The surface science of titanium dioxide

In the area of water purification, nanotechnology offers the possibility of an efficient removal of pollutants and germs. Today nanoparticles, nanomembrane and nanopowder used for detection and removal of chemical and biological substances include metals (e.g. Cadmium, copper, lead, mercury, nickel, zinc), nutrients (e.g. Phosphate, ammonia, nitrate and nitrite), cyanide, organics, algae (e.g. cyanobacterial toxins) viruses, bacteria, parasites and antibiotics. Basically four classes of nanoscale materials that are being evaluated as functional materials for water purification e.g. metal-containing nanoparticles, carbonaceous nanomaterials, zeolites and dendrimers. Carbon nanotubes and nanofibers also show some positive result. Nanomaterials reveal good result than other techniques used in water treatment because of its high surface area (surface/volume ratio). It is suggested that these may be used in future at large scale water purification. It is also found that the coliform bacteria treated with ultrasonic irradiation for short time period before Ag- nanoparticle treatment at low concentration, enhanced antibacterial effect. In future, combination of both may be the best option for treatment of waste water.

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Application of Nanoparticles in Waste Water Treatment

Hydrodynamic cavitation reactors: a state of the art review

The catalytic CO oxidation results revealed that nanosized ceria-lanthana (CL) solid solution exhibits superior catalytic performance and thermal stability in comparison to ceria-zirconia (CZ) solid solution. The rationale for excellent catalytic behavior of the CL sample was elucidated from the viewpoint of structure, redox behavior, and bulk oxygen mobility. Accordingly, in this investigation CL solid solution has been synthesized by a modified coprecipitation method, and the structural and redox properties have been deeply investigated employing various characterization techniques, namely, X-ray diffraction (XRD), BET surface area, transmission electron microscopy (TEM), Raman spectroscopy (UV-RS and Vis-RS), UV-visible diffuse reflectance spectroscopy (UV-vis DRS), and temperature programmed reduction (TPR). The catalytic efficiency has been evaluated for oxygen storage/release capacity (OSC) and CO oxidation activity. The analyses of the characterization results provided a deep insight on the physica...

Novel Nanocrystalline Ce1−xLaxO2−δ (x = 0.2) Solid Solutions: Structural Characteristics and Catalytic Performance

Experimental quantification of chemical effects of hydrodynamic cavitation

We have developed the WPI cavitational materials process for the production of phase-pure, nanostructured materials. Hydrodynamic cavitation is generated mechanically using a high-pressure fluid system. The method begins with a precipitant stream that experiences a large pressure drop (21 000 psi ambient) across a patented geometry interaction chamber. Due to the large pressure drop, bubbles are formed and collapse, causing localized heating of the solvent. In addition, the precipitate undergoes a high degree of mechanical shear in the interaction chamber. This paper deals with the application of this novel technique to the synthesis of several nanostructured oxides. The nanophase oxides are characterized using transmission electron microscopy, X-ray diffraction, thermal gravimetric analysis, differential scanning calorimetry, and Fourier transform infrared spectroscopy. Select area diffraction patterns of the dried (110 °C) oxide samples in this study show distinct rings indicating nanosized particles. T...

General Route to Nanocrystalline Oxides by Hydrodynamic Cavitation

Publisher Summary The synthesis of materials by hydrodynamic cavitational processing in a Microfluidizer resulted in a large variety of catalysts in the form of nanometer-sized grains. The grains are agglomerated into particles of 100 nm to a few microns. The process provides higher purity than classical synthesis in the preparation of catalysts containing several metal ions. The technique offers a good route to the synthesis of homogeneous solid solutions of complex catalysts where one attempts to understand the relationship between ion modification of a host and catalytic performance. Although no commercial-scale quantities of catalysts have been fabricated using the Worchester Polytechnic Institute (WPI) cavitational materials process to the available knowledge, the process is capable of synthesizing a wide range of industrially important complex catalysts using currently manufactured equipment. An additional benefit from this type of commercial synthesis is the fact that the consistency of catalysts fabricated in this way is very high, resulting in very reliable and reproducible batches of catalysts. Thus, the fabrication of a variety of currently used commercial catalysts, where synthesis reproducibility is a problem, might be consistently conducted using the cavitational process.

Joseph E. Sunstrom

Papers

General Route to Nanocrystalline Oxides by Hydrodynamic Cavitation

The Synthesis of Nanostructured Pure-Phase Catalysts by Hydrodynamic Cavitation