Sorption Mechanisms Of Durion Onto Soils And Carbon Adsorbent

In this paper, the differences of physical and chemical property, as well as surface character between several adsorbents were studied. These adsorbents include soil, charcoal, and three kinds of plantash with different carbon content. The adsorbate was Diuron, used as herbicide. The adsorption isotherm, adsorption/desorption dynamics and thermodynamics of different adsorbents were contrasted with each other. Through these researches, I try to establish the relationship between the adsorbents property and adsorption character, seek the adsorption/desorption mechanism of adsorbents contain carbon. It has supplied science basis when assess the security of organic herbicide. Meanwhile, it also provide theory basis for discuss the action and end-results in nature environment.The results demonstrated that:(1) The physical and chemical property and surface character of absorbents have significance influence. The carbon content and the specific surface area are the important factors on adsorption, in addition, pore volume, pore size, total concentration surface active point position Hs, would also affect the adsorption process.(2) Adsorption isotherms of soil, charcoal and three kinds of plantash are nonlinear characteristics of multi-layer adsorption. The fitting coefficient of Polanyi-Manes is better than Freundlich and Langmuir model. The best fitting adsorption kinetic is the pseudo second order kinetics equation, meanwhile, Elovich equation and diffusion within spherical particles model are not as better as that.(3) The calculated values of adsorption enthalpyâ–³H are negative except plantash-1#, the adsorption is an exothermic process; Gibbs free energyâ–³G are negative, except the plantash-1# in 313K and soils, adsorption process carries out spontaneously; the calculated values of entropyâ–³S are positive, except the soil, the system disorder level increases after durion was adsorbed.(4) When temperature going up, the maximum adsorption capacity qmax of soil, charcoal and plantash-2# increased, and that of plantash-1# and 3# increased in 306K and then reduced, as well as the equilibrium adsorption capacity qe of soil, but qe value of charcoal and plantash-1# increased with the temperature, that of plantash-2# and plantash-3# obtained the maximum value in 298K but minimum value in 306K.(5) Adsorption kinetics curves show that the adsorption process is divided into two phases:rapid adsorption and slow adsorption. In initial stage, it is faster to reach adsorption equilibrium, then adsorption curves decrease, adsorption proceeds slowly over the time.Desorption process is divided into two phases:rapid desorption and slow desorption, fast desorption process occurred in the fast adsorption stage, the slow desorption occurred in the slow adsorption stage.