Removal of phenolic compounds from aqueous solution using MgCl2-impregnated activated carbons derived from olive husk: the effect of chemical structures

摘要

Activated carbon (BC) prepared from olive oil solid waste (olive husk) by slow pyrolysis was chemically activated using MgCl2(BC-MgCl2). The BC and BC-MgCl(2)were used as adsorbents for removal of three phenolic compounds, namely, phenol (P), p-methoxyphenol (PMP) and p-nitrophenol (PNP), from aqueous solution. The uptake of these three phenolic compounds by the BC and BC-MgCl(2)was better expressed by the Langmuir and Dubinin-Radushkevich (D-R) isotherm models than by the Freundlich isotherm, and the kinetics of the adsorption process followed the pseudo-second order kinetic model. The maximum monolayer adsorption capacity of P, PMP and PNP were increased from 24.938, 45.455 and 61.728 on BC to 43.860, 98.039 and 121.951 mg/g on BC-MgCl(2)by factors of 1.76, 2.16 and 1.98, respectively. Therefore, the chemical activation of BC by MgCl(2)is indeed of importance for improving its adsorption performances. For both adsorbents, the adsorption phenomenon for different substituted phenols is a strong function of solubility, polarity, molecule structure, and size. At the tested temperatures (25, 35 and 45 degrees C), the negative values of Delta G degrees and positive values of Delta H degrees and Delta S degrees for the adsorption of P, PMP and PNP on BC and BC-MgCl(2)demonstrated that the adsorption was a spontaneous, endothermic and entropy-increasing process.