Prolonged toxicity characteristic leaching procedure for nickel and copper aluminates

Abstract

The toxicity characteristic leaching procedure (TCLP) is a regulatory testing method widely employed to evaluate the environmental friendliness of waste materials. TCLP analysis provides a fast, easy and economical way to determine the mobility of waste pollutants under simulated landfill conditions. Recent studies on metal stabilization have reported the potential for nickel and copper aluminates to form in thermal treatment conditions, and suggested a more reliable method of stabilizing hazardous metals, particularly when products are to be reused. There is thus an urgent need for a convenient and effective method of quantifying metal leachability and identifying the metal leaching behavior of sparingly soluble materials. In this study, standard TCLP analysis was modified into a prolonged leaching experiment to investigate the leaching behavior of nickel and copper oxides (NiO and CuO) and their aluminates (NiAl(2)O(4), CuAl(2)O(4) and CuAlO(2)). The results demonstrate the difficulty of differentiating the leachability of highly insoluble phases, such as NiO and NiAl(2)O(4), using the standard TCLP. The prolonged TCLP method, however, confirmed NiAl(2)O(4) to have a lower degree of intrinsic leachability than NiO and that it could be expected to undergo congruent dissolution under landfill conditions. For the more soluble copper system, the aluminates were still found to possess a much lower degree of leachability, and their leaching behavior to follow an incongruent dissolution pattern. The results of this study prove prolonged TCLP analysis to be a convenient and effective way to evaluate the environmental friendliness of metal waste and to identify the leaching behavior of waste materials.

Incorporation of zinc for fabrication of low-cost spinel-based composite ceramic membrane support to achieve its stabilization

“…The leachability of single-phase ZnO and ZnAl 2 O 4 samples was performed by a modification of the U.S. EPA Toxicity Characteristic Leaching Procedure (TCLP) (TCLP) [25], with a pH 2.9 acetic acid solution (extraction fluid #2) as the leaching fluid. Each leaching vial was filled with 40 mL of TCLP extraction fluid and 2.0 g of ground powder.…”

Alumina polymorphs affect the metal immobilization effect when beneficially using copper-bearing industrial sludge for ceramics

“…When a-Al 2 O 3 was used as the sintering precursor, the leaching of aluminum was extremely low at temperatures <850°C. Although low aluminum leachability has been reported for CuAl 2 O 4 (Tang et al, 2010;Shih and Tang, 2011), because the aluminum concentration in the leachate gradually increased with an increase in sintering temperature, CuAl 2 O 4 is likely still slightly more vulnerable to acidic attack compared to a-Al 2 O 3 . At temperatures >1100°C, the leachability of aluminum further increased and the formation of the CuAlO 2 phase at higher temperatures made the aluminum even more leachable from the solid.…”

“…The increase in copper in the leachate is likely due to the reappearance of CuO and the generation of the CuAlO 2 phase in the sample. Shih and Tang (2011) reported the weaker resistance of CuAlO 2 than CuAl 2 O 4 under acidic attack and this may explain why the copper concentration in the leachate rose again for samples sintered at P1150°C.…”

Mechanisms of zinc incorporation in aluminosilicate crystalline structures and the leaching behaviour of product phases

“…Previous studies have reported that nickel and copper sludge can be incorporated into aluminate and ferrite structures in ceramics through a wellcontrolled sintering process, significantly reducing product leachability through the intrinsic properties of the product phases. [13][14][15][16][17] Ceramics encompass a wide variety of construction and industrial products (e.g. tiles, bricks, and insulation and refractory products).…”