Sorption Mechanisms Of Carbaryl Onto Soils

The reaction of organic contaminants and natural adsorbents strongly influenced the migration and ultimate destination of polluting substances in the environment,also the next slow release, At present, organic adsorption mechanism has not been completely understanding,and the actual quantitative model has not been established. In this paper,The adsorption of carbaryl in the soil is studied by HPLC,and the planting soil as absorbent. The objective is to identify the characteristics of sorbent and sorbate that play a predominant role in the sorption process and to establish a sorption model of natural geosorbents for organic contaminants. The following results were obtained by the research :(1) The bimodal phenomenon of hydrophobic chemicals uptake by natural particles was verified,that is,the initial stage of rapid adsorption and subsequent slow adsorption.Elovich equation can be used to describe carbaryl on soil adsorption kinetics curves.The adsorption of carbaryl in the soil is the result of linear distribution and the internal diffusion. The time to reach to the apparent equilibrium of carbaryl adsorption in the soil is 24h.(2) The bimodal phenomenon showed two different adsorption region of the sorbent: "rubber" amorphous organic matter region and "glass" dense organic regional. in different stages, the different regions played the role,and the adsorption model and mechanism are also different. When the carbaryl concentration was low, the linear adsorption isotherm is superior to the high concentration, To further evidenc the "two-phase" adsorption.(3) The adsorption isotherm of carbaryl in the soil was nonlinear, Freundlich isotherm equation and the Langmuir isotherm equation can be better describe adsorption isotherm. Nonlinear absorption was caused by the surface adsorption of " glass " organic matter, rather than the adsorbent pore.(4) The experiments for the influence of system Ca²⁺ concentration indicat that the time for fast adsorption to slow adsorption is increasing. The adsorption capacity of carbaryl are lower,with CaCl₂ concentration increased.(5) This study established a "two-phase" adsorption model formula on the base of previous research results."two-phase" adsorption equation was well describe adsorption of carbaryl in the soil.The "two-stage" phenomenon of carbaryl adsorption in the soil of was verified again. The quantify of condensed organic carbon and the amorphous inorganic carbon in the total adsorption capacity, which can be judged for the effect of the adsorption region in two different adsorption stage. That will be well to determine the organic pollutants resolution, enrichment, biodegradable.It is great importance to soil remediation technologies.