The role of titanium dioxide on the behaviour and fate of plastics in the aquatic environment.

Although titanium dioxide (TiO2) is the most widely used pigment in plastics, there is limited quantitative information available for consumer goods and environmental samples. Moreover, and despite its photocatalytic activity, the potential impacts of TiO2 on the behaviour and fate of environmental plastics has received little attention. This paper compiles measurements of Ti in plastic samples from aquatic environments and in consumer goods that are known to make important contributions to environmental pollution. These data, along with a critical evaluation of experimental studies using TiO2-pigmented plastics, are used to formulate an understanding of how the pigment modifies the properties and persistence of environmental plastics. Titanium is heterogeneously distributed amongst different categories and sources of plastic, with concentrations ranging from <1 mg kg-1 in transparent-translucent materials to over 50,000 mg kg-1 in brightly coloured samples. Concentrations towards the higher end are sufficient to change positively buoyant polyolefins into negatively buoyant plastics, suggesting that environmental fractionation based on Ti content might occur. Accelerated leaching of TiO2 from aged plastic has been demonstrated empirically, and while mobilised particles are reported within a size range greater than biotically-active titania nanoparticles, modeling studies suggest that the latter could be derived from TiO2 pigments in the environment. Although rutile appears to be the most important polymorph of TiO2 in non-fibrous plastics, the degree and type of engineered surface modification in consumer and environmental plastics are generally unknown. Surface modification is likely to have a significant impact on the photo-oxidative degradation of plastics and the mobilization of fine (and, possibly, nano-sized) TiO2 particles and requires further research

Hazardous chemical elements in cleaning cloths: A potential source of microfibres.

Although potentially hazardous chemical elements (e.g., Cu, Cr, Pb, Sb, Ti, Zn) have been studied in clothing textiles, their presence in cleaning textiles is unknown. In this study, 48 cleaning cloth products (consisting of 81 individual samples) purchased in Europe, and consisting of synthetic (petroleum-based), semi-synthetic or natural fibres or combinations of these different types, have been analysed for 16 chemical elements by X-ray fluorescence (XRF) spectrometry. Titanium was detected in most cases (median and maximum concentrations ~3700 and 12,400 mg kg-1, respectively) and Raman microspectroscopy revealed that TiO2 was present as anatase. Barium, Br, Cr, Cu, Fe and Zn were frequently detected over a range of concentrations, reflecting the presence of various additives, and Sb was present at concentrations up to about 200 mg kg-1 in samples containing polyester as catalytic residue from the polymerisation process. Lead was detected as a contaminant in four samples and at concentrations below 10 mg kg-1. Overall, the range of the chemical element profiles and concentrations was similar to those for clothing materials published in the literature, suggesting that broadly the same additives, materials and processes are employed to manufacture cloths and clothing textiles. The mechanisms by which potentially hazardous chemical elements are released into the environment with microfibres or mobilised into soluble or nano-particulate forms remain to be explored

Dispersion of antimony from oxidizing ore deposits

The solubilities of brandholzite, [Mg(H2O)6][Sb(OH)6]2, and bottinoite, [Ni(H2O)6][Sb(OH)6]2, at 25 °C in water have been measured. Solubilities are 1.95(4) × 10-3 and 3.42(11) × 10-4 mol dm-3, respectively. The incongruent dissolution of romeite, Ca2Sb2O7, and bindheimite, Pb2Sb2O7, at 25 °C in 0.100 mol dm-3 aqueous HNO3 was also investigated. Equilibrium dissolved Sb concentrations were 3.3 ± 1.0 × 10-7 and 7.7 ± 2.1 × 10-8 mol dm-3, respectively. These values have been used to re-evaluate the geochemical mobility of Sb in the supergene environment. It is concluded that the element is geochemically immobile in solution and in soils. This was in part validated by an orientation soil geochemical survey over the Bayley Park prospect near Armidale, New South Wales, Australia. Anomalous soil Sb levels are confined to within 100 m of known stibnite mineralizatio

Towards the global plastic treaty: a clue to the complexity of plastics in practice

Following the decision of the United Nations Environment Assembly (UNEA) to start negotiations for a legally binding treaty to end plastic pollution, discussions and reflections are ongoing on why and how plastic chemicals and polymers of concern should be integrated into the global plastics treaty. One of the points that has been identified as requiring attention is the reduction of the complexity of the composition of plastic objects. This article, addressed to decision-makers and other stake-holders involved in the negotiations, illustrates in a practical and graphical way what complexity means in the case of the presence of inorganic additives

Polyvinyl chloride in consumer and environmental plastics, with a particular focus on metal-based additives

Polyvinyl chloride (PVC) is one of the most widely used thermoplastics but is also a material of concern because of the generation and release of harmful chemicals during its life cycle.</jats:p