Adsorption of Cr(VI) on γ-alumina in the presence and absence of CO2: Comparison of three surface complexation models

Modelling of the adsorption of phenolic acids onto α,γ–alumina particles

“…For the three ionic strengths, the optimized C values do not satisfy condition (9) (see Fig. 3), but they are of the same order of magnitude or lower than those used by other authors in low ionic strength conditions [35,[66][67][68][69]72]. As shown in Table 3, int K 1 , int K 2 and N s do not vary with ionic strength.…”

“…Due to the large linear part of the titration results, the fitting with DLM cannot converge. As some authors used this model at ionic strengths lower than 0.1 mol L −1 [35,[67][68][69], Lützenkirchen [50] stressed that some precautions must be taken so that this model makes sense under low ionic strength conditions. First, the relationship between the oxide charge (or sorbed H + ) and pH must be linear, which is verified in this work for our values of ionic strength, as shown in Fig.…”

“…However, to our knowledge, no constant-pH isotherm of this latter acid has been described yet. Adsorption of salicylic acid (2-hydroxybenzoic acid) onto oxides [21,26,28,34,35] is greater than that of H 2 Phb [26,28,30], due to the chelate formation [26]. It cannot give direct information on the influence of distal phenolic groups.…”

“…Moreover, a large body of organic acid adsorption works exists, which can be used for comparison [10,[21][22][23][24][26][27][28]30,31,[33][34][35]. Hence, our aim was to probe the role of the number of phenolate group for adsorption of phenolic acids (H 2 Phb, H 2 Proto and H 2 Gal, hereafter noted H 2 A, i.e., only the two proton will be apparent) onto aluminum oxide.…”

Surface complexation modeling of Cr(VI) adsorption at the goethite–water interface

“…The interactions of Cr(VI) on (hydroxy)oxides have been examined extensively as a function of pH, ionic strength and surface loading over the last few decades [9][10][11][12][13][14][15]. A variety of surface complexation models were developed to describe the adsorption behavior of chromate (Table 1), such as Constant Capacitance Model (CCM) [12], Diffuse Layer Model (DLM) [16], and Triple Layer Model (TLM) [9,13,14,17].…”