A Humins-Derived Magnetic Biochar for Water Purification by Adsorption and Magnetic Separation

Abstract

In this study, the use of magnetic biochar particles recovered from biorefinery by-products (humins) for adsorption of hydrophilic organic pollutants was investigated. The biochar was prepared by thermal treatment of crude humins followed by a grinding step after which a magnetic iron oxide was co-precipitated on the biochar surface. The resulting iron oxide content of the biochar composite was found to be 9 % by volume, and the presence of a characteristic Fe-O vibrational band was observed by FTIR-ATR. XPS analysis of Fe2p spectrum enabled the nature of iron oxide to be identified as maghemite. Finally, magnetometry measurements demonstrated the superparamagnetic properties of maghemite.The adsorption of methylene blue on the biochar composite was found to be fast (less than 1 hour at pH 6 with an initial concentration of methylene blue of 2•10 -5 mol.L -1 ). Kinetics data were satisfactorily modelled by both first and second order models. Freundlich and Langmuir models were applied to adsorption isotherms data. Maximum adsorption capacity (3.35•10 -5 mol.g -1 ), and Langmuir and Freundlich constants (2.33•10 4 L.mol -1 and 5.70•10 -5 mol 0.913 .L 0.087 .g -1 respectively) were found to be comparable to the average of those found in the literature. Electrostatic attraction between oppositely charged methylene blue and magnetic biochar was presumed to be the dominant interaction governing adsorption at environmental pH values. Lastly, a laboratory-scale experimental device with magnetic filtration under flow allowed the complete separation of the magnetic biochar composite from the liquid phase. This study shows that this magnetic biochar composite is a promising and economically interesting recovery route for biorefinery by-products and could be used for adsorption purposes.

Comparative Study on the Performance and Mechanism of Adsorption–Oriented Phosphorus–Modified High–Efficiency and Durable Activated Biochar from Fast Pyrolysis

“…Both the Langmuir and Freundlich isotherm models match with the sorption data, yet the former fit is obviously better (Figure 11b,d, and Table 3). This means the adsorption by the two samples is relatively uniform and monolayer [54]. The calculated R L values (Supplementary Material) range from 0.00034-0.001 and 0.11-0.26 depending on b and different C 0 , confirming that both samples are favorable for MB adsorption.…”

“…The adsorption capacity of P-H-0.5 tends to be stable when pH > 5, while P-2-H-2 still slightly increases, indicating that the two-step sample is more acidic and more sensitive to pH [14,53]. The surfaces of both samples are negatively charged when pH > pH PZC (insets), whereas in the relatively acidic (pH < pH PZC ) system, MB molecules mainly undergo protonation [54]. Thereafter, with increasing pH, deprotonation dominates and the proportion of cation in the dye molecule gradually rises.…”

On the gelation of humins: from transient to covalent networks

“…Moreover, the use of raw humins as a feedstock for the preparation of new materials is a particularly promising route due to its simplicity and straightforward applicability. Polymeric materials such as porous foams, [21][22][23][24] thermoset resins, [25][26][27] elastomers 28 or polymer blends 29 have been investigated for value-added applications including capacitors, 30 binders, 31 catalysis, 32,33 adsorbents, 34,35 reinforced composites 36,37 or self-healing robotics. 29 As described above, humins are becoming an increasingly popular choice for the preparation of novel polymeric materials.…”

Novel Fe3O4‐Modified Biochar Derived from Citrus Bergamia Peel: A Green Synthesis Approach for Adsorptive Removal of Methylene Blue

“…Several investigations were reported describing MB remediation by magnetic biochar. Humin‐derived magnetic biochar was obtained by co‐precipitation method in alkali medium having maximum adsorption capacity 10.7 mg g −1 towards MB [19] . Single step hydrothermal carbonization method was employed for the magnetic biochar synthesis from waterworks sludge, sewage sludge, and iron mud having specific surface areas between 40 and 50 m 2 g −1 [20] .…”