Transformation from halloysite nanotubes to gobbinsite zeolite improves the fixation capacity of Cd(II)

Abstract

Gobbinsite (GOBZ) is rare zeolite with a disordered framework cation distribution, which is likely beneficial to Cd(II) fixation. This study developed a simple hydrothermal crystallization route to synthesize the novel GOBZ using natural halloysite nanotubes minerals (HNTS). In micropore and mesoporous of BET data analysis, a large number of HNTS microporous structures transformed into GOBZ mesoporous structures, which could greatly facilitate the adsorption ability of GOBZ. The XPS and FTIR exhibited the mesoporous coordination and the interaction of different hydroxyl functional groups, is the main adsorption mechanism to strengthen the Cd(II) fixation capacity. Liu isotherms described well of the adsorption of Cd(II), indicating the process was heterogeneous and multilayers simultaneously. General order kinetics assumed that the adsorption occur accompanied by a chemical reaction on GOBZ. Reusability of GOBZ show that it has good recycling performance and application value in Cd(II) adsorption. The TEM and XRD showed that the adsorption of Cd(II) affected the elemental composition, surface morphology and internal structure of GOBZ, which contributed to in-situ formation of phillipsite-Ca, otavite, garronite and gmelinite-Na. Above all, hydrothermal crystallization (GOBZ technology) can provide viable options for the removal of toxic metal pollution, showing the prospect of clay minerals in the removal. • Halloysite was first used in the synthesis of gobbinsite. • Gobbinsite's adsorption capacity of Cd(II) is 10 times higher than HNTS. • The main adsorption mechanism is the mesoporous coordination.