Assessment of growth, reproduction, and vermi-remediation potentials of Eisenia fetida on heavy metal exposure.

Heavy metal pollution is a significant environmental concern with detrimental effects on ecosystems and human health, and traditional remediation methods may be costly, energy-intensive, or have limited effectiveness. The current study aims were to investigate the impact of heavy metal toxicity in Eisenia fetida, the growth, reproductive outcomes, and their role in soil remediation. Various concentrations (ranging from 0 to 640 mg per kg of soil) of each heavy metal were incorporated into artificially prepared soil, and vermi-remediation was conducted over a period of 60 days. The study examined the effects of heavy metals on the growth and reproductive capabilities of E. fetida, as well as their impact on the organism through techniques such as FTIR, histology, and comet assay. Atomic absorption spectrometry demonstrated a significant (P < 0.000) reduction in heavy metal concentrations in the soil as a result of E. fetida activity. The order of heavy metal accumulation by E. fetida was found to be Cr > Cd > Pb. Histological analysis revealed a consistent decline in the organism's body condition with increasing concentrations of heavy metals. However, comet assay results indicated that the tested levels of heavy metals did not induce DNA damage in E. fetida. FTIR analysis revealed various functional group peaks, including N-H and O-H groups, CH2 asymmetric stretching, amide I and amide II, C-H bend, carboxylate group, C-H stretch, C-O stretching of sulfoxides, carbohydrates/polysaccharides, disulfide groups, and nitro compounds, with minor shifts indicating the binding or accumulation of heavy metals within E. fetida. Despite heavy metal exposure, no significant detrimental effects were observed, highlighting the potential of E. fetida for sustainable soil remediation. Vermi-remediation with E. fetida represents a novel, sustainable, and cutting-edge technology in environmental cleanup. This study found that E. fetida can serve as a natural and sustainable method for remediating heavy metal-contaminated soils, promising a healthier future for soil.

Photocatalytic degradation of rhodamine B dye pollutants by Fe3O4/SiO2 core-shell magnetic nanocomposite functionalized with TiO2.

Significant efforts have been dedicated to creating recyclable and efficient methods for treating waste dyes, including rhodamine B (RhB). Nevertheless, challenges such as complex operational techniques, high costs, energy consumption, and inefficacy in dye removal persist. Here, the synthesis and application of TiO2/Fe3O4/SiO2 for photocatalytic degradation of RhB dye pollutants have been explored. This research was initiated with magnetite (Fe3O4) synthesis using the coprecipitation method, followed by silica (SiO2) extraction from rice husk waste using the sol-gel process, and a hydrothermal method for synthesizing titanium dioxide (TiO2) and TiO2/Fe3O4/SiO2 nanocomposite. The crystalline structure of TiO2/Fe3O4/SiO2 was obtained with Fe3O4 as the core, while TiO2 and SiO2 as the shell. The particle size analysis showed the nanosize of TiO2/Fe3O4/SiO2 (1.04 ± 0.46 nm). TiO2/Fe3O4/SiO2 nanocomposite boasts a high surface area of 48.025 m2/g, 2.2 times higher than unmodified TiO2. This nanocomposite also displayed paramagnetic properties with a saturation magnetization of 9.117 emu/g, facilitating easy separation in photocatalytic applications. The photocatalytic activity of TiO2/Fe3O4/SiO2 exhibited effectively degraded RhB, achieving a degradation rate of 53.58% and an excellent rate constant of 0.7303 min-1. The RhB photodegradation in this study requires a moderate irradiation time (60 min), uses only a tiny amount of photocatalyst (100 mg), and does not need additional chemicals. Moreover, this study has another advantage of utilizing rice husk as a silica source, offering an eco-friendly and sustainable approach.

Efficient photocatalytic bactericidal performance of green-synthesised TiO2/reduced graphene oxide using banana peel extracts.

In this study, the fabrication of titanium dioxide/reduced graphene oxide (TiO2/rGO) utilising banana peel extracts (Musa paradisiaca L.) as a reducing agent for the photoinactivation of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was explored. The GO synthesis was conducted using a modified Tour method, whereas the production of rGO involved banana peel extracts through a reflux method. The integration of TiO2 into rGO was achieved via a hydrothermal process. The successful synthesis of TiO2/rGO was verified through various analytical techniques, including X-ray diffraction (XRD), gas sorption analysis (GSA), Fourier-transform infrared (FT-IR) spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS), scanning electron microscope-energy dispersive X-ray (SEM-EDX) and transmission electron microscopy (TEM) analyses. The results indicated that the hydrothermal-assisted green synthesis effectively produced TiO2/rGO with a particle size of 60.5 nm. Compared with pure TiO2, TiO2/rGO demonstrated a reduced crystallite size (88.505 nm) and an enhanced surface area (22.664 m2/g). Moreover, TiO2/rGO featured a low direct bandgap energy (3.052 eV), leading to elevated electrical conductivity and superior photoconductivity. To evaluate the biological efficacy of TiO2/rGO, photoinactivation experiments targeting E. coli and S. aureus were conducted using the disc method. Sunlight irradiation emerged as the most effective catalyst, achieving optimal inactivation results within 6 and 4 h.

The potency of hydrothermally prepared sulfated silica (SO4/SiO2) as a heterogeneous acid catalyst for ethanol dehydration into diethyl ether.

The dehydration of ethanol into diethyl ether over a SO4/SiO2 catalyst was investigated. The SO4/SiO2 catalysts were prepared by the sulfation method using 1, 2, and 3 M of sulfuric acid (SS1, SS2, and SS3) via hydrothermal treatment. This study is focused on the synthesis of a SO4/SiO2 catalyst with high total acidity that can be subsequently utilized to convert ethanol into diethyl ether. The total acidity test revealed that the sulfation process increased the total acidity of SiO2. The SS2 catalyst (with 2 M sulfuric acid) displayed the highest total acidity of 7.77 mmol/g, whereas the SiO2 total acidity was only 0.11 mmol/g. Meanwhile, the SS3 catalyst (with 3 M sulfuric acid) has a lower total acidity of 7.09 mmol/g due to the distribution of sulfate groups on the surface having reached its optimum condition. The crystallinity and structure of the SS2 catalyst were not affected by the hydrothermal treatment or the sulfate process on silica. Furthermore, The SS2 catalyst characteristics in the presence of sulfate lead to a flaky surface in the morphology and non-uniform particle size. In addition, the surface area and pore volume of the SS2 catalyst decreased (482.56-172.26 m2/g) and (0.297-0.253 cc/g), respectively, because of the presence of sulfate on the silica surface. The SS2 catalyst's pore shape information explains the formation of non-uniform pore sizes and shapes. Finally, the activity and selectivity of SO4/SiO2 catalysts in the conversion of ethanol to diethyl ether yielded the highest ethanol conversion of 70.01% and diethyl ether product of 9.05% from the SS2 catalyst (the catalyst with the highest total acidity). Variations in temperature reaction conditions (175-225 °C) show an optimum reaction temperature to produce diethyl ether at 200 °C (11.36%).

Photocatalytic degradation of naphthol blue from Batik wastewater using functionalized TiO2-based composites.

This work provides a first-time comparative study examining the photocatalytic activity of functionalized TiO2-based composites to eliminate naphthol blue in Batik wastewater. Reduced graphene oxide (RGO) was synthesized by oxidizing solid graphite using the Hummers' method followed by sonication and reduction. N-doped TiO2 (N-TiO2) was synthesized from titanium tetrachloride (TiCl4) and urea (CH4N2O) precursors by the sol-gel method. N-TiO2 modified RGO (RGO/NT) was synthesized using a hydrothermal method from N-TiO2 and RGO. Prepared TiO2-based composites and commercial TiO2, for comparison were characterized using Fourier transform infrared spectrometer (FTIR), X-Ray diffractometer (XRD), scanning electron microscope-energy dispersive X-ray (SEM-EDX), and UV-Vis diffuse reflectance spectrometer (UV-Vis DRS). FTIR characterization indicated Ti-N bonding in N-TiO2 and RGO/NT. XRD patterns showed that commercial TiO2 had a rutile phase, while N-TiO2 and RGO/NT had an anatase phase with crystal sizes of 30.09, 16.28, and 12.02 nm, respectively. SEM results displayed the presence of small and glossy white N-TiO2 dispersed on the surface of RGO. Characterization using UV-Vis DRS showed that the band gap energy values for TiO2, N-TiO2, and RGO/NT were 3.25, 3.12, and 3.08 eV with absorption regions at the wavelengths of 382, 398, and 403 nm, respectively. The highest photocatalytic activity for RGO/NT for degrading naphthol blue was obtained at pH 5, with a photocatalyst mass of 60 mg, and an irradiation of 15 min. Photocatalytic degradation by RGO/NT on Batik wastewater under visible light showed higher effectivity than under UV light.

Simultaneous photocatalytic removal of organic dye and heavy metal from textile wastewater over N-doped TiO2 on reduced graphene oxide.

Methylene blue (MB) and hexavalent chromium(Cr(VI)) are hazardous pollutants in textile waste and cannot be completely removed using conventional methods. So far, there have been no specific studies examining the synthesis and activity of N-TiO2/rGO as a photocatalyst for removing MB and Cr(VI) from textile wastewater. This work especially highlights the synthesis of N-TiO2/rGO as a photocatalyst which exhibits a wider range of light absorption and is highly effective for simultaneous removal of MB-Cr(VI) under visible light. Titanium tetrachloride (TiCl4) was used as the precursor for N-TiO2 synthesis using the sol-gel method. Graphite was oxidized using Hummer's method and reduced with hydrazine to produce rGO. N-TiO2/rGO was synthesized using a hydrothermal process and then analyzed using several characterization instruments. The X-ray diffraction pattern (XRD) showed that the anatase N-TiO2/rGO phase was detected at the diffraction peak of 2θ = 25.61. Scanning electron microscopy and transmission electron microscopy (SEM-EDS and TEM) dispersive X-ray spectrometry images show that N-TiO2 particles adhere to the surface of rGO with uniform size and N and Ti elements are present in the N-TiO2/rGO combined investigated. Gas absorption analysis data (GSA) shows that N-TiO2/rGO had a surface area of 77.449 m2/g, a pore volume of 0.335 cc/g, and a pore size of 8.655 nm. The thermogravimetric differential thermal analysis (TG-DTA) curve showed the anatase phase at 500-780 °C with a weight loss of 0.85%. The N-TiO2/rGO composite showed a good photocatalyst application. The photocatalytic activity of N-TiO2/rGO for textile wastewater treatment under visible light showed higher effectiveness than ultraviolet light, with 97.92% for MB and 97.48% for Cr(VI). Combining N-TiO2 with rGO is proven to increase the light coverage in the visible light region. Removal of MB and Cr(VI) can be carried out simultaneously and results in a removal efficiency of 95.96%.

Hydrothermal preparation of a platinum-loaded sulphated nanozirconia catalyst for the effective conversion of waste low density polyethylene into gasoline-range hydrocarbons.

A platinum-loaded sulphated nanozirconia (Pt/nano ZrO2-SO4) bifunctional metal-acid catalyst was synthesized using a hydrothermal process. The nano ZrO2-SO4 was initially prepared by dispersing the nano ZrO2 in H2SO4, followed by wet impregnation via heating in an aqueous PtCl4 solution. This material was subsequently calcined and reduced under hydrogen gas to produce the catalyst. The Pt/nano ZrO2-SO4 was found to be a highly active, selective and stable solid acid catalyst for the conversion of waste low density polyethylene (LDPE) to high value hydrocarbons. The catalytic activity and stability of this material were evaluated during the hydrocracking of waste LDPE while optimizing the reaction temperature, time and catalyst-to-feed ratio. The activity of catalyst prepared by hydrothermal was attributed to highly dispersion of Pt species interacting with the support and inhibition of the agglomeration process. The impregnation method of hydrothermal generated highly active and selective catalyst with Pt loads of 1 wt%. The hydrocracking of waste LDPE over Pt/nanoZrO2-SO4 at 250 °C for 60 min with a catalyst-to-feed proportion of 1 wt% gave the largest gasoline fraction.