Magnetic Behavior of Carbon Materials Made from Biomass by Fe-Assisted Hydrothermal Carbonization

Advancement of biochar-aided with iron chloride for contaminants removal from wastewater and biogas production: A review

The use of fossil fuels, emission of greenhouse gases (GHG) into the atmosphere, and waste pose a problem to the environment and public health that urgently needs to be dealt with. Among numerous chemical activating agents that can be added to anaerobic digestion (AD) to enhance nutrient removal and increase the quality and quantity of biomethane, iron chloride (FeCl₃) is the one that has the lowest cost and is the most environmentally friendly. This state-of-the-art review aims to revise the influence of FeCl₃ on the Brunauer-Emmett-Teller (BET) surface area of biochar and its ability to increase methane (CH₄) yield and remove contaminants from biogas and wastewater. The novelty of the study is that FeCl₃, an activating agent, can increase the BET surface area of biochar, and its efficacy increases when combined with zinc chloride or phosphoric acid. Regarding the removal of contaminants from wastewater and biogas, FeCl₃ has proven to be an effective coagulant, reducing the chemical oxygen demand (COD) of wastewater and hydrogen sulfide in biogas. The performance of FeCl₃ depends on the dosage, pH, and feedstock used. Therefore, FeCl₃ can increase the BET surface area of biochar and CH₄ yield and remove contaminants from wastewater and biogas. More research is needed to investigate the ability of FeCl₃ to remove water vapor and carbon dioxide during biogas production while accounting for a set of other parameters, including FeCl₃ size.

Optimizing Al and Fe Load during HTC of Water Hyacinth: Improvement of Induced HC Physicochemical Properties

Nowadays, several alternatives have been proposed to increase the porosity and/or modify the surface groups of hydrochars from biomasses as well as to develop additional features on them. These alternatives can include specific modifications for the process, as previous steps or as postreatments, and the wide variety of forms in which they can be made can substantially affect the product distribution and properties. In this study, the hydrothermal carbonization process of an invasive floating plant (Water hyacinth) has been modified by introducing different amounts of iron (FeCl3) and aluminium alloy (shaving scrap waste) during the hydrothermal reaction. The effects on process reactivity, phase distribution, and physicochemical properties of the samples obtained were studied by means of different characterization techniques such as thermogravimetry (TG-DTG), physical adsorption/desorption of N2 at −196 °C, FT-IR spectroscopy, and scanning electron microscopy (SEM). In the case of iron-catalyzed reactions, the magnetite formation and magnetic behavior of the prepared hydrochars after a pyrolytic treatment was also estimated. The results obtained indicate that the porosity of the hydrochars was clearly improved to different extents by the addition of Al or Fe during direct synthesis. In addition, porous carbons with a moderate magnetic character were obtained.

Arsenic removal via a novel hydrochar from livestock waste co-activated with thiourea and γ-Fe2O3 nanoparticles

Arsenic (As) contaminants post tremendous threats to environment safety. Pristine hydrochar (PHC), thiourea-activated hydrochar (THC), and thiourea-Fe(NO₃)₃-activated hydrochar (Fe₂O₃@THC) were fabricated from dairy cattle manure via one-pot hydrothermal carbonization at 250 ℃ and applied for aqueous As(V) removal. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were conducted to characterize hydrochars and As(V) adsorption. Thiourea increased N and S functional groups (-NH₂, C-N, C=S and S=O). Fe(NO₃)₃ introduced γ-Fe₂O₃ nanoparticles and provided Fe₂O₃@THC with Fe-O. The combination of thiourea and Fe(NO₃)₃ granted Fe₂O₃@THC with the largest surface area (33.45 m²/g), and the highest total pore volume (0.095 cm³/g) among three hydrochars. As(V) adsorption was a physicochemical process involving electrostatic attraction, complexation, ion exchange and H-bond interaction. The maximum As(V) adsorption capacities and partition coefficients decreased as follows: Fe₂O₃@THC (44.80 mg/g; 38.44 L/g) > THC (38.77 mg/g; 5.94 L/g) > PHC (19.05 mg/g; 1.17 L/g). Three hydrochars exhibited preferable reusability in NaOH solution with only 24.2%, 11.8% and 14.1% decrease in adsorption rates after four cycles for PHC, THC and Fe₂O₃@THC, respectively. Fe₂O₃@THC is a promising adsorbent for efficient As(V) removal. This study explored the efficient As(V) removal by activated hydrochars with future research potential.

In situ preparation of magnetic hydrochar by co-hydrothermal treatment of waste vinasse with red mud and its adsorption property for Pb(II) in aqueous solution

Herein, a new magnetic hydrochar was prepared through co-hydrothermal treatment of vinasse with red mud, two abundant industrial wastes, and its adsorption property was evaluated on Pb(II), selected model ion in aqueous solution. During co-hydrothermal process, Fe₂O₃ species in red mud was reduced to Fe₃O₄ form, hereby, in situ magnetization of hydrochar was achieved, which was confirmed by characterization studies. Produced hydrochar with porous structure (V_total = 0.071 cm³/g and BET surface area = 23 m²/g) had saturation magnetization (44.7 emu/g), providing easier separation from water by a magnet. Maximum Pb(II) adsorption was favored at pH ≥ 5.0 within 120 min of equilibrium time and Freundlich isotherm model was preferable. The contribution percentage of different mechanisms including cation-exchange (40.8 %), (electrostatic attraction + "cation-π" interaction) (31.2 %), precipitation (25.4 %) and complexation (2.6 %) to overall Pb(II) adsorption indicated that cation-exchange was the dominant mechanism. Finally, application to fortified real water demonstrated that in situ magnetic hydrochar produced by suggested approach was successful at adsorptive removal of Pb(II) from water with no matrix effects.