Removal of phenolic pollutants in single and binary solutes from water onto carbons derived from corncobs

ABSTRACT

Activated carbons derived from corncobs as well as their metal-loaded chars were investigated to find the suitability of their application for the removal of ortho-, meta- and para-nitrophenols besides phenol in single and bi-solute aqueous systems. Three types of activations namely; thermal activation via one step steam pyrolysis at 700°C and two step steam at 850 C as well as chemical activation using H3PO4 impregnation then pyrolysis at 500 C. The non-activated carbon sample, char, was impregnated with calculated amount of each of iron, nickel, copper or calcium nitrates then pyrolysed at 500 C to obtain four metal-loaded carbons. The adsorption capacity of the investigated carbons was carried out via measuring their phenol and/or nitrophenols numbers in single and bisolute systems at 25°C in their aqueous solutions. The results indicate that in bi-solute systems the presence of two solutes decreases the phenolic number of each component than that in the single system, which ascribed to the competition arising between the two solutes on the same number of adsorption sites on the adsorbent surface. It is clear that there are other factors, beside porosity and surface nature, controlling the adsorption process of phenol and/or nitrophenols. The removal capacity of nitrophcnol was found to be affected with the orientation in the nitro-group site and the obtained uptake was ordered 4NP > 3NP > 2NP. The results indicate that in bi-solute systems the presence of two solutes decreases the phenolic number of each component than in the single system, which ascribed to the competition arising between the two solutes on the same number of adsorption sites on the adsorbent surface. Para-nitrophenol measured the highest uptake compared with its other mono-substituted phenols which may be attributed to its ability to form intermolecular hydrogen bonding structure and the absence of steric hindrance which may control the adsorption of the ortho- and meta-nitrophenols. Among the investigated adsorbent, the highest adsorption capacity was exhibited by the one step steam pyrolysis activated carbon sample which refers to its surface nature of highly basic surface and porosity