Renewable P-type zeolite for superior absorption of heavy metals: Isotherms, kinetics, and mechanism

Zeolite is a characteristic material for removing heavy metals exhibiting by low tolerance quantities. It is particularly desirable although challenging to cultivate an unmodified and reusable zeolite for eradicating heavy metals with great capacity. Herein, we sought out and firstly synthesized the uniform octahedral zeolite Na6Al6Si10O32·12H2O for heavy metal ions trap, proven extraordinarily effective decontamination of M2+ (Pb2+, Cd2+, Cu2+, and Zn2+). The maximum capacities of Pb2+, Cd2+, Cu2+, and Zn2+ were 649, 210, 90 and 88 mg/g, and the distribution coefficients (Kd) was ~108 mL/g for Pb2+ which emphasized the superior effectiveness of Na6Al6Si10O32·12H2O contrasted with other zeolites. Rapid adsorption was observed that Pb2+ concentration (7.5 ppm) was reduced to 0.6 ppb in 2 min. The removal mechanism was ascribed to the ion exchange and hydroxyl groups thereby affording high adsorption capacity. We also investigated the heavy metal removal of zeolite 13X and 4A for comparison and concluded the determining factor affecting absorption capacity. The removal rate of Pb remained at 97% even after five regeneration recycles. The zeolite was therefore promising for practical water purification and industrialization. Herein, we firstly synthesized the octahedral zeolite Na6Al6Si10O32·12H2O without modification for eradicating heavy metal ions, proven great absorption capacity. Rapid adsorption and stable recycling performance made the zeolite to be promising for practical water purification and industrialization. [Display omitted] •The synthetic NASO zeolite without modification for eradicating heavy metals•The great absorption capacities for Pb and Cd are 649 and 210 mg/g.•Rapid purification for Pb wastewater to drinkable level is in 2 min.•Adsorption involves both ion exchange reaction and electrostatic interaction.•Concluding the determining factor affecting absorption capacity of zeolites