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

Schematic of porous geopolymeric spheres by a suspension and solidification method (SSM) with metakaolin-based geopolymers. •Porous geopolymeric sphere was obtained by a suspension and solidification method.•It exhibited higher capacity for Cu(II) removal than spherical 4A molecular sieves.•It provided a new possible way for continuous-mode removal of heavy metal ions. 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 52.63mg/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.