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•Good performance on arsenic removal is achieved with composite materials.•Chitosan beads show good mechanical properties both in batch and column experiments.•Magnetic materials are ...obtained with specific metal solution/plant extract ratios.•Magnetic properties are only observed during nanoparticle immobilization in chitosan beads.
New magnetic hybrid materials were developed by the encapsulation of iron oxide nanoparticles into a chitosan matrix. A green synthesis method to obtain metallic nanoparticles was conducted using eucalyptus extract as reducing agent. Well-formed iron oxide nanoparticles were successfully synthesized. Under precise conditions, the encapsulation of the synthesized iron oxide nanoparticles in chitosan beads leads to the formation of magnetic hybrid organic/inorganic materials. The XRD pattern of these materials shows peaks that match with structure similar to maghemite for those materials showing magnetic properties. The new hybrid materials were proved as sorbent in a complete arsenic removal study (pH dependence, kinetic and equilibrium experiments) showing good features and sorption capacity. The large scale sorption capacity of the new material was also successfully proved in a continuous flow study using a column filled with beads of the hybrid magnetic material.
The extensive use of silver nanoparticles (AgNPs) in consumer products, medicine, and industry leads to their release into the environment. Thus, a characterization of the concentration, size, fate, ...and toxicity of AgNPs under environmental conditions is required. In this study, we present the characterization and optimization of an asymmetric flow field-flow fractionation (AF4) system coupled with UV/Vis spectrophotometer and dynamic light scattering (DLS) detector as a powerful tool for the size separation and multi-parameter characterization of AgNPs in complex matrices. The hyphenated AF4-UV/Vis-DLS system was first characterized using individual injections of the different size fractions. We used electrostatically stabilized AgNPs of 20-, 50-, and 80-nm nominal diameters coated with lipoic acid. We investigated the effect of applied cross-flows, carrier solutions, focus times, and quantity of injected particles on the nature of the AF4 fractograms and on the integrity of the AgNPs. Best size separation of a 1:1 mixture of 20- and 80-nm AgNPs was achieved using cross-flows of 0.5 and 0.7 mL/min with 1 mM NaCl and 0.05% v/v Mucasol as carrier solutions. We also researched the behavior of AgNPs in natural waters using the hyphenated AF4-UV/Vis-DLS system, under determined optimal conditions.
Graphical abstract
Schematic and photograph of the AF4 setup with numbered hardware devices. Dashed lines represent electrical connections; continuous lines represent fluidic connections. For a better overview, not all fluidic connections between pump/6-way valve (2) and the Eclipse AF4 device (3) are shown in the schematic. The fluorescence detector (FL (7)) was not used in the study presented herein.
•The STEMM-CCS project completed a unique field experiment in the central North Sea.•The experiment mimicked a leakage of CO2 from an offshore storage site.•A custom setup released CO2 into shallow ...sediment at relevant leakage rates.•Diverse established methods and novel technologies characterised the CO2.•The outcomes show such a release can be detected, attributed, and quantified.
Carbon capture and storage (CCS) is a key technology to reduce carbon dioxide (CO2) emissions from industrial processes in a feasible, substantial, and timely manner. For geological CO2 storage to be safe, reliable, and accepted by society, robust strategies for CO2 leakage detection, quantification and management are crucial. The STEMM-CCS (Strategies for Environmental Monitoring of Marine Carbon Capture and Storage) project aimed to provide techniques and understanding to enable and inform cost-effective monitoring of CCS sites in the marine environment. A controlled CO2 release experiment was carried out in the central North Sea, designed to mimic an unintended emission of CO2 from a subsurface CO2 storage site to the seafloor. A total of 675 kg of CO2 were released into the shallow sediments (∼3 m below seafloor), at flow rates between 6 and 143 kg/d. A combination of novel techniques, adapted versions of existing techniques, and well-proven standard techniques were used to detect, characterise and quantify gaseous and dissolved CO2 in the sediments and the overlying seawater. This paper provides an overview of this ambitious field experiment. We describe the preparatory work prior to the release experiment, the experimental layout and procedures, the methods tested, and summarise the main results and the lessons learnt.
Crystalline molecular sieves with large pores and high adsorption capacities have many potential applications. Of these materials, zeolites are of particular interest owing to their stability in a ...wide range of experimental conditions. An aluminophosphate with very large circular channels5 containing 18 oxygen atoms (18-ring channels) has been synthesized, but in the search for large-pore zeolites, most of the materials which have been synthesized up to now contain only 14-ring channels; the synthesis of zeolites with larger ring structures has been believed to be hindered by the low Si-O-Si bond angles available. A silicogaloaluminate (ECR-34) with unidirectional 18-ring channels was recently reported, but exhibited low micropore volume, thus rendering the material less attractive for catalytic applications. Here we report the structure and catalytic activity of the silicogermanate zeolite ITQ-33; this material exhibits straight large pore channels with circular openings of 18-rings along the c axis interconnected by a bidirectional system of 10-ring channels, yielding a structure with very large micropore volume. The conditions for synthesis are easily accessible, but are not typical, and were identified using high-throughput techniques.
Total alkalinity (TA) is a variable that reflects the acid buffering capacity of seawater, and is key to studies of the global carbon cycle. Daily and seasonal TA variations are poorly constrained ...due to limitations in observational techniques, and this hampers our understanding of the carbonate system. High quality and high temporal resolution TA observations are required to constrain the controlling factors on TA. Estuarine and coastal waters usually have low TA values and may experience enhanced remineralization of organic matter in response to processes such as eutrophication and terrestrial organic matter input. Therefore, these waters are considered vulnerable to acidification as a consequence of ongoing atmospheric anthropogenic carbon dioxide uptake. An In Situ Analyzer for seawater Total Alkalinity (ISA-TA) was deployed for the first time in low salinity, dynamic estuarine waters (Kiel Fjord, southwestern Baltic Sea). The ISA-TA and a range of additional sensors (for pH, pCO2, nitrate and temperature, salinity, dissolved oxygen) used to obtain ancillary data to interpret the TA variability, were deployed on a pontoon in the inner Kiel Fjord for approximately four months. Discrete samples (for TA, nutrients including NO3−, soluble reactive phosphorus (SRP) and H4SiO4, chlorophyll a) were collected regularly to validate the ISA-TA and to interpret the TA data. The effects on TA in the study area of nitrate uptake and of other processes such as precipitation, run-off and mixing of different waters were observed. The difference between the TA values measured with the ISA-TA and TA of discretely collected samples measured with the Gran titration method was −2.6 ± 0.9 μmol kg−1 (n = 106), demonstrating that the ISA-TA provides stable and accurate TA measurements in dynamic, low salinity (13.2–20.8), estuarine waters. The TA and ancillary data recorded by the sensor suite revealed that physical mixing was the main factor determining the variability in TA in Kiel Fjord during the study period.
•An In Situ Analyzer for seawater Total Alkalinity was deployed in a dynamic estuarine system.•Seasonal and diurnal total alkalinity variations in Kiel Fjord were observed.•Variability in total alkalinity was mainly controlled by mixing of various waters.•A non-linear total alkalinity-salinity relationship was observed in mid-summer.
•Environmental monitoring for offshore carbon dioxide storage sites.•Analysis of water column in situ measurements for the determination of baseline conditions at an experimental site for CO2 storage ...in the North Sea.•Assessment of the variability between carbonate variables and physicochemical parameters at the near seabed for the identification of potential non-natural CO2 emissions at offshore storage sites.
Monitoring operations at the seafloor above a storage complex area are required to demonstrate that offshore storage of CO2 in the deep subsurface is safe and effective. Within the framework of the STEMM-CCS project, the Goldeneye area was identified as an offshore experimental site for CO2 storage. In this work, the physico-chemical characteristics of the water column at the Goldeneye site were determined by an in-depth analysis of measurements collated from CTD casts, discrete water samples and seafloor landers. The results showed a clear tidal, seasonal and inter-annual variability in the measured parameters within the monitoring period (Oct 2017- May 2019). Variations in pH and pCO2 over a single tidal cycle were in the order of ±0.008 and ±1.5 μatm, respectively. The temporal variability of water column carbonate chemistry parameters was further defined with the aim to provide a solid background for the discrimination from natural changes of potential impacts of CO2 emissions at the potential storage site. Here, we demonstrated how the combination of new and existing methods and technologies could be used for an effective assessment of water column conditions at a potential offshore carbon storage site.
Crude oil is an important feedstock for the petrochemical industry and the dominant energy source driving the world economy, but known oil reserves will cover demand for no more than 50 years at the ...current rate of consumption. This situation calls for more efficient strategies for converting crude oil into fuel and petrochemical products. At present, more than 40% of oil conversion is achieved using catalysts based on faujasite; this zeolite requires extensive post-synthesis treatment to produce an ultrastable form, and has a large cavity accessible through four 0.74-nm-wide windows and thus limits the access of oil molecules to the catalytically active sites. The use of zeolites with better accessibility to their active sites should result in improved catalyst efficiency. To date, two zeolites with effective pore diameters exceeding that of faujasite have been reported, but their one-dimensional pore topology excludes use in oil refining. Similarly, zeolites with large pores and a three-dimensional pore topology have been reported, but in all these materials the pore openings are smaller than in faujasite. Here we report the synthesis of ITQ-21, a zeolite with a three-dimensional pore network containing 1.18-nm-wide cavities, each of which is accessible through six circular and 0.74-nm-wide windows. As expected for a zeolite with this structure, ITQ-21 exhibits high catalytic activity and selectivity for valuable products in preliminary oil refining tests.
•Real-time monitoring of CO2 release.•Measurements of water column pH and pCO2 via towed Video-CTD system.•Assessment of towed sensors capacity to detect potential CO2 leakage in the water ...column.•Estimation of thresholds for the detection of anomalous pCO2.
Within the framework of the STEMM-CCS project, a controlled CO2 release experiment was conducted under real-life conditions in the Goldeneye complex area, a depleted gas field located in the UK sector of the North Sea. Here, the viability of water column monitoring for the detection of the injected CO2 is evaluated. Real-time pH and pCO2 measurements were taken in the water column during the CO2 release experiment. Monitoring was carried out throughout the full water column, from the near-seafloor to the sea surface, in order to assess the spatial extent of the CO2 release. The dispersion of the CO2 plume was strongly influenced by tidal circulation in the area. The strongest signals were detected within 8 m of the bubble stream during low tide. The lowest pH and highest pCO2 values were 7.965 and 942.1 µatm, respectively, corresponding to variations of 16.4% H+ and 125.6% from baseline values. The pCO2 baseline dynamics of Goldeneye area were assessed by the evaluation of the natural pCO2-O2 covariance. The estimation of seasonal thresholds for anomalous pCO2 (pCO2:O2 ratio May= 1.63 ± 0.04) allowed us to assess with confidence the non-biological origin of the detected CO2 during the release experiment.
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•Chitosan constitutes a good polymer for iron oxide immobilization.•Sorption properties of iron oxides are not inhibited by chitosan coating.•Hybrid materials present good mechanical ...properties for water pollution treatment.•Arsenic can be efficiently removed using cost-effective hybrid polymeric materials.
Red mud (RM), a waste product generated in the industrial production of aluminium, was recovered for a second use as As(V) adsorbent. RM adsorption properties were compared to those obtained with a nanostructured in-lab synthesized iron oxide, magnetite. Operational problems associated with powdery consistency of raw materials were solved with the synthesis of new polymeric/inorganic hybrid sorbents by dispersing red mud and magnetite in chitosan. The behaviour of raw red mud and magnetite towards As(V) adsorption has been critically compared with that observed for the hybrid materials. pH dependence studies demonstrated that near neutral environments favour As(V) elimination. The sorption kinetics for the iron oxides showed that equilibrium was reached in less than 3h for raw materials and up to 15h for immobilized red mud and magnetite. The amount of arsenic sorbed on the four different sorbents as a function of the equilibrium arsenic concentration has been fitted to a Freundlich isotherm and a multilayer adsorption mechanism is proposed. Finally, continuous flow experiments were developed using chitosan immobilized red mud. Results allowed selecting batch conformation as the most effective for As(V) removal.
In this work, water extracts from different bio-based products of plant origin were studied to evaluate their antioxidant capacity and their potential to form metal nanoparticles from aqueous ...solutions. Two traditional tests, the Folin–Ciocalteu assay and the DPPH radical scavenging capacity method were compared with a more recent one, SNPAC, based on the formation of silver nanoparticles. The silver nanoparticle antioxidant capacity method (SNPAC) was optimized for its application in the characterization of the extracts selected in this work; kinetic studies and extract concentration were also evaluated. The extracts were obtained from leaves of oak, eucalyptus, green tea, white and common thyme, white cedar, mint, rosemary, bay, lemon, and the seaweed Sargassum muticum. The results demonstrate that any of these three methods can be used as a quick test to identify an extract to be employed for nanoparticle formation. Additionally, we studied the synthesis of Cu, Fe, Pb, Ni, and Ag nanoparticles using eucalyptus extracts demonstrating the efficiency of this plant extract to form metallic nanoparticles from aqueous metal salt solutions. Metal nanoparticles were characterized by transmission electron microscopy and dynamic light scattering techniques.
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