resumo
This work describes the formulation and synthesis of Ni-olivine green pigments from industrial wastes, namely foundry sand and a sludge resulting from the wastewater treatment of the Ni/Cr galvanising process. This second one is considered as hazardous waste since the leached levels of nickel and chromium are above legal concentrations. Pigments were prepared by the solid state reaction method and Ni2SiO4 is formed at only 1050 degrees C. SiO2 (in excess) and NiCr2O4 are present as secondary phases. By using pure reagents and following similar processing conditions, the Ni-olivine phase is only observed at 1200 degrees C. The green colour of the pigments is due to spin-allowed transitions of Ni2+ in octahedral M1 and M2 positions. The sample prepared from wastes shows a stronger and darker green hue. The colouring performance of ceramic glazes and bodies is also optimal, confirming the potential of the use of such wastes for ceramic pigments production. (C) 2010 Elsevier Ltd. All rights reserved.
palavras-chave
GALVANIC SLUDGE; SILICATE MELTS; CHROMIUM; SPECTRA; NICKEL; LIEBENBERGITE; GLASSES; IONS; RECOVERY; NI2SIO4
categoria
Materials Science
autores
Esteves, D; Hajjaji, W; Seabra, MP; Labrincha, JA
nossos autores
João António Labrincha Baptista
Professor Catedrático
Maria Paula Seabra
Professor Auxiliaragradecimentos
The work was supported by FCT (project PTDC/CTM/72318/2006 and grant BII/Lab/0011/2008 for D. Esteves). Thanks to Dr R. C. Pullar for comments and corrections to the English and to Dr. M. J. Ribeiro for the help with ATG/TG measurements and discussion.