Synthesis of novel diol modified chitosan and their enhanced selective adsorption behavior for germanium(Ⅳ)

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

“…In contrast, the PSO assumes chemisorption/chemical reaction of the adsorbate as the rate-limiting step. , The PSO kinetics better fits the experimental kinetics data than PFO based on R 2 value for both C–Cat and S108 (Table ). Hence for both adsorbents, the adsorption mechanism is the chemisorption of Ge onto the surface sites . For C–Cat, the rate-limiting step is the chemisorption of Ge(IV) onto surface catechol sites of C–Cat, and in S108, the rate-limiting step is chemisorption onto N -methylglucamine.…”

“…The equilibrium pH of the C–Cat adsorbent in different pH solutions is lower than the initial pH (Figure B). The combined effect of protonation–deprotonation of amine on the surface of the C–Cat and surface Ge–Catechol complexation reactions caused the change in pH . The surface catechol-Ge complexation reaction releases H + as per the following possible surface reaction 3 ≡ normalL − false( normalO normalH false) 2 + normalG normale false( normalO normalH false) 4 = ≡ false[ false( L − normalO 2 false) 3 normalG normale false] 2 − + 2 normalH + + 4 normalH 2 normalO …”

“…Chitosan grafted with poly (hydroxyethyl methacrylate) showed maximum capacity of 73.91 mg/g at pH 4 but was not selective against Pb. 8 Another hydroxyl-based ligand N-methylglucamine has shown high capacity 10 but lacked selectivity, still, many commercial adsorbents with N-methylglucamine ligand are available such as Purolite S108, Amberlite IRA743, and Diaion CRB 02. 14,15 The dihydroxyl ligand catechol has shown high selectivity for Ge in solvent extraction, 16−18 complexation followed by ionexchange, 16,19,20 and SPE.…”

“…Solid-phase extraction (SPE), using functionalized adsorbents with ligands selective for target-ion, can efficiently recover germanium from dilute sources and provide advantages of high reusability, high selectivity and capacity, and elimination of environmentally harmful chemicals. , Functionalized adsorbents have been used to recover critical elements from secondary sources. − …”

“…Few have shown high capacity among these adsorbents due to a large number of hydroxyl groups, but they lack selectivity for Ge against competing ions. − Cellulose grafted with di­(2-hydroxyethyl)­amine showed 130.7 mg/g Ge adsorption capacity at pH 8 with Ge selectivity factors (SFs) ranging from 5 against Te to 12 against As, Sb, Si, and Ni. Chitosan grafted with poly (hydroxyethyl methacrylate) showed maximum capacity of 73.91 mg/g at pH 4 but was not selective against Pb . Another hydroxyl-based ligand N -methylglucamine has shown high capacity but lacked selectivity, still, many commercial adsorbents with N -methylglucamine ligand are available such as Purolite S108, Amberlite IRA743, and Diaion CRB 02. , …”