Simultaneous removal of selenite and selenate from drinking water using mesoporous activated alumina

Abstract

The present study reports detailed evaluation of mesoporous activated alumina (MAA) for simultaneous removal of two hazardous inorganic species of selenium, namely selenite and selanate, from drinking water. MAA was used after washing with deionized water followed by drying at 110 °C for 8 h. The material was characterized using pXRD, FTIR, zeta potential, SEM and BET surface area measurements. Batch adsorption studies were performed, and various adsorption isotherms and kinetic parameters were computed to delineate the mechanism of adsorption. It was observed that Freundlich adsorption isotherm was the best-fit model for both the species of selenium. The adsorption capacity obtained from Freundlich isotherm for selenite and selenate was found to be 9.02 µg g −1 and 5.38 µg g −1 , respectively. Kinetics studies revealed that adsorption of selenite follows pseudo-second-order model, whereas selenate adsorption follows pseudo-first-order model. The efficiency of the material was also evaluated at different pH and in the presence of different competitive co-ions, which confirms efficacy of MAA at near-neutral pH and lower concentrations of competitive co-ions. Negligible changes in the pH were observed during the course of adsorption. Further, the saturated adsorbent was subjected to regeneration and reuse studies up to ten cycles, showing insignificant reduction in adsorption efficiency of the adsorbent during few initial cycles. The study infers the effectiveness of MAA as a potential adsorbent for drinking water treatment contaminated with selenium.

Selenite Removal from Aqueous Solution Using Silica–Iron Oxide Nanocomposite Adsorbents

“…Graphene oxide nanocomposite hydrogel beads 1.62 [36] Fly ash extracted char carbon 0.68 [37] Chitosan beads 2.00 [38] Iron-Oxy hydroxides 0.001 [28] Mesoporous activated alumina 0.0054 [39] Fly ash extracted char carbon 0.44 [37] Hematite 0.24 [40] Magnetite 0.25 [41] Iron-coated granular activated carbon 0.39 [42] Corundum 0.59 [43] Nano-Jacobsite 0.77 [44] Aluminum-oxide-coated sand 0.92 [45] Binary oxide [Fe (III)/SiO 2 ] 1.33 [46] Table 5. Cont.…”

Selenium in the environment

“…The behaviour of selenium in solution is mostly as complexed oxyanion which is strongly influenced by the presence of natural particles of aluminium and iron oxy-hydroxides. These phases, in turn, with their high surface areas and point of zero charge (Chan et al, 2009;Sparks, 2003) might adsorb dissolved selenium species, although it is reported that selenite is less prone to surface adsorption (Christophersen et al, 2013;Meher et al, 2020) due to its high tendency to remain in the aqueous phase. It must be stressed that selenite has been found to be more toxic than selenate and organo-selenium compounds due to its higher solubility and bioavailability (Torres et al, 2011).…”

Thermodynamic insights into selenium oxyanion removal from synthetic flue gas desulfurization wastewater with temperature-swing solvent extraction

“…) (He et al, 2018;Meher et al, 2020). Removing these selenium oxyanions from water remains challenging (Gingerich et al, 2018), especially the removal of the former ion due to its kinetically non-reactive behavior along with its structural similarity to sulfate (SO 4 2− )-a co-contaminated anion in most circumstances (Ali and Shrivastava, 2021).…”