| At present,with the continuous improvement of the level of economic development,the crisis of water resources shortage is aggravating,and now it is the first risk in the world.In addition,"green development"has become the theme of the development of The Times.Water environmental pollution,as one of the top ten environmental problems in China,has attracted wide attention from all walks of life.As a refractory organic pollutant,p-nitrophenol（PNP）has been listed as a priority pollutant by the United States Environmental Protection Agency（EPA）.How to economically and efficiently remove p-nitrophenol from industrial wastewater has become a research hotspot in the field of water treatment at present.Yellow phosphorus slag,as a solid waste slag of industrial yellow phosphorus production,contains high Si and Ca components and is an excellent material for preparing composite adsorbent.In this paper,high activity,rich pore structure and ordered silicon dioxide matrix materials was prepared by leaching yellow phosphorus slag with nitric acid solution.The composite adsorption material（SiO2-CTAB）was prepared with cetyltrimethyl ammonium bromide（CTAB）as the supporting agent and the SiO2 matrix materials.Taking the adsorption rate of PNP as the index,the extraction process of silicon dioxide,the modified conditions of CTAB and the adsorption conditions were optimized through single factor conditions,so as to achieve the best adsorption effect of the composite adsorbent on PNP,and the raw material and the modified silicon dioxide before and after SEM,XRD,FT-IR and other series of characterization analysis.Finally,the adsorption kinetics,thermodynamics,regeneration properties and mechanism of SiO2-CTAB composite adsorbent were briefly discussed.（1）The optimal extraction conditions for leaching yellow phosphorus slag with nitric acid solution are as follows:liquid-solid mass ratio 13:1,nitric acid mass concentration 12%,acid leaching time 120 min,stirring speed 450 r/min,reaction temperature 60℃.Under these conditions,the adsorption rate of SiO2-CTAB composite adsorbent on 50 mg/L PNP simulated wastewater can reach82.78%,and the adsorption capacity is 41.39 mg/g.The optimum composite conditions of SiO2matrix and CTAB are as follows:p H of the composite solution is 12.5,reaction temperature is 75℃,the mass and mass fraction of CTAB are 260 g and 1.6%,respectively,and the composite time is 5 h.Under these conditions,the removal rate of PNP by SiO2-CTAB composite adsorption material is86.78%,and the adsorption capacity is 43.39 mg/g.The optimum conditions for the adsorption of PNP by SiO2-CTAB composite adsorbent are as follows:water bath temperature is 20℃,solution p H is 6,SiO2-CTAB input is 1.5 g/L,and adsorption time is 50 min.Under these conditions,the removal rate of 50 mg/L PNP simulated wastewater is 96.95%,and the adsorption capacity is 32.32 mg/g.（2）The characterization results showed that,compared with the raw material,the Ca-related compounds were dissolved out,and the components were mainly SiO2;The small particles attached to the surface of large particles are reduced and the surface is smooth.The average particle size decreased significantly from 81.78μm to 63.99μm.The BET specific surface area increased from1.307 m2/g to 519.2 m2/g,and the pore volume increased from 6.683×10-3 cm3/g to 0.7603 cm3/g,which was conducive to the loading of CTAB.After the modification of SiO2 matrix by CTAB,the morphology changes obviously and the surface folds increase.The relative contents of Si,O,C and N changed greatly,and the contents of C and N increased obviously.The particle size is close to normal distribution,and the size difference between particles becomes smaller.A new N1s peak appeared in the XPS spectra,indicating that CTAB was successfully loaded on the surface of the silica matrix.（3）The kinetic research results show that the adsorption behavior of PNP by SiO2-CTAB is more consistent with the pseudo-second-order kinetic model,and the adsorption process is mainly controlled by chemical adsorption.The isothermal data show that Langmuir can more accurately describe the adsorption behavior of SiO2-CTAB on PNP.The maximum adsorption capacity is 157.2mg/g,and the adsorption mode is mainly single layer adsorption.The adsorption process can be spontaneous,and the low temperature promotes the adsorption forward.PNP is loaded on the organic phase on the surface of SiO2-CTAB through distribution,solute absorption and non-competitive adsorption.FT-IR and XPS showed that PNP,as an adsorbent,could successfully adhere to the surface of SiO2-CTAB adsorbent.（4）The research results showed that with 0.1 mol/L HCl as desorption agent,the removal rate of PNP decreased to 38.98%at the fifth adsorption,maintaining the initial adsorption rate of 40.21%.When anhydrous ethanol was used as desorption agent,the adsorption rate of PNP was 65.98%at the fifth adsorption.With 0.01 mol/L Na OH as desorption agent,the regeneration of SiO2-CTAB composite adsorbent can be realized effectively.After four cycles,the removal rate of 50 mg/L PNP remains above 95%. |
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