Antimonate Removal from Polluted Mining Water by Calcined Layered Double Hydroxides

Abstract

Calcined layered double hydroxides (LDHs) can be used to remove Sb(V), in the Sb(OH)6− form, from aqueous solutions. Sorption batch experiments showed that the mixed MgAlFe oxides, obtained from calcined hydrotalcite-like compound (3HT-cal), removed Sb(OH)6− through the formation of a non-LDH brandholzite-like compound, whereas the mixed ZnAl oxides, resulting from calcined zaccagnaite-like compound (2ZC-cal), trapped Sb(OH)6− in the interlayer during the formation of a Sb(V)-bearing LDH (the zincalstibite-like compound). The competition effect of coexistent anions on Sb(OH)6− removal was HAsO42− >> HCO3− ≥ SO42− for 2ZC-cal and HAsO42− >> HCO3− >> SO42− for 3HT-cal. Considering the importance of assessing the practical use of calcined LDHs, batch experiments were also carried out with a slag drainage affected by serious Sb(V) pollution (Sb = 9900 μg/L) sampled at the abandoned Su Suergiu mine (Sardinia, Italy). Results showed that, due to the complex chemical composition of the slag drainage, dissolved Sb(OH)6− was removed by intercalation in the interlayer of carbonate LDHs rather than through the formation of brandholzite-like or zincalstibite-like compounds. Both 2ZC-cal and 3HT-cal efficiently removed very high percentages (up to 90–99%) of Sb(V) from the Su Suergiu mine drainage, and thus can have a potential application for real polluted waters.

Mineralogy and Zn Chemical Speciation in a Soil-Plant System from a Metal-Extreme Environment: A Study on Helichrysum microphyllum subsp. tyrrhenicum (Campo Pisano Mine, SW Sardinia, Italy)

“…Quartz and dolomite were observed both in the bulk soil and rhizosphere samples from CP (Campo Pisano mine dump) and OCP (outside the mine dump of Campo Pisano), and they represent the gangue minerals of the ore deposits. Pyrite (FeS 2 ) was detected in soils and rhizospheres from CP and not in OCP samples, whereas gypsum (CaSO 4 ) and jarosite (KFe 3+ 3 (SO 4 ) 2 (OH) 6 ) were found in soil samples collected in the mine dump (CP). Smithsonite was found only in the soils collected outside the mine dump (OCP samples), probably resulting from the oxidation of the primary Zn sulfides [57].…”

Layered Double Hydroxides for Remediation of Industrial Wastewater from a Galvanic Plant

“…This substitution produces a net positive charge balanced by the entrance of an anionic species in the interlayer, giving as a general formula M 2+ 1−x M 3+ x (A z− ) x/z (OH) 2 •nH 2 O. Their capacity to easily exchange the interlayer anions makes LDHs attractive as carriers or scavengers of potential toxic anions [3][4][5][6]. Furthermore, their flexible structure, which can be reproduced using several bivalent and trivalent cations, suggests the possibility to use LDHs as a getter of pollutant cations [7,8].…”

Synthesis of MgFe Layered Double Hydroxide from Iron-Containing Acidic Residual Solution and Its Adsorption Performance

“…Because issues arise when the contaminants are in trace amounts but still at a concentration which exceeds the maximum admitted values, one of the most studied water treatment methods is adsorption. The adsorption process has gained researchers' interest due to its simple operating conditions and the versatile types of adsorbent materials which exist on the market [1][2][3]. Among the multitude of adsorbent materials, a considerable amount of attention has been paid to layered double hydroxide (LDH) compounds.…”