The role of biochar properties in influencing the sorption and desorption of Pb(II), Cd(II) and As(III) in aqueous solution

Abstract

15The chemical and physical properties of 20 biochars produced at 350, 450, 550 and 650 o C were 16 investigated to determine the key roles they play in the sorption and desorption of three 17 potentially toxic elements (Pb, Cd, As). Biochar surfaces were studied using scanning electron 18 microscopy, Fourier transform infra-red spectroscopy, X-ray diffraction and X-ray photoelectron sorption by all 20 biochars (97.5 -99.8 %) while Cd(II) and As(III) sorption (< 90 % and 42 % 24 respectively) were controlled by two mechanisms (precipitation and electrostatic attraction) only. 25Thermodynamic studies suggested that Pb and Cd sorption on a majority of biochars was 26 spontaneous and endothermic while As sorption was also endothermic but not spontaneous. 27Sorbed PTEs were observed to be very stable over a wide range of pH values (3.5 -9.5) with

Role of Nutrient-Enriched Biochar as a Soil Amendment during Maize Growth: Exploring Practical Alternatives to Recycle Agricultural Residuals and to Reduce Chemical Fertilizer Demand

“…The observed heavy metal immobilization in the soil could be directly linked to the biochar surface chemistry. In particular the studied biochar had a high CEC, large surface area, and a wide variety of surface functional groups (OH − , C-H, O-C=O, and C=C) (see FT-IR results in Supplementary Material) all of which could facilitate the chemisorption and complexation of metalloids making them less bioavailable for plant uptake [70,71]. The complexation of the heavy metals with biochar may have occurred via physical adsorption or surface functional group interactions involving metalloid exchange with biochar alkali and alkaline earth cations [71].…”

Adsorption and Desorption of Cd by Soil Amendment: Mechanisms and Environmental Implications in Field-Soil Remediation

“…In the case of Ad3, except for Cd(OH)2 and CdCO3, a new diffraction peak 2θ = 32.6° representing KCdCl3 was observed after the loading of Cd. A new diffraction peak of around 2θ = 38.7° was observed with Cd loading, indicating the formation of complex Cd(OH)Cl, related to the complexation between Cd 2+ and organic functional groups (e.g., C-O, C-OH, C-O-C) on the surface of Ad4 [35].…”

“…Electrostatic attraction with anions such as Cd could occur on the negatively charged surface of biochar [41]. The electron-rich domains on functional groups of biochar bearing π-electrons such as C=O or C=C to form cation-π interactions with Cd can also be associated with Cd adsorption [35,42,43]. Finally, ion exchange of Cd with exchangeable cations such as calcium and magnesium ions on biochar could also be an important adsorption mechanism [35,44].…”

“…X-ray diffraction patterns of amendments with/out Cd loading (a = KAlSi 3 O; b = KAlCdSi 2 O 8 ; c = SiO 2 ; d = Cd(OH) 2 ; e = CaMg(CO 3 ) 2 ; f = CaCd(CO 3 ) 2 ; g = CdCO 3 ; h = KCdCl 3 ; i = CaCO 3 ; j = Cd(OH)Cl).In the case of Ad3, except for Cd(OH) 2 and CdCO 3 , a new diffraction peak 2θ = 32.6 • representing KCdCl 3 was observed after the loading of Cd. A new diffraction peak of around 2θ = 38.7 • was observed with Cd loading, indicating the formation of complex Cd(OH)Cl, related to the complexation between Cd 2+ and organic functional groups (e.g., C-O, C-OH, C-O-C) on the surface of Ad4[35].…”

Changes of sewage sludge digestate-derived biochar properties after chemical treatments and influence on As(III and V) and Cd(II) sorption

“…During the pyrolysis step of biochar preparation, the organic matter from biomass undergoes structural modifications such as oxidation and conversion of aliphatic forms to aromatic forms (Zama et al, 2017). The resulting biochar generally harbors negative and positives charges on its surface depending on the neighboring pH.…”