Browsing by Author "Rosales, Emilio"
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- Electro-osmotic transport of nano zero-valent iron in Boom ClayPublication . Rosales, Emilio; Loch, J. P. Gustav; Ferreira, CéliaOne ofthe many problems thatimpede the successful remediation of soil and groundwater contaminated with chlorinated hydrocarbons occurs when pollutants diffuse into low permeability zones, and become difficultly accessible. Remediation by reductive dechlorination using nanoscale zero-valent iron (nZVI) is possible, but its delivery into contaminated hot spots is difficult using solely hydraulic gradients. Recently, electrokinetics has been proposed to transport nZVI, with the assumption that both electrophoresis and electro-osmosis are involved. However, so far no study has focused solely on transport driven by electro-osmotic flow. This driving force could significantly improve field remediation, allowing nZVI to reach low permeability hotspots. This work describes the experiments carried out to evaluate if nanoscale zero-valent iron can be transported by electro-osmotic advection in a dense clay using a specifically designed laboratory apparatus. It explores how working parameters (such as voltage, injection point and pH) influence transport, and provides an insight into the subsurface behaviour of nanoparticles using micro-XRF. The results confirm the transport of nZVI by electro-osmotic advection, with an electro-osmotic conductivity in the range (0.5-1.0)·10−10 m2V−1s−1. The presence of nZVI decreases electro-osmotic conductivities by approximately half and affects geochemical conditions of the system, inducing sharper pH profiles and enhancing cation exchange in the clay.
- Green zero-valent iron nanoparticles synthesised using herbal extracts for degradation of dyes from wastewaterPublication . Rosales, Emilio; Sanromán, Ángeles Sanrománb; Ferreira, CéliaNano zero-valent iron (nZVI) is an effective way to degrade different compounds. The green synthesis of nZVI showed potential as an alternative to NaBH4 synthesised nanoparticles. In this study, a comparison among different nanoparticles (green, bare and polyacrylic acid coated) was carried out. Based on the higher stability of green nanoparticles, new extracts obtained from herbal aromatic leaves (rooibos, lemon verbena and camphora) were evaluated for the synthesis of nZVI. Two different extraction procedures were compared: decoction and infusion. The results showed that using a constant temperature of 100°C during the extraction increases the quantity of polyphenols and antioxidants extracted. The antioxidant content was highest in green tea (Camellia sinensis), but reactivity of synthesised nanoparticles of zero-valent iron is higher when using rooibos (Aspalathus linearis) extracts. Synthesised rooibos green nZVIs have been applied to degrade a textile dye, Reactive black 5, directly and as catalyst in an electro-Fenton process, reaching a decolourisation of 90% and 70% in 60 min, respectively. The synthesised nanoparticles demonstrated a good performance in the treatment of the polluted wastewater.