Enhanced chromium adsorption capacity via plasma modification of natural zeolites

Abstract

Natural zeolites such as mordenite are excellent adsorbents for heavy metals. To enhance the adsorption capacity of zeolite, sodium-exchanged samples were irradiated with 13.56 MHz capacitively coupled radio frequency (RF) argon gas discharge. Hexavalent chromium [Cr(VI)] was used as the test heavy metal. Pristine and plasma-treated zeolite samples were soaked in 50 mg/L Cr solution and the amount of adsorbed Cr(VI) on the zeolites was calculated at predetermined time intervals. Compared with untreated zeolite samples, initial Cr(VI) uptake was 70% higher for plasma-treated zeolite granules (50 W 30 min) after 1 h of soaking. After 24 h, all plasma-treated zeolites showed increased Cr(VI) uptake. For a 2- to 4-month period, Cr(VI) uptake increased about 130% compared with untreated zeolite granules. X-ray diffraction analyses between untreated and treated zeolite samples revealed no major difference in terms of its crystal structure. However, for plasma-treated samples, an increase in the number of surface defects was observed from scanning electron microscopy images. This increase in the number of surface defects induced by plasma exposure played a crucial role in increasing the number of active sorption sites on the zeolite surface.

Effects of γ-irradiation on the Cu2+ sorption behaviour of NaOH-modified Philippine natural zeolites

“…Minor quartz (Levien et al , 1980) is also present. These results are consistent with the reported composition of the PNZ based on previous works (Cagomoc & Vasquez, 2017; Gili et al , 2019a, 2019b).

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“…Minor quartz (Levien et al, 1980) is also present. These results are consistent with the reported composition of the PNZ based on previous works (Cagomoc & Vasquez, 2017;Gili et al, 2019aGili et al, , 2019b. The effects of γ-radiation on the XRD traces of the raw zeolite can be deduced from Fig.…”

“…Peaks from quartz (Levien, et al, 1980) were also identified. These results are consistent with the reported composition of the Philippine natural zeolite-based on previous works (Cagomoc & Vasquez, 2017). The effects of γ-radiation in the x-ray diffractograms of the raw zeolite can be deduced from Fig.…”

“…Ion exchange removes cations initially present on the zeolite, providing additional sites for cation adsorption (Inglezakis et al , 2001; Taffarel & Rubio, 2009; Gili et al , 2019b). Other methods employ plasma modification to increase adsorption (Cagomoc & Vasquez, 2017; Taaca et al , 2019).…”

Impregnation of silver in zeolite–chitosan composite: thermal stability and sterility study

“…In addition, there are previous studies focusing on Ch–zeolite composites for biomedical application (Yu et al ., 2013; Zhang et al ., 2015). However, surface modification via plasma treatment to tailor the surface properties of the composite has scarcely been reported, although it has been considered an effective method for enhancing the wettability and surface roughness of polymers, such as Ch, and ceramic materials, such as zeolites (Cagomoc & Vasquez Jr, 2016; Osonio & Vasquez Jr, 2018). The porosity and the surface properties (roughness and wettability) of Ch were greatly enhanced with the presence of AgZ particles coupled with plasma treatment (Taaca & Vasquez Jr, 2017).…”