Study On Adsorption Of Crystal Violet And Methylthionine Chloride By Peat In Wastewater

The adsorption performance of two dyes,crystal violet and methylthioninechloride,on natural peat and nitrifying peat were studied by research．The effects ofthe dosage of sorbent,initial concentration of dye,initial pH value,temperature andadsorption time on the adsorption were discussed. Furthermore,adsorption dynamicsand adsorption uniform temperature types of two kind of absorbent were studied.Theresearch conclusions indicated:Peat had strong adsorption performance. Actived by nitric acid could improveand enhace adsorption capacity of peat. The factor that affecting the adsorption ofdyes on peat included:dosage of sorbent,initial concentration of the dye,pH,temperature and adsorption time when the experimental range was as follows: dosageof adsorbent 0.03g～0.09g, initial concentration of the dye 10～15mg/L,pH value5.0～8.0, temperature 298K～328K, and shaking time 5～90mins. The removal of basicdyes onto peat as an adsorbent was increased by decreasing ionic strength,and byincreasing pH,sorbent dosage and adsorption time, while,the adsorption capacity ofdyes was increased by decreasing sorbent dosage,and by increasing pH value andionic strength.The adsorption ability of crystal violet and methylthionine chlorideonto peat as an adsorbent were increased by increasing temperature.When thetemperature was 298K,the adsorbing effective of the two sorbents were adsorbing ofmethylthionine chloride onto nitrifying peat>adsorbing of crystal violet ontonitrifying peat>adsorbing of methylthionine chloride onto natural peat>adsorbing ofcrystal violet onto natural peat.The rate of adsorption of two dyes on the two sorbents were rapid.The removaland adsorption capacity of dyes rose rapidest at the begin of 5min.The adsorptionequilibrium 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.Theadsorption isotherm date of methylthionine chloride on peat fitted the Langmuir andFreundlich adsorption isotherm both well,and the adsorption isotherm date of crystalviolet on peat fitted the Langmuir isotherm better than Freundlich isotherm.Thethermodynamic analysis indicated:on the one hand,the standard thermodynamicfunction changes of the adsorbtion of crystal violet onto peat wereΔH＞0,ΔG＜0,ΔS＞0,which explained that the adsorption was a spontaneous endoergicprocess.At the same time,the adsorption enthalpy changes absolute value was lowerthan 40kJ/mol which showed the adsorption was primarily due to physical adsorptionand the increased temperature was advantageous to the adsorption.After theadsorption,the system became disorder even more；on the other hand,the standardthermodynamic function changes of the adsorbtion of methylthionine chloride ontopeat wereΔH＞0,ΔG＜0,ΔS＞0,which expressed that the adsorption was aspontaneous endoergic process.The adsorption enthalpy changes value was lower than40kJ/mol which explained that the adsorption was mainly due to physical adsorptionand the increased temperature was advantageous to the adsorption.After theadsorption,the system became disorder even more.