The FDA is reviewing the safety of titanium dioxide in response to an April petition from EWG and other environmental and public health groups. This is the FDA’s first comprehensive review of titanium dioxide since 1973.

Available studies in humans and postmortem analysis of tissues suggested that the oral bioavailability of titanium dioxide in humans is very low. JECFA noted that there are currently no epidemiological studies that allow any conclusions to be drawn with respect to an association between dietary exposure titanium dioxide and human health effects.

Historically, the first mentions of zinc sulfide being utilized as a pigment were approximately sixty years before the everyday use of lithopone. Originally, it was thought to be appropriate for coloring rubber. In England, a patent was granted for this process. Two decades after this, the focus shifted to zinc sulfide as a suitable pigment for paint. The year 1874 witnessed the patenting of a manufacturing process for a novel white pigment composed of zinc sulfide and barium sulfate. Dubbed Charlton white or Orr’s white enamel, this began a new era for white pigments.

At the present JECFA meeting, the committee considered additional toxicological studies relevant to the safety assessment of the chemical that investigated its toxicokinetics, acute toxicity, short-term toxicity, long-term toxicity and carcinogenicity, genotoxicity, and reproductive and developmental toxicity, as well as special studies addressing its short-term initiation/promotion potential for colon cancer. The experts acknowledged that a large number of toxicological studies have been conducted using test materials, including nanoparticles, having size distributions and physico-chemical properties not comparable to real-world uses of titanium dioxide as a food additive. The studies on non-representative materials were evaluated by JECFA, but the committee concluded that such studies are not relevant to the safety assessment of the additive.

Conclusion:

Other food manufacturers use titanium dioxide to absorb water and keep moisture from clumping or degrading, Paul Westerhoff, PhD, an environmental engineer at Arizona State University who researches the biological and cellular effects of titanium dioxide, told Health.

Titanium dioxide R-996 is mainly used in powder coatings, water-based and solvent-based external coatings, high-grade color masterbatches, plastics, rubber, inks, high-grade paper and wax paper and leather upholstery fabrics, cosmetics, suitable for high-grade interior coatings, high-solid paints, Road marking paints, marine paints and inks, and also used in the plastics, rubber, paper and leather industries.

2: Clarification mechanism of coagulant

Chemical coagulation is a process in which chemical agents (coagulants) are added to water treatment to make colloidal dispersion system destabilize and agglomerate. In the coagulation process, small suspended particles and colloidal impurities are aggregated into larger solid particles to separate particulate impurities from water, which is called coagulation clarification.

After adding coagulant into water, colloidal particles and other small particles can be polymerized into larger flocs through the comprehensive action of mixing, coagulation and flocculation. The whole process of coagulation and flocculation is called coagulation.

(1) Destabilization and condensation of colloids

Adding electrolyte to water can compress the electric double layer and destabilize the colloid. The main mechanism is that the electric double layer of colloidal particles in water is compressed or neutralized by adding aluminum salt or iron salt coagulant. The coagulant and raw water are mixed rapidly and evenly, and a series of chemical reactions are produced to destabilize. This process takes a short time, generally about 1 min. Some cationic polymers can also play a role in the destabilization and condensation of colloids in water. These polymers have a long chain structure and positive charge in water. Their destabilization and condensation of colloids in water is due to the interaction of van der Waals force adsorption and electrostatic attraction.

(2) Flocculation and formation of floc (alum)

The particle size of the initial flocculate formed by colloid destabilization and coagulation in water is generally more than 1 m. at this time, Brownian motion can no longer push them to collide and form larger particles. In order to make the initial flocs collide with each other to form large flocs, it is necessary to input additional energy into the water to produce a velocity gradient. Sometimes it is necessary to add organic polymer flocculant into water, and the adsorption bridging effect of long chain molecules of flocculant is used to improve the probability of collision and adhesion. Flocculation efficiency usually increases with the increase of flocculate concentration and flocculation time.

Compared with polyaluminum chloride, polyaluminum chloride has the advantages of high density, fast settling speed and wide pH adaptability; the coagulation effect is less affected by temperature than that of polyaluminum sulfate; however, when adding ferric salt, it should be noted that when the equipment is not in normal operation, the iron ions will make the effluent color, and may pollute the subsequent desalination equipment.

Absorption

History