Redox Sorption and Recovery of Silver Ions as Silver Nanocrystals on Poly(aniline‐co‐5‐sulfo‐2‐anisidine) Nanosorbents

Abstract

Poly[aniline(AN)-co-5-sulfo-2-anisidine(SA)] nanograins with rough and porous structure demonstrate ultrastrong adsorption and highly efficient recovery of silver ions. The effects of five key factors-AN/SA ratio, Ag(I) concentration, sorption time, ultrasonic treatment, and coexisting ions-on Ag(I) adsorbability were optimized, and AN/SA (50/50) copolymer nanograins were found to exhibit much stronger Ag(I) adsorption than polyaniline and all other reported sorbents. The maximal Ag(I) sorption capacity of up to 2034 mg g(-1) (18.86 mmol g(-1)) is the highest thus far and also much higher than the maximal Hg-ion sorption capacity (10.28 mmol g(-1)). Especially at <or=2 mM Ag(I), the nanosorbents exhibit >or=99.98 % adsorptivity, and thus achieve almost complete Ag(I) sorption. The sorption fits the Langmuir isotherm well and follows pseudo-second-order kinetics. Studies by IR, UV/Vis, X-ray diffraction, polarizing microscopy, centrifugation, thermogravimetry, and conductivity techniques showed that Ag(I) sorption occurs by a redox mechanism mainly involving reduction of Ag(I) to separable silver nanocrystals, chelation between Ag(I) and -NH-/-N=/-NH(2)/-SO(3)H/-OCH(3), and ion exchange between Ag(I) and H(+) on -SO(3) (-)H(+). Competitive sorption of Ag(I) with coexisting Hg, Pb, Cu, Fe, Al, K, and Na ions was systematically investigated. In particular, the copolymer nanoparticles bearing many functional groups on their rough and porous surface can be directly used to recover and separate precious silver nanocrystals from practical Ag(I) wastewaters containing Fe, Al, K, and Na ions from Kodak Studio. The nanograins have great application potential in the noble metals industry, resource reuse, wastewater treatment, and functional hybrid nanocomposites.

Potash alum doped polyaniline: Structure and properties

“…2. The absorption spectra of EB PANI shows two distinct absorption bands located at λ max = 330 and 633 nm, which are due to the π-π* transition of the benzoid ring and exciton absorption from benzoid ring to quinoid rings respectively [30][31][32][33]. In case of 22, 19, and 14% doped PANI the peak at 330 nm is shifted to 345, 343, and 336 nm respectively.…”

Poly(ethyleneimine) nanofibrous affinity membrane fabricated via one step wet-electrospinning from poly(vinyl alcohol)-doped poly(ethyleneimine) solution system and its application

“…It is known that the main adsorption sites for heavy metal ions are the nitrogen atoms in the macromolecular chains because the nitrogen atom has a lone pair of electrons which can bind a metal ion through sharing an electrons pair to form a metal complex [39,40]. A possible interaction mechanism between the three heavy metal ions and nitrogen atoms in the polymer PEI chains has been proposed as shown in Fig.…”

Preparation, Structure, and Properties of Hybrid Polymer Composites Containing Silver Clusters and Nanoparticles

“…Replacing poly(An) on polypyrrole decreases the stability of nanocomposites, which leads to a high degree of SN aggregation [131,132]. The enhanced adsorption capacity relative to Ag + ions (up to 1.85·10 -2 mol/g with adsorption efficiency >99.98%) and reducing activity of the copolymer of An and 5-sulfo-2-anisidine may be used for the preparation of conducting composites and adsorbents for the concentration and separation of silver from waste water [133]. The formation of a layer of SN on the surface of fibers of the interpolymer complex poly(o-methoxyaniline)(PoMA)/ribonucleic acid (RNA) imparts semiconductor properties to the composites, which is attributed to features of the charge transfer between the matrix and SN [134].…”