Lignin Quaternary Ammonium Salt As Templates For Preparation Of SiO₂ Porous Materials And Its Adsorption Properties Of Cu²⁺

SiO₂ porous materials has broad application prospects in catalysis,adsorption and separation of biological materials,energy and environment,and other fields,mesoporousmasoporous composite materials and multi-porous synthesis was popular in recent years. Template had controled aperture in synthesis porous materials caused researchers widespread concern,especially biological polymer template.As a biological polymer materials,lignin had great productions all over the world,but lignin template for the preparation of porous materials were rarely.In this paper,pulp and paper black liquor recovery of lignin as raw materials,with modified system in the lignin three-quatemary ammonium salt as template,TEOS as silicon source,the sol-gel method for preparation SiO₂ porous materials.By controlling the lignin fractionation,the quality of template,silicon than water,condensation temperature and other factors,control the SiO₂ porous material's surface area and pore size,preparation of mesoporous -masoporous SiO₂ porous materials more uniform pore size and structure stability. SiO₂ porous materials charactered on X-ray diffraction(XRD),infrared spectroscopy(IR), Scanning electron microscopy(SEM),differential thermal analysis-thermogravimetric(TG-DTA), BET surface area and BJH pore size distribution.Analysis of the SiO₂ porous material crystal structure,composition,microstructure,thermal stability,pore size distribution and BET surface area.Researched of SiO₂ porous materials adsorption properties of Cu²⁺and calculate adsorption thermodynamic functions,discussion on the principle of adsorption.The results showed that:The largest surface area of porous materials was 626.37 m² / g,at the condition of silicon water ratio of 1:10,hydrolysis 50℃for 5 h,condensation 80℃for 24 h,the template content was 12%.At the condition of silicon water ratio of 3:20,SiO₂ porous materials surface area reduced with the template quality increased.When the template quality greater than 15%, the porous material was solid;SEM analysis showed that the surface of porous material about 100 nm in diameter,pore size with the increased in quality of template increased,the materials are mainly in masoporous;XRD analysis showed that the SiO₂ amorphous particle state;TG-DTA analysis showed that the removal of templates divided into three stages,at the temperature reached 550℃,lignin was completely removed,when temperature reached 800℃the porous materials no decomposition,proved that the material has good thermal stability;IR analysis showed that lignin quaternary ammonium salt in the composite materials,but not in the porous materials.Lignin through dissolution - precipitation fractionation was divided into three 3 points, P1(pH=6),P2(pH=5),P3(pH=2),GPC analysis showed that Mw and Mw/Mn lower than raw material.P2 as raw material,synthesis lignin quaternary ammonium salt as template, preparation of SiO₂ porous materials,it had the minimum surface area of 143.42 m² / g;N₂ adsorption - desorption isotherm analysis showed that this material had large-shape or slit-parallel-plate porous.Pore size distribution analysis showed that the average pore size was 21.4 nm,the total pore volume was 0.521 cm³ / g,between 2.7-5.6 nm.SEM results showed that the bigest pore 200 nm in diameter,α-K₇[Si W₉Co₃(OH₂)₃O₃₇]degradation of lignin,GPC analysis showed that Mw and Mn lower than raw material,but the Mw/Mn had incresed,it not suitable for preparation uniform pore size of porous materials.SiO₂ porous materials for Cu²⁺ adsorption balance for 5 h,the greatest adsorption capacity of 3.175 mg / g.In acidic conditions,porous materials for Cu²⁺ adsorption capacity increased with pH gradually increase.The enthalpy changesΔH＜0,it was a exothermic process. The energy changesΔG values in the -20 to 0 kJ / mol,belong to physical adsorption.