Synthesis of iron oxide nanoparticles mediated by Camellia sinensis var. Assamica for Cr(VI) adsorption and detoxification

Exploring the potential of biologically synthesized nano-adsorbents in removal of hexavalent chromium (Cr (VI)): Mechanistic studies and circular economy integration

Heavy metals, particularly chromium (VI), cause severe environmental and health risks due to its toxicity and persistence in environment. Thus, it is essential to remediate such metals from the environment owing to its detrimental effects. A key promising method for removing environmental pollutants from such contamination is adsorption. However, conventional adsorbents often face limitations in efficiency and reusability, necessitating synthesizing methods for nanoparticles. Nanotechnology has demonstrated superior capabilities in this regard, particularly through the modification and functionalization of nanoparticles to enhance adsorption capacity and regeneration potential. These nanoparticles fabricated using various biological sources offer an eco-friendly and cost-effective alternative methods. Furthermore, biologically synthesized nanoparticles demonstrate high adsorption efficiency, with removal rates for Cr (VI) ranging up to 99 % with multiple regeneration cycles. The adsorption process has predominantly followed pseudo second-order kinetics, with maximum adsorption capacities reaching up to 459 mg g-1 and the best fitted isotherm model for these nanoparticles is the Langmuir isotherm, which depends on the nano-adsorbent type and operating conditions. Taking an extensive literature review method, this review looks into the importance of surface modification of nano-adsorbents and highlighting the role of biologically synthesized nanoparticles as effective adsorbents. Additionally, it provides the management of spent adsorbents with a focused on circular economy to address sustainability. Moreover, it covers computational analyses to optimize nanoparticle design and predict adsorption performance and addresses the challenges of scalability, suggesting future research directions to ensure sustainable and effective heavy metal remediation.

Green synthesis an eco-friendly route for the synthesis of iron oxide nanoparticles using aqueous extract of Thevetia peruviana and their biological activities

This study reports the plant extract-assisted synthesis of iron oxide (Fe3O4) using the aqueous extract of Thevetia peruviana. The synthesized IONPs were confirmed via UV-Vis spectroscopy (295 nm) and characterized using FTIR and SEM. Density Functional Theory (DFT) calculations indicated a thermodynamically and mechanically stable system with semimetallic behavior and visible light absorption. The biological activities of the IONPs were evaluated, including enzyme inhibition assays for urease, α-glucosidase, carbonic anhydrase-II, and xanthine oxidase, as well as anticancer activity. The Fe₃O₄ NPs exhibited potent enzyme inhibition, including urease (94.78%, IC₅₀ = 24.98 µg/mL), α-glucosidase (86.09%), and carbonic anhydrase-II (82.98%, IC₅₀ = 24.78 µg/mL). Additionally, molecular docking was performed to evaluate the interaction of Fe₃O₄ NPs with target enzymes, supporting their inhibitory potential. The NPs also demonstrated notable anticancer activity, particularly against MDR 2780AD (IC₅₀ = 0.39 µg/mL). These results showed significant enzyme inhibition and anticancer properties, indicating the potential of these green-synthesized IONPs in biomedical applications.

Three-Dimensional Porous Artemia Cyst Shell Biochar-Supported Iron Oxide Nanoparticles for Efficient Removal of Chromium from Wastewater

Chromium-containing wastewater poses severe threats to ecosystems and human health due to the high toxicity of hexavalent chromium (Cr(VI)). Although iron oxide nanoparticles (IONPs) show promise for Cr(VI) removal, their practical application is hindered by challenges in recovery and reuse. Herein, a novel three-dimensional porous nanocomposite, Artemia cyst shell biochar-supported iron oxide nanoparticles (ACSC@ IONP), was synthesized via synchronous pyrolysis of Fe3+-impregnated Artemia cyst shells (ACSs) and in situ reduction of iron. The optimized composite C@Fe-3, prepared with 1 mol/L Fe3+ and pyrolyzed at 450 °C for 5 h, exhibited rapid removal equilibrium within 5-10 min for both Cr(VI) and total chromium (Cr(total)), attributed to synergistic reduction of Cr(VI) to Cr(III) and adsorption of Cr(VI) and Cr(III). The maximum Cr(total) adsorption capacity was 110.1 mg/g at pH 2, as determined by the Sips isothermal model for heterogeneous adsorption. Competitive experiments demonstrated robust selectivity for Cr(VI) removal even under a 64-fold excess of competing anions, with an interference order of SO42- > NO3- > Cl-. Remarkably, C@Fe-3 retained 65% Cr(VI) removal efficiency after four adsorption-desorption cycles. This study provides a scalable and eco-friendly strategy for fabricating reusable adsorbents with dual functionality for chromium remediation.

Eco-friendly Synthesis of Iron Oxide Nanoparticles Using Parietaria alsinifolia Extracts and Evaluation of Biological Applications

The current research was conducted to synthesize Parietaria alsinifolia-mediated iron oxide nanoparticles (P.A@FeONPs) using the green and eco-friendly protocol. The biosynthesized P.A@FeONPs were characterized using various approaches like UVs, FTIR, SEM, EDX, and DLS. The mean crystallite size was calculated to be ~ 21.48 nm using the Debye-Scherrer equation. Further, various in vitro biological assays were performed to analyze the therapeutic potentials of FeONPs. 2,2-Diphenyl-1-picrylhydrazy (DPPH) antioxidant activity was performed to reveal the DPPH radical scavenging potential of P.A@FeONPs and was calculated as 72%. Similarly, the total reducing power was determined as 65.45 ± 1.77%. In addition, P.A@FeONPs exhibited a significant total antioxidant capacity of 87 ± 4.8%. Antibacterial and antifungal assays were performed using the disc diffusion method. Among the different bacterial strains accession (EFB-10-2023 M.B), Rhodococcus jostii has shown the highest zone of inhibition (23.9 mm at 1000 μg/mL), while Escherichia coli displayed a 22.65 mm zone of inhibition at (1000 μg/mL). Similarly, Aspergillus niger exhibited a substantial zone of inhibition (28.75 mm). A brine shrimp cytotoxicity assay revealed the cytotoxicity potential (LC50 244.92 μg/mL). P.A@FeONPs were also tested against red blood cells, HEK-293, and VERO cell lines (< 200 μg/mL) to validate their biocompatibility. An alpha-amylase inhibition assay demonstrated 68.66% inhibition and substantial cytotoxicity against Hep-2 liver cancer cells (IC50 100 μg/mL). In conclusion, P.A@FeONPs have shown significant bioactivities. In the future, we recommend other biological and catalytic activities using different animal models to explore its potential further.

Adsorption sites and interactions of pigments in molasses-based distillery effluent on starch-based composites: Ternary competitive adsorption and theoretical calculations

The pigment present in molasses-based distillery effluent constitutes a primary factor influencing its degradation. Adsorption is an effective approach to eliminate pigment from wastewater. In this study, a cationic cassava starch (CCS) magnetic composite (CCS@Fe3O4) was prepared and used as adsorbents for the removal of undesirable pigments. The adsorption behaviors of caffeic acid (CA), gallic acid (GA), and melanoidin (ME) on CCS@Fe3O4 in the wastewater were investigated using single and ternary competitive adsorption systems. The equilibrium adsorption capacities of CA, GA, and ME on CCS@Fe3O4 were 197.04, 195.55, and 623.97 mg/g at the optimized conditions (0.3 mg/mL CCS@Fe3O4 dosage, temperature of 38 °C, and pH of 7). The adsorption kinetic model showed that chemisorption accounted for most of the adsorption of CA, GA, and ME on CCS@Fe3O4. The adsorption mechanisms of pigments on CCS@Fe3O4 were explored at the molecular level through quantum chemical calculations. The electrostatic potentials (ESP), average local ionisation energy (ALIE), and Fukui indices calculation indicated that the quaternary ammonium group in CCS@Fe3O4 was more susceptible to electrophilic reactions. The CC and benzene rings in CA and GA, and the COO- in ME, represent sites of attack for quaternary ammonium during adsorption. Furthermore, the competitive adsorption results, adsorption energy, and electron transfer data demonstrated that the adsorption capacity of CCS@Fe3O4 for pigments followed the order ME>GA>CA. Overall, the competitive adsorption mechanisms of CA, GA, and ME on CCS@Fe3O4 were unveiled, with quantum chemical calculations offering crucial insights into the adsorption process.

Green synthesis of iron nanoparticles using mulberry leaf extract: characterization, identification of active biomolecules, and catalytic activity

The synthesis of iron-based nanoparticles (Fe NPs) using traditional preparation methods suffered from the disadvantages of high cost, environmental harm, and easy agglomeration. In this study, a novel eco-friendly method was proposed for the synthesis of iron nanomaterials (ML-Fe NPs): using antioxidant components extracted from mulberry leaf to reduce divalent iron (II). The preparation conditions of ML-Fe NPs were optimized by orthogonal tests. The prepared ML-Fe NPs exhibited an amorphous core-shell structure, displaying excellent dispersion and stability. During the synthesis process of ML-Fe NPs, the polyphenol molecules in mulberry leaf extract played a dominant role. A possible synthetic mechanism involving complexation, reduction, and encapsulation was proposed. Furthermore, the ML-Fe NPs were utilized to construct an ML-Fe NPs/peroxymonosulfate catalytic system for the degradation of Rhodamine B dye wastewater. The ML-Fe NPs demonstrated remarkable catalytic potential, achieving a 99% degradation efficiency for Rhodamine B within a span of 40 min.

Synthesis of Silver Nanoparticles Using Camellia sinensis Leaf Extract: Promising Particles for the Treatment of Cancer and Diabetes

Both diabetes and cancer pose significant threats to public health. To overcome these challenges, nanobiotechnology offers innovative solutions for the treatment of these diseases. However, the synthesis of nanoparticles can be complex, costly and environmentally toxic. Therefore, in this study, we successfully synthesized Camellia sinensis silver nanoparticles (CS-AgNPs) biologically from methanolic leaf extract of C. sinensis and as confirmed by the visual appearance which exhibited strong absorption at 456 nm in UV-visible spectroscopy. The fourier transform infrared spectroscopy (FTIR) analysis revealed that phytochemicals of C. sinensis were coated with AgNPs. Scanning electron microscopy (SEM) analysis showed the spherical shape of CS-AgNPs, with a size of 15.954 nm, while X-ray diffraction spectrometry (XRD) analysis detected a size of 20.32 nm. Thermogravimetric analysis (TGA) indicated the thermal stability of CS-AgNPs. The synthesized CS-AgNPs significantly inhibited the ehrlich ascites carcinoma (EAC) cell growth with 53.42±1.101 %. The EAC cell line induced mice exhibited increased level of the serum aspartate aminotransferase (AST), alanine transaminase (ALT), and alkaline phosphatase (ALP), however this elevated serum parameter significantly reduced and controlled by the treatment with CS-AgNPs. Moreover, in a streptozotocin-induced diabetic mice model, CS-AgNPs greatly reduced blood glucose, total cholesterol, triglyceride, low-density lipoprotein (LDL) and creatinine levels. These findings highlight that the synthesized CS-AgNPs have significant anticancer and antidiabetic activities that could be used as promising particles for the treatment of these major diseases. However, pre-clinical and clinical trial should be addressed before use this particles as therapeutics agents.

Pure Epigallocatechin-3-gallate-Assisted Green Synthesis of Highly Stable Titanium Dioxide Nanoparticles

Nanoparticles (NPs) are conventionally produced by using physical and chemical methods that are no longer in alignment with current society's demand for a low environmental impact. Accordingly, green synthesis approaches are considered a potential alternative due to the plant extracts that substitute some of the hazardous reagents. The general mechanism is based on the reducing power of natural products that allows the formation of NPs from a precursor solution. In this context, our study proposes a simple, innovative, and reproducible green approach for the synthesis of titanium dioxide (TiO2 NPs) that uses, for the first time, the major component of green tea (Camellia sinensis)-epigallocatechin-3-gallate (EGCG), a non-toxic, dietary, accessible, and bioactive molecule. The influence of EGCG on the formation of TiO2 NPs was analyzed by comparing the physicochemical characteristics of green synthesized NPs with the chemically obtained ones. The synthesis of bare TiO2 NPs was performed by hydrolysis of titanium isopropoxide in distilled water, and green TiO2 NPs were obtained in the same conditions, but in the presence of a 1 mM EGCG aqueous solution. The formation of TiO2 NPs was confirmed by UV-VIS and FTIR spectroscopy. SEM micrographs showed spherical particles with relatively low diameters. Our findings also revealed that green synthesized NPs were more stable in colloids than the chemically synthesized ones. However, the phytocompound negatively influenced the formation of a crystalline structure in the green synthesized TiO2 NPs. Furthermore, the synthesis of EGCG-TiO2 NPs could become a versatile choice for applications extending beyond photocatalysis, including promising prospects in the biomedical field.

Iron oxide nanoparticles in the soil environment: Adsorption, transformation, and environmental risk

Iron oxide nanoparticles (IONPs) have great application potential due to their multifunctional excellence properties, leading to the possibility of their release into soil environments. IONPs exhibit different adsorption properties toward environmental pollutants (e.g., heavy metals and organic compounds), thus the adsorption performance for various contaminants and the molecular interactions at the IONPs-pollutants interface are discussed. After solute adsorption, the change in the environmental behavior of IONPs is an important transformation process in the natural environments. The aggregation, aging process, and chemical/biological transformation of IONPs can be altered by soil solution chemistry, as well as by the presence of dissolved organic matter and microorganisms. Upon exposure to soil environments, IONPs have both positive and negative impacts on soil organisms (e.g., bacteria, plants, nematodes, and earthworms). Moreover, we compared the toxicity of IONPs alone to combined toxicity with environmental pollutants and pristine IONPs to aged IONPs, and the mechanisms of IONPs toxicity at the cellular level are also reviewed. Given the unanswered questions, future research should include prediction and design of IONPs, new characterization technology for monitoring IONPs transformation in soil ecosystems, and further refinement the environmental risk assessment of IONPs. This review will greatly enhance our knowledge of the performance and impact of IONPs in soil systems.