Facile synthesis of poly(1,8-diaminonaphthalene) microparticles with a very high silver-ion adsorbability by a chemical oxidative polymerization

Poly(1,8-diaminonaphthalene) (PDAN) was traditionally synthesized by an electrochemical polymerization that has some limitations such as low productivity and single form of a film. Here we report a relatively large mass synthesis of PDAN micrometer particles by a chemical oxidation of 1,8-diaminonaphthalene by (NH4)(2)S2O8 or FeCl3 with high yield. Elemental analysis, IR, and solid-state high-resolution C-13 NMR spectroscopies indicate that the PDAN chain contains imine (-N=C), amine (-NH-C), and free amine (-NHZ) units as linkages between naphthalene rings. A double-stranded ladder or single-stranded structure via the linkages is deduced. The structure and Ag+ absorbability of PDAN particles were characterized by laser particle-size analyzer, wideangle X-ray diffractometer, IR, and inductively coupled plasma techniques. The Ag+ adsorbability of the particles was examined and optimized systematically by varying the adsorption time, the dose and size of the particles, the temperature, pH, and concentration of Ag+ solution. The fine particles obtained using (NH4)(2)S2O8 exhibit high adsorbability by complexation between Ag+ and amine/imine groups as well as the redox between Ag+ and free -NH2 group. The Ag+ adsorbance reaches 1.92 g/g (PDAN) with exposure to a solution containing 82 mM Ag+ ion for 24 h at an initial Ag+/PDAN ratio of 103 mmol/g. Total Ag+ adsorbance was 1.92 times the PDAN weight, remarkably surpassing the largest Ag+ adsorbance of 1.36 g/g (the best activated carbon fiber) for 30 days. The PDAN particles could be very useful in collection and removal of heavy metallic ions from water effluents. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.