Adsorption Behaviors Of Phenanthrene And Aniline On The Yellow River Sediment

In this paper,absorption behaviors of phenanthrene and aniline on the Yellow River sediment were studied.Various factors affecting the adsorption process,such as time,pH,temperature,surfactants,dissolved organic matter etc.were examined in detail.Adsorption kinetics,thermodynamics of the process,and effects of sediment properties(eg.organic carbon content,specific surface area)were also discussed.Some meaningful scientific conclusions were got as follows:1.Two sediment samples,Xiwo and Xiaolangdi,from Yellow River were tested mainly for phenanthrene in the experiment.The results showed that Xiwo sediment reachs equilibrium adsorption amount 0.021 mg/g when the initial concentration of phenanthrene is 0.40 mg/L,p H 8.0,temperature 298 K,adsorption time 16 h.And for the Xiaolangdi sediment,equilibrium adsorption amount 0.015 mg/g in the same condions as Xiwo sediment except equilibrium time 20 h.Combining with the properties of these two sediments and others tested,we found that the adsorption of nonpolar phenanthrene has close relation with organic carbon content in the sediments also.By fitting the kinetics of adsorption process on pseudo first-order,pseudo second-order models and Elovich equation,its showed that the pseudo secondary kinetics model fitted the adsorption process well,speculating that the adsorption process of phenanthrene on the sediments is more complexed,propably controlled by multiple diffusion mechanism,such as aqueous film,surface diffusion and adsorbent internal microporous diffusions.Langmuir,Freundlich and Henry models were employed for fitting the adsorption isotherms.The results showed that the Freundlich and Henry models are fitting better,accounting for a partition mechanism adsorption.The adsorption thermodynamics parameters calculated were?G~0(-10.679 KJ/mol,298K),?H~0(-26.01 KJ/mol),the?S0(-0.051 kJ/(mol·K)).The negative?H~0 and?S~0 indicated that the adsorption process is exothermic and the temperature has unfavourble effect to the adsorption.Three surfactants,cationic surfactant cetyl trimethyl ammonium bromide(CTAB),anionic surfactant sodium dodecyl sulfate(SDS)and nonionic surfactant polysorbate 80(Tween-80)were used to their effect on the absorption of phenanthrene.The result showed that all they can promote the adsorption capacity of the sediments for phenanthrene.Disolved organic matter was proved to be positive effect on the adsorptiontoo.2.Aniline,a relative polar organic matter compared to phenanthrene,was used as adsorbate in the experiment.The results showed that aniline is far less adsorbed on the woxi sediment.When the initial concentration of aniline was 5.0 ?g/L,pH 3.0,temperature 318 K,the adsorption time 12 h,adsorption equilibrium reached and the according adsorption amount was 0.06?g/g.By using pseudo first-order,pseudo secondary-order and Elovich kinetics equation to fit the adsorption process of aniline,the results showed that the adsorption process meet with pseudo secondary kinetics.Langmuir,Freundlich and Henry equation fitting show that the Freundlich and Henry model fit well,and the adsorption is mainly controlled by partition provcess.The thermodynamics parameters calculated were?G~0(-7.043KJ/mol,288K),?H~0(2.152KJ/mol),?S~0(0.032kJ/(mol·K)),indicating the temperature is favourable to the adsorption and the driving force of adsorption the process is entropy.The effect of surfactants used on the sediments adsorption for aniline was different from that for phenanthrene.The result showed that both cationic surfactant CTAB and non-ionic surfactants Tween-80 can increase aniline the adsorption,whereas anionic surfactant SDS decreases sediment the adsorption capacity.Disolved organic matter has the similar effect as surfactants CTAB or Tween-80.