| Yellow phosphorus slag is a high-silicon calcium solid waste formed during the production of yellow phosphorus by the electric furnace method.The accumulation of a large amount of yellow phosphorus slag not only pollutes the environment but also affects the growth of animals and plants and human health.Hexavalent chromium is also of great concern to the environment and human body because of its unique toxicity.By recycling the yellow phosphorus slag,not only can comprehensive utilization of secondary resources be achieved,but also the environmental pollution of heavy metal ions can be reduced,which has important social,economic and environmental significance.In this experiment,yellow phosphorus slag was used as the raw material,a high specific surface area silica carrier was obtained by acid leaching,and a SiO2-based composite adsorbent(SiO2+NH2)was prepared by modifying 3-aminopropyltriethoxysilane.Taking the removal rate of Cr(VI)as the main performance evaluation index,the adsorption performance was studied.The process conditions for the preparation of SiO2 from the yellow phosphorus slag and the process conditions for the aminosilane compound process were optimized.The optimal process conditions for the SiO2 preparation process are:nitric acid concentration 14%,liquid-solid mass ratio 9:1,reaction time 30min,stirring speed 300 r/min,reaction temperature 60℃.At this time,the removal rate of Cr(VI)by the adsorbent in 100mL,50mg/L simulated chromium wastewater is 87.1%,and the adsorption capacity is 29.03 mg·g-1;the optimal process conditions for the aminosilane compounding process are:the solvent is The input amount of pure water and aminosilane is 3 mL,the compounding time is 1h,the compounding temperature is 70℃,the solvent volume is 30 mL,the removal rate of Cr(VI)by the adsorbent increases to 97.61%,and the adsorption capacity rises to 32.54 mg·g-1.Scanning electron microscope,laser diffraction,specific surface area determination,infrared measurement and elemental analysis were used to characterize the morphology,pore size distribution and immobilization of aminosilane on silica support:modified silica Compared with before modification,the composite adsorbent has a more uniform particle size and improved dispersion.The energy spectrum analysis results show the presence of O and Si elements,indicating that the calcium ions have been removed.The nitrogen adsorption and desorption curve is a Class IV adsorption isotherm curve,indicating that it is a mesoporous material,and the pore size distribution curve also proves this.The specific surface area and particle size have been reduced.The specific surface area is 304.98 m2·g-1,the average particle size is 40.56 μm,and the particle size is closer to the normal distribution.The results of infrared measurement and elemental analysis both prove that the amino group has been successfully grafted onto silica.Explore the influence of various factors in the adsorption process on the removal rate of Cr(Ⅵ):when the pH is 4,the adsorbent input is 200 mg,the adsorption time is 30 min,the adsorption temperature is 25℃,and the initial concentration of hexavalent chromium is 50 mg/L,The removal rate of Cr(Ⅵ)by the adsorbent in 100mL,50 mg/L simulated chromium wastewater is 99.21%.The quasi-first-order kinetic model and the quasi-second-order kinetic model were used to fit the kinetic data obtained by adsorption at different Cr(Ⅵ)concentrations,and it was found that the correlation coefficients of the two fittings are higher,but the comparison can be found that The experimental data of the adsorption of valence chromium on amino-modified silica materials is more in line with the pseudo-second-order kinetic equation.The Langmuir isotherm equation and the Freundlich isotherm equation were used to fit the adsorption equilibrium data obtained at different temperatures.The adsorption equilibrium data of hexavalent chromium on the amino-modified silica material is more in line with the Freundlich isotherm equation,which is explained as multilayer adsorption.It was found in the experimental research scope that the maximum adsorption capacity of the adsorbent could reach 100.125 mg·g-1.After the adsorption-saturated functionalized material was regenerated for 5 times by acid pickling(HC1)and reused in the adsorption experiment,the removal rate of Cr(Ⅵ)and the regeneration rate of the adsorbent remained above 94%and 97%The research results show that the amino-modified silica adsorbent prepared with yellow phosphorus slag as raw material is an environmentally friendly,low-cost,high-quality adsorbent with stable and renewable quality. |
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