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The selective extraction of trace-level metal ions from unconventional sources such as wastewaters is a long-standing challenge, due to the large concentration difference between the target metal ions and the interfering ions in the matrix. We show here that an adsorbent based on crown ether functionalized mesoporous silica (MS-C-D) overcomes this limitation for selective sequestration of Ag(I) ion. This new adsorbent has hierarchical structure with large specific area and pore framework, which is conducive to the selective adsorption of trace levels of Ag(I) from a complex solution containing concentrated interfered ions such as Cu(II), Zn(II) and Pb(II) ions. The adsorption affinity (b value of 1.45) and selectivity coefficient (distribution coefficient K D of 1.50 * 10 5 mL/g) of Ag(I) by using MS-C-D were dramatically higher than many other reported adsorbents (e.g. an Ag(I)-ion-imprinted materials with K D of 392 mL/g) in literatures. Furthermore, the lower ion concentration corresponded to higher selectivity for Ag(I). The hierarchically structure of MS-C-D and the rigid cavity of dibenzo-18-crown-6 contributed to the selective adsorption of Ag(I). The adsorbent keeps high capacity (about 39.8 mg/g) and selectivity for Ag(I) adsorption after three regeneration cycles. This new composite adsorbent is promising in extracting trace levels of Ag(I) from unconventional wastewaters containing high concentrations of interfered ions. [ABSTRACT FROM AUTHOR]

A sheet-on-sheet and metal-free graphene/C 3 N 4 /carbon dots (GR/C 3 N 4 /CDots) ternary heterostructure with efficient visible-light photocatalysis for pollutants degradation has been reported. Via a convenient and hydrothermal method, large-sized GR nanosheets can serve as substrate for monodispersed dispersion of C 3 N 4 nanosheets. A subsequent loading of very small amount of CDots (1 wt%, 2–5 nm) onto sheet-on-sheet heterostructure significantly enhance visible-light-driven photoredox performances of catalysts, including oxidation of organics pollutant (RhB, 96.0%) and reduction of heavy metals [Cr(VI), 83.6%]. Excellent catalytic properties of GR/C 3 N 4 /CDots heterostructure can be predominantly ascribed to the intimate interfacial contact among constructing ingredients, increased specific surface area and enhanced light adsorption derived from GR and CDots carbon materials. Particularly, the synergistic sheet-on-sheet interaction between C 3 N 4 and carbon materials (GR and CDots) remarkably accelerate the electrons/holes separation, giving rise to significantly enhanced photoredox performances of GR/C 3 N 4 /CDots in comparison with other counterparts. The synergism effect between organic contaminants and heavy metals also contributed to the efficient performance of GR/C 3 N 4 /CDots, wherein the O 2− and OH were the main active species in the photoredox reactions. This metals-free heterostructure shows favorable photostability in cyclic experiments. We anticipate that our work could provide a classical paradigm for rational design of efficient and visible-light-driven photocatalysts for their sustainable applications in wastewater treatment. [ABSTRACT FROM AUTHOR]

The electrochemical oxidation of ciprofloxacin (CIP) using a SnO 2 -Sb/Ti electrode was systematically investigated. The effects of the current density, initial concentration of CIP, and initial pH were evaluated. The results showed that electrochemical oxidation, using a SnO 2 -Sb/Ti electrode was highly effective for the degradation of CIP. After 120 min, the removals of CIP (50 mg/L), COD and TOC at a current density of 30 mA/cm 2 were about 99.5%, 86.0%, and 70.0%, respectively. The reaction followed a first-order kinetics model. The current density and initial concentration of the CIP exerted a prominent effect on the degradation of CIP, COD, and electrical energy demand, while the initial pH had no effect. The electrochemical degradation pathways, of CIP in aqueous solution, were studied using ion chromatography and liquid chromatography coupled with mass spectrometry (LC–MS). Three major degradation pathways were proposed: oxidation of the piperazine ring, hydroxylation of the quinolone moiety, and defluorination (OH/F substitution). Inorganic N compounds were NH 4 + and NO 3 - . F was reduced to F − . [ABSTRACT FROM AUTHOR]