Analysis of sorption-desorption hysteresis phenomena of chromium in bentonite

Author(s): R.Jayanthi,G.Swaminathan, K.Palanichamy

Hysteresis or irreversibility has been observed to occur in the sorption and esorption of inorganic contaminants by many soils and sediments under varying environmental conditions. Knowledge of the sorption and desorption of Chromium in the environment can be important for predicting its mobility and threats fromits presence. Hence the main objective of this study is to analyse and quantify the sorption and desorption hysteresis phenomenon of Cr III in commonly found clay mineral Bentonite. Batch experiments were conducted for both sorption and desorption under conditions of (i) varying pH from 4-10 (ii) soil solution ratios ranging from1:60 to 1:100 and (iii)Chromiumconcentrations ranging from5mg/l to 30mg/l with increments of 5-mg/l. Linear and Freundlich isotherms are fitted with curve fitting tool built inMATLAB and best estimated parameters are tabulated for both sorption and desorption stages. Hysteresis indices are developed with Freundlich exponents and the first derivatives of the functions describing the sorption and desorption isotherm branches. Both pH and soil solution ratio have remarkable influence on the irreversibility of Cr III in Bentonite. At higher pH and SSR the irreversibility is less produced and at lower pH and lower SSR the irreversibility is more produced.

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