Simultaneous removal of aqueous Zn2+, Cu2+, Cd2+, and Pb2+ by zeolites synthesized from low-calcium and high-calcium fly ash

Abstract

In this study, zeolites were synthesized from low-calcium (LCZ) and high-calcium (HCZ) fly ash, respectively. Subsequently, the zeolites were tested for their removal effectiveness for four aqueous cations, namely, Zn, Cu, Cd, and Pb, as a function of contact time, pH value, adsorbent dosage, and initial concentration of heavy metals. Both zeolites were characterized by X-ray diffraction, X-ray fluorescence spectrometry, scanning electron microscopy, specific surface area, and cation exchange capacity. The results show that HCZ mainly consists of an unnamed zeolite (Na[AlSiO]·4HO), whereas LCZ mainly consists of faujasite-type zeolite. The optimum sorption conditions were pH = 6.0; adsorbent dosage = 1.0 g·L; temperature = 25 °C; contact time = 100 min; and initial heavy metal concentration = 100 mg·L. The sorption kinetics of the four aqueous cations on both LCZ and HCZ followed the pseudo-second-order kinetic model, and the sorption isotherm data fitted well with the Langmuir isotherm model. For LCZ, the maximum adsorption capacities of Zn, Cu, Cd, and Pb were 155.76, 197.86, 123.76, and 186.22 mg·g, respectively. For HCZ, the values were 154.08, 183.15, 118.91, and 191.94 mg·g, respectively. The zeolites were regenerated by NaCl solution (1 mol·L) and showed high removal efficiency. In conclusion, zeolites produced by fly ash are promising materials for removing Zn, Cu, Cd, and Pb from wastewater.

Using Modified Fly Ash for Removal of Heavy Metal Ions from Aqueous Solution

“…e change in crystal structure of the unmodified and modified FAN particles is evaluated according to the XRD patterns presented in Figure 4. As reported in our previous research [21] and some other research studies [3][4][5]24], the XRD spectrum of the FA demonstrates that the structure of FA0 particles is composed of mullite, quartz, and hematite while the FAN particles has a zeolite P (Na 6 Al 6 Si 10 O 32 .12H 2 O or NaP) structure (at 2θ � 13°, 2θ � 16°, 2θ � 27°, and 2θ � 55°).…”

“…Chemical treatment of FA is an important tool to make FA a more effective absorbent for gas and water cleaning. In some reports, the authors studied on FA as zeolite for removal of heavy metal ions in solution [3][4][5][6] and catalytic [7], hydrocarbon contamination [8], lignite mine [9], oxamyl [10], resorcinol [11], phenol [12], and dye in waste water [13]. Based on an optical Fenton system, Visa et al used FA to adsorb Cd 2+ ion, methyl orange, and polyion water [14,15].…”

“…e NaOH-treated FA modified by organic substances could improve the ions adsorption capacity of FA, leading to the potential application of FA as excellent adsorption materials. In some studies, the authors indicated that organic substances grafted onto the surface of FA could react with metal ions to form the complex [3][4][5]. As a result, percent removal of heavy metal ion using modified FA was increased significantly.…”

Effect of radial impeller size in the presence and absence of baffles on the copper exchange on zeolite NaX

“…This process seems to be very effective for removal of various heavy metals and adsorbents can be easily recovered and reused by regeneration operation. [1][2][3][4] It is known that overall rate in heterogeneous process depends on film diffusion, particle diffusion and reaction. By changing the hydrodynamic conditions and zeolite particle size the slowest step of the process could be defined.…”

Adsorption of Mercuric Ion From Aqueous Solutions Using Modified Fly Ash

“…Using fly ash as an adsorbent of organic substances and heavy metals in pollution water, for example, resorcinol [3], textile dyes [5], phenol [6], metal ions [7][8][9], hydrocarbon contamination [10], oxamyl [11], methyl-orange and cadmium [12], multi-cation wastewater [13] and so on is attracted by scientists in recent years. The heavy metal ion adsorption capacity of materials depends on different factors such as pH of solution, initial concentration of adsorbed substance, adsorption volume, adsorption time, etc.…”