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The strong adsorbability of Ag(I) and Hg(II) ions onto fine poly(o-phenylenediamine) (PoPD) microparticles synthesized through a chemically oxidative polymerization of o-phenylenediamine was systematically examined and PoPD/Ag nanocomposites were facilely prepared through the reactive sorption method. The effect of the (NH4)2S2O8 oxidant/o-phenylenediamine monomer ratio on the polymerization yield, macromolecular structure, conductivity, and insolubility of the PoPD microparticles was studied. The Ag(I) adsorbability of the microparticles was significantly optimized by varying the oxidant/monomer ratio, doping state, Ag(I) concentration, sorption time, and solution pH. The Ag(I) adsorbance steadily increases with changing oxidant/monomer molar ratio from 3/1 to 1/1, reaching up to the highest Ag(I) adsorbance of 533 mg.g(-1) at the oxidant/monomer ratio of 1/1. The sorption process fits the pseudosecond-order kinetics. The sorption is rapid because both the adsorbance and adsorptivity within 30 min reach up to 76% of the final values. The initial sorption rate of silver ions obtained from the pseudosecond-order equation is 12.9 mg.g(-1).min(-1). The highest adsorptivity of silver ions is up to 99.1%. The optimal solution pH for Ag(I) sorption is around 5.0. The sorption mechanism may include the chelation and redox reaction between Ag(I) ions and amine/imine groups on the PoPD chains. Similarly, the microparticles also have powerful Hg(II) adsorbability with 96.7% adsorptivity at an initial Hg(II) concentration of 4 mM. Competitive sorption between Ag(I) and Hg(II) in their mixture solution onto the microparticles was studied, exhibiting a preferential sorption toward Ag(I). The microparticles as a cost-effective sorbent demonstrate a promising application in the removal and even recovery of heavy-metal ions from wastewater. The PoPD/Ag nanocomposites possess (1) high Ag content of 34.8 wt %, (2) small diameter of Ag nanoparticles of around 10-20 nm, (3) narrow size distribution, (4) intrinsic electrical conductivity that is much higher than that of original PoPD microparticles without Ag.

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Fine microparticles of poly(p-phenylenediamine) (PpPD) and poly(m-phenylenediamine) (PmPD) were directly synthesized by a facile oxidative precipitation polymerization and their strong ability to adsorb lead ions from aqueous solution was examined. It was found that the degree of adsorption of the lead ions depends on the pH, concentration, and temperature of the lead ion solution, as well as the contact time and microparticle dose. The adsorption data fit the Langmuir isotherm and the process obeyed pseudo-second-order kinetics. According to the Langmuir equation, the maximum adsorption capacities of lead ions onto PpPD and PmPD microparticles at 30 degrees C are 253.2 and 242.7 mg g(-1), respectively. The highest adsorptivity of lead ions is up to 99.8 %. The adsorption is very rapid with a loading half-time of only 2 min as well as initial adsorption rates of 95.24 and 83.06 mg g(-1) min(-1) on PpPD and PmPD particles, respectively. A series of batch experiment results showed that the PpPD microparticles possess an even stronger capability to adsorb lead ions than the PmPD microparticles, but the PmPD microparticles, with a more-quinoid-like structure, show a stronger dependence of lead-ion adsorption on the pH and temperature of the lead-ion solution. A possible adsorption mechanism through complexation between Pb(2+) ions and ==N-- groups on the macromolecular chains has been proposed. The powerful lead-ion adsorption on the microparticles makes them promising adsorbents for wastewater cleanup.

An initiator is applied to synthesize single-walled carbon nanotube/polyaniline composite nanofibers for use as high-performance chemosensors. The composite nanofibers possess widely tunable conductivities (10(-4) to 10(2) S/cm) with up to 5.0 wt % single-walled carbon nanotube (SWCNT) loadings. Chemosensors fabricated from the composite nanofibers synthesized with a 1.0 wt % SWCNT loading respond much more rapidly to low concentrations (100 ppb) of HCl and NH(3) vapors compared to polyaniline nanofibers alone (120 s vs 1000 s). These nanofibrillar SWCNT/polyaniline composite nanostructures are promising materials for use as low-cost disposable sensors and as electrodes due to their widely tunable conductivities.

A series of novel copolymer microparticles from 4-sulfonic diphenylamine (SDP) and 1,8-diaminonaphthalene (DAN) was facilely prepared by a chemically oxidative polymerization. The structures and properties of the microparticles were systematically characterized by several important techniques. The microparticles exhibit good water resistance and high thermostability. Their electrical conductivity significantly rises after HCl doping or Ag adsorption. The Ag+ reactive adsorbability of the microparticles was optimized by carefully regulating the SDP/DAN ratio, particle size, and Ag+ solution pH. Both the introduction of SDP units into DAN polymer chains and the diminution of the particle size can effectively increase the capacity and rate of Ag+ adsorption. In particular, the Ag+ adsorbance on SDP/DAN (30/70) copolymer microparticles reaches 2.0 g g-1, which is the highest silver adsorption capacity reported thus far. A novel mechanism of Ag+ reactive adsorption on the microparticles containing a large number of reactive groups such as amino, imino, and sulfonic groups has been proposed. The microparticles could be very applicable to elimination and recovery of noble metallic ions in wastewater.

The highest Hg-ion adsorbance so far, namely up to 2063 mg g(-1), has been achieved by poly(aniline-co-5-sulfo-2-anisidine) nanosorbents. Sorption of Hg ions occurs mainly by redox and chelation mechanisms (see scheme), but also by ion exchange and physisorption.Poly(aniline (AN)-co-5-sulfo-2-anisidine (SA)) nanoparticles were synthesized by chemical oxidative copolymerization of AN and SA monomers, and their extremely strong adsorption of mercury ions in aqueous solution was demonstrated. The reactivity ratios of AN and SA comonomers were found to be 2.05 and 0.02, respectively. While AN monomer tends to homopolymerize, SA monomer tends to copolymerize with AN monomer because of the great steric hindrance and electron-attracting effect of the sulfo groups, despite the effect of conjugation of the methoxyl group with the benzene ring. The effects of initial mercury(II) concentration, sorption time, sorption temperature, ultrasonic treatment, and sorbent dosage on mercury-ion sorption onto AN/SA (50/50) copolymer nanoparticles with a number-average diameter of around 120 nm were significantly optimized. The results show that the maximum Hg-ion sorption capacity on the particulate nanosorbents can even reach 2063 mg of Hg per gram of sorbent, which would be the highest Hg-ion adsorbance so far. The sorption data fit to the Langmuir isotherm, and the process obeys pseudo-second-order kinetics. The IR and UV/Vis spectral data of the Hg-loaded copolymer particles suggest that some mercury(II) was directly reduced by the copolymer to mercury(I) and even mercury(0). A mechanism of sorption between the particles and Hg ions in aqueous solution is proposed, and a physical/ion exchange/chelation/redox sorption ratio of around 2/3/45/50 was found. Copolymer nanoparticles may be one of the most powerful and cost-effective sorbents of mercury ions, with a wide range of potential applications for the efficient removal and even recovery of the mercury ions from aqueous solution.

Pure polypyrrole (PPy) nanoparticles that are well-applicable for nanocomposite and nanocarbon precursor were productively synthesized by necessarily unstirred oxidative polymerization of pyrrole in acidic aqueous media at 0°C without any template. The species and concentration of acid and oxidant have been carefully investigated to optimize the polymerization yield, conjugated structure, size, and conductivity of the PPy particles. Laser particle-size analysis, field-emission scanning electron microscopy, transmission electron microscopy, and atomic force microscopy all revealed that the PPy particles produced in still acid media have narrow size distribution and uniform spheroid morphology. Homogeneous nucleation and static repulsion are proposed as the formation and self-stabilization mechanisms of the PPy nanoparticles. Combination of HNO 3 medium and (NH 4 ) 2 S 2 O 8 oxidant is optimal for the synthesis of PPy nanoparticles possessing maximal yield of 87.2%, small diameter, and high conductivity which has been confirmed by a strong UV-vis band due to a large π-conjugated chain structure. This quiescent polymerization could be simply scaled up or down to synthesize a larger or smaller amount of PPy nanoparticles without compromising their yield, structure, and properties. Furthermore, the conductivity of the nano-PPy could reach 2.8 S/cm upon doping in 2.0 M HClO 4 . Simultaneous thermogravimetry-differential thermal analysis technique demonstrates that the PPy nanoparticles at 1000°C can be efficiently carbonized into carbon nanoparticles with narrower size distribution, smaller diameter of 62 nm, and much higher conductivity of about 21 S/cm. In particular, the conductivity will dramatically be enhanced to 219 S/cm and even 370 S/cm at the carbonization and graphitization temperatures of 1300 and 2300°C in nitrogen and argon, respectively. A conductive nano-PPy/cellulose diacetate nanocomposite film with low percolation threshold down to 0.2 wt %, good conductivity stability for at least 8 weeks, and potential bioapplicability was simply fabricated. The present synthesis requires no external templates and provides a facile and direct route to scalable synthesis of PPy exclusive nanoparticles with high yield, controllable size, strong re-dispersibility, high purity, adjustable conductivity, and high nanocarbon yield.