Catechol-Functionalized Chitosan Synthesis and Selective Extraction of Germanium (IV) from Acidic Solutions

Abstract

Germanium (Ge) is one of the critical elements that lack an efficient economic recovery process from dilute sources. An improved catechol-based adsorbent, catechol-functionalized chitosan (C–Cat), was synthesized to recover germanium (Ge) from dilute acidic solutions. The adsorbent was also compared with an N-methylglucamine-based commercial adsorbent (Purolite S108) for optimum pH conditions, ion selectivity, adsorption isotherm, adsorption kinetics, and regeneration ability. The newly synthesized C–Cat exhibited higher selectivity against various competing ions than the commercial one (their respective Langmuir capacity was 22.72 and 79.66 mg/g at pH 3) and was more selective for Ge than other adsorbents reported in the literature. Linear free-energy relationships between the distribution coefficients and the metal hydrolysis constants were developed for both C–Cat and S108 at pH 3 and can be used for preliminary prediction of the selectivity of the adsorbents. Adsorptions data followed Langmuir isotherm for both adsorbents, and the kinetics data were well-fitted with pseudo-second-order kinetics. The C–Cat was proven to be completely reusable for multiple cycles after initial re-equilibration.

Powdered Hierarchically Porous Silica Monoliths for the Selective Extraction of Scandium

“…Both a pseudo-first-order and a pseudo-second-order kinetics model were applied to the data (Figure a) . The pseudo-second-order model provided a better fit ( R 2 of 0.9653 compared to 0.8195), which suggests that the adsorption reaction kinetics are likely the limiting factor rather than intraparticle diffusion (Figure a). , A Weber and Morris model was also applied to the data (Figure b), and the intercept of the initial rapid phase of adsorption is well above zero, which again indicates that intraparticle diffusion is not the sole factor influencing extraction kinetics. , The batch reaction data and the three models applied to it, in combination with the results of the fractal-like Bohart–Adams model for the continuous-flow system, show that the adsorption reaction kinetics rather than internal diffusion is most likely the primary process controlling the rate of Sc extraction, although small effects from internal and external diffusion may also be present. The mechanism(s) of Sc adsorption onto the silica surfaces are complex, potentially involving van der Waals forces, electrostatic interactions between Sc 3+ cations and the negatively charged silica, and the formation of covalent Si–O–Sc bonds. , While the former two processes occur rapidly, the Si–O–Sc covalent bonds form more slowly, , which could explain the observed behavior of the DPS powder in column and in batch.…”

“…18 The pseudo-second-order model provided a better fit (R 2 of 0.9653 compared to 0.8195), which suggests that the adsorption reaction kinetics are likely the limiting factor rather than intraparticle diffusion (Figure 5a). 18,26 A Weber and Morris model was also applied to the data (Figure 5b), and the intercept of the initial rapid phase of adsorption is well above zero, which again indicates that intraparticle diffusion is not the sole factor influencing extraction kinetics. 18,26 The batch reaction data and the three models applied to it, in combination with the results of the fractal-like Bohart−Adams model for the continuous-flow system, show that the adsorption reaction kinetics rather than internal diffusion is most likely the primary process controlling the rate of Sc extraction, although small effects from internal and external diffusion may also be present.…”

“…18,26 A Weber and Morris model was also applied to the data (Figure 5b), and the intercept of the initial rapid phase of adsorption is well above zero, which again indicates that intraparticle diffusion is not the sole factor influencing extraction kinetics. 18,26 The batch reaction data and the three models applied to it, in combination with the results of the fractal-like Bohart−Adams model for the continuous-flow system, show that the adsorption reaction kinetics rather than internal diffusion is most likely the primary process controlling the rate of Sc extraction, although small effects from internal and external diffusion may also be present. The mechanism(s) of Sc adsorption onto the silica surfaces are complex, potentially involving van der Waals forces, electrostatic interactions between Sc 3+ cations and the negatively charged silica, and the formation of covalent Si−O−Sc bonds.…”

One‐Step Photo‐Patterning Process for Multi‐Modal and Transformative Structural Coloration: Toward Anti‐Counterfeiting Applications

“…The average ζ values of the 0.1, 0.3, and 0.5 wt.% solutions are −25.1, −22.2, and −14.4 mV, respectively (see Figure S2c, Supporting Information). These surface charges arise from the deprotonation [ 27 ] of ─OH, carboxymethyl, and azide groups on the UVCC, making the surface negatively charged. The highly concentrated (0.5 wt.%) solution was unstable and formed an irregular film with polymer aggregates, which scatter light and yield no colors, as illustrated in Figure S3c (Supporting Information).…”

Some Recent Advances in Germanium Recovery from Various Resources

“…Catechol-functionalized chitosan (C-Cat) has been synthesized and used to recover germanium from dilute acidic solutions [30]. With maximum metal uptake in the 4-11 pH range, the adsorption fits the Langmuir isotherm and pseudo-second-order kinetic models.…”