Yerba Mate Tea Extract: a Green Approach for the Synthesis of Silica Supported Iron Nanoparticles for Dye Degradation

Abstract

This work describes a green approach to the synthesis of iron nanoparticles supported in silica using tea extract of the South American plant yerba mate (Ilex paraguariensis). Catalysts with different iron contents were obtained according to the reaction conditions employed. Characterization by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) revealed the amorphous nature of the nanoparticles, tentatively ascribed to iron(II)/iron(III) oxide composites, as Fourier transform infrared (FTIR) and thermogravimetric analyses confirmed their functionalization by the tea polyphenolic compounds. For the sake of comparison, crystalline zero-valent iron nanoparticles were prepared by the classical method using NaBH 4 . Both materials were tested in the degradation of methyl orange and led to complete decolourization; the green nanoparticles were very active as heterogeneous Fenton-like catalysts in presence of hydrogen peroxide, while the nanoparticles prepared with NaBH 4 were efficient in the reductive degradation of the dye.

Green Synthesis of Iron Oxides and Phosphates via Thermal Treatment of Iron Polyphenols Synthesized by a Camellia sinensis Extract

“…The as-prepared nanoparticles named BT Fe presented an X-ray diffraction profile (Figure S1) typical of an amorphous material, with broaden peak around 23° attributed to FeONPs coated with TP, in accordance with the literature. − SEM images of BT Fe showed completely undefined, agglomerated particles of irregular shape and large size in the range of 10 μm (Figure S3). SEM-EDS spectra of BT Fe (Figures S5) showed C, O, Fe, and P as the main elements.…”

“…FTIR spectra of BT Fe (Figure a) show the bands of TP compounds present in the black tea extract. − The vibration centered at 3414 cm –1 is attributed to hydroxyl groups, the bands at 2925 and 2851 cm –1 are characteristic of C–H bonds, and the band at 1696 cm –1 corresponds to carboxylic acids. The absorptions at 1628, 1516, and 1453 cm –1 correspond to the aromatic and aliphatic C–H angular vibrations, and the bands at 1238 and 1086 cm –1 may be assigned to C–O groups.…”

“…TPs are biorenewable, biodegradable, nontoxic, and water soluble at room temperature and can act as biotemplates for the formation of FeONPs, avoiding the thermodynamically favorable agglomeration . The interaction of iron ions with TPs makes it difficult to form repeating lattice structures required for crystallinity; thus usually amorphous materials are produced, as reported for green tea, black tea, white tea, Yerba Mate, and eucalyptus leaf extracts. − Moreover, the TP alcoholic functional groups form metal complexes through chelation that can help to stabilize the NPs . Finally, TPs also act as reducing agents, whose reduction potentials range between +0.3 and +0.8 V, while the redox potentials of Fe 3+ /Fe 2+ and Fe 2+ /Fe 0 are +0.77 and −0.44 V, respectively. , This indicates that Fe 3+ can be reduced to Fe 2+ by TP, but it is difficult to further reduce Fe 2+ to Fe 0 .…”

“…The most investigated application of green FeONPs is in the removal of pollutants from contaminated sites. Dye and textile industries are the major sources of water contamination due to improper waste disposal containing recalcitrant and polluting organic dyes, which inhibits photosynthesis, presents high toxicity to aquatic and human lives, and creates aesthetic problems. , The highly complex and stable organic dyes are resistant to biodegradation, where treatment with iron compounds plays a central role in remediation processes. − Therefore, green FeONPs have been widely used in organic pollutant removal by heterogeneous Fenton-like degradation, presenting promising results. − ,,, For instance, FeONPs prepared with black tea, Yerba Mate, , and green tea extracts removed the dye methyl orange completely. In addition to the aforementioned advantages of the green FeONPs, TP can help to restore Fe 2+ by reduction of Fe 3+ ions (eqs S1–S4), can increase the stability of Fe 2+ by chelation, and can prevent iron sludge formation as well as increase the production of OH • radicals due to the lowering of the reaction pH by the release of acidic hydrogen to the medium, thus improving the overall Fenton efficiency …”

Alumina Coated Silica Nanosprings (NS) Support Based Cobalt Catalysts for Liquid Hydrocarbon Fuel Production From Syngas

“…The TGA thermograms of the calcined Co/NS, Co/Al 2 O 3 , Co/NS-Al-A and Co/NS-Al-B catalysts (Figure 2a) indicates that the overall weight loss up to 900 °C were 6.9%, 6.3%, 5.4% and 4.0%, respectively. The first stage mass loss (about 3%) of all catalysts occurred between the temperature range of 30–150 °C, which is likely due to evaporation of adsorbed water, solvent and organic compounds on the catalysts; this is supported by an exothermic peak in the DTA thermograms (Figure 2b) [15,16]. Weight loss was observed above 600 °C and can be attributed to complete removal of material during calcination.…”