THE EFFICIENCY OF MODIFIED BENTONITE FOR REMOVAL OF PHENOL FROM WATER ENVIRONMENT

to describe experimental data of adsorption isotherms. The Langmuir and Freundlich models are the most frequently employed models. In this work, both models were used to describe the relationship between the amount of phenol adsorbed and its equilibrium concentration in solutions at different pH values. The linear form of the Langmuir isotherm model can be represented by the following relation: 1/qe = 1/Q0 + (1/bQ0)(1/Ce) where qe is the amount adsorbed at equilibrium (mg/g), Ce is the equilibrium concentration of the adsorbate (mg/1), and Q° (mg/g) and b (1/mg) are the Langmuir constants related to the maximum adsorption capacity and the energy of adsorption, respectively. These constants can be evaluated from the intercept and the slope of the linear plot of experimental data of 1/q, versus 1/ Ce.The linear form of the Freundlich isotherm model is given by the following equation: lnqe=lnKf +1/n ln Ce where kF (mg/g)(1/mg)1/n and 1/n are Freundlich constants related to adsorption capacity and adsorption intensity, respectively, of the sorbent. The values of kF and 1/n can be obtained from the intercept and slope, respectively, of the linear plot of experimental data of Inqe versus 1nCe. The three equilibrium curves that were obtained at the three pH values in this study are well represented by the Freundlich isotherm model. When the Langmuir isotherm model was applied to these data, a very good fit was obtained at pH 3 and 7, while some deviation from experimental data was observed at pH 10. But in general, this model is also applicable to describe the experimental equilibrium data for all pH values. The Langmuir constants Q° and b and Freundlich constants kF and 1/n at various pH values are displayed in Table l. It is obvious that the parameters Q° and kF, which are related to the sorption capacity, increase with a decrease in the pH values. This is consistent with the experimental observation. RI values, which are a measure of goodness-of-fit (Table

, show that both the langmuir and freundlich isotherm models can adequately describe the adsorption data. Table 1 –parameters of Langmuir and Freundlich isotherm models at various pH values pH Langmuir constants Freundlich constants _____________________________ _________________________ Q0 (mg/g) b(1/mg) R2 Kf (mg/g)(1/g)1/n 1/n R2

1.824 0.0162 0.972 0.15 0.481 0.98

0.925 0.0178 0.963 0.11 0.39 0.91

0.633 0.0096 0.941 0.085 0.478 0.948 CONCLUSION Modification of natural bentonite by cationic detergent enhances it's adsorptive capacity for organic contaminants. Due to the interaction between modified bentonite and organic constituents of wastes, it could be used : as adsorbent to remove floating oil on water, as adsorbent for organic contaminants in numerous industrial wastewater treatment systems, in liner systems for fuel oil storage tanks, and hazardous waste storage and disposal sites. REFERENCES

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