Estimation of liquid vapor pressures for low-volatility environmental chemicals

Two structural descriptors were chosen as possible model descriptors for predicting subcooled-liquid vapor pressures of polychlorinated biphenyls (PCBs), chlorophenols (CPs), chlorobenzenes (CBs) and alkylphenols and predictive power of the two descriptors are discussed. The Characteristic Root Index (CRT) and third order cluster-type molecular connectivity index ((3) chi(c)) were calculated exclusively on the basis of information readily available for all chemicals. To apply the regression model to a wide range of chemicals multiple linear regression has been tried, however, collinearity was observed between the two structural descriptors. Subcooled-liqiud vapor pressures obtained by using the best correlative equation with the CRI for 54 PCB congeners, all chlorophenols and chlorobenzenes and several alkylphenols have been reported. (C) 1997 Elsevier Science Ltd

Prediction of the soil sorption coefficient of organic pollutants by the characteristic root index model

Quantitative Structure-Property Relationship (QSPR) technique was used to develop a simple predictive model for the soil sorption coefficient (K-oc) of Polychlorinated Biphenyls (PCBs), chlorinated phenols (CPs) and chlorinated benzenes (CBs). Tests performed on 36 such compounds clearly demonstrate that this simple model accurately predicts the soil sorption coefficients of these chemicals. The correlation equation was then used to predict the unknown soil sorption data of chlorinated biphenyls, phenols and benzenes. The result of these tests also demonstrates that the CRI can be an alternative and a very accurate predictive tool for the soil sorption coefficients of structurally similar compounds. Copyright (C) 1996 Elsevier Science Lt

Homogenous and heterogenous advanced oxidation of two commercial reactive dyes

Two commercial reactive dyes, the azo dye Reactive Black 5 and the copper phythalocyanine dye Reactive Blue 21, have been treated at a concentration of 75 mg l(-1) by titanium dioxide mediated photocatalytic (TiO2/UV), dark and UV-light assisted Fenton (Fe2+/H2O2) and Fenton-like (Fe3+/H2O2) processes in acidic medium. For the treatment of Reactive Black 5, all investigated advanced oxidation processes were quite effective in terms of colour, COD as well as TOC removal. Moreover, the relative growth inhibition of the azo dye towards the marine algae Dunaliella tertiolecta that was initially 70%, did not exhibit an increase during the studied advanced oxidation reactions and complete detoxification at the end of the treatment period could be achieved for all investigated treatment processes. However, for Reactive Blue 21, abatement in COD and UV-VIS absorbance values was mainly due to the adsorption of the dye on the photocatalyst surface and/or the coagulative effect of Fe3+/Fe2+ ions. Although only a Limited fraction of the copper phythalocyanine dye under-went oxidative degradation, 47% of the total copper in the dye was already released after 1 h photocatalytic treatment