Nickel aluminate spinel formation during sintering of simulated Ni-laden sludge and kaolinite

ncorporating Ni-laden waste sludge into kaolinite-based construction ceramic materials appears promising based on the identified nickel bearing hases, evaluated incorporation efficiency and nickel leachability of the products. Nickel aluminate spinel (NiAl2O4) results from sintering kaolinite nd nickel oxide between 990 and 1480 ◦C, with more than 90% incorporation efficiency achieved at 1250 ◦C and 3 h sintering. At lower temperature 990 ◦C), NiAl2O4 formed from the reaction between nickel oxide and the defect spinel generated from the kaolinite–mullite reaction series. In ddition to sintering temperature and time, four raw material mixing procedures were employed, and the ball-milled slurry samples had the highest ickel incorporation efficiency. Prolonged leach testing of NiO, NiAl2O4 and the product from sintered kaolinite + NiO mixtures was carried out sing the TCLP extraction fluid #1 (pH 4.9) to evaluate the product stability, and the results revealed the superiority of spinel products over NiO n stabilizing nickel. 2006 Elsevier Ltd. All rights reserved.