Rapid and selective recycling of Ag(I) from wastewater through an allylrhodanine functionalized micro-filtration membrane

Abstract

Balance between membrane flux and ion rejection rate of filtration membranes is an important crucial technology to achieve an efficient wastewater treatment. In this work, a polyvinylidene fluoride (PVDF) with 3-allylrhodanine (3-AR) modified composite 3-AR/PVDF membrane was fabricated by non-solvent induced phase separation method. Some parameters, such as water flux, selectivity and rejection, were investigated during the membrane treatment. Morphology characterizations, such as scanning electron microscope (SEM), nitrogen adsorption–desorption and contact angle techniques confirmed 3-AR/PVDF had hydrophilic surface and uniform porous structure with average pore size about 65.67 ∼ 39.32 nm. Surface chemical structure characterizations, such as Fourier transformed infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) uncovered that the retention of Ag+ was mainly relied on the chemical bonding of C = S and C-S groups on 3-AR. 3-AR/PVDF-0.130 membrane exhibited excellent performance in adsorption (46.42 mg cm−2), water flux (196.04 L m-3 h−1), rejection (8.75 mg), and selectivity (β > 10). Membrane thickness exhibited good linear relationships with water flux and interception (R2 > 0.94), which could be regulated by the thickness of membrane. The membranes maintained excellent stability in wide pH range 1 ∼ 5, and retained >95% rejection and water flux after 6 cycles. Most important, the costs of membrane and operation were assessed during the long-term filtration, which is of significance for practical applications.