Preparation Of Fly Ash Based Adsorbent And Its Adsorption Performance On Dyes

Fly ash(FA),which is a waste and mainly composed of vitreous and burnt carbon derived from the coal burning for energy production.Lots of Si and A1 active sites are on the surface of FA,and the specific surface area and particle size is bigger.It can be used in wastewater treatment for removal of dyes to realize the utilization.FA usualy can be as the silica-based materials for the high content of Si.On the basis of the traditional modification of FA,the paper studied inorganic,inorganic,organic-inorganic hybrid modification and combined extraction purification technology,and discussed the adsorption of dye wastewater.The main research contents and results are as follows:(1)Fly ash(FA)modified by Ca(OH)2/Na2FeO4 was used as adsorbent for methyl orange(MO)wastewater treatment.The effect of parameters(contact time,dosage ofadsorbent,initial concentration of MO)on MO adsorption are optimized.At the optimized conditions:4.00 X 10-3g/mL of adsorbent,50 mg/L MO,40 min,the raw pH value(pH = 10),99.2%color removal was achieved at room temperature.The thermodynamic and kinetic of the adsorption processes were also studied,and further discussed correlated with the surface structure(XRD)and morphology(SEM,BET).(2)High-efficient inorganic/organic hybrid composite adsorbents derived from(Ca(OH)2/Na2FeO4)modified FA(MF)was fabricated.The hydrophilic cationic polymer(P(DMDAAC-co-AAM)or hydrophobic modifier(KH-570)were used.The prepared composites were characterized by X-ray fluorescence spectroscopy,energy dispersive spectroscopy,scanning electron microscopy,Brunauer-Emmett-Teller,Fourier transform infrared spectroscopy,thermogravimetry,and contact angle test.The adsorption of cationic compos-ites MF/P(DMDAAC-co-AAM)towards Orange Ⅱ in wastewater was investigated.The results show that:adsorption amount of 24.8 mg/g with 2000 mg/L of composites,50 mg/L Orange Ⅱ,original pH(6-8),at 40 min and room temperature,was obtained.Meanwhile,oil adsorption ratio Q(g/g)of hydrophobic composites MF/KH-570 was also evaluated.The maximum Q of 17.2 g/g to kerosene was obtained at 40 min.The isotherm and kinetics of these two adsorption processes were also studied.(3)Here,high-purity SiO2 was extracted from FA via organic acid/inorganic alkali/ultrasonication-assisted joint process and characterized by scanning electron microscopy,transmission electron microscopy,Brunauer-Emmet-Teller,X-ray fluorescence spectroscopy,X-ray diffraction,and X-ray photoelectron spectroscopy.The optimal extracting conditions were optimized:with acetic acid(HAc)leaching at 25 ℃ for 1 h and FA/HAc of 1:3;then with 15%NaOH dissolution at 100℃ for 2 h and FA/15%NaOH ratio of 1:4,5;cooled and introduced water(5.42 g/100 mL);ultrasonication-assisted for 20 min.The final yield and purity of SiO2 were 51%and 98.65%,respectively.This joint method could be applied in several various FA raw materials,which extended the application and recycling of FA.And discussed the adsorption properties of cationic dyes MB and MG,the results shows that SiO2 has a good removal efficiency of all two dyes but the adsorption rates are different,99.9%and 99.7%color removal on MG and MB was achieved at 3h and 500s respectively.