| This paper,by using anodic stripping voltammetry as the analytical method,had investigated Adsorption characteristics of arsenite on goethite under the condition of the solution p H,concentration and temperature by using a flow-stirring dynamic device for the adsorption mechanism.In order to monitor arsenic and arsenic pollution of soil restoration and control measures to provide theoretical basis.The results showed as follows:1.Anodic stripping voltammetry was with 0.5 mol·L-1 H2SO4 as bottom liquid,concentration time of 120 s,the enrichment of potential of 1.2 V.the detection limit to the arsenite could be as low as 5?g·L-1,and the test results were consistent with atomic fluorescence and higher accuracy.2.The dynamics of the improved experiment device cooperated to the anodic stripping voltammetric method,which could realize continuous automatic detection adsorption desorption of arsenic on goethite.3.The adsorption process of arsenic could be divided into rapid and slow reactions under different conditions.The maximal of arsenite adsorption fitted by the first order equation remarkably decreased with increase in the solution p H,such as 246.9 mg·kg-1 by the solution p H 3.0 and 99.8mg·kg-1 by the solution p H 7.0,respectively.The rate constant?k'?of the apparent adsorption increased gradually along with the solution p H increase,and so the half reaction time?t1/2?was smaller,shorter the equilibrium time of arsenic adsorption was.At the same time,the b values of diffusion rate constant were reduced gradually.4.With the increase of arsenic concentration,the amounts of arsenic adsorption and the k'values increased gradually.The maximum amount of adsorption of arsenic was 96.5 mg·kg-1 and249.1 mg·kg-1 by 0.1 mg·L-1 and 1.0 mg·L-1 arsenic concentration,respectively.Adsorption constant?Kf?by the Freundlich equation decreased gradually with the extension of the reaction time and ability of adsorption on goethite of arsenite was gradually weakened.Distribution factor?RL?by Langmuir equation was between 0-1,and the adsorption of arsenic on goethite was accounted for the preferential adsorption.5.With the increase of temperature,the maximum amount of adsorption of arsenic was increased,such as 241.1 mg·kg-1 by the temperature of 298 K and 315.6 mg·kg-1 by the temperature of 313 K,respectively.And the k' values of the apparent adsorption rate constant gradually rose in the meantime.The false thermodynamic constants were calculated by the b values of the diffusion rate by the parabolic diffusion equation.The reaction activation energy?Ea*?of Arsenic adsorption was 14.60 k J·mol-1.The change of arsenic diffusion activation enthalpy??H??decreased with the increase of temperature,and ?H? were positive in values and on behalf of the endothermic process.So the rising temperature was beneficial to the diffusion of arsenic.?G? of activation free energy was increased as the temperatures rose,and helpful to accelerate the diffusion process.Entropy of activation??S??was negative in all cases,suggesting that system could improve its degree of order. |
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