Adsorption Of Anionic Dyes From Aqueous Solutions Onto Organic Modified Sepiolite

Dye wastewater with high concentration, high turbidity and difficult degradationare discharged into water without treated, which has caused great harm toenvironment and human health. Sepiolite is an adsorbent with large surface area, ionexchange capacity and low prices, which is widely used in the treatment of varioustypes of wastewater. The adsorption of three anionic dyes, acid orange II, reactiveblue and acid Fuchsin onto modified sepiolite was studied, which had a greatsignificance on dye wastewater treatment.Heating and organic modification were combined to modify the sepiolite. Resultsshowed that the modification effect of CTMAB-sepiolite was the best when thecalcination temperature was200℃and the amounts of CTMAB was1.0CEC. Themaximum adsorption capacity of104.17mg/g of acid orange II was achieved when pHwas1, oscillation rate was180r/min, dosage was2g/L, equilibrium time was120min.A concentration of0.8mol/L NaOH was used in regeneration for2h, and thedecolorization rate was62.23%after regeneration. The adsorption of acid orange IIfollowed pseudo second order model, and the activation energy of adsorption was12.56kJ.mol-1, which indicated that the adsorption assigned to a chemisorption.Thermodynamic study showed that the adsorption of acid orange II followedLangmuir model, H=－10.31kJ·mol-1<0， G0， S=－1.676J·mol-1·K-1, thewhole adsorption process was spontaneous exothermic reaction and the degree offreedom decreased.The Scanning Electron Microscope analysis showed that the CTMAB-sepiolitewas more loosely and the gap seemed clean. Surface area analysis showed that thesurface area decreased from48.54m2/g to16.52m2/g after modification. The FT-IR,XRD and XPS results showed that CTMAB did not expand the bore but attached tothe edges of sepiolite. The adsorption was dominated by ion exchange, namely thecounter-ion bromide on the CTMAB-sepilite was replaced by the dye anion. Theadsorption amount by ion exchange accounted for65.42%of the total adsorptioncapacity. Besides, Van der Waals’ force, hydrogen bonds and partition effects had aneffect on the adsorption.The adsorption of single and multisoulute dyes onto CTMAB-sepiolite wasinvestigated in a series of batch adsorption experiments with three anionic dyes (Acid Orange II, Reactive Blue, Acid Fuchsin). The experiments determined the optimal pHthat was1in single and multisolute systems. Competition adsorption existed inmultisolute systems, the descending extent of decolorization rate in the system wasAcid Orange II> Reactive Blue> Acid Fuchsin. Adsorption kinetics of single andmultisolute systems followed pseudo second order model, the equilibrium time ofmultisolute was much shorter due to the high initial concentration.The relationship between the total amount of absorbed dyes and total equilibriumconcentration in single and multisolute systems followed Langmuir isotherm model.The isotherm of each individual dye followed expanded Langmuir isotherm model andthe dye was adsorbed easier when the value of Langmuir adsorption equilibriumconstant was larger.