On the adsorption mechanisms of diethylamine by medically-certified activated carbons: Investigation of critical parameters controlling sorption properties

This study investigates the adsorption mechanisms and reaction pathways involved in the adsorption of diethylamine (DEA) by medically-certified activated carbons (ACs). DEA is used as a model of amines secreted during healing process of chronic wounds. DEA adsorption kinetics/isotherms were performed in liquid phase. Based on a preliminary assumption of a sorption favoured by surface chemical functions, it was found that the sorption kinetics followed accurately a pseudo-second order model. In addition, our analysis revealed that surface diffusion strongly influenced DEA sorption. If Langmuir and Redlich-Peterson models provided the most accurate fit of the adsorption isotherms, the Freundlich isotherm gave a fair representation of experimental data as well. L-type isotherms supported the occurrence of strong surface interactions. Also, a negative correlation was drawn between the micropore volume percentage and adsorption capacity at equilibrium. Further, acid/base reactions were believed to occur, along with the establishment of numerous H-bonds between the sorbent and DEA. This study is ended by a discussion of the effect of AC entrapment within a polymeric matrix on the adsorption properties. If DEA removal was still observed, a serious decrease of sorption properties was measured. We concluded that AC must be treated during the activation process in order to possess a high BET surface, an important mesopore/macropore content and a high content of acidic surface functions, in order to balance the decreasing of adsorption properties owed to its entrapment.