Abstract
A hydroxy-sodalite/cancrinite zeolite composite was synthesized from low-grade calcite-bearing kaolin by hydrothermal alkali-activation method at 160 °C for 6 h. The effect of calcite addition on the formation of the hydroxy-sodalite/cancrinite composite was investigated using artificial mixtures. The chemical composition and crystal morphology of the synthesized zeolite composite were characterized by X-ray powder diffraction, infrared spectroscopy, scanning electron microscopy, and N2 adsorption/desorption analyses. The average specific surface area is around 17–20 m2·g−1, whereas the average pore size lies in the mesoporous range (19–21 nm). The synthesized zeolite composite was used as an adsorbent for the removal of heavy metals in aqueous solutions. Batch experiments were employed to study the influence of adsorbent dosage on heavy metal removal efficiency. Results demonstrate the effective removal of significant quantities of Cu, Pb, Ni, and Zn from aqueous media. A comparative study of synthesized hydroxy-sodalite and hydroxy-sodalite/cancrinite composites revealed the latter was 16–24% more efficient at removing heavy metals from water. The order of metal uptake efficiency for these zeolites was determined to be Pb > Cu > Zn > Ni. These results indicate that zeolite composites synthesized from natural calcite-bearing kaolin materials could represent effective and low-cost adsorbents for heavy metal removal using water treatment devices in regions of water shortage.
Highlights
The use of treated wastewater has become a potential solution to alleviate seasonal water shortages caused by drought or problems of infra structure in many dry countries and is important for use in irrigation, toilet flushing, and firefighting [1,2]
The X-ray diffraction (XRD) patterns zeolite of chinaphase clay and its hydrothermal alkali-activation show the characteristic reflections of kaoliniteattributable (Figure 1a) completely disappeared to patterns form a of the extra reflections upon alkali-activation to cancrinite (Figureafter crystalline hydroxy-sodalite zeolite phase (Figure 1b)
This study highlights the suitability of a synthetic hydroxy-sodalite/cancrinite zeolite composite obtained from the hydrothermal alkali-activation of regionally available Jordanian calcite-bearing kaolin
Summary
The use of treated wastewater has become a potential solution to alleviate seasonal water shortages caused by drought or problems of infra structure in many dry countries and is important for use in irrigation, toilet flushing, and firefighting [1,2]. Local water treatment systems rely on the removal of heavy metals and organic pollutants largely by chemical adsorption. This is often achieved by complicated and expensive methods such as ion exchange, membrane filtration, and electrochemical processes [3,4]. Heavy metals are considered the most hazardous groundwater pollutants and originate from industrial activities as well as the overuse of fertilizers in agriculture. Among these heavy metals, Pb, Cu, Zn, and Ni are considered to be the most studied and problematic of water pollutants [5,6].
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