Titania-Clay Mineral Composites for Environmental Catalysis and Photocatalysis

The use of titania-based composite materials in the field of heterogeneous catalysis and photocatalysis has a long and rich history. Hybrid structures combining titania nanoparticles with clay minerals have been extensively investigated for nearly four decades. The attractiveness of clay minerals as components of functional materials stems primarily from their compositional versatility and the possibility of using silicate lamellae as prefabricated building blocks ready to be fitted into the desired nanoconstruction. This review focuses on the evolution over the years of synthetic strategies employed for the manufacturing of titania–clay mineral composites with particular attention to the role of the adopted preparative approach in shaping the physical and chemical characteristics of the materials and enabling, ultimately, tuning of their catalytic and/or photocatalytic performance.

Effects of initial concentration and irradiation dose to degradation of di butyl phthalate from phosphoric acid (30 % P2O5)

The pretreatment of the phosphoric acid is a stage of utmost importance leading to an optimal recovery of the uranium present in this acid. To this end, the degradation of the organic matter which obstructs considerably this recovery was tested by γ irradiation. This study lies within the scope of the radiation/matter interaction; concerning the use of the γ irradiator as proceed of phosphoric acid purification by the degradation of di butyl phthalate (DBP). Studies of the interaction of γ radiation with phosphoric acid solutions polluted by an organic matter concern the study of the influence of some parameters such as: dose rate (0.5–35 kGy), initial concentration (50–500 mg/L) of the pollutant, pH and % in P2O5 on the degradation of organic matter by γ irradiation. The reactions followed pseudo first order kinetics for different initial concentrations. The results made it possible to say that the degradation of di butyl phthalate by γ irradiation is dependent on the amount of the concentration of DBP and pH. The G-values decreased with absorbed doses, and increased with higher initial concentrations.Purification of phosphoric acid by γ radiation does not degrade the quality of this acid.

Synthesis of TiO2-loaded silicate-1 monoliths and their application for degradation rhodamine B

TiO₂-loaded silicate-1 monoliths, with TiO₂ (Degussa P25) nanoparticles loaded in silicate-1 crystal, were directly synthesized by combining sol–gel method and hydrothermal method.

Treatment of nonylphenol with laccase in a rotating reactor

The effects of operation conditions on reaction rate in the enzymatic oxidative treatment of nonylphenol with laccase in a rotating reactor were studied. Sea sand that adsorbed nonylphenol was used as a polluted soil model. Nonylphenol concentration decreased with laccase treatment five times faster at 40 degrees C than at 10 degrees C and the apparent activation energy of the enzyme reaction was 39 kJ mol(-1), which was in the range of the values reported for similar laccase reactions. Reaction rate increased when the angle of the axis of the rotating reactor from the vertical line increased and when the speed of revolution was increased to 10 rpm at different volumes of the enzyme solution. Thus, mixing is important for the oxidation of nonylphenol with laccase. The nonylphenol released from the sand into the enzyme solution in the initial stage of the treatment was easily oxidized. However, the nonylphenol adsorbed on the sand reacted slowly. Reaction rate increased nearly proportional to the square root of enzyme concentration, which suggests that the nonylphenol radical reacted with unoxidized nonylphenol (nonenzymatic propagation) during the enzymatic oxidative treatment. The dependence of reaction rate on the nonylphenol concentration was similar to the Michaelis-Menten type. The residual estrogenic activity of the treated sand was measured by medaka vitellogenin assay. The estrogenic activity decreased to 1/6-1/90 after 24 h of the treatment.

Treatment of model soils contaminated with phenolic endocrine-disrupting chemicals with laccase from Trametes sp. in a rotating reactor

An enzymatic treatment system for the remediation of sand contaminated with endocrine-disrupting chemicals (EDCs) was studied. Laccase from Trametes sp. (Laccase Daiwa) decreased the amounts of nonylphenol, octylphenol, bisphenol A and ethynylestradiol (synthetic estrogen) adsorbed on sea sand (2 micromol g(-1)) in a test tube with shaking. The phenolic endocrine-disrupting chemicals might have polymerized via enzymatic conversion to their phenoxy radicals. The optimum pH for the enzymatic treatment was approximately 5. A rotating reactor was used for scaling up the enzymatic treatment. The reaction rate increased by rotating the reactor. The optimum speed of revolution was 10-15 rpm for the treatment of nonylphenol. The amounts of octylphenol, bisphenol A, and ethynylestradiol also decreased enzymatically in the reactor. Our enzymatic treatment system with a rotating reactor will be useful for the treatment of soil highly polluted with phenolic EDCs.

Layered double hydroxide hybrids with dicetylphosphate

Dicetyl phosphate (DCP) ions incorporated into layered double hydroxide (LDH) clays to form a DCP/LDH hybrid were prepared and structurally characterized by X-ray diffraction analysis, scanning electron microscopy, thermogravimetry, and differential thermal analyses. DCP was concluded not only to form well-aligned bilayer structures along the vertical axis of the LDH layers but also to be arranged in a distorted hexagonal packing orientation in the lateral planes within the DCP/LDH hybrid interlayers.