Immobilization of Heavy Metal Ions (Cu^II, Cd^II, Ni^II, and Pb^II) by Broiler Litter-Derived Biochars in Water and Soil

Abstract

Chars, a form of environmental black carbon resulting from incomplete burning of biomass, can immobilize organic contaminants by both surface adsorption and partitioning mechanisms. The predominance of each sorption mechanism depends upon the proportion of organic to carbonized fractions comprising the sorbent. Information is currently lacking in the effectiveness of char amendment for heavy metal immobilization in contaminated (e.g., urban and arms range) soils where several metal contaminants coexist. The present study employed sorbents of a common biomass origin (broiler litter manure) that underwent various degrees of carbonization (chars formed by pyrolysis at 350 and 700 degrees C and steam-activated analogues) for heavy metal (Cd(II), Cu(II), Ni(II), and Pb(II)) immobilization in water and soil. ATR-FTIR, (1)H NMR, and Boehm titration results suggested that higher pyrolysis temperature and activation lead to the disappearance (e.g., aliphatic -CH(2) and -CH(3)) and the formation (e.g., C-O) of certain surface functional groups, portions of which are leachable. Both in water and in soil, pH increase by the addition of basic char enhanced the immobilization of heavy metals. Heavy metal immobilization resulted in nonstoichiometric release of protons, that is, several orders of magnitude greater total metal concentration immobilized than protons released. The results suggest that with higher carbonized fractions and loading of chars, heavy metal immobilization by cation exchange becomes increasingly outweighed by other controlling factors such as the coordination by pi electrons (C=C) of carbon and precipitation.

Effect of Biochars from Rice Husk, Bran, and Straw on Heavy Metal Uptake by Pot-Grown Wheat Seedling in a Historically Contaminated Soil

“…Phosphorus contained in the biochar, especially in the case of bran-char, can induce the formation of metal-phosphate precipitates with low solubility products, and these are responsible for soil Cd, Zn, and Pb immobilization (McGowen et al 2001;Cao et al 2003a). These results have also been supported by other studies, although different biochars were used (Uchimiya et al 2010;Park et al 2011;Cao et al 2011). In addition to increasing soil pH and developing phosphate precipitates, surface adsorption by biochar was also thought to be one of the mechanisms for stabilizing Cd, Zn, and Pb in soil.…”

“…Concentrations of Cd and Zn in soil pore water decreased significantly, whereas that of As increased markedly in a multi-element polluted soil amended with biochar under various soil moisture conditions (Beesley et al 2010). Biochar-induced increases in soil pH, the number of oxygen functional groups, and/or phosphorous levels caused the formation of ligands, which contribute greatly to the immobilization of toxic metals in soils and may result in As activation (Cao et al 2011;Uchimiya et al 2010;Uchimiya et al 2012;Sadiq 1997). In addition to changing the mobility of metal(loid)s in soils, the blocking capacity of iron plaque, root-to-shoot translocation in the plant, and the accumulation of metal(loid)s in rice shoot were influenced by biochar amendments .…”

Appraisal of changes in sewage sludge management

“…Sequential fractionation of metals carried out by Park et al (2011) indicated that biochar treatments substantially modified separation of Cd, Cu and Pb from the easily exchangeable phase to a less bioavailable organicbound fraction. This is in good agreement with earlier findings by Uchimiya et al (2010) who suggested that Cd, Cu, Ni and Pb immobilization during higher pyrolysis temperatures and activation lead to disappearance of certain functional groups (e.g., aliphatic -CH2 and -CH3) and formation of others (e.g., C-O) that are partly leachable. Immobilization of heavy metals resulted in non-stoichiometric release of protons, i.e., the total concentration of the immobilized metals was greater by several orders of magnitude than the protons released.…”

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

“…The adsorption of heavy metals by biochars from aqueous environments has been explored by numerous studies (Rao et al 2009;Uchimiya et al 2010). Chen et al (2011) studied the ability of two different biochars, derived from hardwood and corn straw, to adsorb Cu(II) and Zn(II) from an aqueous solution.…”