Adsorption, desorption and fractionation of As(V) on untreated and mussel shell-treated granitic material

As(V) adsorption and desorption were studied on granitic material, coarse and fine mussel shell and granitic material amended with 12 and 24 t ha⁻¹ fine shell, investigating the effect of different As(V) concentrations and different pH as well as the fractions where the adsorbed As(V) was retained. As(V) adsorption was higher on fine than on coarse shell. Mussel shell amendment increased As(V) adsorption on granitic material. Adsorption data corresponding to the unamended and shell-amended granitic material were satisfactory fitted to the Langmuir and Freundlich models. Desorption was always <19% when the highest As(V) concentration (100 mg L⁻¹) was added. Regarding the effect of pH, the granitic material showed its highest adsorption (66%) at pH <6, and it was lower as pH increased. Fine shell presented notable adsorption in the whole pH range between 6 and 12, with a maximum of 83%. The shell-amended granitic material showed high As(V) adsorption, with a maximum (99%) at pH near 8, but decreased as pH increased. Desorption varying pH was always <26%. In the granitic material, desorption increased progressively when pH increased from 4 to 6, contrary to what happened to mussel shell. Regarding the fractionation of the adsorbed As(V), most of it was in the soluble fraction (weakly bound). The granitic material did not show high As(V) retention capacity, which could facilitate As(V) transfer to water courses and to the food chain in case of As(V) compounds being applied on this material; however, the mussel shell amendment increased As(V) retention, making this practice recommendable

Adsorption, desorption and fractionation of As(V) on untreated and mussel shell-treated granitic material

As(V) adsorption and desorption were studied on granitic material, coarse and fine mussel shell and granitic material amended with 12 and 24 t ha⁻¹ fine shell, investigating the effect of different As(V) concentrations and different pH as well as the fractions where the adsorbed As(V) was retained. As(V) adsorption was higher on fine than on coarse shell. Mussel shell amendment increased As(V) adsorption on granitic material. Adsorption data corresponding to the unamended and shell-amended granitic material were satisfactory fitted to the Langmuir and Freundlich models. Desorption was always <19% when the highest As(V) concentration (100 mg L⁻¹) was added. Regarding the effect of pH, the granitic material showed its highest adsorption (66%) at pH <6, and it was lower as pH increased. Fine shell presented notable adsorption in the whole pH range between 6 and 12, with a maximum of 83%. The shell-amended granitic material showed high As(V) adsorption, with a maximum (99%) at pH near 8, but decreased as pH increased. Desorption varying pH was always <26%. In the granitic material, desorption increased progressively when pH increased from 4 to 6, contrary to what happened to mussel shell. Regarding the fractionation of the adsorbed As(V), most of it was in the soluble fraction (weakly bound). The granitic material did not show high As(V) retention capacity, which could facilitate As(V) transfer to water courses and to the food chain in case of As(V) compounds being applied on this material; however, the mussel shell amendment increased As(V) retention, making this practice recommendable

Amendment Type and Dose Effects onto Coexisting Copper, Lead, and Nickel Ions Distribution in Soil

The use of soil additives for toxic metals chemical stabilization aims to decrease in situ the pollutants' mobility and availability. In this study, the effectiveness of rinsed red mud (RBRM) and annealed animal bones (B400) was compared in terms of Cu, Pb and Ni stabilization in two contaminated soils with contrasting properties Dystric Cambisol (CM dy) and Rendzic Leptosol (LP rz). The mobility of metals in unamended soil samples (control) and samples amended with 1% and 5% of selected additives were compared using sequential extraction protocol. The relative content of metals in readily and potentially available fractions was higher in CM dy (62% Pb, 13% Cu, and 31% Ni in exchangeable fraction) than in LP rz ( lt 5% of Pb, Cu, Ni in exchangeable fraction). In CM dy, both additives have caused a decrease in metal mobility with an increase of their doses. The effect of 5% sorbent addition was most pronounced related to Pb immobilization, provoking decrease of exchangeable Pb content to lt 10%. Furthermore, B400 addition has redistributed investigated metals from the exchangeable to the residual phase more effectively than RBRM, and its effect on metal mobility decreased in the order Pb gt Cu gt Ni. Amending of LP rz soil had limited effects with no apparent decrease in exchangeable metal content. The effects of soil type variation, the type of additive and the additive dose onto metal mobility were compared according to ANOVA results. The content of readily and potentially available forms of metals was found to be (i) significantly correlated with all investigated variables for Pb, (ii) significantly correlated with soil type for Cu, and (iii) not in significant correlation with selected variables for Ni. Complex impacts of soil properties and treatment conditions on the mobility of co-contaminants emphasize the need for an individual approach to each case of contamination