Titanium dioxide is a common additive in many food, personal care, and other consumer products used by people, which after use can enter the sewage system and, subsequently, enter the environment as treated effluent discharged to surface waters or biosolids applied to agricultural land, incinerated wastes, or landfill solids. This study quantifies the amount of titanium in common food products, derives estimates of human exposure to dietary (nano-) TiO(2), and discusses the impact of the nanoscale fraction of TiO(2) entering the environment. The foods with the highest content of TiO(2) included candies, sweets, and chewing gums. Among personal care products, toothpastes and select sunscreens contained 1% to >10% titanium by weight. While some other cremes contained titanium, despite being colored white, most shampoos, deodorants, and shaving creams contained the lowest levels of titanium (<0.01 μg/mg). For several high-consumption pharmaceuticals, the titanium content ranged from below the instrument detection limit (0.0001 μg Ti/mg) to a high of 0.014 μg Ti/mg. Electron microscopy and stability testing of food-grade TiO(2) (E171) suggests that approximately 36% of the particles are less than 100 nm in at least one dimension and that it readily disperses in water as fairly stable colloids. However, filtration of water solubilized consumer products and personal care products indicated that less than 5% of the titanium was able to pass through 0.45 or 0.7 μm pores. Two white paints contained 110 μg Ti/mg while three sealants (i.e., prime coat paint) contained less titanium (25 to 40 μg Ti/mg). This research showed that, while many white-colored products contained titanium, it was not a prerequisite. Although several of these product classes contained low amounts of titanium, their widespread use and disposal down the drain and eventually to wastewater treatment plants (WWTPs) deserves attention. A Monte Carlo human exposure analysis to TiO(2) through foods identified children as having the highest exposures because TiO(2) content of sweets is higher than other food products and that a typical exposure for a US adult may be on the order of 1 mg Ti per kilogram body weight per day. Thus, because of the millions of tons of titanium-based white pigment used annually, testing should focus on food-grade TiO(2) (E171) rather than that adopted in many environmental health and safety tests (i.e., P25), which is used in much lower amounts in products less likely to enter the environment (e.g., catalyst supports, photocatalytic coatings).

Titanium Dioxide Nanoparticles in Food and Personal Care Products

Nitrogen-doped titanium dioxide as visible-light-sensitive photocatalyst: designs, developments, and prospects.

https://opus.lib.uts.edu.au/bitstream/10453/43832/3/MED%2027143286%20am.pdf

Progress in the biological and chemical treatment technologies for emerging contaminant removal from wastewater: A critical review.

Although mesoporous materials have well-defined pore structures, these fine materials can surprisingly be produced by employing a set of conventional and simple procedures such as mixing, heating, filtration, and washing, using low-cost materials. They can be regarded as easy-to-make bulk nanostructured materials. Mesoporous materials have great potential for use in both macroscopic applications and nanotechnology. In this account, we introduce examples of recent developments in mesoporous materials involving innovations in their components and structural designs and concentrating on our own recent progress. These examples include syntheses of mesoporous silica, metal oxides, semiconductive materials, metals, alloys, organic composites, biomaterial composites, carbon, carbon nitride, and boron nitride, as innovative components. As structural innovations for mesoporous materials, various film preparations, pore alignments, and hierarchic structures are described together with their related functions including sensing and controlled release of target molecules.

Nanoarchitectonics for mesoporous materials

In heterogeneous single-metal-site catalysts (HSMSCs) the active metal centres are located individually on a support and are stabilized by neighbouring surface atoms such as nitrogen, oxygen or sulfur. Modern characterization techniques allow the identification of these individual metal atoms on a given support, and the resulting materials are often referred as single-atom catalysts. Their electronic properties and catalytic activity are tuned by the interaction between the central metal and the neighbouring surface atoms, and their atomically dispersed nature allows for metal utilization of up to 100%. In this way, HSMSCs provide new opportunities for catalysis, and with respect to structure build a bridge between homogeneous and heterogeneous catalysis. Herein, selected publications from 2010 in this area are reviewed and their perspectives for the near future are highlighted. Where appropriate, comparisons between HSMSCs and homogeneous/heterogeneous counterparts are presented. Single-atom catalysts have drawn increasing attention as methods for their preparation and characterization improve. Here, Beller and co-workers discuss the latest developments in the field of single-metal-site catalysts, discussing how this catalyst class bridges heterogeneous and homogeneous catalysis, and providing a perspective on how the field might continue to develop.

Bridging homogeneous and heterogeneous catalysis by heterogeneous single-metal-site catalysts

Nanomaterials, defined as particles ranging from 1 to 100 nm diameter, have become widely utilized because of their unique physicochemical properties. Among those nanoparticles, titanium dioxide (TiO2) is frequently used in the production of paints, paper, plastics, welding rod-coating material, cosmetics, etc. TiO2 is the most commonly used semiconductor photocatalyst. Among the different nanomaterials, it is the most studied. Activated by UV-A irradiation, its photocatalytic properties have been utilized in various applications. A wealth of information on TiO2 photocatalytic in activation of bacteria has been acquired over the last 20 years. Hence, in this review article we have described synthesis methods mainly sol–gel type method like sol–gel method, ultrasonic-assisted sol–gel method, microemulsion method, colloidal synthesis, and also other method are discussed like solvo-thermal method, thermal plasma process, supersonically expanded plasma jet method, induction plasma torch, reactive plasma processing, plasma electrolytic oxidation, hydrolysis method, thermohydrolysis method, coprecipitation method, citrate–nitrate autocombustion method, etc. Also applications of TiO2 like medical applications, environmental application, sensor application, photocatalytic applications, and also its health impact for long-term exposure are discussed.

A review on nano-TiO2 sol–gel type syntheses and its applications

https://cyberleninka.org/article/n/551703.pdf

Applications of nano-catalyst in new era

A review on the use of nanometals as catalysts for the thermal decomposition of ammonium perchlorate

In this review data from the literature on thermal decomposition of ammonium nitrate (AN) and the effect of additives to their thermal decomposition are summarized. The effect of additives like oxides, cations, inorganic acids, organic compounds, phase-stablized CuO, etc., is discussed. The effect of an additive mainly occurs at the exothermic peak of pure AN in a temperature range of 200°C to 140°C.

Shalini Chaturvedi

Papers

A review on nano-TiO2 sol–gel type syntheses and its applications

Applications of nano-catalyst in new era

A review on the use of nanometals as catalysts for the thermal decomposition of ammonium perchlorate

Review on Thermal Decomposition of Ammonium Nitrate

Removal of iron for safe drinking water