| It has been the research focus for dyeing wastewater treatment due to its serious pollution and difficult treatment.Chemical method,physical method and biological method have their own advantages and disadvantages,among which physical adsorption method always takes a certain place because of its simple operation,low cost and and renewability both for dye molecules and adsorbents.Otherwise,the development of new adsorbents,which are efficient,rapid,environmentally friendly and reusable,has always been an urgent topic in this field.Hydrotalcite could be used to adsorpt and exchange anion dyes due to its own special structural that the main layers are positive and has exchangable anions in the interlayers.However,cations and anions coexist in the real dyeing wastewater.Thus it has become a hot research topic to develop an adsorbent which can remove both cationic and anionic dyes high-efficiently.In this paper,modification of magnesium aluminum layered double hydroxide(LDH)with two anionic surfactants,sodium dodecyl sulfate(SDS)and sodium dodecyl benzene sulfonate(SDBS),was made by direct co-precipitation method and theirs adsorptive properties for rhodamine b(Rh B)and methyl orange(MO)were investigated.The effects of adsorbent amount,the inicial concentration of Rh B and MO solution,p H,contact time on remval efficiency were also been investigated.Combined the charaterizations of XRD、SEM、FTIR and TGA etc.with the adsorption kinetics model and adsorption isotherm model,the following conclusions could be drawn:(1)Mg-Al hydrotalcite intercalated with dodecyl sulfate ion and sodium dodecyl benzene sulfonate can be synthesized directly by co-precipitation method,after which the interlayer spance becomes wider without changing the structure of the laminate.(2)Both the synthesized MgAl-SDS-LDH and MgAl-SDBS-LDH could adsorb the cationic dye Rhodamine B(Rh B)and the anionic dye methyl orange(MO)in a broad p H range.(3)The adsorption processes of Rh B and MO by both MgAl-SDS-LDH and MgAl-SDBS-LDH tend to conform to the quasi-second-order kinetic model.(4)The adsorption of Rh B by MgAl-SDS-LDH and MgAl-SDBS-LDH accords with the Langmuir isotherm model,which is a monolayer adsorption.The maximum adsorption capacity of MgAl-SDBS-LDH for Rh B adsorption is 98.61mg/g;the adsorption of MO by MgAl-SDS-LDH and MgAl-SDBS-LDH accords well with the Freundlich isotherm model,but the maximum adsorption capacity of MgAl-SDS-LDH for MO adsorption is larger,which is 1648.33 mg/g.(5)The experimental mechanism analysis showed that Rh B molecules were adsorbed on the surface of the MgAl-SDBS-LDH by electrostatic force,while MO could not only be adsorbed on the surface of the MgAl-SDBS-LDH by electrostatic force,but also enter into the interlayer of the MgAl-SDBS-LDH by ion exchange.Moreover,the regeneration performance of MgAl-SDS-LDH is better than that of MgAl-SDBS-LDH. |
