Cobalt and nickel uptake by silica-based extractants

Abstract

© 2017 Taylor & Francis The pK a s of ethyl/butyl phosphonate silica (EBP-Si) have been determined, and the removal of cobalt and nickel from solution was investigated as a function of various parameters and compared with those of Purolite S950. pH uptake experiments suggested a combination of ion exchange and acid dissociation of the surface occurring. Isotherm data, fitted using the Langmuir and Dubinin–Radushkevich (D-R) models, indicated that stronger complexes formed with S950 than with EBP-Si. Kinetic data, fitted using a pseudo-second-order model, suggested that the rate-determining process is the reaction of metal ions with the chelating functionality of the resin. Uptake by EBP-Si is two to three times faster than that on S950

Towards the implementation of an ion-exchange system for recovery of fluoride commodity chemicals. Kinetic and dynamic studies

“…S4c and S6c). Elovich plots that exhibit sections of linearity, as is the case here, have been proposed to describe heterogeneous adsorption processes[40,45], which agrees with existing knowledgeof this system. Calculated parameters from fitting of the same data to the PFO model and the full range of associated R 2 values are also presented in the Supporting Information, Table S8.…”

“…Data plots of qt vs t 1/2 were produced. It is accepted that, if such a plot has a linear gradient and passes through the origin, the adsorption is entirely controlled by intraparticle-diffusion [40,41]. We finally studied the adherence of the uptake to the Elovich model [42], applying the Chien and Clayton simplification [43], which has frequently been applied to chemisorption-dominated systems [41].…”

Calcium-loaded hydrophilic hypercrosslinked polymers for extremely high defluoridation capacity via multiple uptake mechanisms

“…Nevertheless, they are predicted by most of the simpler models, with fewer pKas (Tables S11-S12). It is known that hydrophobic environments, such as micropores, can lower pKa values substantially, 43,58 although not to the degree seen here. It is notable however, that there appear to be similar acidic functionalities present in both networks, which produce slightly lower pKas in the HHCP2 network (10.1 vs 10.5; 9.90 and 9.19 vs 9.99; 7.54 vs 8.48), which likely has more hydrophobic pore environments, because of the alkyl bridges between phenol rings.…”

“…The polyamine resin Purolite MTS9850 has an anion-exchange capacity of ~6.25 mmol•g -1 and the chelating resin Puromet MTS9501 (which has selectivity for alkali earth metals) has a reported cation-exchange capacity of only ~1.83 mmol•g -1 . 58,59 The capacity of HHCP2 was rather lower than expected in comparison, even given the extra mass present in the theoretical repeating unit of the polymer. This would suggest that HHCP2 featured a greater % of partial crosslinking, with the extra methoxy groups adding to the mass ( Figure S8).…”

“…As seen in Figure 4, a number of models gave feasible fittings to the data within experimental error and these possibilities are shown in Tables S11-S12. It should be noted that, while this technique is versatile, having been applied successfully to polymeric adsorbents, 43,58 it assumes that the molar concentrations of all different acidic groups throughout the adsorbent or ligand are equivalent, which, as has been discussed, is unlikely in these networks. However, the experiments gave an indication of the variety of acidic environments present within the polymers.…”