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.