The effect of UV-C irradiation and EDTA on the uptake of Co2+ by antimony oxide in the presence and absence of competing cations Ca2+ and Ni2+

In nuclear power plants and other nuclear facilities the removal of cobalt from radioactive liquid waste is needed to reduce the radioactivity concentration in effluents. In liquid wastes containing strong organic complexing agents such as EDTA cobalt removal can be problematic due to the high stability of the CoEDTA complex. In this study, the removal of cobalt from NaNO3 solutions using antimony oxide (Sb2O3) synthesized from potassium hexahydroxoantimonate was investigated in the absence and presence of EDTA. The uptake studies on the ion exchange material were conducted both in the dark (absence of UVlight) and under UV-C irradiation. Ca2+ or Ni2+ were included in the experiments as competing cations to test the selectivity of the ion exchanger. Results show that UV-C irradiation noticeably enhances the cobalt sorption efficiency on the antimony oxide. It was shown that nickel decreased the sorption of cobalt to a higher extent than calcium. Finally, the sorption data collected for Co2+ on antimony oxide was modeled using six different isotherm models. The Sips model was found to be the most suitable model to describe the sorption process. The Dubinin-Radushkevich model was further used to calculate the adsorption energy, which was found to be 6.2 kJ mol-1. (c) 2021 Korean Nuclear Society, Published by Elsevier Korea LLC. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Peer reviewe

Efficient separation of precious metals from computer waste printed circuit boards by hydrocyclone and dilution-gravity methods

To fulfill the different aspects of green chemistry and to achieve full use of the secondary resources (waste printed circuit boards (WPCB)), the necessity of developing green methods for recovery of precious metals (Au, Pd, and Ag) is highly demanded. In this study, a novel environment-friendly physical separation approach; the combination of crushing, grinding, sieving as pretreatment steps alongside hydrocyclone and the dilution-gravity method (DGM) as the main final steps; is proposed. Inductively coupled plasma-mass spectrometry (ICP-MS), atomic absorption spectroscopy (AAS), and energy-dispersive X-ray spectroscopy (EDS) characterization methods were utilized to understand the effects of different separation steps applied in this research. The size and shape of grinded materials and the ones produced after hydrocyclone and DGM were evaluated using scanning electron microscopy. The results showed that the sieving step separated the highest gold fraction in the finer classification (<75 μm) while placed the copper (70 wt.%) into the coarser contents. The overflow to underflow outlet diameter ratio and inlet pressure was evaluated to determine the separation efficiency of a hydrocyclone effect of parameters. In the best-case scenario at 3 bar hydrocyclone operation pressure where the overflow to underflow outlet diameter (Do/Du) was 6.5, the highest metal fraction (87 wt.%) was achieved in the sink of the DGM. In this case, the total separation efficiency of gold, palladium, silver, and copper was 75%, 78%, 64%, 72%, respectively. Thus, this study demonstrates the feasibility of utilizing the sieving as mentioned above classification pretreatment steps followed by hydrocyclone and DGM methods as promising approaches for recovering precious metals from WPCBs that contain annually almost 50 million tons of e-waste

Utilization of sludge-based alginate beads for the application of rare earth elements (REEs) recovery from wastewater : A waste to resource approach

The main purposes of this research work were to realize the potential of sludge valorization by converting the sludge into adsorbents and to investigate the performance of sludge-based adsorbents for rare earth elements (REEs) recovery from dilute aqueous solutions. Hydrochloric acid and Fenton reagents were employed as pretreatment procedures to enhance the surface area and adsorption yield. Following this, sludge-based alginate beads were prepared by using HCl treated (HT) and Fenton treated (FT) sludge materials. The chemical composition and surface chemistry of sludge-based adsorbent beads were thoroughly analyzed by state-of-the-art analytical techniques, such as Scanning Electron Microscope (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Brunauer-Emmett-Teller (BET) analysis. The prepared beads were then investigated for the recovery of REEs. The batch adsorption studies revealed that the FT sludge beads performed better in comparison to the HT sludge beads. Among REEs, the HT- and FT-sludge beads demonstrated higher affinity towards Sm3+ ions, displaying the maximum adsorption capacities of 2.83 mg/g and 4.16 mg/g, respectively, in a multi-component system (C o = 25 ppm of each REE; pH = 5, t = 24 h and dosage = 5 g/L). In conclusion, the results from this work showed that the prepared sludge-based alginate beads can be used for REEs recovery from diluted waste streams and the tested sludge treatment options were also found effective in converting the waste to resource i.e., sludge to adsorbent for REEs recovery.Peer reviewe

The stability of green nanoparticles in increased pH and salinity for applications in oil spill-treatment

AbstractThe melting of the permanent ice cover in the arctic region due to the climate change is increasing industrial activity in the region and also consequently there is the enhanced risk for oil-spills. Therefore, there is a need for the development of green chemicals for oil-spill treatment in the arctic region. Carboxymethylated chitosan nanoparticles were cross-linked with Mg, Ca or Sr and the stability of nanoparticles in increased pH and salinity was studied. The carboxymethylation of chitosan was investigated with FTIR and the nanoparticles were studied with dynamic light scattering and SEM. The nanoparticles cross-linked with Ca ions were found to be most stable in increased salinity and pH. The interaction of Ca cross-linked nanoparticles with dodecane in water was also demonstrated. The nanoparticles showed promising potential for applications in oil-spill treatment

Electrochemical Approach for Advanced Flow Reactors via Additive Manufacturing of High Surface Area Ti-6Al-4V Anode

Electrochemical processes use expensive noble metal-based anodes which limit industrial implementation. In this study, a noble-metal-free Ti-6Al-4V anode is introduced in an advanced flow reactor. We demonstrate that the 3D additively manufactured electrode can provide a more projected surface area and facilitate anodic reactions under controlled electrolyte conditions. Alkaline NaOH and KOH electrolytes act as anodic electrolytes that are toxic compounds-free and enable corrosion control. Impedance and voltammetry responses to electrochemical reactions are studied. The electrochemical active surface area of the 4 rods scaffold geometry is 42 times higher than a flat plate anode. Therefore, improved charge transfer is achieved in the flow reactor incorporating the 3D Ti-6Al-4V electrode due to the increased surface area and wettability. The structure of almost non-conductive passivation on a flat plate anode is changed to unstable passivation due to the 3D scaffold structure. This enables effective charge transfer of 911 mA cm−2 at higher potentials up to 5 V for 1.5 m KOH in a non-flow condition. Furthermore, a 1 m KOH solution delays metal ion dissolution from the anode surface by acting as a corrosion-controlling medium. 3D Ti-6Al-4V is likely to be an affordable alternative anode in alkaline environmentally friendly electrochemical applications

A powdered orange peel combined carboxymethyl chitosan and its acylated derivative for the emulsification of marine diesel and 2T-oil with different qualities of water

The traces of hazardous chemicals used in oil spill response have harmed marine creatures with long-term cytoxic impacts, so, a greener alternative is to use biodegradable components in the dispersant formulation. This study demonstrates the efficiency of carboxymethylated and acylated chitosan combined with powdered orange peel (OP-D) in the emulsification of marine diesel and 2 T-oil with different qualities of water. OP-D particles undergo Pickering emulsions, whereas the amphiphilic behaviour of the Blend and hydrophobically modified carboxymethyl chitosan-orange peels (CSOP-A) favours conventional emulsions through steric and electrostatic stabilization. The emulsion formation rate was maximum with OP-D in saline water and autonomous of the water quality with Blend. Additionally, different hydrophobic moieties on the surface of the Blend and CSOP-A affected the oil droplets' stabilization rate. Changing pH altered the surface properties of particles and hence the nature of the formed emulsion range from gel-like to creamy, suggesting particle-particle to particle-oil interactions. An increase in electrolyte concentration enhanced the coalescence rate of marine diesel with CSOP-A. The oil droplet size in the formed emulsion increases with a temperature decrease up to 2 °C, and the emulsion stabilization rate wasPeer reviewe

Sähkökemiallinen molekyylikytkin

Tämän työn tarkoitus oli löytää sähkökemialliseksi molekyylikytkimeksi sopiva kuparikompleksi. Kolmen erilaisen kompleksin rakenteita ja ominaisuuksia analysoitiin mittausten ja kirjallisuuden pohjalta. Kompleksien sähkökemiaa tutkittiin syklisellä voltammetrialla. Kirjallisuusosassa käsiteltiin molekyylikytkinsovelluksia ja esiteltiin siirtymämetallikompleksit ja niiden sähkökemialliset ominaisuudet. Kompleksien UV-VIS-absorptiospektrit mitattiin eri liuottimissa. Spektreihin vaikuttivat sekä ligandit että käytetty liuotin. Absorptiospektreissä voitiin nähdä myös muutoksia, kun kompleksit pelkistettiin kemiallisesti. Syklisellä voltammetrialla tutkittiin kuparikompleksien hapetus-pelkistys -reaktioiden reversiibeliyttä ja reaktiomekanismeja. Cu(py)2(CO2Ph)2 havaittiin liian epästabiiliksi kytkinsovelluksia ajatellen. Cu(bipy)(CO2Ph)2H2O:n reaktiomekanismiksi arveltiin kvasireversiibeliä elektroninsiirtoa seuraava disproportioituminen, mutta simuloitujen käyrien muoto ei vastannut täysin mitattujen käyrien muotoa. Cu(TMEDA)(CO2Ph)2:n elektroninsiirtoreaktio havaittiin hyvin hitaaksi. Komplekseja yritettiin syntetisoida myös suoraan kultaelektrodin pinnalle, mutta varmoja todisteita synteesin onnistumisesta ei vielä saatu. Jatkossa erilaisia menetelmiä molekyylikerrosten muodostamiseen elektrodien pinnalle voidaan tutkia. Koordinaatiogeometrian ja hitaan elektroninsiirtoreaktion perusteella voidaan olettaa, että Cu(TMEDA)(CO2Ph)2 sopii parhaiten kytkinsovelluksiin