A Comparison among Synthetic Layered Double Hydroxides (LDHs) as Effective Adsorbents of Inorganic Arsenic from Contaminated Soil–Water Systems
The need for cost-effective adsorbents of inorganic arsenic (As(III) and As(V)) stimulates the academia to synthesize and test novel materials that can be profitably applied at large-scale in most affected areas worldwide. In this study, four different layered double hydroxides (Cu-Al-, Mg-Al-, Mg-F...
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doaj-b4cb627fde3b4a94964dd6b762d9c9d02020-11-25T03:49:20ZengMDPI AGSoil Systems2571-87892020-06-014373710.3390/soilsystems4020037A Comparison among Synthetic Layered Double Hydroxides (LDHs) as Effective Adsorbents of Inorganic Arsenic from Contaminated Soil–Water SystemsMassimo Pigna0Antonio Violante1Antonio Giandonato Caporale2Department of Agricultural Sciences, University of Naples Federico II, 80055 Portici, Naples, ItalyDepartment of Agricultural Sciences, University of Naples Federico II, 80055 Portici, Naples, ItalyDepartment of Agricultural Sciences, University of Naples Federico II, 80055 Portici, Naples, ItalyThe need for cost-effective adsorbents of inorganic arsenic (As(III) and As(V)) stimulates the academia to synthesize and test novel materials that can be profitably applied at large-scale in most affected areas worldwide. In this study, four different layered double hydroxides (Cu-Al-, Mg-Al-, Mg-Fe- and Zn-Al-LDH), previously synthesized and studied for As(III) removal capacity, were evaluated as potential adsorbents of As(V) from contaminated systems, in absence or presence of common inorganic anions (Cl<sup>−</sup>, F<sup>−</sup>, SO<sub>4</sub><sup>2−</sup>, HCO<sub>3</sub><sup>−</sup> and H<sub>2</sub>PO<sub>4</sub><sup>−</sup>). The As(V) desorption by H<sub>2</sub>PO<sub>4</sub><sup>−</sup> was also assessed. Lastly, the As(V) adsorption capacities of the four layered double hydroxides (LDHs) were compared with those observed with As(III) in a complementary paper. All the LDHs adsorbed higher amounts of As(V) than As(III). Fe-Mg-LDH and Cu-Al-LDH showed higher adsorption capacities in comparison to Mg-Al-LDH and Zn-Al-LDH. The presence of competing anions inhibited the adsorption of two toxic anions according to the sequence: Cl<sup>−</sup> < F<sup>−</sup> < SO<sub>4</sub><sup>2−</sup> < HCO<sub>3</sub><sup>−</sup> < < H<sub>2</sub>PO<sub>4</sub><sup>−</sup>, in particular on Mg-Al-LDH and Zn-Al-LDH. The kinetics of As(V) desorption by H<sub>2</sub>PO<sub>4</sub><sup>−</sup> indicated a higher occurrence of more easily desorbable As(V) on Zn-Al-LDH vs. Cu-Al-LDH. In conclusion, synthetic Cu- and Fe-based LDHs can be good candidates for an efficient removal of inorganic As, however, further studies are necessary to prove their real feasibility and safety.https://www.mdpi.com/2571-8789/4/2/37inorganic arsenic contaminationlayered double hydroxidesarsenatearseniteadsorptionLangmuir isotherm |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Massimo Pigna Antonio Violante Antonio Giandonato Caporale |
spellingShingle |
Massimo Pigna Antonio Violante Antonio Giandonato Caporale A Comparison among Synthetic Layered Double Hydroxides (LDHs) as Effective Adsorbents of Inorganic Arsenic from Contaminated Soil–Water Systems Soil Systems inorganic arsenic contamination layered double hydroxides arsenate arsenite adsorption Langmuir isotherm |
author_facet |
Massimo Pigna Antonio Violante Antonio Giandonato Caporale |
author_sort |
Massimo Pigna |
title |
A Comparison among Synthetic Layered Double Hydroxides (LDHs) as Effective Adsorbents of Inorganic Arsenic from Contaminated Soil–Water Systems |
title_short |
A Comparison among Synthetic Layered Double Hydroxides (LDHs) as Effective Adsorbents of Inorganic Arsenic from Contaminated Soil–Water Systems |
title_full |
A Comparison among Synthetic Layered Double Hydroxides (LDHs) as Effective Adsorbents of Inorganic Arsenic from Contaminated Soil–Water Systems |
title_fullStr |
A Comparison among Synthetic Layered Double Hydroxides (LDHs) as Effective Adsorbents of Inorganic Arsenic from Contaminated Soil–Water Systems |
title_full_unstemmed |
A Comparison among Synthetic Layered Double Hydroxides (LDHs) as Effective Adsorbents of Inorganic Arsenic from Contaminated Soil–Water Systems |
title_sort |
comparison among synthetic layered double hydroxides (ldhs) as effective adsorbents of inorganic arsenic from contaminated soil–water systems |
publisher |
MDPI AG |
series |
Soil Systems |
issn |
2571-8789 |
publishDate |
2020-06-01 |
description |
The need for cost-effective adsorbents of inorganic arsenic (As(III) and As(V)) stimulates the academia to synthesize and test novel materials that can be profitably applied at large-scale in most affected areas worldwide. In this study, four different layered double hydroxides (Cu-Al-, Mg-Al-, Mg-Fe- and Zn-Al-LDH), previously synthesized and studied for As(III) removal capacity, were evaluated as potential adsorbents of As(V) from contaminated systems, in absence or presence of common inorganic anions (Cl<sup>−</sup>, F<sup>−</sup>, SO<sub>4</sub><sup>2−</sup>, HCO<sub>3</sub><sup>−</sup> and H<sub>2</sub>PO<sub>4</sub><sup>−</sup>). The As(V) desorption by H<sub>2</sub>PO<sub>4</sub><sup>−</sup> was also assessed. Lastly, the As(V) adsorption capacities of the four layered double hydroxides (LDHs) were compared with those observed with As(III) in a complementary paper. All the LDHs adsorbed higher amounts of As(V) than As(III). Fe-Mg-LDH and Cu-Al-LDH showed higher adsorption capacities in comparison to Mg-Al-LDH and Zn-Al-LDH. The presence of competing anions inhibited the adsorption of two toxic anions according to the sequence: Cl<sup>−</sup> < F<sup>−</sup> < SO<sub>4</sub><sup>2−</sup> < HCO<sub>3</sub><sup>−</sup> < < H<sub>2</sub>PO<sub>4</sub><sup>−</sup>, in particular on Mg-Al-LDH and Zn-Al-LDH. The kinetics of As(V) desorption by H<sub>2</sub>PO<sub>4</sub><sup>−</sup> indicated a higher occurrence of more easily desorbable As(V) on Zn-Al-LDH vs. Cu-Al-LDH. In conclusion, synthetic Cu- and Fe-based LDHs can be good candidates for an efficient removal of inorganic As, however, further studies are necessary to prove their real feasibility and safety. |
topic |
inorganic arsenic contamination layered double hydroxides arsenate arsenite adsorption Langmuir isotherm |
url |
https://www.mdpi.com/2571-8789/4/2/37 |
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