Adsorption Characteristics Of Organobentonites Towards Organic Compounds: Quantitative Structure-Property Relationship Study

Organobentonites are widely used in controlling organic pollution due to their excellent sorption capacity towards organic pollutants. They have been used as adsorbents in wastewater treatment and liner in landfill. And they have also found application in remediation of organic compounds contaminated soil. The pollution control efficiency of organobentonties was controlled by their sorption capacity. Therefore, clarifying the sorptive characteristics of organobentonites is critical for improving their sorption capacity and thus improving their pollution control efficiency.In this work, the sorption capacities of three organobentonites with various cetyltrimethylammonium loading towards organic compounds were first determined, and then their sorptive characteristics were investigated by applying quantitative structure-property relationship (QSPR). The QSPR equations using the parameters of both linear solvation energy relationship (LSER) and quantum chemistry were calculated. And then the relative contribution of different parameters to the sorption capacity of organobentonite was determined. New information on the sorption characteristics of organobentonites could therefore be obtained and predicted by the results from the present study, which were as follows:(1) The sorption capacity of organobentonites can be successfully predicted and their sorptive characteristics can also be revealed by LSER analysis. LSER models for organics in water with a relatively good R²adj were obtained for organobentonites (40C-Bt, 100C-Bt and 160C-Bt). The equation showed that the excess molar refraction term (eE), hydrogen-bond basicity term (aA) and cavity formation term (vV) played positive roles for the sorption of organic compounds from water to organobentonites, while the polarity and polarizability term (sS) and hydrogen-bond acidity term (bB) played negative roles.(2) The QSPR model based on quantum chemical parameters for the sorption of organic compounds on organobentonites was obtained, which further revealed the sorptive characteristics of organobentonites. Fourteen quantum parameters of the organic compounds were calculated using MOPAC-PM3 in chemoffice2004. Then the QSPR model of logK_oc against these parameters was conducted by partial least squares regression of Simca software. The optimal model had better R²X(adj) (cum), R²Y(adj) (cum),Q²cum,RMSE values. The model extracted three important components of PLS, which explained 84.1% of the variance of the independent variables and 87.7% of the variance of the dependent variables. Model analysis showed that the polarizability parameter (α), octanol/water partition coefficient (logK_ow), molecular weight (M_w), molecular total core repulsion energy (CCR) are of the greatest significance determining the adsorption of organic bentonite to organics, while the lowest unoccupied molecular orbital (E_lumo) and ionization potential (IP) took the second place.