The interaction of dibenzo-p-dioxin (DD), from aqueous suspension, with smectite was investigated using in situ vibrational spectroscopy (FTIR and Raman), structural and batch sorption techniques. Batch sorption isotherms were integrated with in situ attenuated total reflectance (ATR)-FTIR and Raman spectroscopy and X-ray diffraction. Sorption isotherms revealed that the affinity of DD for smectite in aqueous suspension was strongly influenced both by the type of smectite and by the nature of the exchangeable cation. Cs-saponite showed a much higher affinity over Rb-, K- and Na-exchange saponites. In addition, DD sorption was found to depend on clay type with DD showing a high affinity for the tetrahedrally substituted trioctahedral saponite over SWy-2 and Upton montmorillonites. A structural model is introduced to account for the influence of clay type. Raman and FTIR data provided complementary molecular-level insight into the sorption mechanisms. In the case of Cs-saponite, the selection rules of DD based on D(2h) symmetry were broken indicating a site-specific interaction between DD and intercalated Cs(+) ions in the interlayer of the clay. Polarized in situ ATR-FTIR spectra revealed that the molecular plane of sorbed DD was tilted with respect to the clay surface which was consistent with a d-spacing of 1.49 nm. Finally, cation-induced changes in both the skeletal ring vibrations and the asymmetric C-O-C stretching vibrations provided evidence for site specific interactions between the DD and exchangeable cations in the clay interlayer. Together, the combined macroscopic and spectroscopic data show a surprising link between a hydrophilic material and a planar hydrophobic aromatic hydrocarbon.
Plastics are high molecular weight organic source materials. It is necessary to devise systems to decompose plastic polymers because their disruptive effects are threatening the ecosystem. Biotic and abiotic strategies are being employed to convert plastics into monomers. The objective of both techniques is to reduce polymers to monomers. Microbes act on monomers for their degradation by releasing enzymes on polymers. The rate of microbial degradation is affected by both the environmental conditions as well as by polymer characteristics. Different methods are used to check the rate of biological degradation However, some plastics oppose microbial action. The environment condition and polymer characteristics affect the rate of degradation. Different approaches are used to check the rate of biological degradation. The need of the time is to generate bio based plastics material which can be degraded effi ciently. These polymers can be recycled by degradation to monomers and then convert back to petrochemical products. This will contribute to fulfi ll the increasing demand of organic fuels and may serve as next generation fuel. There is no effective technique that can degrade plastics with effi cacy, so scientists are struggling to develop techniques which not only degrade these polymers but also results into benefi cial products. This review is an attempt to organize some of the most common strategies for degradation of various types of polymers along with a list of potential microbes capable of feeding on them.
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