| Behaviors of adsorption and desorption of organic pollutants on suspended particulate play an important role in their transport, transformation and bioavailability in natural environment, and are influenced by factors such as hysical-chemical properties of organic pollutants, composition of sorbent, vironmental condition and coexistent organic compounds.In this dissertation, Phthalic Acid Esters(dimethyl phthalate, dibutyl phthalate (2-ethylhexyl) ester, dioctyl phthalate) was selected to study their behaviors of adsorption and desorption on suspended particulate from the Wanzhou Reach of Yangtze River and the effects of envionmental factors on the adsorption process. Experimental results are as follows:①Sorption equilibrium of DMP DEHP and DOP on the suspended particulate was reached quickly, 2h after the adsorption curve flattening, 12h after the adsorption equilibrium was achieved and stabilized. But the adsorption rate in suspended sediment particles treated by H2O2 is faster than in the natural suspended sediment, which achieved a balance in the 5h, and after stabilization. The adsorption quantity of suspended sediments treated by H2O2 is higher than suspended sediments not treated by H2O2 when the adsorption equilibrium has reached. Sorption ability of DEHP and DOP on suspended particulate was significantly higher than that of DMP. But the adsorption quantity of suspended sediments treated by H2O2 was the same.②The adsorption isotherms of DMP, DEHP, and DOP show obvious"S"shape. Freundlich and Langmuir sorption isotherm can describe the sorption behaviors when the initial concentration of PAEs is bellow 500μg/L while Linear sorption isotherm is better when the concentration of PAEs is between 500μg/L and 1000μg/L, which shows that surface sorption plays leading role when the adsorbate concentration is low and partition strengthens gradually as the concentration grows.③Several significant results were obtained from the study that environmental factors affect the adsorption properties: 1)the adsorption capacity unit decreased with the increase of particles concentration, but with the increase of particles concentration, the total adsorption capacity of DMP on the suspended sediments decreased, while the total adsorption capacity of DEHP and DOP increased. 2)the adsorption capacity of DMP increased with the increase of temperature, while the adsorption capacity of DEHP and DOP decreased. 3)the adsorption capacity of DMP increased with the increase of pH, while the adsorption capacity of DEHP and DOP decreased. 4)the effect of ionic strength on adsorption of organic pollutants have no obvious regularity.④The study of the adsorption mechanism of PAEs on suspended sediment shows that: Freundlich and Langmuir sorption isotherm can describe the sorption behaviors when the adsorbent is the suspended sediment treated by H2O2 , which shows that surface sorption plays leading role. With the increase of humic acid concentration, the adsorption capacity deceased when suspended sediments treated by H2O2 were added humic acid. The reason is that soluble humic acid is combined with organic compounds, and increase aqueous solubility of pollutants, and inhibit the absorption of pollutants in the solid phase.⑤Desorption process of DMP, DEHP and DOP in the suspended sediment particles are fast processes. DMP basically reached after 1.5h desorption equilibrium, while DEHP and DOP after 4h reached desorption equilibrium. There is hysteresis phenomenon during the process that suspended sediment particles sorpt PAEs. With the large of the hysteresis coefficient, particle retention capability of the PAEs become stronger. Form the retention factor, we find that hysteresis effect of DMP is stronger than that of DEHP and DOP.
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