Akademik Veri Yönetim Sistemi
EURO CERAMICS VIII, PTS 1-3, ss.41-44, 2004 (SCI-Expanded)
Structure of nickel precipitate from decomposition of urea was found to be alpha-Ni(OH)(2). FTIR analysis revealed the intercalation of cyanate (OCN-), which is an intermediate product of urea decomposition. This observation implied that the assumption of single step decomposition of urea to carbon dioxide and ammonia was over simplified. For quantitative analysis on the effects of critical system parameters like initial pH and metal ion concentration, a detailed analysis of the possible reactions in urea system was carried out. Numerical solutions to reaction pathways predicted significant accumulation of the intermediate cyanate in the time-temperature range investigated. Further elaboration was possible by considering the effects of hydrolysis products of Ni2+ and Ni-amine, Ni-cyanate, and Ni-carbonate complexes in the numerical simulations. Chemical analysis of the precipitate showed a decrease in nitrogen content with increasing reaction times. This was consistent with the predicted decrease in concentration of Ni-cyanate complexes with time. At extended digestion times, formation of Ni-amine complexes limits the complete recovery of the Ni2+.