Sorption Of Pentachlorophenol Onto The Surficial Sediments And Its Main Components And Effect Of Cu～(2+)

The pentachlorophenol (PCP) was once applied widely in the world as herbicide, antiseptic and pesticide. It is considered as one of the main persistent organic pollutants (POPs) in the environment because of its broad-spectrum toxicity and mutation for organism. Studying its sorption behavior in surficial sediments of natural water body can further understand the rule of migration and transformation for organic pollutants in the sediments-water environment and the final end-result and biological and ecology effect in the environment.The sorption behavior of organic pollutants in the sediment will be affected by many factors, such as their own physical and chemical properties, composition and structure of the sediment, environmental conditions and the co-existing pollutants. Organic matter in sediments/soils has been the key-studying field of sorption mechanism of organic pollutants. The researches have been studying on the content, composition and structure of organic matter in the sediments. With its polar surface, minerals occured dipole in the water which makes polar water molecules combine with the surface of minerals, so that surface sorption sites are occupied, As a result, non-polar organic pollutants are difficult to combine with the minerals. Thus the mineral composition on the sorption of organic pollutants is considered as secondary. However, besides non-polar organic pollutants, there are still mass larger polar/ion organic pollutants in sediments/soils. As the effect of variable charge in the mineral surface and the corresponding interface reaction, such as electrostatic interactions, ion exchange or surface complexation, the sorption of polar or ion organic compounds in the mineral surface becomes very important. In considering the effect of composition and structure of the sediments on the sorption behavior of organic pollutants, the present study of sorption always apply single component. In reality, these components are alone very few in the environment. These components often coexist with the other components and interact on the sorption of organic pollutants. In addition, in considering the effect of co-existing pollutants on the sorption behavior of organic pollutants in sediments, organic pollutants are often more selected as co-existing pollutants, while the study on combined pollution caused by organic pollutant and heavy metal is less. It is necessary to consider the effect of the main chemical components in sediments and heavy metal on the sorption behavior of the organic pollutants from an integral perspective.With pentachlorophenol as the targeted pollutants, The objectives of this paper were to find the best method for batch determination, to study the sorption behavior of pentachlorophenol in the surficial sediments of the Songhua River and to explore the role of the main chemical components during the sorption and the effect of co-existing inorganic pollutants Cu²⁺ on the sorption of PCP.In this paper, the following results were obtained:(1) Ultraviolet spectrophotometric method of determining pentachlorophenol in water was established. Pentachlorophenol was dissolved in sodium hydroxide solution, and then the content of alkaline pentachlorophenol in the water sample was measured at the wavelength of 320 nm. The linear regressive equation is Y = 0.0052X+0.0002. The correlation coefficient r is 0.9999. The detection limit is 0.27μmol/L. The relative standard division (RSD) obtained is less than 5%. The recovery range is 100.70%¹03.75%.The linear relationship is well. The method is convenient, fast and repeatable. It avoids the use of lots of organic solvents. The requirement for equipment is not very high. It's applicable for batch determination of pentachlorophenol in the course of studying its environmental behaviors.(2) The thermodynamics sorption experiments of pentachlorophenol in four sediment samples (original sediments, sediments removed organic matter, sediments removed Mn oxides and sediments removed Fe-Mn oxides) showed that: The quantity of PCP adsorbed in sediments removed Mn oxides rises quickly with the increase of its concentration, sediments removed Fe-Mn oxides followed. The quantity of PCP adsorbed in original sediments and sediments removed organic matter rises slowly with the increase of its concentration, and the sorption of PCP in sediments removed organic matter tends to achieve equilibrium in the larger concentration.Sorption isotherms of PCP in original sediments, sediments removed Mn oxides and sediments removed Fe-Mn oxides were well fitted with the Langmuir and Freundlich equation. The correlation is good and it achieves a significant level. The sorption capacities of PCP in four different sediments have a huge difference. The order of the sorption capacities of PCP in four sediment samples follows the order: sediments removed Mn oxides > sediments removed Fe-Mn oxides > original sediments > sediments removed the organic matter.(3) Fe oxides and organic matter are the main sorption sites in surficial sediments for PCP. The quantity of PCP adsorbed in sediments increase with the organic matter content. The removal of organic matter from surficial sediments largely reduced the sorption capacity of PCP. As the content of Mn oxides in the original sediments collected is very low, the sorption of PCP in Mn oxides can be neglected. However, after removing Mn oxides, parts of the sorption sites and the effective sorption area of PCP in sediments increase so that the sorption capacity of PCP has increased greatly. The sorption capacity of PCP in sediments removed Fe-Mn oxides decreased greatly than in sediments removed Mn oxides. The sorption capacity of PCP in sediments removed Fe-Mn oxides is strong. Besides absorbed in organic matter of surficial sediments, PCP can also absorb in Fe oxides.(4) The co-existing inorganic pollutants Cu²⁺ have competitive effects on the sorption of PCP in surficial sediment samples. The competitive sorption sites are mainly organic matter and Fe oxides. In four sediment samples (original sediments, sediments removed organic matter, sediments removed Mn oxides and sediments removed Fe-Mn oxides), the absorbed quantity of PCP decreases with the increase of the concentrations of Cu²⁺. With the co-existence of Cu²⁺, sorption isotherms of PCP in three sediment samples (original sediments, sediments removed Mn oxides and sediments removed Fe-Mn oxides) were well fitted with the Freundlich equation. The correlation coefficient was above 0.96. The sorption coefficient Kd shows that the relative sorption capacity of PCP in sediments removed Mn oxides reduces even more apparent.