Yufei Wang,Shuang Liu,Junyao Pan,Haoyang Zhang,Binyu Wang,Wenfu Yan
MER zeolite, a low-silica zeolite with an 8-membered ring aluminosilicate framework, has been recognized as a promising material in sorption, separation, and ion-exchange applications. Herein, we developed a cost-effective and rapid method to convert parent zeolite H-STI, which was derived from natural stellerite, into MER zeolite through interzeolite conversion with a crystallization time of 8 h. This MER zeolite exhibits high efficiency in removing Pb2+ and Cd2+ from simulated heavy metal wastewater over a pH range of 3–8. It also shows excellent selectivity in the presence of competitive cations, including Na+, K+, Ca2+, Mg2+, Zn2+, Cu2+, and Co2+. At 25 °C, with a MER-S dosage of 1/3000 g·mL–1 for Pb2+ and 1/500 g·mL–1 for Cd2+, the removal efficiencies were 99.7 and 99.9%, respectively. The distribution coefficients were 1097 L·g–1 for Pb2+ and 550 L·g–1 for Cd2+, and the sorption capacities reached 513 mg·g–1 for Pb2+ and 171 mg·g–1 for Cd2+, indicating that the product MER zeolite is one of the highest sorbents for Pb2+ and Cd2+ reported for zeolitic materials. The sorption for Pb2+ and Cd2+ both follows the chemisorption-dominated mechanism, driven by the ion-exchange process between the K+ in the channels MER-S and the Pb2+ or Cd2+ in solution. This work highlights the potential of rapidly synthesized MER zeolite for the effective removal of heavy metal cations, emphasizing its performance and practical applicability.
Merlinoite(MER) zeolite membranes were synthesized on the outer surface of porous α-alumina tubular support by in-situ hydrothermal synthesis method without organic template. The synthetic MER zeolite membranes (sample 1, sample 2 and sample 3) were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). The thickness of sample 2 without cracks is about 15 μm. The synthetic MER membrane which is mainly composed of Si, Al, O and K is typical merlinoite structure. The performance of sample 2 for potassium extraction in simulated seawater was researched by the membrane tube reactor. The continual ion-exchange reaction was carried out for 108 h at room temperature. The average exchange rate for K + ion was 32.8% and the average rejection rates for Na + , Ca 2+ and Mg 2+ ions were 93.4, 98.4 and 98.2% respectively. So the MER zeolite membrane (sample 2) has preference selectivity for K + ion and can be used as a potential inorganic membrane for potassium extraction from seawater.
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