Study On Adsorption Of Acid Red 57 And Acid Blue 62 By Sepiolite In Wastewater

The adsorption performance of two dyes,acid red 57 and acid blue 62,on natrual sepiolite and heating sepiolite were studied by research.The effects of the dosage of sorbent,initial pH value,initial concentration of dye,temperature and adsorption time on the adsorption were discussed.Also, adsorption dynamics and adsorption uniform temperature types of two kind of absorbent were studied.The research conclusions indicated:Sepiolite had strong adsorption performance. Heating actived by muffle could improve and enhace adsorption capacity of sepiolite. The factor that affecting the adsorption of dyes on sepiolite included: dosage of sorbent,pH,initial concentration of the dye,temperature and adsorption time.The removal of acid dyes onto sepiolite as an adsorbent was increased by decreasing pH and ionic strength ,and by increasing sorbent dosage and adsorption time, while, the adsorption capacity of dyes was increased by decreasing sorbent dosage and pH value,and by increasing ionic strength.The adsorption ability of acid red 57 onto sepiolite as an adsorbent was decreased by decreasing temperature while the adsorption ability of acid blue 62 was increased with higher temperture. When the temperature was 298K,the adsorbing effective of the two sorbents were adsorbing of acid blue 62 onto heating sepiolite > adsorbing of acid red 57 onto heating sepiolite> adsorbing of acid blue 62 onto natural sepiolite > adsorbing of acid red 57 onto natural sepiolite.The rate of adsorption of two dyes on the two sorbents were rapid . The removal and adsorption capacity of dyes rose rapidest at the begin of 5min.The adsorption equilibrium was nearly reached at 90min.The adsorption dynamics of two dyes on the two sorbents all followed the law of the second-order eqution of Lagergren. The adsorption isotherm date of acid red 57on sepiolite fitted the Freundlich and Langmuir adsorption isotherm both well,and the adsorption isotherm date of acid red 57 on sepiolite fitted the Freundlich isotherm better than Langmuir isotherm.The thermodynamic analysis indicated :on the one hand,the standard thermodynamic function changes of the adsorbtion of acid red 57 onto sepiolite wereΔH<0,ΔG<0,ΔS<0, which explained that the adsorption was a spontaneous exothermic process. At the same time,the adsorption enthalpy changes absolute value was higher than 40kJ/mol which showed the adsorption was primarily due to chemical adsorption and the reduced temperature was advantageous to the adsorption.After the adsorption, the system became order even more;on the other hand, the standard thermodynamic function changes of the adsorbtion of acid blue 62 onto sepiolite wereΔH>0,ΔG<0,ΔS>0, which expressed that the adsorption was a spontaneous endoergic process.The adsorption enthalpy changes value was lower than 40kJ/mol which explained that the adsorption was mainly due to physical adsorption and the increased temperature was advantageous to the adsorption.After the adsorption ,the system became disorder even more.