Hollow Polyaniline Microsphere/Fe3O4 Nanocomposite as an Effective Adsorbent for Removal of Arsenic from Water

Abstract

polyaniline hollow microsphere (pnHM)/fe 3 o 4 magnetic nanocomposites have been synthesized by a novel strategy and characterized. Subsequently, PNHM/Fe 3 o 4-40 (Fe 3 o 4 content: 40 wt.%) was used as an adsorbent for the removal of arsenic (As) from the contaminated water. Our investigations showed 98-99% removal of As(III) and As(V) in the presence of PNHM/Fe 3 o 4-40 following pseudo-second-order kinetics (R 2 > 0.97) and equilibrium isotherm data fitting well with Freundlich isotherm (R 2 > 0.98). The maximum adsorption capacity of As(III) and As(V) correspond to 28.27 and 83.08 mg g −1 , respectively. A probable adsorption mechanism based on X-ray photoelectron spectroscopy analysis was also proposed involving monodentate-mononuclear/bidentate-binuclear As-Fe complex formation via legend exchange. In contrast to NO 3 − and SO 4 2− ions, the presence of PO 4 3− and CO 3 2− co-ions in contaminated water showed decrease in the adsorption capacity of As(III) due to the competitive adsorption. The regeneration and reusability studies of spent PNHM/Fe 3 o 4-40 adsorbent showed ~83% of As(III) removal in the third adsorption cycle. PNHM/Fe 3 o 4-40 was also found to be very effective in the removal of arsenic (<10 μg L −1) from naturally arsenic-contaminated groundwater sample. Arsenic (As) remains one of the major sources of toxic pollutant in groundwater, affecting millions of people throughout the world. It associated into groundwater from several sources of natural and anthropogenic origins. The chronic exposure of arsenic contaminants in water beyond the World Health Organization (WHO) permissible limit (10 µg L −1) results in a serious toxicological and carcinogenic effect on human health 1. It is also widely established that the presence of arsenite [As(III)] in water is more toxic and soluble compared to arsenate [As(V)] 2,3. As a result, several technologies namely, co-precipitation, coagulation, oxidation, ion exchange, adsorption, membrane separation, etc. have been adopted for the treatment of such contaminated water 4,5. However, many conventional and other approaches are not cost-effective and environmental friendly towards arsenic removal selectivity. For example, the precipitation of iron coagulation is cost-effective; however, it generates huge amounts of sludge, leading to secondary pollution problems 6. Similarly, membrane separation exhibits high efficiency but involves high operational cost 6. In this regard, the removal of toxic pollutants from water through adsorption has been receiving considerable attention due to its sludge-free operation, cost-effectiveness, high efficiency/selectivity, ease of use, and reusability facilities 7. Several nanoparticles, such as activated carbon, carbon nanotubes, graphene, manganese oxide, zinc oxide, titanium oxide, and ferric oxides emerged as effective nanoadsorbents give better performance compared to other conventional adsorbents in removal of arsenic, phosphate, selenium and nitrite anions, and other heavy metals from drinking water 8-13. In this co...

Geogenic arsenic removal through core–shell based functionalized nanoparticles: Groundwater in-situ treatment perspective in the post–COVID anthropocene

“…At higher pH, stong competition between hydroxyl anions and complexed ligands causes desorption of adsorbed As(V). The obtained results are in line with the previously published work where alkaline solution has been reported as the favorable regenerant for desorption of anionic (negatively charged) geogenic contaminants from bio–nano polymer based composite adsorbents because of the high affinity of the complexed metal oxides for hydroxyl anions ( Dutta et al, 2020 ). The results clearly demonstrates that the engineered adsorbent (bilayer–OA@FeO NPs) could be sustainably regenerated with NaOH treatment and reutilized multiple times for the management of geogenic contaminants to provide potable water for the human development which is considered to be one of the prime challenges of the Anthropocene era.…”

“…3 (e)). The proposed sorption mechanism is in agreement with previously reported results where it has been very–well documented that the inner–sphere complexes are mainly responsible for the sorption of As(V) onto various iron–based adsorbents ( Henke, 2009 ; Dutta et al, 2020 ).…”

“…1 (f)). The obtained outcomes are in good aggreement with the earlier reported results where authors have speculated the textural changes of synthesized nanocomposite adsorbent due to heterogenous dispersion of magnetic NPs onto supporting polyaniline hollow microsphere surface ( Dutta et al, 2020 ).

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“…Degassing was performed under the flow of nitrogen gas at 200 °C temperature for 1 h. In order to ascertain the stability of adsorbent against temperature, thermogravimetric analysis (TGA) was performed using a PerkinElmer thermogravimetric analyzer (TGA 4000). The point of zero charge (pH ZPC ) of the Bilayer–OA@FeO NPs was exained according to the method proposed by ( Dutta et al, 2020 ).…”

“…The aggregarted and structurally unstable NPs finally leach into an aqueous medium. These leached NPs require sophisticated instrumentation facilities to separate out from the drinking water source such as groundwater aquifer after their application ( Dutta et al, 2020 ; Zaid et al, 2020 )…”