Alkali-activated materials containing mine tailings and zeolite for seepage water treatment in a closed nickel mine

Abstract In the present study, alkali-activated materials were assessed as adsorbents for mine water treatment. The composition of alkali-activated materials, involving mixtures of metakaolin, blast-furnace slag, mine tailings, and zeolite, was optimized based on their leaching behavior and adsorption performance. The most effective adsorbent contained solely blast furnace slag as an aluminosilicate precursor and was selected for a pilot-scale study at a closed nickel mine in Finland. In the pilot, seepage water from a gangue area with an influent flow rate of 0.5 m3/d was treated using a permeable reactive barrier set-up containing 10 kg of slag-based adsorbent prepared by a granulation-alkali activation process. During a one-week experiment, the adsorbent granules were capable of effectively uptaking Ni, Fe, and Mn from the seepage water; the removal percentages of Ni, Fe, and Mn were 82.4%, 81.6%, and 82.5%, respectively. The results indicated the feasibility of blast furnace slag-based adsorbents for toxic element removal in a potentially sustainable approach.Abstract In the present study, alkali-activated materials were assessed as adsorbents for mine water treatment. The composition of alkali-activated materials, involving mixtures of metakaolin, blast-furnace slag, mine tailings, and zeolite, was optimized based on their leaching behavior and adsorption performance. The most effective adsorbent contained solely blast furnace slag as an aluminosilicate precursor and was selected for a pilot-scale study at a closed nickel mine in Finland. In the pilot, seepage water from a gangue area with an influent flow rate of 0.5 m3/d was treated using a permeable reactive barrier set-up containing 10 kg of slag-based adsorbent prepared by a granulation-alkali activation process. During a one-week experiment, the adsorbent granules were capable of effectively uptaking Ni, Fe, and Mn from the seepage water; the removal percentages of Ni, Fe, and Mn were 82.4%, 81.6%, and 82.5%, respectively. The results indicated the feasibility of blast furnace slag-based adsorbents for toxic element removal in a potentially sustainable approach

Preparation and characterization of porous and stable sodium- and potassium-based alkali activated material (AAM)

AbstractThe aim of this work is to produce highly porous and stable alkali-activated material (AAM) prepared from two combinations of sodium (Na)- and potassium (K)-based alkali solutions (NaOH/Na₂SiO₃ and KOH/K₂SiO₃). The reactive metakaolin as precursor and AAM were characterized using X-ray diffraction spectroscopy (XRD), X-ray fluorescence spectroscopy (XRF), aluminum nuclear magnetic resonance spectroscopy (27Al MS-NMR), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), field emission scanning electron microscopy (FESEM), compressive strength measurement and Brunauer–Emmett–Teller (BET) surface analysis. The porosity of the AAMs were increased by using hydrogen peroxide and sodium percarbonate as foaming agents. Characterization results showed the viscosity of the K-AAM paste was 70% lower than that of the Na-AAM paste. However, the volume of the Na-AAM paste in an air-tight plastic tube was three times higher than that of K-AAM, but the specific surface area (SSA) of K-AAM were 30% higher than those of Na-AAM. In terms of compressive strength, the blank AAM (foaming agent-free) demonstrated the highest strength values: 6.1 MPa for K-AAM and 9.0 MPa for Na-AAM. When the concentration of the foaming agent was increased, the compressive strength of both the materials decreased but were still around 1.0 MPa. The FESEM images of the Na-AAM and K-AAM produced with H₂O₂ indicated the high porosity of materials which were also observed in SSA values of AAM. Furthermore, the XRD data showed that the Na-AAM contained water in hydrate form (halloysite) compared with the K-AAM, suggesting the different polymerization reaction route and speed between these AAM.Abstract The aim of this work is to produce highly porous and stable alkali-activated material (AAM) prepared from two combinations of sodium (Na)- and potassium (K)-based alkali solutions (NaOH/Na₂SiO₃ and KOH/K₂SiO₃). The reactive metakaolin as precursor and AAM were characterized using X-ray diffraction spectroscopy (XRD), X-ray fluorescence spectroscopy (XRF), aluminum nuclear magnetic resonance spectroscopy (27Al MS-NMR), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), field emission scanning electron microscopy (FESEM), compressive strength measurement and Brunauer–Emmett–Teller (BET) surface analysis. The porosity of the AAMs were increased by using hydrogen peroxide and sodium percarbonate as foaming agents. Characterization results showed the viscosity of the K-AAM paste was 70% lower than that of the Na-AAM paste. However, the volume of the Na-AAM paste in an air-tight plastic tube was three times higher than that of K-AAM, but the specific surface area (SSA) of K-AAM were 30% higher than those of Na-AAM. In terms of compressive strength, the blank AAM (foaming agent-free) demonstrated the highest strength values: 6.1 MPa for K-AAM and 9.0 MPa for Na-AAM. When the concentration of the foaming agent was increased, the compressive strength of both the materials decreased but were still around 1.0 MPa. The FESEM images of the Na-AAM and K-AAM produced with H₂O₂ indicated the high porosity of materials which were also observed in SSA values of AAM. Furthermore, the XRD data showed that the Na-AAM contained water in hydrate form (halloysite) compared with the K-AAM, suggesting the different polymerization reaction route and speed between these AAM

Utilisation of industrial by-products in water treatment:carbon-and silicate-based materials as adsorbents for metals and sulphate removal

Abstract Pollutant (such as metals and sulphate) contamination exists in the wastewaters of many industries, including mining operations, metal plating facilities, and tanneries. Adsorption is one of the most commonly used processes for the removal of pollutants from waters and wastewaters due to its high efficiency and simple operation. Activated carbon is the most frequently used adsorbent material, although its high cost inhibits its widespread use in wastewater treatment. Therefore, there is a need to develop other adsorbents from alternative inexpensive raw materials such as locally available industrial and mineral waste and by-products. The aim of this thesis was to study the possibility of using industrial waste materials such as carbon residue, metakaolin, blast-furnace slag and analcime as an inexpensive sorbent for iron, copper, nickel, arsenic, antimony and sulphate removal from aqueous solutions. To enhance their adsorption capacity, different chemical treatments (i.e. activation, modification, geopolymerisation) were performed. As a result, the level of removal of iron, copper and nickel by carbon residue and zinc chloride activated carbon residue was higher than that by the commercial activated carbon. Iron chloride modified carbon residue was the most effective sorbent material for sulphate removal when compared to the other studied chemically modified/activated carbon residues. Blast-furnace slag and metakaolin geopolymers as well as their raw materials, were examined for the simultaneous removal of nickel, arsenic and antimony from the spiked mine effluent. In the case of blast-furnace slag, geopolymerisation clearly increased the efficiency of nickel, arsenic and antimony removal to a beneficial level. The barium chloride modified blast-furnace-slag geopolymer was a very efficient sorbent material for sulphate removal and it could thus be a technically feasible sulphate sorbent for wastewater treatment (e.g. in the mining industry in applications in which very low sulphate levels are desired). Barium chloride modified acid washed analcime could also be a potential sorbent for sulphate removal.Tiivistelmä Teollisuuden jätevedet kuten kaivosvedet ja metalliteollisuuden prosessien jätevedet voivat sisältää monenlaisia haitallisia ja jopa myrkyllisiä aineita kuten metalleja ja sulfaattia. Adsorptiota käytetään yleisesti esimerkiksi metallien ja orgaanisten yhdisteiden poistossa vesiliuoksista, koska se on tehokas ja yksinkertainen menetelmä. Aktiivihiili on yleisimmin käytetty adsorbenttimateriaali vedenpuhdituksessa, mutta sen hinta joissain tapauksissa rajoittaa sen käyttöä. Tämän vuoksi on tarvetta kehittää vaihtoehtoisia adsorbenttimateriaaleja edullisista raaka-aineista. Viime vuosien aikana on raportoitu mm. teollisuus- ja mineraalijätteistä, joita voidaan hyödyntää vesien ja jätevesien puhdistuksessa. Tämän työn tavoitteena oli hyödyntää teollisuudesta muodostuvia jätemateriaaleja (hiilijäännös, metakaoliini, masuunikuona ja analsiimi) raudan, kuparin, nikkelin, arseenin, antimonin tai sulfaatin poistossa malli- ja jätevesistä. Materiaaleja käsiteltiin erilaisilla kemikaaleilla (aktivointi, modifiointi tai geopolymerointi), jotta niiden adsorptiotehokkuudet paranisivivat poistettavia aineita kohtaan. Tulokset osoittivat, että raudan, kuparin ja nikkelin poisto oli sekä käsittelemättömällä että sinkkikloridilla aktivoidulla hiilijäännöksellä korkeampi kuin kaupallisella aktiivihiilellä. Arseenin, nikkelin ja antimonin poistoa kaivosvedestä tutkittiin masuunikuona- ja metakaoliinigeopolymeereillä, joista masuunikuonageopolymeeri osoittautui tehokkaimmaksi metallien poistajaksi. Bariumkloridilla modifioitu masuunikuonageopolymeeri puolestaan poisti erittäin tehokkaasti sulfaattia kaivoksen jätevedestä. Rautakloridilla modifioitu hiilijäännös ja happopesty bariumkloridilla modifioitu analsiimi osoittatuivat myös lupaavaksi materiaaliksi sulfaatin poistossa

Sulfate Ion Removal from Reverse Osmosis Concentrate Using Electrodialysis and Nano-Filtration in Combination with Ettringite Precipitation

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Alkali-activated materials containing mine tailings and zeolite for seepage water treatment in a closed nickel mine

In the present study, alkali-activated materials were assessed as adsorbents for mine water treatment. The composition of alkali-activated materials, involving mixtures of metakaolin, blast-furnace slag, mine tailings, and zeolite, was optimized based on their leaching behavior and adsorption performance. The most effective adsorbent contained solely blast furnace slag as an aluminosilicate precursor and was selected for a pilot-scale study at a closed nickel mine in Finland. In the pilot, seepage water from a gangue area with an influent flow rate of 0.5 m3/d was treated using a permeable reactive barrier set-up containing 10 kg of slag-based adsorbent prepared by a granulation-alkali activation process. During a one-week experiment, the adsorbent granules were capable of effectively uptaking Ni, Fe, and Mn from the seepage water; the removal percentages of Ni, Fe, and Mn were 82.4%, 81.6%, and 82.5%, respectively. The results indicated the feasibility of blast furnace slag-based adsorbents for toxic element removal in a potentially sustainable approach

Multiple heavy metal removal simultaneously by a biomass‐based porous carbon

Abstract Activated carbon from sawdust was produced with an environmentally friendly process involving single‐stage carbonization and activation with steam at 800°C. Production process is scalable because lignocellulosic biomass is ubiquitous worldwide as a waste or as a virgin material. Single‐stage production without any cooling steps between carbonization and activation is easier in larger scale production. Monometal adsorption and multimetal adsorption of cobalt, nickel, and zinc were investigated by using the produced carbon, with a commercial one as control. Effect of pH, initial metal concentration, adsorbent dosage, and adsorption time was evaluated in batch experiments. Multimetal experiments showed the order of the maximum adsorption capacities: zinc > nickel > cobalt. Experimental adsorption capacities were 17.2, 6.6, and 4.5 mg/g for zinc, nickel, and cobalt, respectively, in multisolute adsorption. In case of monometal adsorption, adsorption capacity was notably lower. Experimental data fitted into the single‐solute and multisolute Freundlich models. The best fit kinetic model varied among the metals. The Weber and Morris intraparticle diffusion model was used. Regeneration was performed with 0.1 M HNO₃, 0.1 M HCl, or 0.1 M H₂SO₄. The adsorption capacity remained at the same within three adsorption–desorption cycles

Adsorption of copper and zinc with alkali-activated blast furnace slag from mine water

Abstract Metal contamination is an alarming problem near mining areas all over the world. Released wastewaters and mining water loose different metals to environment affecting lakes, rivers and other water sources (Jain and Das, 2017). In this study, alkali-activated blast furnace slag was used as an adsorbent for mine effluent treatment. Alkali-activation was conducted by reacting ground granulated blast furnace slag and a mixture of sodium hydroxide and silicate. Water samples are obtained from the last pumping point of infiltration water. Metal content of this water is still above the environmental safety level and the water should be recirculated and repurified. The aim of this work is to find a method to purify the mine water at this testing point to reach the environmental safety level. Then water will be releasable back to the lake. Alkali-activated materials are widely tested and used in different kind of purification applications. These adsorbent materials are known since beginning of 1900 century but interest towards this kind of research has grown during the few last decades. There are a lot of possibilities for water research and purification processes with alkali-activated materials due to their strong and insoluble form and wide range of feasible materials available (Provis, 2014). Alkali-activated blast furnace slag was selected to be an adsorbent material for this work because it is cheap and easy to produce. It has also relatively good metal removing capacity. Same kinds of adsorbent materials have been tested for metals like nickel successfully (Luukkonen et al., 2016). This encouraged us to study more specific mining waters containing copper and zinc

Alkali-activated materials from steel industry slags: optimization of prewashing and its effect on zinc adsorption and regeneration

Abstract Interest in alkali-activated materials (AAMs) has increased because of their effectiveness as adsorbents and their low cost. An additional advantage of AAMs is that raw materials obtained from industrial side streams can support a circular economy. In this study, slags from the steel industry were used as raw materials for an AAM. As the material was highly alkaline, prewashing was mandatory before adsorption studies to avoid precipitation of hydroxides. As washing agents, different concentrations of several chemicals (strong and weak acids) were used. Among them, oxalic acid performed the best by stabilizing the pH near neutral during adsorption and minimizing mass loss. Thus, using oxalic acid, prewashing was optimized in relation to the time and concentration. In adsorption experiments, the adsorption capacity was 78 mg g−1 for zinc, which was 18 times higher than that without optimization. The AAM adsorbent was also regenerable with oxalic acid because its adsorption efficiency remained stable in the next adsorption cycle. The AAM was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), field emission scanning electron microscopy with energy dispersive X-ray spectrometry (FESEM-EDS), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Analyses showed how prewashing affected the surface structure and functional groups in different process stages. The adsorption mechanism was determined to be complex formation. This study not only revealed more environmentally friendly options for material preparation but also showed how to improve environment quality with more advanced material preparation and process optimization methods.Abstract Interest in alkali-activated materials (AAMs) has increased because of their effectiveness as adsorbents and their low cost. An additional advantage of AAMs is that raw materials obtained from industrial side streams can support a circular economy. In this study, slags from the steel industry were used as raw materials for an AAM. As the material was highly alkaline, prewashing was mandatory before adsorption studies to avoid precipitation of hydroxides. As washing agents, different concentrations of several chemicals (strong and weak acids) were used. Among them, oxalic acid performed the best by stabilizing the pH near neutral during adsorption and minimizing mass loss. Thus, using oxalic acid, prewashing was optimized in relation to the time and concentration. In adsorption experiments, the adsorption capacity was 78 mg g−1 for zinc, which was 18 times higher than that without optimization. The AAM adsorbent was also regenerable with oxalic acid because its adsorption efficiency remained stable in the next adsorption cycle. The AAM was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray fluorescence (XRF), field emission scanning electron microscopy with energy dispersive X-ray spectrometry (FESEM-EDS), and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Analyses showed how prewashing affected the surface structure and functional groups in different process stages. The adsorption mechanism was determined to be complex formation. This study not only revealed more environmentally friendly options for material preparation but also showed how to improve environment quality with more advanced material preparation and process optimization methods