The release of petroleum products by leaky underground storage tanks is a serious threat to clean ground water. BTEX compounds (benzene, toluene, ethylbenzene, and xylenes) are of primary concern due to their ability to cause health problems at low concentrations. D.S. Kershaw, B.C. Kulik, and S. Pamukcu (J. Geotech & Geoenvir Engrg. 123,324(1997)) have studied the ability of ground Tyre rubber to sorbs (adsorb and absorb) benzene and 0- xylene. Though sorption involves more than surface interactions, sorption data are usually found to fit one of the adsorption isotherms. In this study, the authors have tested how well their data fit the linear (q =KCeq)' Freundlich (q =KFC~~'), and Langmuir (q =KLMceq/(1 +KLceq) type isotherms, where q is the mass of solvent sorted per gram of ground rubber (in milligrams per gram), the Ks and M are empirical constants, and centre equilibrium concentration of contaminant in solution (in milligrams per liter).
(a) Determine the units of the empirical constants.
(b) Determine which of the isotherms best fits the data in the table below for the sorption of benzene on ground rubber.
(c) Compare the sorption efficiency of ground rubber to that of granulated activated charcoal, which for benzene has been shown to obey the Freundlich isotherm in the form q = 1.0c1.6 with coefficient of determination R2 = 0.94.

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2.48 36.10 10.40 10.40 6.21 Co/(mg dm-) 97.10 6.51 q1(mg g). 7.13 4.60 1.80 1.10 0.55 0.31