One-Step Pyrolysis Fabrication of Magnetic Bagasse Biochar Composites with Excellent Lead Adsorption Performance

A green and economic approach to synthesize magnetic Lagenaria siceraria biochar (γ-Fe2O3-LSB) for methylene blue removal from aqueous solution

In the printing and textile industries, methylene blue (a cationic azo dye) is commonly used. MB is a well-known carcinogen, and another major issue is its high content in industrial discharge. There are numerous removal methodologies that have been employed to remove it from industrial discharge; however, these current modalities have one or more limitations. In this research, a novel magnetized biochar (γ-Fe2O3-LSB) was synthesized using Lagenaria siceraria peels which were further magnetized via the co-precipitation method. The synthesized γ-Fe2O3-LSB was characterized using FTIR, X-ray diffraction, Raman, SEM-EDX, BET, and vibrating sample magnetometry (VSM) for the analysis of magnetic properties. γ-Fe2O3-LSB showed a reversible type IV isotherm, which is a primary characteristic of mesoporous materials. γ-Fe2O3-LSB had a specific surface area (SBET = 135.30 m2/g) which is greater than that of LSB (SBET = 11.54 m2/g). γ-Fe2O3-LSB exhibits a saturation magnetization value (Ms) of 3.72 emu/g which shows its superparamagnetic nature. The batch adsorption process was performed to analyze the adsorptive removal of MB dye using γ-Fe2O3-LSB. The adsorption efficiency of γ-Fe2O3-LSB for MB was analyzed by varying parameters like the initial concentration of adsorbate (MB), γ-Fe2O3-LSB dose, pH effect, contact time, and temperature. Adsorption isotherm, kinetic, and thermodynamics were also studied after optimizing the protocol. The non-linear Langmuir model fitted the best to explain the adsorption isotherm mechanism and resulting adsorption capacity ( q e =54.55 mg/g). The thermodynamics study showed the spontaneous and endothermic nature, and pseudo-second-order rate kinetics was followed during the adsorption process. Regeneration study showed that γ-Fe2O3-LSB can be used up to four cycles. In laboratory setup, the cost of γ-Fe2O3-LSB synthesis comes out to be 162.75 INR/kg which is low as compared to commercially available adsorbents. The results obtained suggest that magnetic Lagenaria siceraria biochar, which is economical and efficient, can be used as a potential biochar material for industrial applications in the treatment of wastewater.

Competitive adsorption of heavy metals onto xanthate-modified sludge hydrochar and its solidification as secondary minerals

In this study, a sulfur-modified magnetic hydrochar was synthesized by grafting thiol-containing groups onto the sludge-derived hydrochar. The modified hydrochar exhibited effective adsorption of Cu2+, Pb2+, Zn2+, and Cd2+ over a wide pH range and in the presence of coexisting ions, and showed almost no secondary leaching in three acidic solutions. In the mult-metal ion system, the modified hydrochar exhibited maximum adsorption capacities were 39.38, 105.74, 26.53, and 38.11 mg g-1 for Cu2+, Pb2+, Zn2+, and Cd2+, respectively. However, the binding capacity and adsorption amount of modified hydrochar for metal ions were lower in the mult-metal ion system compared to the unit-metal ion system. Notably, Pb2+ showed a strong inhibitory effect on the adsorption of other heavy metal ions by modified hydrochar due to strong competition for xanthate functional groups. The Pb2+ occupied the xanthate and native functional groups (-OH, -NH2, and Fe-O etc.), leaving only a small amount of adsorption sites for Cu2+, Zn2+ and Cd2+. Simulation results further supported these findings, indicating that Pb2+ had the highest density profiles near the four functional groups, and the density profiles of the four heavy metals near the xanthate functional groups were greater compared to the other three functional groups. Furthermore, the SEM-EDS, TOF-SIMI, and XPS results indicated that modified hydrochar achieved excellent mineral binding mainly through electrostatic interaction, ion exchange, and chelation. Overall, these results highlight the sulfur-modified magnetic hydrochar as a highly efficient adsorbent for heavy metals in environmental applications.

Fabrication of samarium doped MOF-808 as an efficient photocatalyst for the removal of the drug cefaclor from water

MOFs are emerging photocatalysts designed by tuning organic ligands and metal centers for optimal efficiency. In this study, a samarium decorated MOF-808(Ce) metal organic framework was fabricated by facile hydrothermal synthesis. The synthesized samarium decorated MOF-808(Ce) was characterized by using analytical techniques such as SEM, EDX, XRD and TGA to study its morphological, thermal and structural properties. SEM images showed that MOF-808(Ce) comprised of truncated octahedrons. The morphology of the material was changed upon Sm incorporation. Sm/MOF-808(Ce) exhibited better UV-vis light absorption properties than MOF-808(Ce) as evidenced by its slightly higher band gap value. This material was exploited for the degradation of the drug cefaclor from water. Cefaclor removal followed double a first order in parallel model (DFOP). Under UV light, 97.7% of the cefaclor was removed in only 20 minutes and after 60 minutes this removal efficiency was increased to 99.25%. These features exhibited that samarium decorated MOF has immense potential for the photocatalytic degradation of cefaclor as it generates e- and h+ to enhance the photocatalytic efficiency and it is a promising candidate to treat wastewater without formation of harmful byproducts.

Valorization of sugarcane bagasse with in situ grown MoS2 for continuous pollutant remediation and microbial decontamination

In this study, sugarcane bagasse (SB) was strategically subjected to a delignification process followed by the in situ growth of multi-layered molybdenum disulfide (MoS2) nanosheets with hexagonal phase (2H-phase) crystal structure via hydrothermal treatment. The MoS2 nanosheets underwent self-assembly to form nanoflower-like structures in the aligned cellulose inter-channels of delignified sugarcane bagasse (DSB), the mechanism of which was understood through FTIR and XPS spectroscopic studies. DSB, due to its porous morphology and abundant hydroxyl groups, shows remediation capabilities of methylene blue (MB) dye through physio-sorption but shows a low adsorption capacity of 80.21 mg/g. To improve the removal capacity, DSB after in situ growth of MoS2 (DSB-MoS2) shows enhanced dye degradation to 114.3 mg/g (in the dark) which further improved to 158.74 mg/g during photodegradation, due to catalytically active MoS2. Interestingly, DSB-MoS2 was capable of continuous dye degradation with recyclability for three cycles, reaching an efficiency of > 83%, along with a strong antibacterial response against Gram-positive Staphylococcus aureus (S.aureus) and Gram-negative Escherichia coli (E. coli). The present study introduces a unique strategy for the up-conversion of agricultural biomass into value-added bio-adsorbents, which can effectively and economically address the remediation of dyes with simultaneous microbial decontamination from polluted wastewater streams.

Facile Synthesis of Metal-Impregnated Sugarcane-Derived Catalytic Biochar for Ozone Removal at Ambient Temperature

This study presents the first attempt at employing catalytic biochar to remove ground-level ozone at ambient temperature. With the increase in human activity, ozone has become a critical inorganic pollutant that needs to be addressed, using more sustainable methods. Fe- and Mn-impregnated catalytic biochars were prepared from a sugarcane feedstock via the wet impregnation method and pyrolysis at various temperatures, where the optimum value was determined to be 550 °C. The metal-impregnated biochar samples demonstrated enhanced surface areas and pore volumes compared with the pristine biochar (SCB550), resulting in improved ozone-adsorption capacity. SCB550-Fe exhibited an ozone-adsorption capacity of 52.1 mg/g at 20 ppm, which was approximately four times higher than that of SCB550. SCB550-Fe demonstrated superior ozone-removal performance compared to SCB550-Mn; 122 mg/g capacity as opposed to 116.2 mg/g at 80 ppm, respectively. Isothermal and kinetic modeling are also presented to suggest a plausible mechanism of ozone removal by catalytic biochar. This includes physical adsorption, complexation, electrostatic interaction, and electron transfer during the redox reaction between ozone and metals. Overall, this study should provide preliminary insights into ozone removal using biochar and promote further research regarding material optimization and kinetic studies.