Strong Acid Solutions Research Articles

Germanium silicon oxide achieves multi-coloured ultra-long phosphorescence and delayed fluorescence at high temperature

Colour-tuned phosphors are promising for advanced security applications such as multi-modal anti-counterfeiting and data encryption. The practical adoption of colour-tuned phosphors requires these materials to be responsive to multiple stimuli (e.g., excitation wavelength, excitation waveform, and temperature) and exhibit excellent materials stability simultaneously. Here we report germanium silicon oxide (GSO) – a heavy-metal-free inorganic phosphor – that exhibits colour-tuned ultra-long phosphorescence and delayed fluorescence across a broad temperature range (300 – 500 K) in air. We developed a sol-gel processing strategy to prepare amorphous oxides containing homogeneously dispersed Si and Ge atoms. The co-existence of Ge and Si luminescent centres (LC) leads to an excitation-dependent luminescence change across the UV-to-visible region. GSO exhibits Si LC-related ultra-long phosphorescence at room-temperature and thermally activated delayed fluorescence at temperatures as high as 573 K. This long-lived PL is sensitized via the energy transfer from Ge defects to Si LCs, which provides PL lifetime tunability for GSO phosphors. The oxide scaffold of GSO offers 500-day materials stability in air; and 1-week stability in strong acidic and basic solutions. Using GSO/polymer hybrids, we demonstrated colour-tuned security tags whose emission wavelength and lifetime can be controlled via the excitation wavelength, and temperature, indicating promise in security applications.

One A3B Porphyrin Structure-Three Successful Applications.

Porphyrins are versatile structures capable of acting in multiple ways. A mixed substituted A3B porphyrin, 5-(3-hydroxy-phenyl)-10,15,20-tris-(3-methoxy-phenyl)-porphyrin and its Pt(II) complex, were synthesised and fully characterised by 1H- and 13C-NMR, TLC, UV-Vis, FT-IR, fluorescence, AFM, TEM and SEM with EDX microscopy, both in organic solvents and in acidic mediums. The pure compounds were used, firstly, as sensitive materials for sensitive and selective optical and fluorescence detection of hydroquinone with the best results in the range 0.039–6.71 µM and a detection limit of 0.013 µM and, secondly, as corrosion inhibitors for carbon–steel (OL) in an acid medium giving a best performance of 88% in the case of coverings with Pt-porphyrin. Finally, the electrocatalytic activity for the hydrogen and oxygen evolution reactions (HER and OER) of the free-base and Pt-metalated A3B porphyrins was evaluated in strong alkaline and acidic electrolyte solutions. The best results were obtained for the electrode modified with the metalated porphyrin, drop-casted on a graphite substrate from an N,N-dimethylformamide solution. In the strong acidic medium, the electrode displayed an HER overpotential of 108 mV, at i = −10 mA/cm2 and a Tafel slope value of 205 mV/dec.

Adhesion behavior of different droplet on superhydrophobic surface of cotton fabric based on oxygen plasma etching

Oxygen plasma etching followed with spraying of hydrophobic suspension containing SiO2 nanoparticles were used to construct superhydrophobic cotton fabric, and the adhesion behavior of the superhydrophobic surface to deionized water, dye liquor, sterile defibrinated sheep blood, and simulated blood solutions was studied and evaluated in focus. Results of the present study showed the water contact and water slip angles of the superhydrophobic cotton fabric were 158.6° and 7.3° with 5 wt% of hexadecyltrimethoxysilane (HDTMS). The plasma etching imparted uniform strip grooves on the fiber, which together with the deposition of SiO2 nanoparticles constituted a dual-scale rough structure on the fabric surface. FTIR analysis showed the successful combination of HDTMS and SiO2 nanoparticles and covering on the cotton surface. This superhydrophobic surface possessed hydrophobic effect even after 35 times of abrasion and immersion in strong acid or alkali solutions for 8 h. The surface tension and viscosity of simulated blood and sterile defibrinated sheep blood (SDSB) were similar, with a contact angle of only 139.7° and a slip angle above 20°. And their adhesion forces were calculated by the Cassie-Baxter equation to be 30.93 and 37.88 μN. Moreover, the droplets placement of simulated blood and SDSB on the superhydrophobic surface for 2 h caused trace adhesion but no penetration. This indicated that the superhydrophobic surface had anti-adhesion performance to the liquids. In conclusion, it was evident that the superhydrophobic fabric has good application prospects in the field of textiles for daily life and medical protection.

Synthesis of porous γ-Fe2O3 from scorodite synthesized using ultrasound irradiation and evaluation of its battery performance

The effect of 200 kHz ultrasound on scorodite synthesis at 70 °C and 3 h reaction conditions was investigated using sulfuric acidic solutions of various pH (3.0, 2.0, 1.5, 1.0, and 0.0). In contrast to the case of only O2 gas flow without ultrasound irradiation, oxidizing radicals generated by ultrasound irradiation promote Fe(II) oxidation in solution and precursor, allowing scorodite to synthesize with high crystallinity (>99%), which relates to low solubility, even in strong acid solution at pH 1.0. During synthesis, the particle shape was decided to be polyhedral or spindle type depending on the pH of 0.0–3.0. The spindle-shaped scorodite was probably formed by the reduction in precursor amount produced during the initial stage of synthesis. Furthermore, porous maghemite obtained by alkali treatment of scorodite showed initial discharge capacities of 146 mAh g−1 (polyhedron) and 167 mAh g−1 (spindle), indicating that its potential use as a cathode material for lithium-ion batteries.

Flame-retardant AlOOH/graphene oxide composite coating with temperature-responsive resistance for efficient early-warning fire sensors

The eco-friendly and simple layer-by-layer (LbL) self-assembly process is used to create a graphene oxide (GO) and aluminum oxide hydroxide (AlOOH) functional coating on melamine foam (MF) by utilizing the hydrogen bonding interaction. The manufactured composite foam exhibits good hydrophobicity and structural stability in the both strong acidic and alkaline solutions. The AlOOH-GO composite coating's electrical resistance is susceptible to flame and high temperature, allowing for ultra-fast fire detection and efficient fire-warning response. When the composite foam is attacked by flame, it triggers an alarm signal within 2.5 s and a continuous alarm time access of 256 s, demonstrating exceptional early fire-warning capability. The thermal stability of this combustible foam is improved by the optimized AlOOH-GO composite coating. The AlOOH-GO composite coating endows MF with exceptional flame-retardant properties, including self-extinguishing and structural integrity after combustion. This work proposes an efficient method for considerably reducing the fire hazard of flammable materials and expanding the applications in a fire early detection and warning.

Preparation of a GO/PB-modified nanofiltration membrane for removal of radioactive cesium and strontium from water

In this study, a novel modified nanofiltration (NF) membrane was fabricated to treat radionuclide-contaminated water by incorporation of Prussian blue (PB), graphene oxide (GO) and polyethylene glycol (PEG) into polysulfone (PSf) substrate. In this work, PB provided a large number of adsorption sites for the membrane, GO improved the Donnan effect of the polyamide (PA) layer by enhancing the negative charge, and PEG promoted the uniform dispersion of PB through interparticle electrostatic interaction and steric hindrance while increasing the adsorption sites on the surface of channels in the substrate by adjusting the pore structure. A conceptual model for the role of substrate in interfacial polymerization was then proposed. The modified membrane achieved efficient rejection of cesium (Cs+, 99.5%) and strontium (Sr2+, 97.5%). Its Cs+ rejection rate still remained high (about 96%) even in the treatment of natural surface water containing various inorganic salts and organic matters. What’s more, the modified membrane exhibited excellent stability in both strong acid solutions and long-term operation. Then, potassium chloride (KCl) solution was applied to regenerate the modified membrane, which achieved high generation rate as compared to traditional acid regenerants. The excellent filtration performance inferred that the novel GO/PB-modified NF membrane holds great application potential for the application of simultaneous removal of radioactive Cs+ and Sr2+ from contaminated water.

Three-dimensional acanthosphere-like hierarchical Co@graphitic carbon for dispersive magnetic solid-phase extraction of nitroimidazole

Herein, a magnetic three-dimensional acanthosphere-like hierarchical Co@graphitic carbon (3D Co@GC) is introduced as an efficient adsorbent for extraction of three nitroimidazoles (NMZs: metronidazole (MNZ), ornidazole (ONZ) and tinidazole (TNZ)) from environmental water and food samples. The proposed 3D Co@GC was synthesized by a simple template-free method, which consisted of plentiful freely arranged one-dimensional nanowires. The adsorption properties of 3D Co@GC for three NMZs were investigated systematically by adsorption kinetic and isotherm studies. 3D Co@GC exhibits good adsorption capacity and fast adsorption kinetics toward three NMZs by virtue of its unique hierarchical structure. In addition, it was also found that a bit of methanol can effectively elute the adsorbed NMZs, eliminating the need for other dangerous strong acid or base solutions. Thus, 3D Co@GC as adsorbent to extraction three trace NMZs followed by direct quantification detection of targets with high-performance liquid chromatography with ultraviolet–visible detector (HPLC-UV) was developed. The parameters of dispersed magnetic solid-phase extraction (d-MSPE) were optimized by univariate and multivariate methods (Box-Behnken design). This established method revealed wide linear range and low limits of detection. Furthermore, the satisfactory recoveries of NMZs (86.7–106.7%) were acquired in spiked river water, honey, milk, and muscle samples. This study might provide a potential strategy for the efficient extraction and sensitive analysis of trace NMZs in river water, honey, milk, and muscle samples.

An acid baking approach to enhance heavy rare earth recovery from bituminous coal-based sources

The recovery of rare earth elements (REEs) from secondary resources, particularly coal-based materials, has recently received attention due to supply and demand imbalance. Research reported to date indicates that a high REE recovery can be realized when treating bituminous coal sources using strong acid solutions of approximately100 g/L or higher. This study introduces an approach to enhance the total rare earth recovery (TREE), especially for heavy rare earth elements (HREEs), from these coal sources at significantly lower acid concentrations. Based on the presence of REE minerals like monazite and xenotime, a detailed investigation was undertaken to quantify three pre-leach treatment methods, i.e., 1) roasting, 2) direct acid baking, and 3) acid baking after roasting. Roasting tests at 600 °C revealed that the recovery of light REEs (LREEs) was enhanced while the recovery of HREEs remained relatively unaffected. LREE and HREE recovery values of 38.3% and 21.3%, respectively, were achieved using a 50 g/L (0.5 M) sulfuric acid solution at 5% solid concentration and a solution temperature of 75 °C for 2 h. Comparatively, direct acid baking at 250 °C provided substantial increases in LREE and HREE recovery values to approximately 49.4% and 53.0%, respectively, using an equivalent acid dosage. Recoveries were maximized to 77.0% and 79.6% for LREE and HREE, respectively, by roasting followed by acid baking. Similar results were obtained from the treatment of a second bituminous coal source. Due to strong correlations between REE and Al recovery values, tests were performed on kaolinite and illite, which were prominent clay minerals within the source coals. These experiments revealed that the REE recovery improvements were likely a result of dehydroxylation of clays and subsequent release and decomposition of REE-bearing minerals such as monazite, xenotime and zircon.

A sacrificial protective layer as fouling control strategy for nanofiltration in water treatment

High-performance nanofiltration (NF) membrane with super antifouling capability as well as reusability is highly desired in water treatment. A new antifouling strategy by a coating-decoating-recoating cycle was investigated for effective removal of fouling and restoring the original membrane performance. The functional membrane surface was fabricated by in-situ coating a ‘green’ and biodegradable carboxymethyl chitosan (CMCS) layer as physical barrier. The CMCS layer can be decoated and re-coated by simple procedures. Results showed that (i) the CMCS layer enhanced surface hydrophilicity, surface smoothness and fouling resistance of NF membrane, (ii) both the unfouled and fouled CMCS layer were easily decoated by the strong acid solution, (iii) the CMCS layer was easily re-coated by facile recoating and (iv) the water flux recovery ratio of membrane with coating layer was maintained more than 88.8% during fouling testing by natural organic matter (NOM) after four sequential cycles of coating, decoating and recoating process. The re-coated membrane exhibited stable, improved membrane operational and antifouling performance. The coating-decoating-recoating approach is proven to be low-cost and eco-friendly strategy for NOM fouling control on NF membrane in water treatment applications.

Recovery of Gold from Strong Acidic Solution using Sulfur-Impregnated Carbonaceous Bamboo

Recovery of Gold from Strong Acidic Solution using Sulfur-Impregnated Carbonaceous Bamboo

Treatment and management of the effluents generated by hydrometallurgical processes applied to End-of-Life Photovoltaic Panels

Photovoltaic (PV) technology is a low-carbon and efficient option to produce electricity with an expected growing market. In the next years, end-of-life PV panels (EoL PV) will generate a new type of waste whose management implies environmental concerns but also opportunities to recover secondary raw materials. As part of a European project, a 1,500 panels/year capacity pilot plant to recover valuable resources from EoL PV panels using hydrometallurgical processes was operated in real environment. It represents the first time that a hydrometallurgical treatment was applied, at industrial scale, to EoL PV panels. This study focuses on the specific topic of treating the wastewater generated by the end of the hydrometallurgical process. Different chemical and physical tests were tried in laboratory on such streams loaded with metal species. The experimental results indicated that induced precipitation by adding strong acid or alkaline solutions allows obtaining high metal removal rates (greater than 95%). The optimal pH was around neutrality. Results suggested testing whether mixing the two wastewater at different rates could result in similar decontamination effects. pH neutrality was again the optimal condition. A further test at industrial scale was carried out by using a treatment plant specially assembled for the purpose. The study showed as the approach allowed to: 1) achieve a final supernatant to be reused within the recycling panel process; 2) avoid the use of lab-made high-grade solutions to modify pH; 3) minimize the production of waste (less than 60%) avoiding costs for the final out-side treatment and disposal.

Influence of Chlorine Oxyacid on the Electrooxidation of Methanol in Strong Acid

An electrochemical oxidation of methanol in a strong acid solution was investigated at a polycrystalline platinum electrode in the presence of different concentrations of hypochlorite. The addition of a slight amount of hypochlorite brought about drastic increase in the oxidation current of methanol, because the presence of hypochlorite inhibited the formation of a platinum oxide film on platinum electrodes. However, the oxidation current of methanol decreased with increasing the concentration of coexisting hypochlorite. The result may be due to i) the enhancement of the methanol adsorption to the surface of platinum electrodes by the inhibition of the formation of oxide film, and ii) the inhibition of methanol adsorption on platinum electrodes by higher concentration of NaClO and chemical compounds generated by the chemical reaction between methanol and increased hypochlorite.

Recovery of palladium(II) from strong nitric acid solutions relevant to high-level liquid waste of PUREX process by solvent extraction with pyrazole-pyridine-based amide ligands

The extraction of Pd2+ with N,N-dialkyl-2-(3-(pyridine-2-yl)-1H-pyrazole-1-yl) acetamide (A-C-PzPy) and N,N-dialkyl-3-(pyridine-2-yl)-1H-pyrazole-1-carboxamide (A-PzPy) from HNO3 medium, as well as the complexation of Pd2+ with A-C-PzPy were investigated. The use of tert-butyl benzene (TBB) as a diluent for A-C-PzPy offered significantly better extractability toward Pd2+, compared to that of A-PzPy. This study demonstrated strong extractability, high selectivity, high loading capacity, and fast extraction kinetics for DOct-C-PzPy toward Pd2+ from highly acidic HNO3 solution (up to 5.0 mol/L). Slope analysis showed the formation of 1:1 type of extracted species of Pd2+ with DOct-C-PzPy ligand. The extraction was a spontaneous and endothermic process with increased entropy. The analyses of electrospray ionization mass spectrometry (ESI-MS), Fourier transform infrared (FT-IR) and UV–vis spectrophotometric titration revealed that the composition of the extracted neutral complex species was Pd(NO3)2(DOct-C-PzPy). Combining the results of solvent extraction and complexation study, a neutral complexation extraction model is proposed. Furthermore, the stability constants (log β) for the complexation of Pd2+ with A-C-PzPy are also presented.

Structure of Sulfuric Acid Solutions Using Pair Distribution Function Analysis.

Solvation and mesoscale ordering of sulfuric acid and other strong acid solutions leads to suppressed freezing points and strong rheological changes with varying concentration. While the solid-state structures are well-understood, studies focused on the evolving solvation structure in the solution phase have probed a limited concentration range (∼1-6 M). This study applies a total scattering approach in both the wide-angle X-ray scattering (WAXS) and pair distribution function (PDF) regimes to elucidate the evolving solvation structure over its full range of acid concentration (0-18 M). The emergence of a prepeak in the WAXS regime at intermediate concentrations indicates a transition from noninteracting sulfate molecules in the dilute limit to sterically limited sulfates at concentrations near its deep eutectic point. Fits to the PDF data quantify this trend, showing a transition from octahedrally hydrated sulfates up to 6-7 M concentrations, followed by gradual dehydration, and eventually reaching a solution structure similar to that of water-in-salt electrolyte systems at high acid concentrations.

Chemically stable NH2-MIL-125(Ti)/Sep/PDA composite membranes with high-efficiency for oil/water emulsions separation

Nowadays, oily wastewater is a severe threat to the living environment of humankind. In recent years, MOF materials have shown great application potential in membrane separation and treatment of oily wastewater. In this paper, the mixed cellulose ester membrane (MCEM) was modified by polydopamine, and the NH2-MIL-125 (Ti)/Sep(sepiolite)/PDA composite membrane was prepared by simple vacuum filtration. The composite membrane had super-hydrophilic performance and underwater super-oleophobic performance, and could effectively separate oil-water emulsion separation performance. Also, the composite membrane showed good repeatability. After 10 cycles, the retention rate of petroleum ether-in-water emulsion was still more than 99%, and the flux was more than 2000 L·m−2·h−1. Since strong adhesion ability of PDA and the covalent interaction between NH2-MIL-125(Ti) and Sep, the chemically stable NH2-MIL-125(Ti)/Sep/PDA composite membrane was exposed to the strong acid (pH=1), alkali (pH=11), and salt (5% saturated NaCl) solutions showed excellent chemically stable. These outstanding properties made the composite membrane have great potential in the removal of oily wastewater.

In-situ chemical formation of strong stability GO/rGO hybrid membranes for efficient treatment of organic pollutant

In this study, a strong stability graphene oxide (GO)/reduced graphene oxide (rGO) hybrid membranes were successfully prepared by in-situ chemical reduction method. As the reducing agent, ammonia can effectively promote the deoxygenation of GO surface and the restoration of π-conjugation to produce rGO sheets. Moreover, the weakening of hydration and the enhancement of π-π conjugation promoted the interlayer force of GO/rGO membranes; as a result, the hybrid membranes exhibited extraordinary stability in strong acid and alkali solutions. In organic dyes separation application, the hybrid membranes displayed excellent rejection performance, and the rejection rate up to 100%. In addition, they also showed higher water flux (23.72 L m-2h−1 bar−1) comparing to pristine GO membranes (14.35 L m-2h−1 bar−1) and rGO membrane (8.66 L m-2h−1 bar−1). This work will promote the application scope of graphene-based membranes and provide better performance in water treatment.

Melamine Foam with pH‐Responsive Wettability for Fast Oil Absorption and Desorption

AbstractInnovative 3D materials with the switchable wetting surface attract significant attention due to their application in oil/water separation. Herein, a fast pH‐responsive and highly effective melamine foam (MF) grafted with poly (2‐dimethylaminoethyl methacrylate) is prepared by surface‐initiated chain transfer radical polymerization. The as‐prepared MF displays superhydrophilic and superoleophobic surface in strong acid solution while it becomes superhydrophobic in neutral or basic solution. Therefore, it can be rapid to selectively absorb different types of oils from the oil–water mixture with a great absorption capacity of 54–117 g g−1 and automatically desorb oil in less than 60 s with a desorption efficiency of 99% (dichloromethane) in acid solution. Moreover, the as‐prepared MF possesses excellent recyclability, and the absorption capacity and the desorption efficiency are almost unchanged after 15 cycles. The pH‐sensitive MF with switchable wetting surfaces has great potential for the oily water separation.

A sodium hyposulfite fuel cell for efficient Cr(VI) removal

This work shows a strategy of reducing hexavalent chromium (Cr(VI)) by sodium hyposulfite (Na2S2O3) with self-generated electricity via a dual-chamber non-biological fuel cell (D-nBFC). Therein, Na2S2O3 was electro-oxidized on graphite felt (GF) at anode and Cr(VI) in strong acidic solution was electro-reduced at GF/CCP cathode (GF decorated with conductive carbon paint (CCP)). Additionally, an agar salt bridge, consisting of saturated KCl solution, was introduced to form complete circuit by offering ions. The results showed that Cr(VI) was reduced to trivalent chromium (Cr(III)) and the D-nBFC system could produce electricity in this process. This system could obtain a high Cr(VI) removal efficiency (97.0%), 110 μA maximum current, and 13.4 mW m−2 maximum power density in 4 h. In addition, the proposed system had high reusability after five cycles and the relative standard deviation was only 3.4% (n = 5). Thus, this D-nBFC system provides a promising and eco-friendly method for treatment of Cr(VI) pollution and generating electricity simultaneously, and also has potential application value for other heavy metals remediation.

Production of NMSBA catalyzed by Co/Mn/Br together with the porous carbon made from coconut shell with ZnCl2 as activator

AbstractBACKGROUND2‐nitro‐4‐methylsulfonylbenzoic acid (NMSBA) is commercially produced from the oxidation of 2‐nitro‐4‐methylsulfonyltoluene (NMST) with nitric acid as oxidant and V2O5 as catalyst in a strong acid solution; this process suffers from the following shortcomings: the discharge of large amounts of wastewater and waste gas, as along with the generation of polynitro compounds. It is necessary to develop a technology to avoid the pollution caused by oxidizing NMST with nitric acid. NMSBA can be synthesized by oxidizing NMST with air under the catalysis of the porous carbon made from coconut shell with ZnCl2 as an activator together with Co/Mn/Br.RESULTSThe optimum conditions for the preparation of the porous carbon are as follows: impregnation temperature 60 °C, ZnCl2 concentration 0.50 mol L−1, impregnation duration 6 h, carbonization temperature 600 °C, and carbonization time 4 h. The surface characterization suggests that the carbon made in this study holds smaller surface area, acidic groups, and basic groups than the commercial carbon but owns more carboxyl.CONCLUSIONThe Co/Mn/Br/AC (AC,the porous carbon made in this study) catalytic system is superior to the Co/Mn/Br/H3PMo12O40@CAC(CAC,commercial activated carbon) catalytic system in the production of NMSBA from the oxidation of NMST. The NMSBA selectivity gained by the former is 93.40%, while that gained by the latter is 87.14%. The former can cut down the consumption of NMST and the expenditure of catalysts. The catalytic ability of the AC catalyst relies on its surface chemical characteristics and physical properties. More carboxyl on AC is the reason for the upgrade of NMSBA selectivity. © 2022 Society of Chemical Industry (SCI).

Fabrication of superamphiphobic surface on Cu substrate via a novel and facile dip coating method

Preparation of superamphiphobic surfaces with extreme repellency toward both water and oil remains a time-consuming and complicated task. A superamphiphobic surface was obtained by a special and facile dip coating method with polypropylene and polytetrafluoroethylene as raw materials. The prepared samples have repellency and low viscosity not only to water but also to liquids with low surface tension. The superamphophobic surface also exhibits excellent chemical stability, repels solutions with different pH values and does not fail after long-term soaking in strong acid or alkali solutions. In addition, both water and ethylene glycol can achieve self-cleaning effects on the resulting surface. The preparation process involves no sophisticated equipment and fluorine-containing modifiers. For its advantages in simple operation, low cost and high efficiency, this method has broad prospect of applications and is of great significance to the development of superamphiphobic surface.