| The paper take the agricultural soils include purple soil,yellow soil,paddy soil in the Mingshan River Basin for example,study on the adsorption characteristics of chromium(Ⅵ) between different soils and particle size,due to the impact of organic matter in the soil,it is difficult to distinct the adsorption and reduction reactions,in order to find out the role of soil organic matter,through study the adsorption characteristics of chromium(Ⅵ)between the removal of organic matter and different soils including particle size,include:It can be described with a rapid reaction and a slow reaction that Acidic soil, neutral soil,calcareous purple soil, yellow soil and two paddy soils adsorb chromium (Ⅵ) in the changes over time within 24h.Using five common kinetic equation describ the adsorption of 6 soil and each particle, in addition to calcareous purple soil, the fittingwere highly significant correlation.In addition to calcareous soil, the soil of the original soil and different particle size adsorb chromium (Ⅵ) ption in the 24h time-varying regularity in the performance of the consistency. Between the various soil and different particle sizes, the clay (<0.002mm) of adsorb chromium (Ⅵ) is the most obvious advantages of adsorption, the adsorption in the different periods were higher than the original soil and other particle size.The overall trend of the adsorption sequence is clay (<0.002mm)> silt (0.02mm-0.002mm)> original soil> sand (> 0.02mm). In the acidic soils, the adsorption is consistented with free iron oxide content,the adsorption sequence of neutral and calcareous soil is Inconsistent.With free iron oxide content, and the organic matter Inhibit the adsorption. Acidic soil, neutral soil, calcareous purple soil, yellow soil and two paddy soils adsorb chromium (Ⅵ) in the gradient of concentration range,the adsorption increased with the increase of equilibrium concentration, generally speaking, the adsorption amount of clay (<0.002mm) is largest in all soil,the advantage of the adsorption is most obvious.The yellow soil of adsorption capacity is strongest.The maximum adsorption concentration was significantly higher than other soil. Uising Langmuir and Freundlich equation fit the Isothermal adsorption curve to the six kinds of soils, the fitting is significantly correlated. After the removal of organic matter,the Kinetic curve of acidic soil, calcareous purple soil, yellow soil and alternating wet and dry paddy soil showed the process of shocks,it taked adsorption- desorption-adsorption-desorptionbehavior,the neutral purple soil was taked the way of rapid adsorption-desorption-little adsorption finish the adsorption process.The Kinetic curve of winter paddy field was Similar to the unremoval organic matter,take a rapid response and a slow reaction complete the adsorption until the equilibrium.The adsorption rule of the particle size within the group showed consistency. Using equation to describe the 6 soil and each particle, then fitting the dynamic equation, the correlation was not significant.Six soil sorption isotherm curve and the trend is not Consistent with removal of organic matter.The Isothermal adsorption curve of 6 soils was Similar to the unremoval organic matter.When the equilibrium solution of chromium (Ⅵ) concentration was lowwer, adsorption amount increased sharply with the concentration increasing,the adsorption rate is about 90%-100%,but the adsorption capacity of clay was decreased.Only the acid purple soil and calcareous purple soil on chromium (Ⅵ) adsorption to clay was the best. Langmuir and Freundlich equations were used to fit the equation of isotherm, the 24 tested soil samples only accept the part of soils were not significant. By comparing the adsorption amount between before and after remove organic matter, instruct that:In the case of low pH value, between organic matter and free iron oxide of chromium(Ⅵ) adsorption are mutually reinforcing processes, but at high pH (alkaline) conditions, between organic matter and free iron oxide exist mutual inhibition. It can affect that the pH was the key factors for the chromium (Ⅵ) adsorption.At lower pH, the Adsorption amount mainly was controlled with free iron oxide,and organic matter on chromium (Ⅵ) adsorption play a catalytic role; at high pH value condition, the organic matter controled the chromium (Ⅵ) adsorption,and inhibited the free iron oxide adsorbed the chromium (Ⅳ). |
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