Abstract
In this work, adsorption isotherms of magnesium chloride (MgCl2) and magnesium nitrate (Mg (NO3)2) onto tetraphenylporphyrin molecules (H2TPP) are achieved at three temperatures using the Quartz Crystal Microbalance (QCM) method. The equilibrium data expressing the adsorbed quantity of Magnesium per unit of adsorbent area provide interesting information to explain the adsorption mechanism. In fact, statistical physics treatment is applied to attribute new investigations to the complexation process. Some physicochemical parameters are deduced from the analytical models established by the theoretical formalism. It is found that the model describing the layer by layer (LBL) adsorption is the best to reproduce the experimental isotherms of magnesium nitrate on porphyrin. The interaction between magnesium chloride and porphyrin is explained by a mono-layer adsorption expression. The adsorption mechanisms are characterized by an energetic investigation which demonstrates that a physisorption occurs for the Mg(NO3)2-H2TPP system whereas the adsorption of MgCl2 onto H2TPP is characterized by chemical interactions.
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•Adsorption isotherm of Mg(NO3)2 and MgCl2 on H2TPP was achieved using QCM.•Advanced model is developed using grand canonical ensemble.•Physicochemical parameters in relation with the adsorption mechanism were investigated and interpreted.•Steric and energetic interpretations were proposed.