Application of quantum chemical descriptors into quantitative structure-property relationship models for prediction of the photolysis half-life of PCBs in water

Quantitative structure-property relationship(QSPR)models were developed for prediction of photolysis half-life(t_(1/2))of polychlorinated biphenyls(PCBs)in water under ultraviolet(UV)radiation.Quantum chemical descriptors computed by the PM3 Hamiltonian software were used as independent variables.The cross-validated Q^(2)_(cum)value for the optimal QSPR model is 0.966,indicating good prediction capability for lg t_(1/2)values of PCBs in water.The QSPR results show that the largest negative atomic charge on a carbon atom(Q-C)and the standard heat of formation(ΔH_(f))have a dominant effect on t_(1/2)values of PCBs.Higher Q_(C)^(-)values or lowerΔHf values of the PCBs leads to higher lg t_(1/2)values.In addition,the lg t_(1/2)values of PCBs increase with the increase in the energy of the highest occupied molecular orbital values.Increasing the largest positive atomic charge on a chlorine atom and the most positive net atomic charge on a hydrogen atom in PCBs leads to the decrease of lg t_(1/2)values.

Sorption of triclosan on electrospun fibrous membranes: Effects of pH and dissolved organic matter

Three hydrophobic and polyporous electrospun fibrous membranes(EFMs)were prepared by electrospinning methoxy polyethylene glycol-poly(lactide-co-glycolide)(MPEG-PLGA),poly(D,L-lactide-co-glycolide)(PLGA)and poly(D,L-lactide)(PDLLA).The effects of pH and dissolved organic matter(DOM)on triclosan(TCS)sorption by EFMs in aqueous solution were investigated.The results indicated that hydrogen bonding,hydrophobic and π-π bonding interactions led to fast adsorption,which governed the adsorption rates of TCS onto EFMs.The maximum sorption capacities of MPEG-PLGA,PLGA and PDLLA reached 130,93 and 99 mg g^-1,respectively,which were in positive correlation with their pore volumes and influenced by pore filling processes.The solution pH could significantly influence the TCS sorption by EFMs.In acid condition,protonated TCS facilitated their sorption onto EFMs.No obvious sorption was observed in alkaline condition due to repulsive forces between negatively charged EFMs and deprotonated TCS(pKa=7.9).The presence of DOM inhibited TCS sorption onto EFMs due to competitive adsorption.The results could be due to the occupation of the adsorption sites and the blockage of the pore entrance by DOM.