The morphology of vitaminB2@P25TiO₂NPs is coherent with the description of Degussa P25 typical population. Size distribution histograms were made from manual measures of the nanoparticles observed in SEM micrographs using ImageJ®. This data showed that more than 70% is anatase (between 20 and 60 nm) with a minor amount of rutile characteristic bars (between 80 and 100 nm) and a small amount of amorphous phase (<40 nm) [36]. Further analysis of the same sample areas with an EDS probe demonstrated the presence of organic material composed of C and O (Fig. 2). This material was found homogeneously distributed on the surface of the different shapes of P25TiO₂NP, not in the background, indicating a specific interaction that could be attributed to the functionalization of the P25TiO₂NPs with vitamin B2.

Overwhelmingly, research that’s relevant to human eating patterns shows us that E171 is safe when ingested normally through foods and drugs (1,2).

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.