The pH of fly ash varies depending

The surface of obtained adsorbent was characterized by scanning SB269970 HCl microscopy. Fig. 1a shows particles of chitosan powder (CS). Fig. 1b and c shows fly ash (FAI) before and after activation (FAI-573). In Fig. 1c it can be seen that after activation at the temperature 573 K the particles of fly ash are separated and vary in size, but they are still quite smooth and spherical. Fig. 1d shows that in the case of the prepared sorbent (FAICS), chitosan covered the particles of fly ash. The adsorbent has irregular and porous surface. As was also proved by Li [46] the main role of the added chitosan is to coat and bridge the fly ash particles and led to the formation of a more condensed network structure and thus enhances the mechanical behaviour of the composite. It also provides the functional groups. On the other hand the activation process of fly ash by acids, such as nitric acid can provide of an oxygenation of the particle surface by the nitrate ions. In the case of HCl washing the sorption efficiency, for example of lead is poor [47]. Another parameter affecting the sorption efficiency is the washing time. However, in order to improve the capability and selectivity of coal fly ash for the heavy metal ions removal immobilization of an organic ligands on the particle surface is explored. Among them EDTA, glycine, dithizone, mercaptoethanol and mercaptoacetic acid are very important.