Adsorption Of Cationic Dye And Heavy Metals From Aqueous Solutions Onto Organic Sepiolite

Heavy metals and dyes are recognized as two types of hard processing materialin wastewater. Characterized in economic, efficient, sepiolite was widely used invarious wastewater. In this study，sodium dodecyl benzene sulfonate(SDBS) wasintroduced onto sepiolite to obtain a new absorbent with high adsorptionproperties.The newly-synthesized adsorbent was then applied in the treatment ofcrystal violet，lead(Ⅱ)，and cadmium(Ⅱ).Results showed that the saturated adsorption capacity of crystal violet ontomodifided sepiolite was130.30mg/g,which made the sepiolite after modification aeconomical adsorbent. The adsorbent performed well when the initial concentrationwere from50mg/L to400mg/L on the condition that pH was9，oscillation rate was200r/min，dosage was2g/L，equilibrium time was6h. Thermodynamics fitting resultsmet Langmiur adsorption isotherm model, and adsorption was monolayeradsorption.The adsorption of crystal viole met pseudo second order model, and theactivation energy of adsorption was13.05kJ.mol-1, which indicated that the adsorptionassigned to a Chemisorption. A concentration of0.2mol/L HCL was used inregeneration for4h, and the decolorization rate was60.61%after regeneration.Thermodynamic study showed that, G0， H＞0, S＞0, the whole adsorptionprocess was a spontaneous endothermic process.Surface area analysis showed that, the surface area decreased from48.54m2/g to30.14m2/g after modification. Combined with SEM results, the aggregates of thesurface of organically modified sepiolite decreased，surface was covered with a film.The fourier transform-infared spectroscopy analysis showed that SDBS chemicallybonded to the surface of sepiolite or fitted in the pores, and then formed thehydrophobic layer. XRD characterization results showed that there was no big changein crystal structure after the modification compared with the original sepiolite. Theadsorption was dominated by ion exchange, namely sodium on the SDBS-sepilite wasreplaced by the dye cation. The adsorption amount by ion exchange accounted for73.26%of the total adsorption capacity. Besides, Electrostatic adsorption, van derWaals’ force, and partition effects had an effect on the adsorption.In the static adsorption experiment of dye and heavy metal mixture, there werecompetition between crystal violet, lead and cadmium. Compared with that in single system，removal efficiency of each specie was lower than in multisolute systems.Removal efficiency of Pb(Ⅱ), CV, Cd(Ⅱ) were100%,70%,24%respectively insingle system， higher than80.13%,42.43%,21.86%in multisolute systems. Thedropping extent: CV>Pb(Ⅱ)>Cd(Ⅱ). The adsorption met pseudo second ordermodel.Thermodynamic studies showed that the reaction can be successfully describedwith Langmiur isotherm model. Adsorption equilibrium concentration of eachconstituent and adsorption capacity could be described by the extended Langmuirmodel.