Sorption and desorption of cadmium and zinc in two tropical soils amended with sugarcane-straw-derived biochar

Abstract

Purpose Biochars may enhance the retention capacity of metals in soils, especially in highly weathered tropical soil whose low cation exchange capacity renders heavy metals mobile, and thus be able to leach from soils. We evaluated the effect of sugarcane-straw-derived biochar on sorption and desorption of Cd(II) and Zn(II) in two tropical soils in particular to distinguish primary and secondary mechanisms of metal retention. Material and methods To test the efficiency of biochar to retain heavy metals, sugarcane-straw-derived biochar was mixed with a clayey Oxisol and an Entisol both from the state of Sao Paulo, Brazil, in batch testing to obtain sorptiondesorption isotherms of Cd(II) and Zn(II) and measure the release/displacement of cations (Ca 2+ and Mg 2+ ) or precipitation with phosphate during the sorption process. Results and discussion Biochar increased the sorption (including adsorption and precipitation) of both metals in both soils but that most sorption reactions were reversible under buffer acidic conditions, due to dissolution of precipitates in low pH values (<4.9). Exchange of Cd or Zn with Ca and Mg from the biochar was found to play a minor role on the retention mechanism, whereas surface precipitation (mainly in the Entisol) of the metals (e.g. with phosphate) was likely to be the main sorption mechanism. Conclusions Application of sugarcane-straw-derived biochar to heavy-metal-contaminated tropical soils seems justified because of its sorptive capacity for Cd and Zn. However, binding reactions on surfaces were reversible, mainly for Cd(II), resulting in the likelihood that repeat applications of biochar would be required to maintain reduced soil solution concentrations of Cd and Zn over time, thus avoiding phytotoxicity and associated environmental risks.

Phytochemical properties and heavy metal accumulation in wheat grain after three years’ fertilization with biogas digestate and mineral waste

“…The solubility of heavy metals can become problematic under conditions of acidic soils and low Ca and Mg content. Under such conditions, the heavy metal retention mechanisms in which the exchange of heavy metals with Ca and Mg occur, primarily surface precipitation, are disturbed (Melo et al 2016). …”

Influence of Application Methods of Biochar and Poultry Manure on Yield and Nutrients Uptake of Sunflower Plant Fertilized with Different Nitrogen Rates.

“…The previous benefits of biochar depend upon pyrolysis temperature, production conditions and biochar age (Fang et al, 2014 andHouben et al, 2014). In addition, It can be used different materials to produce biochar such as crop residues, woody materials, poultry litter, tree clippings, lawn grass cuttings, sludge and manures (Melo et al, 2015 andQayyum et al, 2015). For saving the environment from pollution, the woody residues from furniture industry was used to produce biochar.…”

Mitigation of Greenhouse Gas Emissions from Tropical Soils Amended with Poultry Manure and Sugar Cane Straw Biochars

“…The straw left in the field retards sprouting and tillering, reduces productivity [16], and also affects the growth and development of sockets [16]. Since two thirds of biomass produced by sugarcane is considered bagasse and straw [17], biochar production is an alternative for the management of this waste [18]. Furthermore, animal residues also have a large contribution in GHG emissions [19], and are difficult in transport and store.…”