Experimental Study on Solidification of Pb2+ in Fly Ash-Based Geopolymers

Abstract

Fly ash from the incineration of domestic waste contains heavy metals, which is harmful to the environment. To reduce and prevent their contamination, heavy metal ions need to be sequestered. In this study, the geopolymer prepared by fly ash, a kind of power plant waste, is used to cure the heavy metal Pb2+, and to investigate the effect of different concentrations of Pb2+ on the compressive strength of the solidified body at different ages; the curing effect is judged by the toxic leaching concentration of heavy metals; the resistance of the solidified body to immersion is evaluated by comparing the change in strength before and after leaching; the fly ash-based geopolymer solidified body is compared with the cement solidified body in terms of curing effectiveness; the properties of the geopolymer and its mechanism of curing heavy metals are explored by microscopic tests. The results show that the fly ash-based geopolymer solidified body has good resistance to immersion; the optimum curing concentration of Pb2+ in fly ash-based geopolymers is 2.0%; compared to pure geopolymers, the strength of the solidified body at 28 d decreases by only 13.0%, and the leaching concentration of Pb2+ is 4.73 mg·L−1, which meets the specification requirements; the curing effect of the fly ash-based geopolymer is better than the cement solidified body; the microscopic test results indicate that the curing of Pb2+ by the fly ash-based geopolymer is a combination of both chemical bonding and physical fixation.

Activation Mechanism of Coal Gangue and Its Impact on the Properties of Geopolymers: A Review

“…Thus, it has better physical fixation and chemical bonding to metal ions. Additionally, it is not easy to leach and has good stability [116,117]. The gel-like substances of CGG are mainly amorphous N-A-S-H (sodium aluminate-silicate hydrate) and C-S-H (calcium silicate hydrate) or aluminum-substituted C-A-S-H forms which are solidified by physical and chemical means due to their porous structure and the presence of negative aluminum tetrahedral charges in these gels [118].…”

Does Current Knowledge Give a Variety of Possibilities for the Stabilization/Solidification of Soil Contaminated with Heavy Metals?—A Review

“…However, despite intensive research and continuous development, this material has failed to revolutionize the binder segment. While the strength and leachability results of S/S products are competitive with those using traditional binders [ 182 , 183 ], the costly activators that enable the synthesis of the geopolymers (sodium or potassium hydroxides, liquid water glass) block their widespread use. The situation is partly alleviated by the fact that geopolymers based on slag [ 184 ] and fly ash [ 58 , 185 ] are currently being produced and studied in addition to metakaolin-based geopolymers [ 99 , 186 ].…”

Solidification Behavior of Heavy Metal Pb2+ for Spontaneous Combustion Coal Gangue-Based Geopolymers

“…Spontaneous combustion of coal gangue (SCCG) is a natural phenomenon that occurs when coal gangue exposed to the open air and subject to long-term wind and sunshine reaches combustible temperatures [1][2][3]. The combustion of coal gangue would release a considerable amount of toxic gases and fly ash, which contain multiple hazardous elements, including SO 2 , H 2 S, Pb, Hg, Cd, and so on.…”