Biochar application to metal-contaminated soil: Evaluating of Cd, Cu, Pb and Zn sorption behavior using single- and multi-element sorption experiment

Abstract

The aim of this study was to evaluate metals (Cd, Cu, Pb and Zn) sorption behavior after biochar application into a metal-contaminated soil. Additionally, two different types of biochar originated from the same organic material (contaminated and uncontaminated) at different application rates (1% and 2% w/w) were evaluated as a novelty of the experiment. Batch sorption/desorption experiments were established to compare the sorption behavior of metals originating from single-and multi-element solutions. Zinc as one of the main contaminants in the studied soil was easily desorbed in the presence of Cu, Pb and to a lesser extent by Cd. This desorption was reduced after biochar application. The obtained results proved the different sorption behavior of metals in the single-metal solution compared to the multi-metal ones due to competition effect. Moreover, during multi-element sorption, Zn was significantly desorbed. The applied biochar enhanced Cu and Pb sorption and no changes were observed when contaminated and uncontaminated biochar was used. Furthermore, the application rate (1% and 2% w/w) had no effect as well. In summary, it is needed to point out that the applied rates of biochars were insufficient for metal immobilization in such contaminated soils.

A model experiment: competitive sorption of Cd, Cu, Pb and Zn by three different soils

“…The results of the model experiment from singlemetal sorption in Chernozem and Fluvisol confirmed the well-known fact that soil sorption decreased in the order Pb > Cu > Zn > Cd, which was previously reported by other authors (Vidal et al 2009;Trakal et al 2011). In Cambisol sorption decreased in order Pb ≈ Zn > Cu > Cd.…”

“…The same effect was found in multi-metal solution, except Fluvisol. Effect of pH decrease was caused by the hydrolysis and loose of H + cation from soil sorption sites (Mouta et al 2008;Trakal et al 2011). Figure 1a shows the isotherm curves obtained for Cd sorption in competitive (multi-metal) and noncompetitive (single-metal) systems.…”

“…According to Trakal et al (2011) this effect caused probably due to (i) extremely high initial Zn content in the soil and (ii) its high desorption efficiency caused by other competitive metals.…”

“…The batch sorption/desorption model experiments were conducted according to Trakal et al (2011). The sorption isotherms of Cd, Cu, Pb and Zn for each soil were obtained by adding 20 ml of the metal solution (disoluted metal-nitrate salts in the 0.01M KNO 3 The suspensions of soil samples in sorption/desorption were shaken according to Boudesocque et al (2007) on an end-over-end shaker for 48 h in order to reach equilibrium and centrifuged at 4000 rpm for 10 min at temperature of 25°C.…”

Characterization of biochars produced from oil palm and rice husks and their adsorption capacities for heavy metals

“…Biochars derived from organic waste have received a lot of attention lately from environmental management because of their ability to decrease methane emissions coming from landfills, reduce industrial energy use and emissions through recycling and waste reduction, recover energy from waste, enhance carbon sequestration in soils, decrease energy use for the long-distance transport of waste, reclaim infertile soils and remove inorganic and organic contaminants from soil, sediment and water (Lehmann 2007;Lehmann and Joseph 2009;Roberts et al 2010;Knowles et al 2011;Trakal et al 2011).…”