Adsorption isotherms and fractal dimension of modified rectorite

Natural reclorile (REC) was modified with dodecyl benzyl dimethyl ammonium chloride [C₁₂H₂₅(CH₃)₂ (C₆H₅-CH₂)NCl, 1227], hexadecyl trimethyl ammonium brornide[C₁₆H₃₃(CH₃)₃ NBr, 1631] and octadecyl trimethyl ammonium bromide [C₁₈H₃₇(CH₃)₃ NBr, 1831], respectively. Then three kinds of organic-modified rectorite were obtained: 1.227-REC, 1631-REC, 1831-REC which were used as adsorbents for phenol or Cr(VI) ions in water. A comparison of adsorption isotherms and of the isotherm fractal model shows that the adsorption reactions for phenol and Cr(VI) are caused by static electric attraction between the cation and anion and surface complexation reaction respectively. The fractal calculation for active absorption sites of absorbents shows that the fractal dimensions of 1227-REC and 1631-REC are respectively 2.85 and 2.91 for phenol and those of 1227-REC, 1631-REC and 1831-REC are respectively 2.65, 2.86 and 2.73 for Cr(VI).