A nickel hydroxide/carbon black/polyvinylidene fluoride (Ni(OH) 2 /CB/PVDF) film was coated on a graphite plate substrate and used for the selective and efficient extraction of W(VI) using self-driven film adsorption. The excellent self-driven adsorption performance of Ni(OH) 2 /CB/PVDF film for W(VI) was demonstrated by the comparison of the experimental performance of film adsorption and electrochemically switched ion exchange (ESIX) process. In the Ni(OH) 2 /CB/PVDF film, the adsorption of W(VI) by Ni(OH) 2 was achieved through the ligand exchange reaction with W(VI) and abundant hydroxyl groups, which ensured the self-driven performance. The adsorption capacity of the self-driven Ni(OH) 2 /CB/PVDF film for W(VI) under neutral conditions could reach up to 37.53 mg·g −1 after 12 h. Moreover, the adsorption kinetics and adsorption thermodynamics showed that the adsorption of W(VI) on Ni(OH) 2 /CB/PVDF films was more in line with the pseudo-second-order kinetic model, and the adsorption was heat-absorbing and spontaneous. After seven cycles of adsorption/desorption, the adsorption capacity of W(VI) by Ni(OH) 2 /CB/PVDF film could reach 79.37 % of its initial value, which showed good adsorption/desorption cycle performance. Moreover, Ni(OH) 2 /CB/PVDF films showed high selectivity for W(VI) when WO 4 2− coexisted with Cl − , NO 3 – , and SO 4 2− , respectively. This study confirmed that the self-driven Ni(OH) 2 /CB/PVDF film had efficient and stable adsorption performance for W(VI), which can be regarded as a promising method for the selective adsorption of W(VI) from aqueous solution.
Amine/quaternary ammonium lignin for adsorption of tungsten was synthesized by amination and quaternization from lignin. The adsorbent was characterized by SEM-EDS and FTIR. The effects of pH, initial concentration of tungsten, adsorption time and dosage of adsorbent on the adsorption effect were investigated. The adsorption mechanism was revealed by SEM-EDS and FTIR and XPS. The results showed that amine/quaternary ammonium lignin was loose and rough and contained a large number of phenolic hydroxyl and amine and quaternary ammonium functional groups. Using the optimum conditions, which included the pH of 4.0 and initial tungsten concentration of 800 mg·L −1 and adsorption time of 960 min, the saturated adsorption capacity of 1 g·L −1 amine/quaternary ammonium lignin for tungsten reached 421.68 mg·g −1 . The adsorption followed Langmuir model and quasi-second-order kinetic model, indicating that the adsorption was monolayer homogeneous chemisorption. When the total concentration of tungsten was 0.005 mol·L −1 and the value of pH was smaller than 4.7, H 2 W 12 O 40 6− was the existing form of tungsten and was adsorbed by electrostatic attraction of hydrogen bond and coordination with amino and ion exchange with Cl − .
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