Immobilization behavior of Sr in geopolymer and its ceramic product

To date, geopolymer has emerged as a promising and inexpensive precursor with potential application in trapping hazardous elements via physical encapsulation or chemical bonding. In this work, different high-temperature products derived from Sr-contained geopolymer precursors were prepared. Different to conventional hazardous elements that immobilized in the geopolymer precursor, which show decreasing leaching rates after high-temperature treatments, leaching rates of Sr in the resulting high-temperature products first increase and then decrease with the increasing heating temperature. Herein, we first shed light on the underlying reasons of such temperature-dependent leaching behaviors by investigating effects of heating temperature on the phase composition, microstructure, and immobilization mechanism. Moreover, a novel immobilization strategy has been proposed based on the blocking effect of formed nepheline structures at 1200°C. Using this strategy, the leaching rate of Sr reduced to 5.82 × 10 −7 g cm −2 d −1 in the deionized water.