Arsenate and arsenite removal from contaminated water by iron oxides nanoparticles formed inside a bacterial exopolysaccharide

Abstract

In the last decades, the presence of high As levels in groundwaters poses a serious limitation to the use of this resources for drinking purposes in several parts of the world. Treatment of As-rich waters selected iron oxides filters as more effective, low cost and selective technology. Green and biologically-driven pathways to synthetize new nanostructured iron oxy-hydroxides are becoming always more attractive. We tested the suitability of FeOOH nanoparticles (9-15 nm) produced by Klebsiella oxytoca strain DSM 29614 and encapsulated in EPS gel structure to treat arsenic rich water. Different gel:water volume ratios were tested to treat 5000 μg As/L solution. 20% FeEPS solution was able to remove 95% of As(V) while in 5% solution removal was reduced to 60%. Arsenic adsorption was very fast and follows pseudo-2 nd order kinetic with maximum adsorption capacity reached at about 30 min. Adsorption followed Langmuir model for As(V) with q max = 31.8 mg As /g Fe and BET for As(III) with 8 mg As /g Fe for the first layer in 10% FeEPS solution. FeEPS dried into powder showed noticeable removal only after 2 h, hence not suitable for drinking water treatment. Treatment of natural As levels in mimicked groundwaters showed 87-95% As(V) and 45-61% As(III) removal after 5 min. FeEPS gel immobilized onto bivalve shell debris was used in packed-bed filters. It retained 49.8 mg As /g Fe from 150 μg/L As(V) spiked groundwater before reaching breakthrough at 8000 BVs. Biologically produced FeEPS gel showed good potentialities as eco-friendly material to remove As from contaminated groundwater.

Biosynthesized Iron Oxide Nanoparticles (Fe3O4 NPs) Mitigate Arsenic Toxicity in Rice Seedlings

“…Physical and chemical techniques are not suitable in the long run due to being costly, having lower efficacy and being less environmentally friendly [ 5 ], whereas, in biologically synthesized nanoparticles, different “functional groups” are naturally present on nanoparticle surfaces and heavy metals can get adsorbed on these functional groups [ 6 ]. Nanotechnology has offered a pervasive solution to these conventional technologies in the form of nanoparticles such as iron oxide nanoparticles (Fe 3 O 4 NPs), which are more convenient for the removal of arsenic from water because of their important features like magnetic and electric properties [ 7 ]. Fe 3 O 4 NPs have high fabrication and adsorption capacities for arsenic and super-paramagnetic properties which allows easy separation from water and makes them popular candidates for remediation of arsenic-contaminated water.…”

Remoción de arsénico (III) en sistemas acuosos por adsorción utilizando sólidos naturales de Ecuador

“…Para evaluar la cinética de adsorción se colocaron 0,5 g de extruidos en 50 mL de solución y se agitaron a 100 r. p. m. empleando un agitador orbital. Los experimentos se realizaron en un ambiente controlado a 30 °C, a un pH de 7,0 [25]. Para la determinación de la cinética de adsorción se prepararon muestras individuales de solución y adsorbente, a diferentes tiempos de tratamiento, utilizando un control a tiempo cero.…”

Multifunctional graphene oxide/biopolymer composite aerogels for microcontaminants removal from drinking water

“…BET model is based on the assumption that exists a multilayer coverage and represents an extension of Langmuir model. A detailed model and relative parameters description are provided by Casentini et al, (2019). Briefly, we summarize hereafter used equations:…”

“…The goodness of fit was then evaluated by calculating the coefficient of determination (R 2 ) and the Root Mean Square Error (RMSE), as described in Casentini et al (2019).…”