Effect of Alkali Fusion Methods on the Preparation of One-Part Geopolymer From Coal Gasification Slag.

This study investigated the one-part geopolymer synthesis by coal gasification slag through a calcination treatment. Two preparation methods, the traditional alkali fusion method (M-I) and the alkali fusion and modification method (M-II), were compared to illustrate the more suitable way for coal gasification slag-based one-part geopolymer (CGS-based geopolymer) synthesis. The reaction products and structure of the geopolymer were tested by XRD, FTIR, TG-DTG, and SEM.

Immobilization mechanism of cesium in geopolymer: Effects of alkaline activators and calcination temperature.

Geopolymer is always regarded as a promising material for the immobilization of radioactive waste. In the present study, the stabilization of Cs in geopolymers activated by NaOH and NaSiO solutions and calcined at various temperatures was studied via toxicity characteristic leaching procedure (TCLP), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope and energy dispersive spectroscopy (SEM-EDS), solid-state nuclear magnetic resonance (SSNMR), and N adsorption-desorption isotherm. For both NaOH-activated and NaSiO-activated geopolymers, the leaching concentrations of Cs decreased with the increase of calcination temperature.

Influence of aluminate and silicate on selenate immobilization using alkaline-earth metal oxides and ferrous salt.

Effects of aluminate and silicate species on the SeO immobilization using alkali-earth metal oxides and ferrous species have not been clearly elucidated. In the present study, Al and Si species were separately added into MgO/Fe(II) and CaO/Fe(II) reactions containing SeO, studied by toxicity characteristic leaching procedure (TCLP), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray absorption fine structure (XAFS), and PHREEQC simulation. Approximately 42 % of SeO was reduced to SeO for MgO/Fe(II) reaction in the presence of Al species, being consistent with the case without Al species.

Application of Geopolymer in Stabilization/Solidification of Hazardous Pollutants: A Review.

Geopolymers, as a kind of inorganic polymer, possess excellent properties and have been broadly studied for the stabilization/solidification (S/S) of hazardous pollutants. Even though many reviews about geopolymers have been published, the summary of geopolymer-based S/S for various contaminants has not been well conducted. Therefore, the S/S of hazardous pollutants using geopolymers are comprehensively summarized in this review.

Effect of Si/Al molar ratio on the immobilization of selenium and arsenic oxyanions in geopolymer.

The effect of Si/Al molar ratio of geopolymer on the immobilization of Se and As oxyanions was studied through leaching test and solid characterizations including XRD, FTIR, TG, NMR, XAFS, and N adsorption-desorption isotherm. As a whole, the leaching percentages of Se and As oxyanions increased with the increase of the Si/Al molar ratio of geopolymer. Linear combination fitting confirmed that most of selenite, selenate and arsenate ions existed in geopolymers through electrostatic interaction.