Cryptands on a Solid Support for the Separation of Europium from Gadolinium.

With the great demand for europium in green-energy technologies comes the need for innovative methods to isolate the elements. We introduce a solid-liquid extraction method using a 2.2.2-cryptand-modified solid support to separate europium from gadolinium using their differences in electrochemical potential. The method overcomes challenges associated with the separation of those two ions that have similar coordination chemistry in the +3 oxidation state. A competitive adsorption study in the cryptand system between EuII/EuIII and GdIII shows greater affinity for EuII relative to GdIII. After separation from GdIII, Eu was released by oxidizing EuII to EuIII with 99.3% purity. The purity of separated Eu is unaffected by pH between pH 3.0 and 5.5. Overall, we demonstrate that by modifying a solid support with 2.2.2-cryptand, divalent europium can be separated from trivalent gadolinium based on the differences of affinities of 2.2.2-cryptand for the two ions.

A novel green synthesized magnetic biochar from white tea residue for the removal of Pb(II) and Cd(II) from aqueous solution: Regeneration and sorption mechanism.

A novel biochar-based magnetic nanocomposite (GSMB) was prepared from white tea waste via green synthesis method. The sorption properties and regeneration of GSMB were studied using Pb(II) and Cd(II) to better understand its ability in heavy metal recovery. The adsorption kinetics data were modelled using pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion models, while Pb(II) and Cd(II) isotherms were modelled with Langmuir, Freundlich, Temkin and Dubinin-Radushkevich models. Results showed that Pb(II) adsorption was well described by pseudo-second order while the Elovich model best described the Cd(II) adsorption trend, indicating the sorption of Pb(II) and Cd(II) onto GSMB were dominated by chemisoprtion rather than physisorption. Langmuir model gave the best fit to Pb(II) sorption, and the Cd(II) adsorption was well described by Temkin model. The maximum adsorption capacity of Pb(II) and Cd(II) onto GSMB were 81.6 mg/g and 38.6 mg/g, respectively. Scanning electron microscope coupled with energy dispersive x-ray, X-ray diffraction and Fourier transform infrared spectroscopy analyses revealed that iron oxides played a key role during adsorption process and the adsorption mechanisms include surface electrostatic attraction and surface complexation for both metals. Among the five regenerating agents studied, 0.1 M EDTA-2Na was favoured for the desorption of Pb(II) onto GMSB. The findings from the regeneration studies revealed ∼54% of Pb(II) adsorption capacity remained after three sorption-desorption cycles implying the adsorbent could potentially be further reused.

A green approach of biochar-supported magnetic nanocomposites from white tea waste: Production, characterization and plausible synthesis mechanisms.

Green synthesized magnetic nanoparticles were impregnated into biochar matrix (EWTWB) to produce biochar-supported magnetic nanocomposite (GSMB). Instead of chemicals, organic matters in white tea waste extract were used as reductant, surfactant and functional capping materials. Magnetic biochar produced from traditional methods of pyrolysis (PMB) and co-precipitation (Co-PreMB) were prepared to compare their properties with GSMB. Xray Diffraction confirmed the main component of green synthesized particles is Fe3O4. When compared with PMB and Co-PreMB, the Fe3O4 produced by co-precipitation method has higher purity while the products from green synthesis method are complex and contain a small portion of other iron-containing compounds. As a consequence, Co-PreMB has higher saturation magnetisation value than GSMB, which are 31.3 and 11.5 Am2/kg, respectively. GSMB was also found to be less stable in acidic conditions (pH ≤ 4) than Co-PreMB. However, the SEM results exhibited that spherical magnetic nanoparticles (20-50 nm) were successfully formed and distributed on the surface of biochar via green synthesis method while serious aggregation occurred on the surface of Co-PreMB. According to the result of BET, the surface area of GSMB increased dramatically from 0.2 m2/g to 59.7 m2/g. Fourier Transform Infrared spectroscopy and Xray photoelectron spectroscopy results showed the presence of rich oxygen-containing functional groups on the GSMB, The high surface area coupled with rich functional groups on the GSMB made the whole synthesis process an environmentally friendly and greener, to prepare magnetic biochar for application in wastewater treatment.

In Situ/Operando Characterization Techniques: The Guiding Tool for the Development of Li-CO2 Battery.

In recent times, the Li-CO2 battery has gained significant importance arising from its higher gravimetric energy density (1876 Wh kg-1 ) compared to the conventional Li-ion batteries. Also, its ability to utilize the greenhouse gas CO2 to operate an energy storage system and the prospective utilization on extraterrestrial planets such as Mars motivate to practicalize it. However, it suffers from numerous challenges such as (i) the reluctant CO2 reduction/evolution; (ii) solid/liquid/gas interface blockage arising from the deposition of Li2 CO3 discharge product on the cathode; (iii) high overpotential to decompose the stable discharge product Li2 CO3 ; and (iv) instability of the electrolytes. Numerous efforts have been undertaken to tackle these challenges by developing catalysts, improving the stability of electrolytes, protecting the anode, etc. Despite these efforts, due to the lack of a decisive confirmation of the reaction mechanisms of the discharging/charging reactions occurring in the system, the progress of the Li-CO2 battery system has been slow. In situ characterization techniques help overcome ex-situ techniques' limitations by monitoring the processes with the progress of a reaction. The current review focuses on bridging the gap in the understanding of the Li-CO2 batteries by exploring the various in situ/operando characterization techniques that have been employed.

Making waves: Uses of real-time, hyperlocal flood sensor data for emergency management, resiliency planning, and flood impact mitigation.

Flooding is expected to increase due to intensification of extreme precipitation events, sea-level rise, and urbanization. Low-cost water level sensors have the ability to fill a critical data gap on the presence, depth, and duration of street-level floods by measuring flood profiles (i.e., flood stage hydrographs) in real-time with a time interval on the order of minutes. Hyperlocal flood data collected by low-cost sensors have many use cases for a variety of stakeholders including municipal agencies, community members, and researchers. Here we outline examples of potential uses of flood sensor data before, during, and after flood events, based on dialog with stakeholders in New York City. These uses include inputs to predictive flood models, generation of real-time flood alerts for community members and emergency response teams, storm recovery assistance and cataloging of storm impacts, and informing infrastructure design and investment for long-term flood resilience project planning.

Biochar admixture cement mortar fines for adsorptive removal of heavy metals in single and multimetal solution: Insights into the sorption mechanisms and environmental significance.

The combined action of biochar and C-S-H (calcium-silicate-hydrate) in the cement mortars as adsorbents was explored for treating heavy metals from water. The biochar admixture cement mortars were ground to fines for use as adsorbents with the rationale that combined action of Ca, Si, Al etc. based industrial waste with conventional adsorbent biochar could enhance the removal efficiency of contaminants and therefore the overarching aim was to study the removal capacity for three selected heavy metals (Pb2+, Cu2+ and Zn2+) commonly found in the aqueous waste stream. Batch adsorption was carried out on single and multi-metal systems to determine the removal efficiency under varied conditions such as pH, dosage of adsorbent, the effect of contact time and the initial concentration of the adsorbate. For Pb(II), Cu (II) and Zn(II), pH 5 was optimized for single and multi-metal batch sorption studies. A dosage of 20 mg for single metal and 70 mg for multi-metal of an adsorbent dose was found to be sufficient to remove about 70-90% of the three heavy metals in 25 mL solution. Langmuir model best described the isotherm data with maximum adsorption capacities of 476, 81, 123 mg/g for Pb2+, Cu2+ and Zn2+ for BC-40 during single metal adsorption, which were quite comparable to other C-S-H and cement-based adsorbents. The metal hydroxides precipitation, the ion exchange between the Ca2+ and metal ions and metal complexation were explained as plausible mechanisms for the heavy metal removal.

Biochar admixtured lightweight, porous and tougher cement mortars: Mechanical, durability and micro computed tomography analysis.

Currently, the global carbon footprint of cement industry is nearly 7 to 8% and this number is expected to grow in the near future given the continued global demand of cement usage in the construction and other sectors. Additionally, extraction of sand from the coastal and riverine environment is detrimental to ecosystem health and also gives rise to sand mafia in many developing countries. Biochar has the potential to sequester CO2 in cement mortars. The purpose of this study was to valorise a waste biomass (poultry litter) to carbon-rich biochar and utilise as filler material to replace the sand in the range of 10-40% of the total weight in cement. A total of four mix designs each with three replicates at 10%, 20%, and 40% replacement of sand and control (0% biochar addition) were investigated for their mechanical, durability and micro-computed tomography (CT) analysis. The results showed that the flexural strength of the composites at 20% biochar replacement of sand was improved by 26% when compared to control. Biochar addition lowered the thermal conductivity of the cement mortars and was optimised at 10% addition. The density of the mortars decreased ~20% with 40% biochar addition. Micro-CT analysis showed nearly a five-fold increase in the 2-dimensional porosity of the samples, from 2.5% (control) to 12% for samples which had 40% biochar; however, no marked changes were noticed for samples at 20% biochar addition. Taking mortar plastering as an example for 100 m2 area with standard 12 mm thickness revealed that CO2 emissions decreased 20% when sand was replaced with 40% biochar as compared to control specimen. It was concluded that biochar has the potential to replace the sand in the mortars for improving toughness, lowering thermal conductivity and density of the cement composites.

Mechanistic investigations in sono-hybrid (ultrasound/Fe2+/UVC) techniques of persulfate activation for degradation of Azorubine.

Persulfate-based oxidation of recalcitrant pollutants has been investigated as an alternative to OH radical based advanced oxidation processes due to distinct merits such as greater stability and non-selective persistent reactivity of SO4- oxidant species. The present study has attempted to highlight mechanistic features of persulfate-based decolorization of textile dye (Azorubine) using sono-hybrid techniques of activation. Three activation techniques, viz. sonolysis, Fe2+ ions and UVC light and combinations thereof, have been examined. UVC is revealed to be the most efficient decolorization technique. The mechanism of sonolysis (i.e. thermal activation of persulfate in the bubble-bulk interfacial region) is revealed to be almost independent of the mechanism of UVC. Fe2+ activation is revealed to have an adverse interaction with UVC due to scavenging of sulfate radicals by Fe2+ ions. The best hybrid activation technique for persulfate-based degradation and mineralization of Azorubine is UVC+ultrasound. Due to independent mechanisms, degradation and mineralization of the dye obtained with simultaneous application of UVC and ultrasound is nearly equal to the sum of degradation and mineralization obtained using individual techniques.