Feasibility Study of Different Biochars as Adsorbent for Cadmium and Lead

Abstract

The objective of this study was to evaluate the effectiveness of different biochars on the removal of heavy metals from aqueous media. The experiment was carried out in aqueous solutions containing 200 mg CdL -1 or 200 mg PbL -1 using two different biochars derived from soybean stover and orange peel (20 mg Cd or Pbg -1 biochar). After shaking for 24 hours, biochars were filtered out, and Cd and Pb in the filtrate were analyzed by flame atomic absorption spectrophotometer (FAAS). In order to provide information regarding metal binding strength on biochars, sequential extraction was performed by modified SM&T (formerly BCR). The results showed that 70∼100% of initially added Cd and Pb was adsorbed on biochars and removed from aqueous solution. The removal rate of Pb (95%, 100%) was higher than that of Cd (70%, 91%). In the case of Cd, orange peel derived biochar (91%) showed higher adsorption rate than soybean stover derived biochar (70%). Cd was adsorbed on the biochar mainly in exchangeable and carbonates fraction (1st phase). In contrast, Pb was adsorbed on it mainly in the form of Fe-Mn oxides and residual fraction (2nd and 4th phase). The existence of Cd and Pb as a form of surface-precipitated complex was also observed on the surfaces of biochars detected by field emission scanning electron microscope (FESEM) and energy dispersive X-ray spectrometer (EDAX).

Biochars Reduce Mine Land Soil Bioavailable Metals

“…Sequential extraction procedures, such as BCR, have been used to operationally define soil metal pools in various settings (Guerra et al, 2007; Ippolito et al, 2009; Nemati et al, 2009), including under biochar application (Houben and Sonnet, 2015; Kim et al, 2015; Zhu et al, 2015). As stated by Houben and Sonnet (2015), sequential extraction procedures suffer from a lack of selectivity and element redistribution during extraction, yet their use is justified when the goal is to compare differences in a soil as affected by different treatments, as in the current study.…”

“…Their results showed that metal sorption was mainly due to precipitation with carbonate or phosphate species, with less sorption due to surface complexation or π electron bonding. Kim et al (2015) used soybean [ Glycine max (L.) Merr.] stover and orange ( Citrus x sinensis ) peel biochars to remove aqueous Cd and Pb.…”

Mechanism of adsorption of cadmium and lead ions by iron-activated biochar

“…Biochar, a carbon-rich byproduct derived from biomass pyrolysis under oxygenlimited conditions (Wang et al 2016), shows significant promise as a heavy metal sorbent (Mohan et al 2014;Kim et al 2015;Ippolito et al 2017). Ippolito et al (2017) found that pine biochar can reduce bioavailable soil metals (Cd, Cu, Pb, and Zn), which were extracted with 0.01 M CaCl2.…”