Fabrication of polyvinylidene fluoride and acylthiourea composite membrane and its adsorption performance and mechanism on silver ions

Silver-containing wastewater poses a great threat to the surrounding living areas due to its toxicity and non -biodegradable. In this study, a novel polyvinylidene fluoride (PVDF)-based composite membrane (PVDF/ BDBTU) was fabricated by blending PVDF and N-benzoyl-N ',N '-dibutyl thiourea (BDBTU) for the enrichment of Ag+ ions from the aqueous solution. The structure and morphology of the membrane were characterized using FTIR, XPS, AFM and SEM, and its adsorption performances for Ag+ ions were deeply studied. The results revealed that the adsorption amount of Ag+ ions adsorbed by the membrane was 1.45 mmol/g at pH 6.0, and the adsorption can be described very well by the pseudo-second-order and Langmuir models, respectively, showing a monolayer chemisorption process. The coexisting substances had little impact on the adsorption of PVDF/BDBTU membrane to Ag+ ions, suggesting an excellent adsorption selectivity to Ag+ ions. In addition, the membrane showed a noticeable reusability for Ag+ ions since no significant loss in adsorption capacity was observed after ten cycles of adsorption-desorption. The adsorption mechanism elucidated that the binding reaction between the C--O and C--S groups in BDBTU and Ag+ ions contributed to the adsorption of Ag+ ions onto the PVDF/BDBTU membrane surface, as confirmed by FTIR, XPS and DFT calculation.