Paraquat adsorption on NaX and Al-MCM-41

Abstract

The aim of this work is to determine paraquat adsorption capacity of zeolite NaX and Al-MCM-41. All adsorbents were synthesized by hydrothermal method using rice husk silica. For Al-MCM-41, aluminum (Al) was added to the synthesis gel of MCM-41 with Al content of 10, 15, 20 and 25 wt%. The faujasite framework type of NaX and mesoporous characteristic of Al-MCM-41 were confirmed by X-ray diffraction. Surface area of all adsorbents determined by N2 adsorption-desorption analysis was higher than 650 m2/g. Al content and geometry were determined by X-ray fluorescence and 27Al nuclear magnetic resonance, respectively. Morphology of Al-MCM-41 were studied by transmission electron microscopy; macropores and defects were observed. The paraquat adsorption experiments were conducted using a concentration range of 80-720 mg/L for NaX and 80-560 mg/L for Al-MCM-41. The paraquat adsorption isotherms from all adsorbents fit well with the Langmuir model. The adsorption capacity of NaX was 120 mg/g-adsorbent. Regarding Al-MCM-41, the 10% Al-MCM-41 exhibited the lowest capacity of 52 mg/g-adsorbent while the other samples had adsorption capacity of 66 mg/g-adsorbent.

Comprehension of paraquat adsorption on faujasite zeolite X and Y in sodium form

“…XRD patterns of NaX, NaY, PQX, and PQY are shown in Figure 2. Main peaks of PQX and PQY were similar to those of the bare zeolites (Rongchapo et al, 2013(Rongchapo et al, , 2015. XRD results indicated that paraquat adsorption did not change the zeolite structure.…”

“…Each supercage has a diameter of 1.3 nm and four open windows with a diameter of 0.74 nm (Guisnet and Gilson, 2002). The Si/Al ratios of NaX and NaY from our works are 1.2 and 2.2, respectively (Rongchapo et al, 2013(Rongchapo et al, , 2015. The presence of an Al atom in the zeolite framework generates a negative charge which requires a charge balancing cation.…”

“…Paraquat, commercial grade (27.6 %w/v, Masda) was used in the adsorption. NaX and NaY were synthesized as described in the literature (Rongchapo et al, 2013(Rongchapo et al, , 2015. Zeolites containing paraquat (PQX and PQY) were prepared by adding 1.0 g of adsorbent into 400 mL of 1000 ppm paraquat solution and stirred at room temperature for 60 minutes (Rongchapo et al, 2013), separated, washed with 5 L of distilled water and dried at 90 C for 24 hours.…”

“…With a high solubility, paraquat can easily contaminate and accumulate in surface water (Pateiro-Moure et al, 2010). There are several reports on paraquat removal from aqueous solutions by adsorption on various porous materials including silica (SiO 2 ), zeolite NaBEA, NaY, NaX, mesoporous materials MCM41 and Al-MCM-41 (Brigante and Schulz, 2011;Ibrahim and Jbara, 2009;Nur et al, 2005;Rongchapo et al, 2013Rongchapo et al, , 2015.…”

Zeolitization of kaolin from M'Batra village (Cote d’Ivoire) by NaOH and Na2O.SiO2 treatment

“…For this sample, the isotherm exhibits an H4 hysteresis loop. This isotherm is of the type I because it presents a quasi-horizontal plate and is characteristic of a microporous material (Rongchapo et al, 2015, Rongchapo et al, 2013, Rongchapo et al, 2018. In the specific surfaces area study, the parameters such as grain size and the degree of crystallization of the samples had a great influence on the meso-structure of the samples.…”