Halim Hamid Redhwi

Environmental effects of ozone depletion and its interactions with climate change: progress report, 2011

The Environmental Effects Assessment Panel (EEAP) is one of three Panels that regularly informs the Parties (countries) to the Montreal Protocol on the effects of ozone depletion and the consequences of climate change interactions with respect to human health, animals, plants, biogeochemistry, air quality, and materials. The Panels provide a detailed assessment report every four years. The most recent 2014 Quadrennial Assessment by the EEAP was published as a special issue of seven papers in 2015 (Photochem. Photobiol. Sci., 2015, 14, 1-184). The next Quadrennial Assessment will be published in 2018/2019. In the interim, the EEAP generally produces an annual update or progress report of the relevant scientific findings. The present progress report for 2015 assesses some of the highlights and new insights with regard to the interactive nature of the effects of UV radiation, atmospheric processes, and climate change.

Environmental effects of ozone depletion and its interactions with climate

The parties to the Montreal Protocol are informed by three panels of experts. One of these is the Environmental Effects Assessment Panel (EEAP), which deals with UV radiation and its effects on human health, animals, plants, biogeochemistry, air quality and materials. Since 2000, the analyses and interpretation of these effects have included interactions between UV radiation and global climate change. When considering the effects of climate change, it has become clear that processes resulting in changes in stratospheric ozone are more complex than believed previously. As a result of this, human health and environmental problems will likely be longer-lasting and more regionally variable. Like the other panels, the EEAP produces a detailed report every four years; the most recent was that for 2006 (Photochem. Photobiol. Sci., 2007, 6, 201-332). In the years in between, the EEAP produces a less detailed and shorter progress report, as is the case for this present one for 2009. A full quadrennial report will follow for 2010.

Durability of LDPE nanocomposites with clay, silica, and zinc oxide: part I: mechanical properties of the nanocomposite materials

Three types of LDPE-based nanocomposites with montmorillonite clay, silica, and zinc oxide were prepared by melt blending the nanofiller with the resin. As a prelude to studying their durability, the extent of reinforcement of the LDPE matrix by the nanofillers was investigated using mechanical, thermal, and microscopic studies of the composites. No significant chemical modification of the polyethylene matrix was observed as a result of the processing of the composite compound. While reinforcement was obtained in all cases, the efficiency of reinforcement appears to be qualitatively influenced by surface functionalization, filler interactions, and the extent of dispersion of the filler in the matrix as well as the specific surface area of the nanoparticle fillers.

Adsorption of Toluene and Paraxylene from Aqueous Solution Using Pure and Iron Oxide Impregnated Carbon Nanotubes: Kinetics and Isotherms Study

Multiwall carbon nanotubes (CNTs) and iron oxide impregnated carbon nanotubes (CNTs-iron oxide) were investigated for the adsorption of hazardous toluene and paraxylene (p-xylene) from aqueous solution. Pure CNTs were impregnated with iron oxides nanoparticles using wet impregnation technique. Various characterization techniques including thermogravimetric analysis, scanning electron microscopy, elemental dispersion spectroscopy, X-ray diffraction, and nitrogen adsorption analysis were used to study the thermal degradation, surface morphology, purity, and surface area of the materials. Batch adsorption experiments show that iron oxide impregnated CNTs have higher degree of removal of p-xylene (i.e., 90%) compared with toluene (i.e., 70%), for soaking time 2 h, with pollutant initial concentration 100 ppm, at pH 6 and shaking speed of 200 rpm at 25°C. Pseudo-second-order model provides better fitting for the toluene and p-xylene adsorption. Langmuir and Freundlich isotherm models demonstrate good fitting for the adsorption data of toluene and p-xylene.

Use of asphaltene filler to improve low-density polyethylene properties

ABSTRACT Asphaltene filled LDPE composite were prepared and characterized. The composites were studied to determine the reinforcement imparted by the asphaltene on the durability of LDPE polymer. The study showed that the composites have higher melting and crystalline behavior, delays the degradation induced by heat and acts as a thermal barrier limiting the emission of the gaseous degradation products, resulting in an increase in the thermal stability of the composites, higher tensile strength, have higher values of the storage and loss modulus. 5 wt% of asphaltenes added in the LDPE afforded the best dispersion in the polymeric matrix, larger crystallite size, enhanced thermal stability, highest relative degree of crystallinity and improved mechanical tensile or thermo-mechanical properties.

Accelerated weatherability of the low-density polyethylene nanocomposites with silica, clay, and zinc oxide

Nanocomposites based on low-density polyethylene (LDPE) with MMT clay, nanosilica, and nanoscale zinc oxide (at 5 wt.%) were prepared by melt processing and evaluated for durability using laboratory accelerated weathering. The changes in tensile properties of the nanocomposites with the duration of exposure were compared to data from natural weathering outdoors. The enhancement of degradation rates of the LDPE matrix by the presence of nanofillers in accelerated weathering is reported.