Thousands of tons of various dyes are annually produced all over the world, from which 15% are wasted during the production or painting process, according to the statistics.
The wasted parts of dyes usually permeate to water sources and damage the environment. The dyes are required to be eliminated in order to purify the polluted water. Various methods have so far been proposed in order to remove the dyes, among which the adsorption method is more cost-effective.
In their studies, the researchers used porous nanosilica functionalized by ethylenediamine (SBA-3/EDA), aminopropyl (SBA-3/APTES), and pentaethylenehexamine (SBA-3/PEHA). Various investigations were carried out on such materials, suggesting that their adsorption capabilities were as follows: SBA-3/PEHA > SBA3/APTES > SBA-3/EDA > SBA-3.
According to the studies, SBA-3/PEHA was identified as a very good adsorbent of acidic dyes. The adsorption mechanism of such nanomaterials is based on the electrostatic attraction and hydrogen bond created between the adsorbent surface and acidic dyes.
The results of the observations showed that the adsorption of SBA-3/PEHA decreased when the pH value increased. The optimum temperature for adsorption process was reported to be 20°C. The amount of adsorption decreases when the temperature increases.
The research has been published in detail in July 2012 in Dyes and Pigments.