Micro-recycling of spent Ni-Cd batteries for the obtention of electrocatalytic coatings

A micro-recycling approach was explored to produce catalytic metallic coatings for the hydrogen evolution reaction (HER). For this aim, discarded Ni-Cd batteries were employed as raw material. After dismantling the batteries, the active powder material, containing Cd and Ni compounds, was leached in a solution containing citric acid and hydrogen peroxide. The dissolved metals were electro-deposited on copper plates using a two electrodes cell at the following potentials (mV): -1900, -2000, and -2100 mV. The CdNi coating produced at -2000 mV, contained 92.6 % Cd and 7.4 % Ni. This coating was studied by cyclic voltammetry (CV) and potentiodynamic analysis in two different KOH solutions (0.1 M and 1.0 M). The CV analysis showed that the CdNi electrode was electrochemically stable in a wide operating voltage range (between oxygen evolution reaction and HER). Using an uncompensated resistance correction, the Tafel slopes for HER were obtained. The potentiodynamic analysis revealed that the synthesized CdNi electrode showed a catalytic activity for HER just 25.5 % smaller than the correspondent response of a standard pure Ni electrode. Our results serve as a proof of concept about the application of micro-recycling of spent batteries to produce sustainable electroactive catalytic materials for hydrogen production.

Physical Characterisation of a Natural Zeolite using a Scanning Electron Microscopy: A Preliminary Study

Zeolite is one of important non-metallic mineral deposites in Indonesia. It has been used for various purposes, including as an adsobent in environmental protection, industry, and agriculture. The most important characteristics of zeolit to be an adsorbent is its surface area and crystal structure. To optimally use zeolite as an adsorbent, it is necessary to understand its physical characteristics. This preliminary study was aimed to characterize physical properties of a natural zeolite obtained from Tasikmalaya, West Java, Indonesia. The zeolite material was crushed into <0.5 mm diameter and divided into two sets of samples. One set of samples was heated in a muffle furnace at 250 oC for two hours and the other set was left untreated. All samples were then observed using a Scanning Electron Microscopy (SEM). The SEM micrographs showed rough and porous structure and defined crystallinity of the zeolite. Thermal treatment at 250 oC increased zeolite crystallinity. These results confirm that this natural zeolite is potential to be used as an adsorbent to remove dissolved metals from acid mine drainage.

Sulphate removal technologies for the treatment of mine-impacted water

Mine-impacted water, including acid mine drainage (AMD), is a global problem. While precipitation of dissolved metals and neutralization of acidity from mine-impacted water is accomplished relatively easily with lime addition, removal of sulphate to permissible discharge limits is challenging. This paper presents a high-level comparison of four sulphate removal technologies, namely reverse osmosis, ettringite precipitation, barium carbonate addition, and biological sulphate reduction. Primarily operating costs, based on reagent and utility consumptions, are compared. Each process is shown to be subject to a unique set of constraints which might favour one over another for a specific combination of location and AMD composition. Access to and cost of reagents would be a key cost component to any of the processes studied. The total cost calculated for each process also depends on the type of effluents that are allowed to be discharged.

Determination of Trace Metal (Mn, Fe, Ni, Cu, Zn, Co, Cd and Pb) Concentrations in Seawater Using Single Quadrupole ICP-MS: A Comparison between Offline and Online Preconcentration Setups

The quantification of dissolved metals in seawater requires pre-treatment before the measurement can be done, posing a risk of contamination, and requiring a time-consuming procedure. Despite the development of automated preconcentration units and sophisticated instruments, the entire process often introduces inaccuracies in quantification, especially for low-metal seawaters. This study presents a robust method for measuring dissolved metals from seawater accurately and precisely using a seaFAST and quadrupole Inductively Coupled Plasma Mass Spectrometer (ICPMS), employed in both offline (2016–2018) and online (2020–2021) setups. The proposed method shows data processing, including the re-calculation of metals after eliminating the instrumental signals caused by polyatomic interferences. Here, we report the blank concentration of Fe below 0.02 nmol kg−1, somewhat lower values than that have been previously reported using high-resolution and triple-quad ICPMS. The method allows for the accurate determination of Cd and Fe concentrations in low-metal seawaters, such as GEOTRACES GSP, using a cost-effective quadrupole ICPMS (Cdconsensus: 2 ± 2 pmol kg−1, Cdmeasured: 0.99 ± 0.35 pmol kg−1; Feconsensus: 0.16 ± 0.05 nmol kg−1, Femeasured: 0.21 ± 0.03 nmol kg−1). Between two setups, online yields marginally lower blank values for metals based on short-term analysis. However, the limit of detection is comparable between the two, supporting optimal instrumental sensitivity of the ICPMS over 4+ years of analysis.

Copper, Zinc and Iron Contamination in Wellington Streams After Rainfall Events

<p>This work set out to determine the concentrations of dissolved copper (Cu), zinc (Zn) and iron (Fe) during base and wet weather flow at streams throughout the Wellington region. The secondary objective was to investigate possible sources of heavy metals during rainfall events. The concentrations of the three dissolved trace metals Cu, Zn and Fe were measured at 13 sites on five streams during base flow conditions and during runoff events (wet weather flow) in the Wellington region between January and July 2011. More than 240 base flow and 100 wet weather flow samples have been analysed for the three dissolved metals. Additionally, rainfall, roof runoff and paved surface runoff samples have been collected and analysed. The analysis was performed by Flame Atomic Absorption Spectroscopy (FAAS). A pre-concentration procedure using Chelex-100, a chelating polymeric resin bead, was developed and successfully used to enhance the concentrations of dissolved Cu and dissolved Zn. The recorded data were compared to the recommended long-term (chronic) toxicity triggers; the Australian and New Zealand Environment and Conservation Council freshwater toxicity trigger values (ANZECC (2000) TV) for dissolved Cu and Zn, and the Canadian trigger value (CTV) for dissolved Fe. Additionally, the concentrations of dissolved Cu and Zn in storm water samples were compared against the recommended short-term (acute) toxicity triggers, the United States Environmental Protection Agency (USEPA 2006) Criteria Maximum Concentrations (CMC). The medians of dissolved heavy metals concentrations; Cu, Zn, and Fe, all of which are potentially toxic to aquatic life, exceeded the long-term (chronic) toxicity guidelines at one of the studied sites for Fe, nine sites (69%) for Cu and 10 sites (77%) for Zn in base flow conditions. Comparison of base flow monitoring data to previous reports showed that the concentrations of the studied metals have increased over the last five years. Storm water (wet weather flow conditions) contained elevated levels of dissolved heavy metals in comparison to base flow concentrations which is consistent with what has been reported previously. Dissolved Cu and Zn exceeded the acute toxicity criteria at sites of suburban residential areas. The median of dissolved Fe concentration exceeded the sustained toxicity exposure trigger at eight of the studied sites (61%). Distinct catchment type contaminant concentrations (dissolved Cu and Zn) were observed during storm runoff events with a concentration pattern of suburban residential > commercial > light residential > rural catchment. Dissolved Fe exhibited a similar pattern but in this case the concentration in rural catchments was higher than in light residential catchments. These observations were attributed to the high traffic of vehicles passing nearby the area; accumulated particulate materials; and corrosion of materials containing heavy metals, such as galvanised and copper roofs, gutter systems and building construction materials. The strongest and most obvious first flush effect was observed with dissolved Cu followed by Zn where the phenomenon was observed in six storm runoff events for Cu and five events for Zn. The first flush effect of dissolved Fe was present in three out of eight storm runoff events. The concentrations of dissolved metals were of the same order of magnitude as those previously reported for the Wellington region, but this work recorded the highest expected concentrations, particularly, for dissolved Fe. The reported data are consistent with data sets from other New Zealand regions. The investigation of possible sources of dissolved heavy metals in storm runoff samples showed that rainfall water contained markedly elevated concentrations of dissolved Zn and smaller Cu concentrations, 0.04-0.075 and 0.0018-0.01 mg/L respectively, in comparison to the ANZECC (2000) TVs, 0.008 and 0.0014 mg/L respectively. The concentrations of dissolved Fe were below the CTV level of 0.3 mg/L. Most studies conducted in New Zealand did not take into account the atmospheric precipitation contribution to the elevated concentrations of dissolved metals during runoff events. Roof runoff samples had similar dissolved Cu and Fe concentration to those recorded in atmospheric rainfall water, but Zn was found to be higher in galvanised roof runoff. First flush samples from roof runoff had higher concentrations of all three metals than the delayed runoff samples, indicating the presence of accumulated particles containing metals. Paved surface runoff samples had concentrations of dissolved Cu and Zn higher than the chronic toxicity triggers, but the medians did not exceed the acute toxicity guidelines. The value of the median for the concentrations of dissolved Fe was below the CTV criteria. Similar results have been published for surface runoff in New Zealand and the international literature related to this field.</p>

Copper, Zinc and Iron Contamination in Wellington Streams After Rainfall Events

<p>This work set out to determine the concentrations of dissolved copper (Cu), zinc (Zn) and iron (Fe) during base and wet weather flow at streams throughout the Wellington region. The secondary objective was to investigate possible sources of heavy metals during rainfall events. The concentrations of the three dissolved trace metals Cu, Zn and Fe were measured at 13 sites on five streams during base flow conditions and during runoff events (wet weather flow) in the Wellington region between January and July 2011. More than 240 base flow and 100 wet weather flow samples have been analysed for the three dissolved metals. Additionally, rainfall, roof runoff and paved surface runoff samples have been collected and analysed. The analysis was performed by Flame Atomic Absorption Spectroscopy (FAAS). A pre-concentration procedure using Chelex-100, a chelating polymeric resin bead, was developed and successfully used to enhance the concentrations of dissolved Cu and dissolved Zn. The recorded data were compared to the recommended long-term (chronic) toxicity triggers; the Australian and New Zealand Environment and Conservation Council freshwater toxicity trigger values (ANZECC (2000) TV) for dissolved Cu and Zn, and the Canadian trigger value (CTV) for dissolved Fe. Additionally, the concentrations of dissolved Cu and Zn in storm water samples were compared against the recommended short-term (acute) toxicity triggers, the United States Environmental Protection Agency (USEPA 2006) Criteria Maximum Concentrations (CMC). The medians of dissolved heavy metals concentrations; Cu, Zn, and Fe, all of which are potentially toxic to aquatic life, exceeded the long-term (chronic) toxicity guidelines at one of the studied sites for Fe, nine sites (69%) for Cu and 10 sites (77%) for Zn in base flow conditions. Comparison of base flow monitoring data to previous reports showed that the concentrations of the studied metals have increased over the last five years. Storm water (wet weather flow conditions) contained elevated levels of dissolved heavy metals in comparison to base flow concentrations which is consistent with what has been reported previously. Dissolved Cu and Zn exceeded the acute toxicity criteria at sites of suburban residential areas. The median of dissolved Fe concentration exceeded the sustained toxicity exposure trigger at eight of the studied sites (61%). Distinct catchment type contaminant concentrations (dissolved Cu and Zn) were observed during storm runoff events with a concentration pattern of suburban residential > commercial > light residential > rural catchment. Dissolved Fe exhibited a similar pattern but in this case the concentration in rural catchments was higher than in light residential catchments. These observations were attributed to the high traffic of vehicles passing nearby the area; accumulated particulate materials; and corrosion of materials containing heavy metals, such as galvanised and copper roofs, gutter systems and building construction materials. The strongest and most obvious first flush effect was observed with dissolved Cu followed by Zn where the phenomenon was observed in six storm runoff events for Cu and five events for Zn. The first flush effect of dissolved Fe was present in three out of eight storm runoff events. The concentrations of dissolved metals were of the same order of magnitude as those previously reported for the Wellington region, but this work recorded the highest expected concentrations, particularly, for dissolved Fe. The reported data are consistent with data sets from other New Zealand regions. The investigation of possible sources of dissolved heavy metals in storm runoff samples showed that rainfall water contained markedly elevated concentrations of dissolved Zn and smaller Cu concentrations, 0.04-0.075 and 0.0018-0.01 mg/L respectively, in comparison to the ANZECC (2000) TVs, 0.008 and 0.0014 mg/L respectively. The concentrations of dissolved Fe were below the CTV level of 0.3 mg/L. Most studies conducted in New Zealand did not take into account the atmospheric precipitation contribution to the elevated concentrations of dissolved metals during runoff events. Roof runoff samples had similar dissolved Cu and Fe concentration to those recorded in atmospheric rainfall water, but Zn was found to be higher in galvanised roof runoff. First flush samples from roof runoff had higher concentrations of all three metals than the delayed runoff samples, indicating the presence of accumulated particles containing metals. Paved surface runoff samples had concentrations of dissolved Cu and Zn higher than the chronic toxicity triggers, but the medians did not exceed the acute toxicity guidelines. The value of the median for the concentrations of dissolved Fe was below the CTV criteria. Similar results have been published for surface runoff in New Zealand and the international literature related to this field.</p>

Inputs of Total and Labile Dissolved Metals from Six Facilities Continuously Discharging Treated Wastewaters to the Marine Environment of Gran Canaria Island (Canary Islands, Spain)

The presence of ten metals (Cd, Ni, Pb, Cr, Cu, Zn, Al, Fe, Mn, and Co) was investigated in the final discharge of six facilities, including four wastewater treatment plants, which were continuously discharging treated wastewater to the coastal environment in Gran Canaria Island. A four-day sampling campaign was carried out at each facility in July 2020, in which both the spot samplings technique and the diffusive gradient in thin-film technique (DGT) were carried out to measure total dissolved metals and the in situ labile metal fraction, respectively. After the necessary sample preparation steps, measurements were carried out by ICP-MS for both samplings. Raw data referred to the spot total dissolved and DGT-labile metal concentrations were reported. In general, the average metal concentrations were dispersed in a broad range. As expected, the highest metal contents were found in those facilities with larger industrial contributions. The values of annual average environmental quality standards (AA-EQS) were used to assess the total dissolved metal concentrations for every metal in every final discharge. In only one of the studied facilities, some metals (Ni and Zn) exceeded these EQS within the receiving waterbody, highlighting the need for more efficient treatment targeted towards a specific discharging-water quality. In addition, the total dissolved and labile metal daily fluxes of discharge were calculated to estimate the contribution of every effluent to the receiving water bodies.

Hydrothermal trace metal release and microbial metabolism in the northeastern Lau Basin of the South Pacific Ocean

Bioactive trace metals are critical micronutrients for marine microorganisms due to their role in mediating biological redox reactions, and complex biogeochemical processes control their distributions. Hydrothermal vents may represent an important source of metals to microorganisms, especially those inhabiting low-iron waters, such as in the southwest Pacific Ocean. Previous measurements of primordial 3He indicate a significant hydrothermal source originating in the northeastern (NE) Lau Basin, with the plume advecting into the southwest Pacific Ocean at 1500–2000 m depth (Lupton et al., 2004). Studies investigating the long-range transport of trace metals associated with such dispersing plumes are rare, and the biogeochemical impacts on local microbial physiology have not yet been described. Here we quantified dissolved metals and assessed microbial metaproteomes across a transect spanning the tropical and equatorial Pacific with a focus on the hydrothermally active NE Lau Basin and report elevated iron and manganese concentrations across 441 km of the southwest Pacific. The most intense signal was detected near the Mangatolo Triple Junction (MTJ) and Northeast Lau Spreading Center (NELSC), in close proximity to the previously reported 3He signature. Protein content in distal-plume-influenced seawater, which was high in metals, was overall similar to background locations, though key prokaryotic proteins involved in metal and organic uptake, protein degradation, and chemoautotrophy were abundant compared to deep waters outside of the distal plume. Our results demonstrate that trace metals derived from the NE Lau Basin are transported over appreciable distances into the southwest Pacific Ocean and that bioactive chemical resources released from submarine vent systems are utilized by surrounding deep-sea microbes, influencing both their physiology and their contributions to ocean biogeochemical cycling.