Novel geochemistry-inspired method for the deep removal of vanadium from molybdate solution

Dual-mode sensing strategy based on carbon dots for sensitive and selective detection of molybdate ions

Two kinds of carbon dots with the maximum fluorescence peak of 492 nm (named as G-CDs) and 607 nm (named as R-CDs) were synthesized. In the presence of MoO42- ions, the fluorescence of R-CDs at 607 nm can be quenched, which can probably be assigned to their aggregation caused by MoO42-, while that of G-CDs at 492 nm remained unchanged. For the first time, a ratiometric fluorescence probe was developed for MoO42- ions detection. In the range 0.25 ~ 100 μM, the fluorescence ratio (F492/F607) of the probe was linearly related to MoO42- concentration, and the detection limit was 61.5 nM, which fully meets the minimum detection requirements of MoO42- ions in drinking water. On the other hand, when MoO42- was introduced, a significant fading phenomenon of R-CDs can be observed with the naked eye; thereby, the colorimetric method can also be proposed. Based on above, the ratiometric fluorometric/colorimetric dual-mode sensing method was established for MoO42- anion quantification. Compared with the traditional analysis methods, the results obtained by multimodal sensing can be mutually verified, which effectively improves the accuracy and reliability. The dual-mode assay proposed in this work provides an alternative scheme to meet the need of sensing target compounds in complex matrices.

Highly reusable bentonite clay@biochar@Fe3O4 nanocomposite for Hg(II) removal from synthetic and real wastewater

The present research investigates the performance of bentonite clay@biochar@Fe₃O₄ nanocomposite in removing mercury ions (Hg²⁺) from aqueous media. The physical and structural properties of bentonite clay@biochar@Fe₃O₄ were determined using Brunauer-Emmett-Teller (BET), vibrating-sample magnetometer (VSM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDX), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), and Raman analyses. The highest uptake efficiency of Hg²⁺ was obtained at pH 6, Hg²⁺ concentration of 10 mg/L, contact time of 80 min, and the composite dose of 1.5 g/L. Under these conditions, the uptake efficiency of bentonite clay@biochar@Fe₃O₄ and bentonite clay was obtained as 98.78% and 97.67%, respectively, which are remarkable values. Also, the q_max values in Hg²⁺ removal using bentonite clay@biochar@Fe₃O₄ and bentonite clay were obtained as 66.66 and 60.98 mg/g, respectively. Moreover, the uptake process of Hg²⁺ ions using bentonite clay@biochar@Fe₃O₄ nanocomposite and bentonite was spontaneous, physical, favorable, and exothermic. Besides, the impact of various divalent ions such as Co²⁺, Cu²⁺, Pb²⁺, Ni²⁺, and Zn²⁺ on the removal efficiency of Hg²⁺ was studied. The results showed that Co²⁺ and Zn²⁺ ions have the highest and lowest interference effect in Hg²⁺ removal, respectively. Also, the reusability of both adsorbents showed that they have high stability and can be used for at least 5 cycles with high uptake efficiency. Additionally, the removal efficiency of chemical oxygen demand (COD), biochemical oxygen demand (BOD₅), Hg²⁺, As³⁺, and As⁵⁺ from real wastewater using bentonite clay@biochar@Fe₃O₄ was obtained as 37.5%, 28.9%, 65%, 60.5%, and 50%, respectively, indicating its remarkable performance.

Synthesis of activated carbon composited with Egyptian black sand for enhanced adsorption performance toward methylene blue dye

The present study reports the feasibility of the synthesis of a novel porous composite adsorbent, prepared from olive stone activated carbon (OS400) and garnet (GA) mineral impregnations (referred to as OSMG). This composite (OSMG) was applied for its ability to adsorb a macromolecular organic dye. The composite's structural characteristics were evaluated using various techniques such as Brunauer-Emmett-Teller (BET), Scanning Electron Microscopy equipped with Energy Dispersive X-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD), and a Fourier transform infrared spectrometer (FT-IR). The specific surface area of the garnet (GA), (OS400), and (OSMG) were found to be 5.157 mg⋅g^-1, 1489.598 mg⋅g^-1, and 546.392 mg⋅g^-1, respectively. The specific surface area of the new composite (OSMG) was promoted to enhance the adsorption of methylene blue (MB). Experiments were conducted under various conditions, including contact time, initial dye concentration, adsorbent dosage, pH, and temperatures. Data from these experiments were analyzed using several adsorption models including Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich (D-R). The results indicated that, the adsorption fit best with the Freundlich model and that the adsorption process followed a pseudo-second-order kinetic mechanism. Additionally, the thermodynamic analysis indicated the adsorption of MB onto garnet(GA) adsorbents is endothermic, while the sorption onto (OS400) and (OSMG) is an exothermic and non-spontaneous process. The OSMG composite can be used for at least five cycles without significant loss of adsorptive performance, and can easily be separated from the water after treatment.

Recovery of spent VOSO4 using an organic ligand for vanadium redox flow battery applications

To recover the spent vanadium compound, Rhodamine-B-based Schiff's base ligand (L₁) was synthesized via ultrasonication process and was evaluated with vanadyl sulfate (VOSO₄), which has shown considerable selectivity towards V(IV). The change of the solution color from colorless to pink is attributed to L₁ after the reaction with vanadium ion owing to the successful formation of the vanadium complex and the opening of the spirolactam ring in the L₁ structure. In FT-IR spectra, the vanadyl peaks are co-existed with the L₁ structure, which confirmed the complex formation of the L₁ with vanadium. Similarly, the binding energy of V(IV) was identified at 516.2 eV for V2p_3/2 in XPS spectra. The new strategy for VOSO₄ recovery was established through solvent extraction and acid leaching. After recovery process, the absence of vanadium peak in the XPS confirmed the complete removal of V(IV) from the complex. The recovered VOSO₄ solution used as an electrolyte in vanadium redox flow battery (VRFB) systems, where the unit cell performance is comparable with the conventional electrolyte solution. The advantage of study is reuse of VOSO₄ as a resource for energy storage applications.

A ligand-anchored optical composite material for efficient vanadium(ii) adsorption and detection in wastewater

A ligand-anchored composite material was prepared for vanadium (V(ii)) ion capturing. The pH was found to be a key factor in both detection and removal operations. The composite material exhibited the high adsorption capacity of 492.61 mg g⁻¹.

Oil removal from spent HDT catalyst by an aqueous method with assistance of ultrasound

Deoiling enjoys great significance in recycling and landfill of spent hydrotreating (HDT) catalyst. In this study, a novel approach for oil removal from spent HDT catalyst with assistance of ultrasound was developed. The effects of variables on oil removal were investigated by response surface methodology and central composite design method. The oil removal efficiency reaches 96.03 ± 0.82% under the optimum conditions of liquid-solid ratio 16.00 ml·g^-1, 75 °C, sodium hydroxide dosage 3.88 wt%, and 40 kHz ultrasonic irradiation for 3.25 h. Under the optimum conditions, the contact angle of spent catalyst is 98.7° before oil removal, and then reduces to 57.2° after deoiling with the help of ultrasound, but turns to 72° after deoiling in the absence of ultrasound, which further verifies that the oil removal efficiency can be improved by ultrasound. Compared to traditional extraction or hydrothermal methods for removing oil from spent catalyst, the proposed approach introduced ultrasonic force field to enhance oil removal efficiency without adding organic solvent or surfactant.