This study investigated the applicability of maghemite (γ-Fe2O3) nanoparticles for the selective removal of toxic heavy metals from electroplating wastewater. The maghemite nanoparticles of 60 nm were synthesized using a coprecipitation method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDX). Batch experiments were carried out for the removal of Pb2+ions from aqueous solutions by maghemite nanoparticles. The effects of contact time, initial concentration of Pb2+ions, solution pH, and salinity on the amount of Pb2+removed were investigated. The adsorption process was found to be highly pH dependent, which made the nanoparticles selectively adsorb this metal from wastewater. The adsorption of Pb2+reached equilibrium rapidly within 15 min and the adsorption data were well fitted with the Langmuir isotherm.

A dual-functional photocatalytic TiO 2 /AC composite was developed by dry impregnation for controlling pollutants through simultaneous adsorption and photocatalytic oxidation. Titanium tetra-isopropoxide (TTIP), the precursor, was effectively converted to the anatase form of TiO 2 on the carbon surface after hydrolysis and calcination. The composites, prepared using various hydrolysis and calcination conditions, were evaluated for their ability to remove methanol from humid air streams. The TiO 2 /AC composite hydrolyzed at 175 °C for 2 h and calcined at 300 °C in air for 2 h was more effective (58%) at removing methanol as compared to the composite prepared by boil deposition (35%). The experimental results demonstrated that a dry impregnation method is an effective method for preparing photocatalytic TiO 2 /AC composites.

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TiO 2 /activated carbon composite photocatalyst was prepared by a microwave-assisted impregnation method and was employed for the removal of methanol from humid air streams. A commercial microwave oven (800 W) was used as the microwave source. Under 2450 MHz microwave irradiation, titanium tetra-isopropoxide (TTIP) was quickly hydrolyzed and anatase TiO 2 was formed in a short time (<20 min). As a result of the volumetric heating and selective heating of the microwave, the solvent and byproducts were quickly removed which reduced energy consumption and processing time. The formed submicrometer TiO 2 particles mainly deposited on the external surface of carbon. In a packed bed reactor with an empty bed contact time of 0.35 s, the prepared materials maintained a 40% removal efficiency at an inlet methanol concentration of 39 ppm. When the TTIP conversion was complete, neither the irradiation time nor the water/TTIP ratio could further change the photocatalytic activity.

I n the modern gem trade, dimensions and facet angles on polished diamonds (figure 1) are usually measured with a computerized non-contact optical scanner (see Reinitz et al., 2005). Such devices are used by gem laboratories as part of the procedure for grading diamonds, and large manufacturers also employ them to determine the most profitable cuts. The scanner typically consists of a high-resolution digital camera, a rotating stage, a light source, and associated software. The camera takes hundreds of profile images as the diamond (usually placed table-down) rotates on the stage. The software then generates a 3D model of the polished diamond and calculates values for the dimensions, proportions, facet angles, and facet positions. The process may take as little as 10 seconds, depending on the number of pictures taken.Makers of non-contact optical scanners usually claim a linear accuracy of ~10 µm and an angular accuracy of ~0.1°. But each manufacturer uses somewhat different algorithms in their proprietary software to generate the final 3D model, so the resulting values of the dimensions and angles can deviate from one maker to another. In fact, the results may vary from instrument to instrument. Therefore, users should establish a master set of standards, in the form of faceted gemstones with known dimensions and angles, so they can check the instrument to ensure accuracy and repeatability for daily operation. Unfortunately, these standard sets are not readily available. In addition, for calibration purposes the angles and dimensions of these "master stones" must be measured to even higher precision than non-contact optical instrumentation can provide. In this study, we examine the feasibility of using a well-established optical instrument-a classical two-circle reflecting goniometer-to measure the angles on faceted diamonds to very high precision, without relying on image analysis and computer algorithms.