Valorisation diagnosis of waste from the decontamination of phosphogypsum leachates through a combined calcium carbonate/hydroxide process.

Phosphogypsum is an industrial waste considered as naturally occurring radioactive material. Stack disposal and exposure to the environmental condition involve the production of acid leachates with high potential pollutant loads as heavy metals and radionuclides. In this study, a sequential neutralisation process was applied for cleaning the generated releases, and the two obtained residues were characterised from the physical-chemical and radiological point of view before their valorisation.

Eco-Friendly Pavements Manufactured from Mixed Recycled Aggregates Obtained from Construction and Demolition Waste: An Industrial-Scale Validation.

This study aimed to validate that laboratory-scale results could be commercially replicated when manufacturing marketable precast concrete. Construction and demolition waste (CDW) was separated into two (fine and coarse) recycled aggregates (RAs). Precast paver and kerb units were fabricated by partial or total substitution of natural aggregates (NAs) by RAs.

A new methodology based on TRU resin to measure U-, Th-isotopes and Po by alpha-particle spectrometry.

This report presents a new methodology to isolate and measure Po, as well as uranium and thorium isotopes. This new methodology reduces the standard time of operation, the minimum amount of chemical reagents and the quantity of resin used in comparison with other standard and well-established procedures for alpha spectrometry. Thus, the amount of chemicals reagent was lower than the amount used in other standard radiochemical processes: only 6 mL of 1 M HCl was used for the thorium elution, and 2 mL of HO and 1 mL of Ammonium Oxalate (0.

Native Hyperaccumulator Plants with Differential Phytoremediation Potential in an Artisanal Gold Mine of the Ecuadorian Amazon.

In tropical forests of southern Ecuador, artisanal gold mining releases heavy metals that become xenobiotic with indefinite circulation and eventual bioaccumulation. Restoration and rehabilitation of degraded mining sites represent a major ecological, technological and economic issue. In this study, we estimate the capacity of two native woody plants to accumulate cadmium (Cd), lead (Pb), zinc (Zn) and mercury (Hg), with the goal of developing effective strategies for phytoremediation of mining sites.

Recycled Aggregates from Construction and Demolition Waste in the Manufacture of Urban Pavements.

Construction and Demolition Waste (CDW) is among the largest waste streams in the world. Therefore, within the Circular Economy concept, there is a growing interest in its reuse. The purpose of this work was to study the use of recycled aggregates (RAs) obtained by a specific separation method from CDW, replacing natural aggregates (NAs) in the manufacture of precast concrete elements, such as kerbstones and paver blocks.

Arsenic removal procedure for the electrolyte from a hydro-pyrometallurgical complex.

Commercial copper (Cu) is obtained by a hydro-pyrometallurgical process, where the Cu anodes obtained in the furnaces (Cu > 99.5%) are enriched up to 99.99% in "cathodes" by electrorefining at an electrolysis plant.

Radiological and chemical risks by waste scales generated in the titanium dioxide industry.

Along the industrial process devoted to the production of titanium dioxide pigments by using ilmenite as main raw material, small residues amounts are generated, remaining clearly enriched in natural radionuclides and chemical pollutants. Between them, we can remark the scales enriched in both radium isotopes and lead, which are formed in the internal walls of pipes and some equipment. These scales are radiological anomalies that demand its mineralogical, elemental and radiometric characterization as a basis for a detailed radiological and toxicological assessment from the occupational and public point of view.

Behaviour of heavy metals and natural radionuclides in the mixing of phosphogypsum leachates with seawater.

Phosphogypsum (PG) is disposed worldwide in large stacks usually placed in coastal zones, as in the case of Huelva (SW of Spain), where around 100 Mt of PG are stored on the salt marshes of the Tinto River estuary covering a surface of about 1000 ha. This management generates the weathering of PG, and due to its high acidity (pH ≈ 2) and pollutant load can provoke significant emissions into their surroundings. In this work were evaluated by laboratory experiments the effects of pH increase in the behaviour of heavy metals and natural radionuclides during the mixing of phosphogypsum leachates with seawater.

Radiological and physico-chemical characterization of materials from phosphoric acid production plant to assess the workers radiological risks.

The industry devoted to the production of phosphoric acid by using as raw material sedimentary phosphate rock (PR) is considered as a NORM activity (Naturally Occurring Radioactive Materials), due to the high levels of U-series radionuclides contained in this ore, which are 1-2 orders of magnitude higher than those in unperturbed soils. This fact allowed us to develop a deep characterization of the raw materials, wastes, main intermediate materials, and final products obtained at a typical phosphoric acid factory. The elemental composition (major, minor and trace elements), radionuclide concentrations, grain size distribution, mineralogy and micro-structural composition were analyzed.

Evaluation of the radioactive pollution in the salt-marshes under a phosphogypsum stack system.

Next to the city of Huelva (SW of Spain), around 100 Mt of phosphogypsum (PG) are stored in stacks on the salt-marshes of the Tinto River estuary covering a surface of about 1000 ha. Due to the high content of U series natural radionuclides of the PG, its acidic nature (pH about 3), and the fact that PG stacks were disposed without any kind of isolation from the substrate, they could produce a potential radioactive impact into the underlying sediments. The aim of this work is to assess the pollution of the underlying sediments by natural radionuclides coming from the PG stacks.

An improved method for radium-isotopes quartet determination by alpha-particle spectrometry by using Ra (Th) as isotopic tracer.

A new method for the determination of radium quartet (Ra) in environmental samples by alpha-particle spectrometry with PIPS detectors is described. This uses Ra as yield tracer, in equilibrium at the beginning with Th. Thorium is removed from the sample by using AG1X8 anion-resin, and then radium isotopes are isolated and purified with a cation-exchange column Biorad AG50X8, verifying that Ac has been fully removed from the sample to ensure the good evaluation of the Ra yield (average decontamination factor > 92%).

Assessment of natural radionuclides mobility in a phosphogypsum disposal area.

The phosphogypsum (PG) stacks located at Huelva (SW Spain) store about 100 Mt of PG, and covers a surface of 1000 ha. It has been very well established in many studies that this waste contains significant U-series radionuclides concentrations, with average activity concentrations rounding the 650, 600, 400 and 100 Bq kg for Ra, Po, Th and U, respectively. However, the radionuclide transfer from this repository into the environment by the aquatic pathway will depend on the mobility of each radionuclide.

Validation of the BCR sequential extraction procedure for natural radionuclides.

Determining the availability of natural radionuclides in environmental conditions is increasingly important in order to evaluate their toxicity. A validated procedure is necessary to ensure the comparability and accuracy of the results obtained by different laboratories. For that, an optimised BCR sequential extraction procedure has been applied to the certified reference material (CRM), coded as BCR-701, and their resulting liquid and solid fractions were subjected to an exhaustive chemical and radioactivity characterisation.

Erato polymnioides - A novel Hg hyperaccumulator plant in ecuadorian rainforest acid soils with potential of microbe-associated phytoremediation.

Mercury (Hg) accumulation capacity was assessed in three plant species (Axonopus compressus, Erato polymnioides, and Miconia zamorensis) that grow on soils polluted by artisanal small-scale gold mines in the Ecuadorian rainforest. Individuals of three species were collected at two sampling zones: i) an intensive zone (IZ, 4.8 mg Hg kg of soil) where gold extraction continues to occur, and ii) a natural zone (NZ, 0.

Selection of a suitable plant for phytoremediation in mining artisanal zones.

A study was undertaken with the aim of identifying a suitable plant for the phytoremediation of metal-polluted soil from an artisanal mining area in Ecuador. Three zones including a natural zone (NZ), abandoned zone (AZ) and intensively mined zone (IZ) were selected. Three common native plants grown in the three zones were identified and collected, including Miconia zamorensis, Axonopus compressus and Erato polymnioides.

Polonium behaviour in reservoirs potentially affected by acid mine drainage (AMD) in the Iberian Pyrite Belt (SW of Spain).

The province of Huelva is one of the areas most affected by acid mine drainage (AMD) in the world, which can produce big enhancements and fractionations in the waters affected by AMD. There are very few studies on this issue, and none on polonium-210. Twenty-two water reservoirs were sampled, and the (210)Po was measured in both dissolution and particulate phases.

Fractionation and fluxes of metals and radionuclides during the recycling process of phosphogypsum wastes applied to mineral CO₂ sequestration.

The industry of phosphoric acid produces a calcium-rich by-product known as phosphogypsum, which is usually stored in large stacks of millions of tons. Up to now, no commercial application has been widely implemented for its reuse because of the significant presence of potentially toxic contaminants. This work confirmed that up to 96% of the calcium of phosphogypsum could be recycled for CO2 mineral sequestration by a simple two-step process: alkaline dissolution and aqueous carbonation, under ambient pressure and temperature.

Radioactive characterization of leachates and efflorescences in the neighbouring areas of a phosphogypsum disposal site as a preliminary step before its restoration.

After the recent closure of certain phosphoric acid plants located in the South-West of Spain, it has been decided to restore a big extension (more than six hundred hectares) of salt-marshes, where some million tonnes of phosphogypsum (PG), the main by-product generated by these plants, had been disposed of. This PG is characterized by its content of high activity concentrations of several radionuclides from the uranium series, mainly (226)Ra, (210)Pb, and (210)Po and, to a lesser extent, U-isotopes. The PG disposal area can be considered as a potential source of radionuclides into their nearby environment, through the waters which percolate from them and through the efflorescences formed in their surroundings.

Mobility of Po and U-isotopes under acid mine drainage conditions: an experimental approach with samples from Río Tinto area (SW Spain).

Under acid mine drainage (AMD) conditions, the solubilities and mobilities of many elements are vastly different from conditions prevailing in most natural waters. Studies are underway in the Río Tinto area (Iberian Pyrite Belt), in order to understand the behavior and mobility of long-lived U-series radionuclides under AMD conditions. A set of leaching experiments utilizing typical country rocks from the Tinto River basin, waste rock pile composite materials, iron-rich riverbed sediments and gossan (weathered naturally rock) were performed towards this purpose.

Valorisation of waste ilmenite mud in the manufacture of sulphur polymer cement.

This paper reports the preparation of sulphur polymer cements (SPCs) incorporating waste ilmenite mud for use in concrete construction works. The ilmenite mud raw material and the mud-containing SPCs (IMC-SPCs) were characterised physico-chemically and radiologically. The optimal IMC-SPC mixture had a sulphur/mud ratio (w/w) of 1.

Real-time continuous glucose monitoring or continuous subcutaneous insulin infusion, what goes first?: results of a pilot study.

Background: Dual devices allow both continuous subcutaneous insulin infusion (CSII) and real-time (RT) continuous glucose monitoring (CGM). Patients usually start with CSII, adding RT-CGM later (CGM post-CSII). Lack of use of RT-CGM is the main limiting factor of dual device results.

Radioactive characterization of the main materials involved in the titanium dioxide production process and their environmental radiological impact.

A study about the distribution of several radionuclides from the uranium and the thorium series radionuclides along the production process of a typical NORM industry devoted to the production of titanium dioxide has been performed. With this end the activity concentrations in raw materials, final product, co-products, and wastes of the production process have been determined by both gamma-ray and alpha-particle spectrometry. The main raw material used in the studied process (ilmenite) presents activity concentrations of around 300 Bq kg(-1) for Th-series radionuclides and 100 Bq kg(-1) for the U-series ones.

Occupational exposures in two industrial plants devoted to the production of ammonium phosphate fertilisers.

In order to fill a gap in the open literature, occupational exposures and activity concentrations have been assessed in two NORM industrial plants, located in the south-west of Spain, devoted to the production of mono-ammonium phosphate (MAP) and di-ammonium phosphate (DAP) fertilisers. The annual effective doses received by the workers from these plants are clearly below 1 mSv yr(-1) and the contribution due to external radiation is similar to that due to inhalation. The contribution to the maximum effective doses due to inhalation of particulate matter has been estimated to be about 0.

Microencapsulation of phosphogypsum into a sulfur polymer matrix: physico-chemical and radiological characterization.

The aim of this work is to prepare a new type of phosphogypsum-sulfur polymer cements (PG-SPC) to be utilised in the manufacture of building materials. Physico-chemical and radiological characterization was performed in phosphogypsum and phosphogypsum-sulfur polymer concretes and modeling of exhalation rates has been also carried out. An optimized mixture of the materials was obtained, the solidified material with optimal mixture (sulfur/phosphogypsum=1:0.

Physico-chemical and radioactive characterization of TiO2 undissolved mud for its valorization.

In order to find a potential valorization of a waste generated in the industrial process devoted to the production of TiO(2) pigments, and as an essential and basic step, this waste must firstly be physically and chemically characterized. Moreover, the content of radioactivity is taken in to account due to it comes from a NORM (Naturally Occurring Radioactive Material) industry. With this end, microscopic studies were performed by applying scanning electron microscopy with X-ray microanalysis (SEM-XRMA), while the mineralogical compositions were carried out by means of the X-ray diffraction (XRD) technique.