In this study, the effectiveness of a softwood-derived biochar (BC) in the retention of potentially toxic elements (PTE, i.e. Cu(II), Pb(II), As(V) and Sb(V)) was evaluated at different pH values (4.5, 6.0 and 7.0), along with its capacity to alleviate PTE phytotoxicity. At all pH values, sorption and kinetic isotherms followed the trend: Pb(II) (e.g. ~ 0.56 mmol g-1 at pH 6.0) >Cu(II) (e.g. ~ 0.33 mmol g-1 at pH 6.0) >As(V) (e.g. ~ 0.29 mmol g-1 at pH 6.0) >Sb(V) (e.g. ~ 0.24 mmol g-1 at pH 6.0). Kinetic data strongly correlated with the pseudo-second-order kinetic equation, Langmuir and Freundlich isotherm models suggested monolayer sorption of Cu(II), Pb(II) and As(V) onto BC surface and the interaction of Sb(V) with BC sites characterized by distinct sorption energy (i.e. multilayer sorption). SEM-EDX analysis of PTE-saturated BC showed that Pb(II) was mainly associated with O, Sb(V) with Ca and Fe, while Cu(II) and As(V) with Fe and O. This suggested that hydroxyl and carboxyl functional groups, amorphous Fe oxy-hydroxides, as well as PTE precipitation with BC components were likely responsible of BC sorption capacity. Treatment of PTE-saturated BC with Ca(NO3)2, and a range of environmentally relevant organic acids indicated that 6-11% of PTE were loosely bound and easily exchangeable, while up to 60% could be mobilized by the organic acids. Hydroponic plant-growth experiments using triticale plants showed that BC stimulated plant growth in presence of PTE and reduced their phytotoxicity.
Softwood-derived Biochar as a Green Material for the Recovery of Environmental Media Contaminated with Potentially Toxic Elements / Pinna, Maria Vittoria; Lauro, Gian Paolo; Diquattro, Stefania; Garau, Matteo; Senette, Caterina; Castaldi, Paola; Garau, Giovanni. - In: WATER, AIR, & SOIL POLLUTION: FOCUS. - ISSN 1573-2940. - 233:5(2022), pp. 1-17. [10.1007/ s11270- 022- 05616-7]
Softwood-derived Biochar as a Green Material for the Recovery of Environmental Media Contaminated with Potentially Toxic Elements
Maria Vittoria PinnaWriting – Original Draft Preparation
;Gian Paolo LauroFormal Analysis
;Stefania DiquattroData Curation
;Matteo GarauData Curation
;Caterina SenetteMembro del Collaboration Group
;Paola Castaldi
Supervision
;Giovanni GarauWriting – Review & Editing
2022-01-01
Abstract
In this study, the effectiveness of a softwood-derived biochar (BC) in the retention of potentially toxic elements (PTE, i.e. Cu(II), Pb(II), As(V) and Sb(V)) was evaluated at different pH values (4.5, 6.0 and 7.0), along with its capacity to alleviate PTE phytotoxicity. At all pH values, sorption and kinetic isotherms followed the trend: Pb(II) (e.g. ~ 0.56 mmol g-1 at pH 6.0) >Cu(II) (e.g. ~ 0.33 mmol g-1 at pH 6.0) >As(V) (e.g. ~ 0.29 mmol g-1 at pH 6.0) >Sb(V) (e.g. ~ 0.24 mmol g-1 at pH 6.0). Kinetic data strongly correlated with the pseudo-second-order kinetic equation, Langmuir and Freundlich isotherm models suggested monolayer sorption of Cu(II), Pb(II) and As(V) onto BC surface and the interaction of Sb(V) with BC sites characterized by distinct sorption energy (i.e. multilayer sorption). SEM-EDX analysis of PTE-saturated BC showed that Pb(II) was mainly associated with O, Sb(V) with Ca and Fe, while Cu(II) and As(V) with Fe and O. This suggested that hydroxyl and carboxyl functional groups, amorphous Fe oxy-hydroxides, as well as PTE precipitation with BC components were likely responsible of BC sorption capacity. Treatment of PTE-saturated BC with Ca(NO3)2, and a range of environmentally relevant organic acids indicated that 6-11% of PTE were loosely bound and easily exchangeable, while up to 60% could be mobilized by the organic acids. Hydroponic plant-growth experiments using triticale plants showed that BC stimulated plant growth in presence of PTE and reduced their phytotoxicity.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.