Xue-min Cui

Porous geopolymeric spheres for removal of Cu(II) from aqueous solution: Synthesis and evaluation

Porous geopolymeric spheres were synthetized by a suspension and solidification method, which were used as adsorbents for the removal of Cu(II) from aqueous solution. The influences of pH, geopolymeric spheres dosage, contact time, and initial Cu(II) concentration on adsorption capacity were investigated in detail. The adsorption kinetics and adsorption isotherms were fitted well by a pseudo-second-order model and a Langmuir isotherm model, respectively. The maximum adsorption capacity of Cu(II) by the spheres calculated from Langmuir isotherm model was 52.63 mg/g. The porous geopolymeric spheres showed higher adsorption capacity than the commercial spherical 4A molecular sieve and some other reported spherical materials. The continuous removal of Cu(II) from an effluent was also conducted in column mode. The results confirmed that porous geopolymeric spheres could be used for the cleanup of heavy metal ions from wastewater in a continuous column process.

Preparation of geopolymer-based inorganic membrane for removing Ni2+ from wastewater

A type of novel free-sintering and self-supporting inorganic membrane for wastewater treatment was fabricated in this study. This inorganic membrane was synthesised using metakaolin and sodium silicate solutions moulded according to a designed molar ratio (SiO2/Al2O3=2.96, Na2O/Al2O3=0.8 and H2O/Na2O=19) which formed a homogenous structure and had a relative concentration pore size distribution, via scanning electron microscopy (SEM) and Brunauer-Emmett-Teller (BET) analyses. In this work, the Ni(2+) removal effect of geopolymer inorganic membrane was studied under different pH value, initial concentration of Ni(2+) solutions and initial operation temperature. Results showed that geopolymer inorganic membrane efficiently removes Ni(2+) from wastewater because of the combined actions of the adsorption and rejection of this membrane on Ni(2+) during membrane separation. Therefore, geopolymer inorganic membrane may have positive potential applications in removing Ni(2+) or other heavy metal ions from aqueous industrial wastewater.

Development of near-zero water consumption cement materials via the geopolymerization of tektites and its implication for lunar construction.

The environment on the lunar surface poses some difficult challenges to building long-term lunar bases; therefore, scientists and engineers have proposed the creation of habitats using lunar building materials. These materials must meet the following conditions: be resistant to severe lunar temperature cycles, be stable in a vacuum environment, have minimal water requirements, and be sourced from local Moon materials. Therefore, the preparation of lunar building materials that use lunar resources is preferred. Here, we present a potential lunar cement material that was fabricated using tektite powder and a sodium hydroxide activator and is based on geopolymer technology. Geopolymer materials have the following properties: approximately zero water consumption, resistance to high- and low-temperature cycling, vacuum stability and good mechanical properties. Although the tektite powder is not equivalent to lunar soil, we speculate that the alkali activated activity of lunar soil will be higher than that of tektite because of its low Si/Al composition ratio. This assumption is based on the tektite geopolymerization research and associated references. In summary, this study provides a feasible approach for developing lunar cement materials using a possible water recycling system based on geopolymer technology.