Optimization of Lignite Particle Size for Stabilization of Trivalent Chromium in Soils

Abstract

Stabilization capacity of 5% by weight lignite added in three particle size ranges (<0.5; 0.5-1.0 and 1.0-2.0 mm) to acidic (pH = 5.0) or calcareous (pH = 7.7) sandy soil samples of <2 mm grain size artificially contaminated with 375 mg/kg Cr(III) was assessed through fitfor-purpose leaching tests performed with CH 3 COOH, NH 2 OH·HCl and EDTA. About 90% and 60% of Cr(III) were immobilized in calcareous and acidic soils per se, respectively. Although the point of zero charge measurements (pH pZC ≈4.5) indicated that lignite could effectively bind positively charged Cr hydroxo complexes at the pH of the calcareous soil, the application of lignite is unnecessary due to the low solubility of these species. Although the acidic soil mobilizes Cr, the addition of lignite has been proven to stabilize it. The phytoavailable Cr fraction in the soils per se was about 10-25%. In spite of the mobilization of Cr by acidic soil, the phytoavailable Cr concentration decreased to about half when the lignite particle size was either 0.5-1.0 or 1.0-2.0 mm. Lignite was suitable for Cr stabilization in acidic soil in a close particle size range, ensuring the dispersibility needed to enhance efficient Cr transfer from the contaminated soil to the stabilizer.

Effect of Re-Used Lignite and Mineral Wool Growing Mats on Plant Growth, Yield and Fruit Quality of Cucumber and Physical Parameters of Substrates in Hydroponic Cultivation

“…After cultivation, lignite can provide a source of organic matter for conventional crops without a detrimental effect on the environment [24]. For instance, currently, waste lignite is used for the reclamation of anthropogenically altered soils, and in agriculture, coal dust and lignite are sometimes used for soil improvement or decontamination [25][26][27][28]. World lignite resources are estimated at 512 billion tonnes, while in Poland about 23 billion tonnes.…”

“…Lignite is formed from peat in the presence of high temperature and pressure. It contains many organic substances, among others, and it is a very rich source of humic and fulvic acids [27]. Lignite has good physical properties due to highly condensed organic matter, it is sufficiently porous, absorbs water well and maintains a stable homogeneous structure [28][29][30], and moreover it is a good absorber of mineral components necessary for plant functioning [27,30,31].…”

Efficacy of Woodchip Biochar and Brown Coal Waste as Stable Sorbents for Abatement of Bioavailable Cadmium, Lead and Zinc in Soil

“…However, BIO and FYM (and not BCW) were the most efficient treatments for Zn and Pb, respectively, and thus indicate a disproportionate pH dependence that is contingent firstly on the type of organic material, and then, the intrinsic properties of the target metal. Other studies (Alamgir et al 2011;Yuan et al 2011;Uzinger et al 2014;Anemana et al 2020) have provided further evidence of bioavailable HM abatement through ion exchange following soil amendments with FYM, BIO and BCW. The CEC of soil provides an estimation of the amount of ion exchange sites (Rieuwerts et al 1998), and thus the strong correlations between HM bioavailability and CEC in all treatments imply that ion exchange is a dominant immobilising mechanism.…”

“…The pots were set up on tables in a well-ventilated laboratory at room temperature for 9 weeks of incubation to ensure maximum sorption and equilibrium. Typically, adsorption of metals in incubated soils increases rapidly in the first 24 h followed by equilibrium between 4 and 8 weeks (Casagrande et al 2004;Wuana and Okieimen 2011;Anemana et al 2020). After incubation, pots were emptied, and soil was airdried and then homogenised for determination of physicochemical properties.…”

Low-Rank Coal as a Source of Humic Substances for Soil Amendment and Fertility Management

“…The SOM of LRC is characterized by its high content (<90% d.w.) of humic substances (HS) [43,44]. HS are mixtures of humic acid (HA, only soluble in water under alkaline conditions), fulvic acid (FA, soluble in water under all pH conditions) and humin (HM, neither soluble in alkali nor in acid) [45].…”