Study On The Preparation Of Mesoporous Silica From Amino-modified Inorganic Silicon Source And Its Adsorption Properties For Cu²⁺ And Pb²⁺

The waste water containing heavy metal ions from industrial production can cause heavy metal pollution.Adsorption method is widely used in the treatment of wastewater containing copper and lead.In the selection of adsorbent materials,mesoporous materials play an important role in many fields such as catalysis and adsorption because of their highly ordered pore structure,large specific surface area and good thermal stability.Their modification enhances the ability to remove heavy metal ions from water.However,current research mostly uses expensive silanol salts and silicate lipids as silicon sources,which restricts its wide practical application.Therefore,finding low-cost raw materials is one of the research hotspots.Fly ash,as one of China’s largest solid wastes,is a good raw material for preparing mesoporous materials because of its rich aluminum and silicon resources.Therefore,this article uses inorganic silicon sources extracted from low-cost fly ash as raw materials and uses surface modification to remove Cu²⁺and Pb²⁺.The main research conclusions are as follows:（1）In this study,different methods are used to synthesize mesoporous Si O₂（GS and SS） using inorganic silicon sources extracted from fly ash.The specific surface areas of GS and SS are 828.918 m²/g and 677.498 m²/g,respectively,and their adsorption capacities for 200mg/L Cu²⁺in water are low at 2.139 mg/g and 10.632 mg/g,respectively.（2）Surface modification is used to modify GS and SS.The effects of different APTES addition amounts,different condensation reflux times,different condensation reflux temperatures,and different ultrasonic times on the amino modification of GS-NH₂ and SS-NH₂ are further investigated.The optimum preparation conditions for GS-NH₂ are:GS 0.5g,ethanol 100 m L,APTES 0.75 m L,condensation time 24 h,condensation temperature 90^oC,and ultrasonic time 30 min.At this time,the amino characteristic peak of GS-NH₂ is the most obvious.GS-NH₂ is a spherical particle with a specific surface area of 415 m²/g.The optimum preparation conditions for SS-NH₂ are:SS 0.5 g,ethanol 50 m L,APTES addition amount 1.25 m L,condensation time 6 h,condensation temperature 50 ^oC,and ultrasonic time 50 min.At this time,the amino characteristic peak of SS-NH₂ is the most obvious.SS-NH₂ is a spherical particle with a specific surface area of 351.382 m²/g.The successful modification of the amino groups in APTES on the surface and pores of GS and SS by surface modification is demonstrated using a series of characterization analyses.（3）GS-NH₂and SS-NH₂ are used as adsorbents for the single-ion adsorption of Cu²⁺and Pb²⁺.Different adsorption times,adsorbent dosages,p H,and initial concentrations are investigated.The removal rates of Cu²⁺and Pb²⁺by GS-NH₂ are 95.97%and 99.78%,respectively,and the maximum adsorption capacities of 200 mg/L Cu²⁺and 200 mg/L Pb²⁺in water by GS-NH₂ are 55.638 mg/g and 46.312 mg/g,respectively.The removal rates of Cu²⁺and Pb²⁺by SS-NH₂ are 90.86%and 97.09%,respectively,and the maximum adsorption capacities of 200 mg/L Cu²⁺and 200 mg/L Pb²⁺in water by SS-NH₂ are 62.212mg/g and 106.032 mg/g,respectively.GS-NH₂ and SS-NH₂ are effective in the adsorption of Cu²⁺and Pb²⁺by virtue of-NH₂.The adsorption kinetics of GS-NH₂ and SS-NH₂ on Cu²⁺and Pb²⁺in water are in accordance with the pseudo-secondary kinetic model,indicating that their adsorption of Cu²⁺and Pb²⁺in water is mainly controlled by chemical interactions.（4）GS-NH₂ and SS-NH₂ are used as adsorbents for competitive adsorption of Cu²⁺and Pb²⁺.Different adsorption time,adsorbent dosage,p H,and initial concentration are investigated.The removal rates of Cu²⁺and Pb²⁺by GS-NH₂ are 75.47%and 65.2%,respectively,and the maximum adsorption capacities of Cu²⁺and Pb²⁺in 200 mg/L Cu²⁺and Pb²⁺mixed solution in water by GS-NH₂ are 20.01 mg/g and 21.96 mg/g,respectively.The adsorption capacity of Cu²⁺is slightly higher than that of Pb²⁺for single ion adsorption by GS-NH₂,while the adsorption capacity of Pb²⁺is slightly higher than that of Cu²⁺for competitive adsorption.The removal of Cu²⁺and Pb²⁺by SS-NH₂ is up to 100%,and the maximum adsorption capacities of Cu²⁺and Pb²⁺in a mixed solution of 200 mg/L Cu²⁺and Pb²⁺in water are 18.72 mg/g and 30.11 mg/g,respectively.It is found that the adsorption capacity of Pb²⁺is much larger than that of Cu²⁺when SS-NH₂ is used for single ion adsorption of Cu²⁺and Pb²⁺in water,and it is also found that the adsorption capacity of Pb²⁺is larger than that of Cu²⁺when SS-NH₂ is used for competitive adsorption.