Some physicochemical properties of partition nanophase formed in sorptive organoclays

Abstract

To examine of partition nanophase of three different sorptive organoclays, OC1, OC2, and OC3 were synthesized, respectively, by exchange of methyltributylammonium (MTBA), methyltrioctylammonium (MTOA), and di(hydrogenatedtallow)dimethylammonium (DHTDMA) for inorganic interlayer cations of a sodium smectite with a cation exchange capacity of 1.08 mol kg −1. The organoclays were investigated X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and nitrogen adsorption–desorption techniques. The thickness ( z) of the intercalated partition nanophases in OC1, OC2, and OC3 were obtained from XRD data as 0.47, 1.29, and 2.18 nm, respectively. The molar volume ( V) and parachor ( P) of the organic cations were calculated from some literature data estimated empirically. The V-values of the organic cations having molar mass ( M) 200, 368, and 522 g mol −1 are 319.0, 585.4, and 829.6 cm 3 mol −1, respectively. The corresponding P-values are 94.1, 189.8 and 267.3 cm 3 mol −1 (N m −1) 1/4. The density ( ρ) and surface tension ( σ) of each partition nanophase were estimated from the P = ( M/ ρ) σ 1/4 = Vσ 1/4 relation taken from literature. The ρ-values of the partition nanophases are found as 0.626, 0.628, and 0.629 cm 3 g −1. The corresponding surface tensions are calculated as 11.90 × 10 −3, 11.03 × 10 −3, and 10.76 × 10 −3 N m −1. It is seen that the ρ-and σ-values of the partition nanophases are constant approximately by the increasing of the z-, V- and P-values. The specific surface area ( S) and specific micro-mesopore volume ( V mm) for OC1, OC2, and OC3 were obtained from the adsorption and desorption data, respectively. The S-values OC1, OC2, and OC3 are 106, 67, and 31 m 2 g −1 and the corresponding V mm-values are 0.251, 0.222, and 0.071 cm 3 mol −1. It is observed that the S and V mm decrease with the z-value along a straight line and as a concave curve, respectively. It is concluded that the density and surface tension of partition nanophase do not depend on the length of aliphatic alkyl groups on alkylammonium cations. The increase in thickness of the nanophase decrease adsorption spaces and hinder the penetration of nitrogen molecules into organoclay.