The importance of presoaking to improve the efficiency of MgCl2-modified and non-modified biochar in the adsorption of cadmium

Bahram Abolfazli Behrooz; Shahin Oustan; Hossein Mirseyed Hosseini; Hassan Etesami; Elio Padoan; Giuliana Magnacca; Franco Ajmone Marsan

doi:10.1016/j.ecoenv.2023.114932

The importance of presoaking to improve the efficiency of MgCl₂-modified and non-modified biochar in the adsorption of cadmium

Ecotoxicol Environ Saf. 2023 Jun 1:257:114932. doi: 10.1016/j.ecoenv.2023.114932. Epub 2023 Apr 19.

Authors

Bahram Abolfazli Behrooz¹, Shahin Oustan², Hossein Mirseyed Hosseini¹, Hassan Etesami³, Elio Padoan⁴, Giuliana Magnacca⁵, Franco Ajmone Marsan⁴

Affiliations

¹ Department of Soil Science, College of Agriculture and Natural Resources, University of Tehran, Tehran, Iran.
² Soil Science Department, Agricultural Faculty, University of Tabriz, Iran.
³ Department of Soil Science, College of Agriculture and Natural Resources, University of Tehran, Tehran, Iran. Electronic address: hassanetesami@ut.ac.ir.
⁴ Dipartimento di Scienze Agrarie, Forestali e Alimentari, Università degli Studi di Torino, Grugliasco, TO, Italy.
⁵ Dipartimento di chimica, Università degli Studi di Torino, Torino, Italy.

PMID: 37080130
DOI: 10.1016/j.ecoenv.2023.114932

Abstract

Investigating the effect of presoaking, as one of the most important physical factors affecting the adsorption behavior of biochar, on the adsorption of heavy metals by modified or non-modified biochar and presoaking mechanism is still an open issue. In this study, the water presoaking effect on the kinetics of cadmium (Cd) adsorption by rice husk biochar (produced at 450 °C, B1, and at 600 °C, B2) and the rice husk biochar modified with magnesium chloride (B1 modified with MgCl₂, MB1, and B2 modified with MgCl₂, MB2) was investigated. Furthermore, the effect of pH (2, 5, and 6), temperature (15, 25, and 35 °C), and biochar particle size (100 and 500 µm) on the kinetics of Cd adsorption was also investigated. Results revealed that the content of Cd adsorbed by the presoaked biochar was significantly higher than that by the non-presoaked biochar. The highest Cd adsorption capacity of MB2 and MB1 was 98.4 and 97.6 mg g^-1, respectively, which was much better than that of B1 (7.6 mg g^-1) and B2 (7.5 mg g^-1). The modeling of kinetics results showed that in all cases pseudo-second-order model was well-fitted (R²>0.99) with Cd adsorption data. The results also indicated that the highest Cd adsorption values were observed at pH 6 in presoaked MB1 with size of 100 µm as well as at the temperature of 35 °C in presoaked MB2, indicating the optimum conditions for this process. The presoaking process was not affected by biochar size and pH, and the difference in adsorbed Cd content between presoaked biochars and non-presoaked ones was also similar. However, the temperature had a negative effect on presoaking. The presoaking process decreased micropores (<10 µm) in the biochars but had no effect on biochar hydrophobicity. Therefore, presoaking, which could significantly increase Cd adsorption and reduce equilibrium time by reducing the micropores of biochars, is suggested as an effective strategy for improving the efficiency of modified biochars or non-modified ones in the adsorption of contaminants (Cd) from aquatic media.

Keywords: Adsorption kinetics; Cadmium removal; Mg-modified biochar; Presoaking mechanism.

MeSH terms

Adsorption
Cadmium* / chemistry
Charcoal* / chemistry
Kinetics
Temperature

Substances

Cadmium
biochar
Charcoal