Biochar immobilizes soil-borne arsenic but not cationic metals in the presence of low-molecular-weight organic acids

Abstract

A batch experiment was conducted to examine the effects of biochar on the behaviour of soil-borne arsenic and metals that were mobilized by three low-molecular-weight organic acids. In the presence of citric acid, oxalic acid and malic acid at a molar concentration of 0.01M, the surface of biochar was protonated, which disfavours adsorption of the cationic metals released from the soil by organic acid-driven mobilization. In contrast, the oxyanionic As species were re-immobilized by the protonated biochar effectively. Biochar could also immobilize oxyanionic Cr species but not cationic Cr species. The addition of biochar increased the level of metals in the solution due to the release of the biochar-borne metals under attack by LMWOAs via cation exchange. Biochar could also have the potential to enhance reductive dissolution of iron and manganese oxides in the soil, leading to enhanced release of trace elements bound to these oxides. The findings obtained from this study have implications for evaluating the role of biochar in immobilizing trace elements in rhizosphere. Adsorption of cationic heavy metals on biochar in the presence of LMWOAs is unlikely to be a mechanism responsible for the impeded uptake of heavy metals by plants growing in heavy metal-contaminated soils.

Simultaneous bioconversion of lignocellulosic residues and oxodegradable polyethylene by Pleurotus ostreatus for biochar production, enriched with phosphate solubilizing bacteria for agricultural use

“…cepa to acquire them from the substrate’s liquid phase. Several authors affirmed nutrients such as Ca 2+ , K and Mg 2+ , contained within bacterial culture or obtained as an organic nitrogen source product from bacteria metabolism, remain in the biofertilizer’s aqueous phase, and along with C and BC stimulate microorganism metabolism of different functional groups from the soil, which are then mixed with BC300 [85,86]. In the present study BYH was the organic nitrogen source.…”

Variability of Physical and Chemical Properties of TLUD Stove Derived Biochars

“…A better understanding of this relation has been pursued by studying laboratory-produced biochars obtained from different source materials in different pyrolysis conditions [24]. Studies of adsorption on such biochars have been carried out with metal cations [25,26], soil-borne arsenic [27] and complex ions as nitrate, ammonium and phosphate [5,28].…”

Differential release of sewage sludge biochar-borne elements by common low-molecular-weight organic acids

“…In general, the added LMWOAs significantly enhanced the release of Mn from the biochar materials, especially for SS550 (Table 2). This may be attributed to cation exchange (replacement of exchangeable Mn by H + from the added organic acids), and dissolution of manganese compounds via complexation to form soluble manganese-citrate/malate/oxalate complexes and reduction to form soluble Mn 2+ (Onireti and Lin, 2016;Alozie et al, 2018). .…”

“…In the rhizosphere, various low-molecular-weight organic acids (LMWOAs) are present due to root exudation (Jones and Darrah, 1994). Therefore, the added biochar materials are likely to be exposed to these naturally occurring LMWOAs, which may cause liberation of the biochar-borne elements through acidification, reduction or/and complexation (Onireti and Lin, 2016;Alozie et al, 2018).…”