N.3)The effects of the loading ratio with Ti O₂and silicon-based,roasting temperature of the material,initial concentration of cyanide-containing wastewater,initial p H of the reaction solution,and the material dosage on the photocatalytic degradation of cyanide-containing wastewater by Mn-N co-doped silicon-based nano-Ti O₂ are investigated.（3）The photocatalytic degradation of cyanide-containing wastewater by Mn-N co-doped silicon-based nano-Ti O₂ is analyzed.1)XPS and density functional theory show that the high catalytic performance is due to the new electronic state that overlaps the valence band when co-doped,which increases the photo-generated electron-hole transfer rate.2)h⁺and·OH are important active substances in the photocatalytic degradation process.3)Cyanide is finally decomposed into NO₂ and CO₂,and Cu ions and Zn ions are adsorbed on the surface of the material in the form of divalent.