Study of the iron(III)-modified clinoptilolite in the adsorption of phosphate from aqueous medium: mechanism and kinetics

Abstract

a b s t r ac tClinoptilolite-rich tuff (Z) enriched with Fe(III) was studied in the removal of phosphate ions present in aqueous medium at pH = 6.5. Fe(III) modification was performed by a simple wet impregnation giving the product (FeZ) with about 18 wt% Fe. Transmission electron microscopy showed the presence of a flaky Fe(III) amorphous precipitate on the clinoptilolite sheets and a preserved clinoptilolite crystallinity. The modification increased the specific surface area from 28.6 to 140.3 m 2 g -1. FeZ effectively adsorbed phosphate, the removal rate at 298 K varying from 86% to 42.5% (for C 0 = 50 mg dm -3 and C 0 = 400 mg dm -3). The sorption isotherms were in accord with the Langmuir model, giving for the Langmuir constant (R L ) values in the range 0-1 that are characteristic of a favourable adsorption. The data for adsorption kinetics were best described by the pseudo-second-order model suggesting chemisorption as the phosphate sorption mechanism. Intra-particle diffusion was present in the adsorption, but it was not the rate-limiting step. A 31 P static spin-echo mapping nuclear magnetic resonance (NMR) measurement was performed for studying the phosphate-FeZ interaction. The results showed that the phosphate adsorption on FeZ proceeds through electrostatic interactions and covalent bonding, the latter being more pronounced.

Reduction of rainwater turbidity using zeolite

“…The adsorption mechanism on the zeolite surface is fully described in Ref [5,6]. Zeolite will, however, turn To determine the kinds of kinetics that occur throughout the rainwater purification process, we matched the experimental data with two adsorption kinetic models [14][15][16]. Equations ( 2) and ( 3) represent the pseudo-first-order kinetic model and the pseudo-second-order kinetic model, respectively.…”

Advances in the Applications of Clinoptilolite-Rich Tuffs

“…The treatments led to an increase in Fe content from 0.21 (ZT) to 18.1 wt.% for Fe-ZT in the clinoptilolite from deposits in Serbia [ 19 ], whereas, from Slovakia, the Fe content was lower [ 50 ] increased from 1.03 (ZT) to 5.82 wt.% (Fe-ZT) under similar conditions. For Fe 3 O 4 -ZT, the increase in Fe was 5.63 wt.%.…”

“…Accumulating the Fe-containing precipitates increases the specific surface area of ZT from 28.6 to 140.3 m 2 g −1 for Fe-ZT and 45.2 m 2 g −1 for Fe 3 O 4 -ZT. Amorphous precipitate in Fe-ZT significantly increases the specific surface area of ZT, whereas in Fe 3 O 4 -ZT, the well’s crystalline magnetite nanoparticles in the range of 5–30 nm cover the surface of ZT [ 17 , 19 ]. Similarly, Fe-ZT obtained from ZT from the deposit Donje Jesenje (Croatia) was found to have a specific surface area around three times larger than that of parent ZT [ 40 ].…”

“…In recent decades, the adsorption, catalytic, and antibacterial characteristics of clinoptilolite-rich tuffs (ZT) from two deposits, Vranjska Banja and Slanci (Serbia), containing up to 80 wt.% clinoptilolite, with quartz and feldspar as the primary mineral impurities, have been extensively studied [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 ]. This review compares these results with ZTs from other regions.…”

Utilisation of waste Cu-, Mn- and Fe-loaded zeolites generated after wastewater treatment as catalysts for air treatment

“…Excess amounts of manganese and iron are also quite frequently found in some groundwater due to the presence of naturally occurring iron and manganese minerals, which are released into waters by weathering processes (Masindi and Muedi, 2018). In previous studies, we and other researchers showed that the natural zeolite clinoptilolite has excellent uptake capacity for manganese, copper and iron, as single type metals (Margeta et al, 2015;Rajic et al, 2009;Krstic et al, 2018;Stojaković et al, 2011;Kaplanec et al, 2017). Simultaneous removal of two metals was studied for Pb, Cd, Zn and Ni (Nuic et al, 2019;Stojakovic et al, 2016).…”