Sonocatalytic recovery of ceria from graphite and inhibition of graphite erosion by ionic liquid based platinum nanocatalyst

Use of ultrasound as an intensified non-destructive decontamination technique for processing graphite limits its reusability beyond a few number of decontamination cycles due to the exfoliation of graphite due to cavitation effects. The current work establishes that the use of platinum nanoparticles in the leachant reduces the erosion of graphite substrate due to cavitation. It presents an improved way of sonochemical recovery of ceria using a mixture of nitric acid, formic acid and hydrazinium nitrate in the presence of platinum nanoparticles and ionic liquid. The platinum nanoparticles catalyst in ionic liquid prevented the generation of the carbon residue due to the combined effect of denitration and reduced sonication. The presence of the catalyst showed a fivefold increase in dissolution kinetics of ceria as well as absence of graphite erosion, facilitating better chances of graphite recycling than the decontamination without the catalyst. The catalytic approach offers a better recycle strategy for graphite with reduced exfoliation and NOx generation due to denitration, making it a more sustainable decontamination process. Since ceria is used as a surrogate for plutonium oxide, the results can be extended to decontaminate such deposits clearly establishing the utility of the presented results in the nuclear industry.

Sonochemical recovery of uranium from nanosilica-based sorbent and its biohybrid

Use of nanomaterials to remove uranium by adsorption from nuclear wastewater is widely applied, though not much work is focused on the recovery of uranium from the sorbents. The present work reports the recovery of adsorbed uranium from the microstructures of silica nanoparticles (SiO2M) and its functionalized biohybrid (fBHM), synthesized with Streptococcus lactis cells and SiO2M, intensified using ultrasound. Effects of temperature, concentration of leachant (nitric acid), sonic intensity, and operating frequency on the recovery as well as kinetics of recovery were thoroughly studied. A comparison with the silent operation demonstrated five and two fold increase due to the use of ultrasound under optimum conditions in the dissolution from SiO2M and fBHM respectively. Results of the subsequent adsorption studies using both the sorbents after sonochemical desorption have also been presented with an aim of checking the efficacy of reusing the adsorbent back in wastewater treatment. The SiO2M and fBHM adsorbed 69% and 67% of uranium respectively in the second cycle. The adsorption capacity of fBHM was found to reduce from 92% in the first cycle to 67% due to loss of adsorption sites in the acid treatment. Recovery and reuse of both the nuclear material and the sorbent (with some make up or activation) would ensure an effective nuclear remediation technique, catering to UN's Sustainable Development Goals.

Cavitation-assisted decontamination of yttria from graphite of different densities

Yttria coated graphite crucibles are widely used to handle molten refractory and radioactive metals like uranium and plutonium. However, the coated layer suffers damages like cracking and peeling off owing to thermal cycles. As a result, removal of the yttria layer from the graphite surface is essential to ensure reuse of the crucible and minimization of radioactive waste. The present work investigates intensified dissolution of yttria from the coated graphite samples using ultrasound as a non-destructive decontamination technique to recycle the graphite substrate. The optimum conditions established for maximum dissolution were 8 M as acid strength, frequency of 30 kHz, temperature of 45 °C and power density of 8 W cm^-2 that resulted in maximum dissolution of 52% in 30 min. Use of an oxidant H₂O₂ to the acid, did not yield any improvement in the dissolution kinetics, instead, increased oxidation of the graphite substrate was observed, leading to the anomalous weight gain of the graphite substrate despite surface erosion. Effect of ultrasound on the dissolution was pronounced, with almost a threefold increase compared to dissolution performed under silent conditions. Rates of dissolution of yttria from the substrate of different densities and pore size distribution were also studied. The dissolution was slowest from graphite of density 1.82 g cm^-3 as the pore size distribution was conducive to accommodate the yttria particles. The dissolution in nitric acid followed ash layer diffusion controlled kinetics. The study has demonstrated the efficacy of application of ultrasound for accelerated decontamination of graphite substrates.

Intensified dissolution of uranium from graphite substrate using ultrasound

Decontamination of graphite structural elements and recovery of uranium is crucial for waste minimization and recycle of nuclear fuel elements. Feasibility of intensified dissolution of uranium-impregnated graphite substrate using ultrasound has been studied with objective of establishing the effect of operating parameters and the kinetics of sonocatalytic dissolution of uranium in nitric acid. The effect of operating frequency and acoustic intensity as well as the acid concentration and temperature on the dissolution of metal has been elucidated. It was observed that at lower acid concentrations (6 M-8 M), the dissolution ratio increases by 15% on increasing the bath temperature from 45 to 70 °C. At higher acid concentration (>10 M), the increase was only around 5-7% for a similar change in temperature. With 12 M HNO₃, pitting was also observed on the graphite surface along with erosion due to high local reaction rates in the presence of ultrasound. For higher frequency of applied ultrasound, lower dissolution rate of uranium was observed though it also leads to high rates of erosion of the substrate. It was thus established that suitable optimization of frequency is required based on the nature of the substrate and the choice of recycling it. The dissolution rate was also demonstrated to increase with acoustic intensity till it reaches to the maximum at the observed optimum (1.2 W/cm² at 33 kHz). Comparison with silent conditions revealed that enhanced rate was obtained due to the use of ultrasound under optimum conditions. The work has demonstrated the effective application of ultrasound for intensifying the extent of dissolution of metal.

Nutritional and therapeutic potential of bael (Aegle marmelos Corr.) fruit juice: a review

Purpose

– The purpose of this paper is to summarize the scientific information of various qualities of bael fruit juice used in traditional system of medicine for variety of purposes. Utilization of bael fruit juice in day-to-day life has great nutritional, therapeutic, and commercial importance. Bael fruit contains nutrients like vitamins (riboflavin), minerals, trace elements, energy and phytochemicals, including flavonoids, polyphenols and antioxidants, that have been shown to have varied health benefits. In past few decades, bael has been extensively studied for its medicinal properties by advanced scientific techniques, and a variety of bioactive compounds like marmelosin, tannins, alkaloids, coumarins, steroids, rutacine, y-sitosterol, psoralin, xanthotoxin, scopolotein, aegelemine, aegeline, marmeline, fragrine, dictamine, cinnamide and different derivatives of cinnamide have been isolated from its fruit juice.

Design/methodology/approach

– The medicinal value of bael fruit is very high when the harvests just begin to ripen. As a result, it has a high demand as alternative medicine for curing the diseases like diabetes, high cholesterol, peptic ulcer, inflammation, diarrhea and dysentery, constipation, respiratory infection. Furthermore, the bael fruit juice has anticancer, cardio protective, antibacterial, antifungal, radio protective, antipyretic, analgesic, antioxidant, antiviral, anthelmintic and anti-inflammatory, hepatoprotective, wound healing properties. The ripe fruit juice is aromatic, has cooling and laxative effects, and arrests secretion or bleeding.

Findings

– The unripe or half-ripe fruit juice is good for digestion, useful in preventing or curing scurvy, and it strengthens the stomach action. It helps in the healing of ulcerated intestinal surfaces and has appreciable activity against intestinal pathogenic organisms. The present review summarizes the scientific information of various qualities of bael fruit juice used in traditional system of medicine for a variety of purposes.

Originality/value

– It is quite evident from this review that bael is an important medicinal herb and extensively used in Ayurveda, Siddha and other medicinal systems. Bael fruit juice is an excellent source of water and natural sugar and is important principally for containing vitamins, minerals, phytochemicals, antioxidants, pigments, energy, organic acids, dietary fiber and other food components, which are the key factors in the medicinal value of this plant. Moreover, mechanisms of action of a few bioactive compounds have been identified so far.