INFLUENCE OF PH, IONIC STRENGTH AND TEMPERATURE ON ADSORPTION OF ENDOSULFAN TO THE AQUACULTURE POND SEDIMENTS

The sorption behavior of endosulfan onto aquaculture pond sediment was determined by using batch experiments. Furthermore, the influence of pH, ionic strength and temperature was investigated. The adsorption equilibrium was established within 4 h, and adsorption process was divided into a rapid and a slow process before and after the equilibrium time, respectively. The Freundlich isotherm model fits the adsorption data with R-2>0.99 in all cases. The sorption increased at pH 5.8 (K-f = 6.62 and n = 1.05) but decreased at pH 8.0 (K-f = 3.19 and n = 0.79). Ionic strength has effects on the sorption; the K-f was two times higher in 35 g/L NaCl solution as a result of salting-out effect. Though lower temperature (20 degrees C, K-f = 7.09 and n = 1.02) was more favorable for adsorption, the effect was not significant. Pond is a relatively close environment, and the transport, transformation and fate of endosulfan mainly occurred in the internal circle. The results may be help to minimize its ecological risk in ponds with proper measures taken to adjust the conditions of pH, temperature and ionic strength.