Spinel Formation for Stabilizing Simulated Nickel-Laden Sludge with Aluminum-Rich Ceramic Precursors

Abstract

The feasibility of stabilizing nickel-laden sludge from commonly available Al-rich ceramic precursors was investigated and accomplished with high nickel incorporation efficiency. To simulate the process, nickel oxide was mixed alternatively with gamma-alumina, corundum, kaolinite, and mullite and was sintered from 800 to 1480 degrees C. The nickel aluminate spinel (NiAl2O4) was confirmed as the stabilization phase for nickel and crystallized with efficiencies greater than 90% for all precursors above 1250 degrees C and 3-h sintering. The nickel-incorporation reaction pathways with these precursors were identified, and the microstructure and spinel yield were investigated as a function of sintering temperature with fixed sintering time. This study has demonstrated a promising process for forming nickel spinel to stabilize nickel-laden sludge from a wide range of inexpensive ceramic precursors, which may provide an avenue for economically blending waste metal sludges via the building industry processes to reduce the environmental hazards of toxic metals. The correlation of product textures and nickel incorporation efficiencies through selection of different precursors also provides the option of tailoring property-specific products.

Stabilization and phase transformation of CuFe2O4 sintered from simulated copper-laden sludge

“…Stabilization of heavy metal sludge by thermal treatment has the potential for converting hazardous metal sludge into mineral phase and reusable product, such as spinel ceramics [5][6][7][8]. Spinel provides advantages of no permeability for liquid and gas, low thermal conductibility, high chemical resistibility, and its Mohs Hardness is equal to 8 [9].…”

“…The formation of spinel materials by thermal process from the parent oxides was extensively studied [5][6][7][8]14,15]. Because of the similar precursors existed in heavy metal sludge, stabilizing heavy metal via thermal treatment has the potential to convert hazardous metal-laden sludge from the waste stream into reusable spinel products.…”

“…Because of the similar precursors existed in heavy metal sludge, stabilizing heavy metal via thermal treatment has the potential to convert hazardous metal-laden sludge from the waste stream into reusable spinel products. Shih et al successfully converted nickel into spinel species by sintering the precursors with alumina (Al 2 O 3 ), hematite (Fe 2 O 3 ) and kaolinite (Al 2 Si 2 O 5 (OH) 4 ) [6][7][8]. The formation of nickel aluminate spinel and nickel ferrite spinel were found after sintering the simulated sludge at 1000 • C with alumina and 600 • C with hematite, respectively.…”

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

“…24,25 At 1000 • C, mullite starts to form; around 1150-1300 • C (depending on the impurity level), amorphous silica crystallized as cristobalite. 26 During the treatment of metal bearing wastewater, lime is often added to precipitate metals, and thus the dominant forms of nickel in sludge are usually the hydroxide and carbonate forms. 1 Researches have simulated nickel-laden sludge by using lime to precipitate nickel from its nitrate and chloride solutions, 2,6 or by directly using nickel hydroxide.…”

Metal Stabilization Mechanisms in Recycling Metal-Bearing Waste Materials for Ceramic Products

“…In the mechanistic study of thermal reaction, simulation of hazardous metals by their oxides may further illustrate the phase transformation process and provide the basic incorporation efficiency information. Recent works involving mechanistic investigation of stabilizing of nickel and copper waste solids in alumina and iron-rich ceramics have had major breakthroughs in understanding of incorporation efficiencies and product leaching behavior (Hu et al 2010;Shih, 2005Shih, , 2006aShih, , 2006bShih, , 2007Tang et al, 2010). Such findings are crucial for the development of beneficial usage of metal bearing waste materials and for safely blending them into ceramic raw materials for manufacturing marketable products.…”