| During the past few years,with the rapid development of industry and agriculture,a large amount of dye and heavy metal wastewater had been produced,which posed a great threat to human health due to its stable structure,refractory degradation and high toxicity.Among all the extensively researched techniques related to the treatment of such contaminants,adsorption was regarded as a promising method because of its low cost and easy handling.Therefore,preparation of efficient and low-cost adsorbents is the prior research field of adsorption method in wastewater treatment.Among the materials applied to adsorb dye and heavy metal compounds from wastewater,hexagonal mesoporous silica attracted more attention for its tunable pore structures,excellent hydrothermal stabilities and readily organic modification.However,this materials lack active sites,which limits its wide application.Hence,it needs to be modified or loaded with other groups to enhance its adsorption effect and stimulate application potential.In this paper,HMS was used as the matrix,which was modified by nanometallic nickel,nano-zero-valent iron and sulfhydryl groups,to obtain composite nano-metal composite materials and reduce the concentration of dyes and heavy metals in water.The adsorption performance of composite materials for dyes and heavy metals was investigated through batch adsorption experiments.The research results were as follows:(1)Two nickel-modified mesoporous silica composite materials(Ni-C,Ni-S)were synthesized by co-precipitation and sol-gel method using hexadecylamine(HAD)as template.The material retaining the template was first used to remove the acid fuchsin(AF),and then recovered by calcination to remove the basic fuchsin(BF),which realized a kind of adsorbent to remove different acid and basic dyes.The obtained materials were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FTIR)and Brunauer-Emmett-Teller(BET)surface area determination.The optional conditions were obtained for the adsorption of AF on Ni-C and Ni-S by batch adsorption experiments,kinetics,isotherms and thermodynamic models.The adsorption data were in accordance with the pseudo-second-order kinetic model and the Langmuir isotherm model,respectively,and the maximum theoretical adsorption capacity of Ni-S for AF could reach 689.66 mg/g.At the same time,the removal effect of BF between the directly calcined materials(Ni-C-C,Ni-S-C)and calcined after the adsorption of AF(Ni-C-CX,Ni-S-C-X)was not much different,and after three cycles the removal rate was still higher than 60%,which manifested Ni-S had potential application value.The main removal mechanism was electrostatic attraction.(2)Nano-zero-velant iron(NZVI)modified,thiol modified and NZVI and thiol modified bifunctional magnetic mesoporous silica composite materials(NZVI-HMS,SH-HMS,NZVI-SHHMS)were synthesized by sol-gel and wet impregnation methods,which were successfully used to remove heavy metal ions(Pb(II)and Cd(II)).Mesoporous silica could protect NZVI and thiol groups from oxidation,at the same time,NZVI could provide a reducing environment for thiol groups to protect the thiol groups and enhance the stability of the composite materials.Characterization by XRD,SEM,TEM,FTIR,BET surface area determination and XPS indicated NZVI and thiol had been loaded successfully.The adsorption performance of NZVIHMS,SH-HMS and NZVI-SH-HMS was studied through batch adsorption experiments.NZVI-SH-HMS had the optimal removal effect and the pseudo-second-order kinetic model and Langmuir isotherm model were more appropriate to explain the adsorption processes for Pb(II)and Cd(II).The main adsorption mechanisms could be precipitation/co-precipitation and surface complexation between the heavy metal ions and the adsorbents.Adsorption-desorption experiments and actual water simulation experiments implied that NZVI-SH-HMS had good excellent regeneration performance and practical application potential,and it could also quickly achieve solid-liquid separation under an external magnetic field.(3)The synthetic bifunctional NZVI-SH-HMS was used to carry out the adsorption experiment of the mixed system of heavy metal ion(Pb(II))and dye(Acid orange II).Through comparative experiments,it was found that the addition of Acid orange II had little effect on the adsorption of Pb(II)by NZVI-SH-HMS.The optimal conditions for the adsorption of Acid orange II and Pb(II)on NZVI-SH-HMS were investigated through batch adsorption experiments,kinetics and isotherm models.The results showed that for the mixed system,the reaction equilibrium of 20 mg adsorbent to 100 m L 50 mg/L Acid orange II and Pb(II)mixed solutions could be reached within 30 and 50 minutes,respectively,and the removal rates were 64.4% and78.7%,respectively. |
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