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- A new application of solvent extraction to separate copper from extreme acid mine drainage producing solutions for electrochemical and biological recovery processesPublication . Nobahar, Amir; Melka, Alemu Bejiga; Pusta, Alexandra; Lourenço, João P.; Carlier, Jorge; Costa, Maria ClaraOver the last decade, AMD waters have gained more attention as a potential source of metals due to the emerging need to recover or recycle metals from secondary resources. Metals recovery supports sustainability and the development of a circular economy with benefits for resource conservation and the environment. In this study, five extractants (Acorga M5640, LIX 54, LIX 622, LIX 622 N, and LIX 864) diluted (15% (v/v)) in Shell GTL with 2.5% (v/v) octanol were compared and evaluated for Cu recovery from an extreme AMD sample (5.3 +/- 0.3 g/L Cu) collected at the inactive Sao Domingos Mine in the Iberian Pyrite Belt of Portugal. Of the five extractants, Acorga M5640 showed the best selective efficiency. Further tests showed that 30% (v/v) of this extractant was able to selectively extract approximate to 96.0% of the Cu from the AMD in one extraction step and all of the remaining Cu (to below detection) in three steps. Among the different stripping agents tested, 2 M sulfuric acid was the most efficient, with approximate to 99% of the Cu stripped, and the recyclability of the organic phase was confirmed in five successive cycles of extraction and stripping. Furthermore, contact time tests revealed that the extraction kinetics allows the transfer of approximate to 97% of the Cu in 15 min, and aqueous to organic phase ratios tests demonstrated a maximum loading capacity of approximate to 16 g/L Cu in the organic phase. Raising the concentration of Cu in the stripping solution (2 M sulfuric acid) to approximate to 46 g/L through successive striping steps showed the potential to recover elemental Cu using traditional electrowinning. Finally, a biological approach for Cu recovery from the stripping solution was evaluated by adding the supernatant of a sulfate-reducing bacteria culture to make different molar ratios of biogenic sulfide to copper; ratios over 1.75 resulted in precipitation of more than 95% of the Cu as covellite nanoparticles.
- Recovery of catalytic metals from leaching solutions of spent automotive catalytic converters using plant extractsPublication . Nobahar, Amir; Carlier, Jorge; Costa, Maria ClaraThis study investigates the potential of hydroalcoholic extracts of Cistus ladanifer L., Erica Andevalensis and Rubus idaeus L. as a green method for the recovery of platinum group metals (PGMs) from both synthetic unimetallic solutions and multimetallic solutions obtained from the leaching of two different spent automotive catalytic converters (SACC). Experiments with unimetallic solutions revealed that E. andevalensis and R. idaeus extracts could separate about 70% of Pd and less than 40% of other tested metals (Al, Ce, Fe and Pt) from the solutions. Then, application of the plant extracts to two different SACCs leachates showed that E. andevalensis and R. idaeus extracts can induce high precipitation (> 60%) of Pd and Pt with co-precipitation of less than 20% of other metals. UV-Visible spectra analysis confirmed the bio-reduction of Pd2+ ions into Pd-0 nanoparticles by R. idaeus extract, and Fourier transform infrared spectroscopy (FTIR) analysis revealed the contribution of functional groups of the phytochemicals present in the extract (such as phenols, flavonoids and anthocyanins) in the Pd2+ bio-reduction and stabilization. Afterward, scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX) analysis of the precipitate obtained from one leachate with R. idaeus extract demonstrated the presence of Pd particles along with organic compounds and particles containing other metals. Therefore, particles were subjected to a washing step with acetone for further purification. Finally, scanning transmission electron microscopy with energy dispersive X-ray spectroscopy (STEM-EDX) analysis showed the high purity of the final Pd particles and high-resolution STEM allowed to determine their size variation of 2.5 to 17 nm with an average Feret size of 6.1 nm and confirmed their crystalline structure with an interplanar lattice distance of similar to 0.22 nm. This green approach offers various benefits including simplicity of Pd separation from the leachates as valuable nanoparticles that makes the process more feasible from economic and environmental standpoints. A process cost of similar to 20 $/g of Pd particles recovered was estimated (excluding manpower).
- Zinc recovery from an extreme copper-free acid mine drainage: studying the prior separation of ferric iron by solvent extraction using AliCy and/or alkalinizationPublication . Nobahar, Amir; Melka, Alemu Bejiga; Marín-Beltrán, Isabel; Neves, Luiz; Costa, Maria Clara; Dias Carlier, JorgeZn recovery attempts from a copper-free extreme Acid Mine Drainage with similar to 53 g/L Fe and similar to 2 g/L Zn revealed Fe co-extraction in solvent extraction with 0.9 M D2EHPA or a mixture of 0.72 M D2EHPA and 0.18 M Cyanex 272, and simultaneous precipitation of Fe during zinc sulfide recovery through biogenic sulfide addition. Therefore, alkalinization, solvent extraction with the self-prepared ionic liquid AliCy diluted in kerosene, and combinations of both these methods were studied for the separation of ferric iron (Fe3+) from such water, prior to Zn recovery. The most efficient strategy tested was a solvent extraction cycle with AliCy followed by alkalinization of its aqueous raffinate to pH 3.25 or 3.5. As a result of this approach, similar to 92% of Fe3+ is separated by SX and the remaining is removed by precipitation, with just similar to 12% or similar to 17% Zn losses, respectively. Afterwards, the highest Zn recovery from water resulting from such combination of processes was achieved by precipitation through addition of biogenic sulfide at pH = 3.5. The obtained precipitates are nanoparticles of Wurzite and Sphalerite (ZnS) of sizes between 2 to 22 nm agglomerated into larger structures. This work shows for the first time the potential of AliCy to separate Fe3+ from acidic multimetallic solutions, a known contaminant of several metal recovery processes.
- A review of plant metabolites with metal interaction capacity: a green approach for industrial applicationsPublication . Nobahar, Amir; Carlier, Jorge Dias; Miguel, Maria Graca; Costa, Maria ClaraRapid industrial development is responsible for severe problems related to environmental pollution. Many human and industrial activities require different metals and, as a result, great amounts of metals/heavy metals are discharged into the water and soil making them dangerous for both human and ecosystems and this is being aggravated by intensive demand and utilization. In addition, compounds with metal binding capacities are needed to be used for several purposes including in activities related to the removal and/or recovery of metals from effluents and soils, as metals' corrosion inhibitors, in the synthesis of metallic nanoparticles and as metal related pharmaceuticals, preferably a with minimum risks associated to the environment. Plants are able to synthesize an uncountable number of compounds with numerous functions, including compounds with metal binding capabilities. In fact, some of the plants' secondary metabolites can bind to various metals through different mechanisms, as such they are excellent sources of such compounds due to their high availability and vast diversity. In addition, the use of plant-based compounds is desirable from an environmental and economical point of view, thus being potential candidates for utilization in different industrial activities, replacing conventional physiochemical methods. This review focuses on the ability of some classes of compounds that can be found in relatively high concentrations in plants, having good metal binding capacities and thus with potential utilization in metal based industrial activities and that can be involved in the progressive development of new environmentally friendly strategies.
- Photochemical oxidation of polyethylene terephthalate microplastics adsorbed on sand and silica surfacesPublication . Q. V. da Costa, Camila; Nobahar, Amir; Egea-Corbacho, Agata; Jockusch, Steffen; Power, Deborah Mary; Ramamurthy, Vaidhyanathan; Silva, José Paulo daThe environmental contamination by plastics, microplastics, and related compounds is a major concern. While the detection and release of micro- and nanoparticles from these materials have been widely studied, the formation and release of molecules resulting from their degradation in the environment have been overlooked. This work presents a study of the products released from poly(ethylene terephthalate) (PET) irradiated as pure particles and adsorbed on silica and sand surfaces under different irradiation conditions. The role of oxygen was also evaluated. The products were identified by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-high resolution mass spectrometry (LC-HRMS). The main released molecules can be accounted for by considering the cleavage of alpha- and beta-bonds next to the ester moiety of the polymer chain. Volatile products such as benzene as well as monomer units of the polymer and related products were identified. In the presence of oxygen, acetic acid and products resulting from hydroxylation at the benzenic ring or at the ethyl moiety were detected. Adsorption on silica and sand has little effect on the photoproduct distributions. The irradiation at 360 nm leads to distributions similar to the ones observed at 257 nm, but the reaction rate is lower. The identified product ethylene terephthalate is a marker of PET plastics and particles and can therefore be used to evaluate the environmental contamination by this polymer material.
- Acid mine drainage bioremediation using bacteria enriched from the confluence zone between its flow and treated sewagePublication . Nobahar, Amir; Fitas, Eduardo Trindadde; Costa, Maria Clara; Carlier, JorgeSediments from the confuence zone between an acid mine drainage stream and a water stream receiving the efuent from a municipal wastewater treatment plant were inoculated in a Postgate B medium base having methanol, glycerol, or etha[1]nol as carbon source/electron donor, over a pH range between 2.00 and 6.00, aiming to obtain native cultures enriched in acidophilic/acid-tolerant sulfate-reducing bacteria. The most efective sulfate reduction observed in acidic conditions was in the enrichment cultures with methanol. Thus, the microbial consortium enriched in these conditions was further used in acid mine drainage bioremediation experiments at an initial pH of 4.50 and using diferent doses of nutrients medium base and methanol as carbon source/electron donor. The most promising results, with more than 99% removal of metals, were obtained in the mixture of 20% Postgate B medium base plus 80% acid mine drainage (v/v), which corresponds to 0.115% basal salts and 0.02% yeast extract (w/v). Metataxonomic analysis based on 16S rRNA gene sequences showed the presence of Desulfosporosinus spp. in all enrichment cultures, with the highest relative abundance in cultures at pH 4.00 with methanol. Furthermore, metataxonomic analysis in the acid mine drainage remediation tests revealed the presence of Desulfosporosi[1]nus spp. in all tested conditions. In addition, the study also revealed Clostridium members in all tests. Plus, their relative abundances were related to the dose of nutrient medium base and in balance with the abundances of Desulfosporosinus spp.
- Innovative combination of chemical and biological strategies for the recovery of metals from metal-bearing wastewaters and leachatesPublication . Nobahar, Amir; Costa, Maria Clara; Carlier, JorgeThis dissertation applied pioneering approaches that benefits the potential of both solvent extraction (SX) and bio-recovery strategies based on the use of bacterial communities and plant extracts as metal separation and recovery technique. In this regard, metal recovery from an extreme acid mine drainage (AMD) was initially performed for Cu SX with Acorga M5640 that was then stripped with 2M sulfuric acid, allowing to rise the Cu concentration to over 46 g/l, which was then recovered as CuS nanoparticles through the addition of biogenic sulfide. Thereafter, the rafiinate from the mentioned SX process, was subjected to Zn recovery studies. In these studies, Fe3+ was found to be nuisance in Zn recovery and was separated from the solution by SX with AliCy followed by alkalinization of its aqueous raffinate to pH 3.25 or 3.50. Thereafter, Zn was recovered as ZnS nanoparticles through precipitation by biogenic sulfide at pH=3.5. In addition, AMD remediation studies were investigated by applying acidophilic SRB consortium that was obtained from the enrichment of sediments of an inactive Cu mine at pH 4.00 with methanol as carbon source. The metal removal from AMD by the mentioned consortium revealed promising results when a 20% (v/v) supplement of Postgate B base (except lactate) was added to AMD. Metataxonomic analysis showed the presence of Desulfosporosinus genus in all enrichment and AMD remediation studies, with highest relative abundances in cultures enriched with methanol at pH 4.00 and in AMD remediation tests with lowest Postgate base supplements. Another part of this study investigated the potential of plant extracts in PGMs and precious metals recovery from different leachates. These studies revealed the high potential of red raspberry (Rubus Idaeus L.) leaves hydroalcoholic extract in Pd precipitation (>60%) from spent autocatalytic converters leachates as nanoparticles and also in Au precipitation (~96%,) from printed circuit boards leachates as microparticle clusters of Au nanoparticles. Contribution of functional groups of the phytochemicals present in the extracts were studied in the Pd and Au ions’ bio-reduction and bio-stabilization. Keywords: acid mine drainage, metal leachate, metal bio-recovery, solvent extraction, sulfate-reducing bacteria, nanoparticles green synthesis