Search

El trabajo realizado consiste en el estudio experimental de la recuperación y purificación de ácido sulfúrico de corrientes residuales mediante un proceso de separación llamado diálisis por difusión con membranas de intercambio aniónico. Las corrientes residuales tratadas provienen de la elución de resinas de intercambio iónico y se caracterizan por contener una elevada concentración de ácido sulfúrico (que se quiere recuperar) y concentraciones variables de distintos metales (Na, Mg, Al, Ca, Ni, Mn, y La e Y como ejemplos de elementos de tierras raras) como impurezas. De manera que se propone como objetivo obtener una corriente con la mayor concentración posible de ácido sulfúrico y menor concentración posible de metales. Para llevar a cabo el procedimiento experimental, inicialmente se han realizado los experimentos mediante un equipo de diálisis por difusión en recirculación a escala de laboratorio para así estudiar las características de la membrana aniónica utilizada (“Fumasep FAQP-375-PP”) en presencia de diferentes concentraciones de ácido y metales. Para el desarrollo de los experimentos se han utilizado soluciones previamente preparadas con concentraciones variables de ácido sulfúrico y metales y operando el sistema con recirculación de las corrientes de salida del módulo de la membrana. Una vez estudiados los efectos en la membrana de los diferentes elementos presentes en el eluato, se realiza un estudio con una disolución sintética a unas composiciones determinadas de metales y ácido sulfúrico, sin recirculación de las corrientes de salida, mediante un sistema de membranas de diálisis por difusión comercial para evaluar la separación del ácido sulfúrico de los diferentes metales en condiciones más cercanas a escala industrial. En este caso se ha estudiado el efecto del flujo en la recuperación del ácido sulfúrico. Basándonos en los experimentos realizados, se concluye que el flujo óptimo de operación es 2,08 L/m2·h consiguiéndose así un 78% de recuperació, El treball realizat consisteix en l’estudi experimental de la recuperació i purificació d’àcid sulfúric de corrents residuals mitjançant un procés de separació anomenat diàlisis per difusió amb membranes d’intercanvi aniònic. Els corrents residuals tractats provenen de l’elució de resines d’intercanvi iònic i es caracteritzen per contenir una elevada concentració d’àcid sulfúric (que es vol recuperar) i concentracions variables de diferents metalls (Na, Mg, Al, Ca, Ni, Mn i La i Y com a exemples d’elements de terres rares) com impureses. De manera que es proposa com a objectiu obtenir un corrent amb la major concentració possible d’àcid sulfúric i menor concentració possible de metalls. Per dur a terme el procediment experimental, inicialment s’han realitzat els experiments mitjançant un equip de diàlisis per difusió en recirculació a escala laboratori per així estudiar les característiques de la membrana aniónica utilitzada (“Fumasep FAQP-375-PP”) en presència de diferents concentracions d’àcid i metalls. Per al desenvolupament dels experiments s’han utilitzat solucions prèviament preparades amb concentracions variables d’àcid sulfúric i metalles i operant el sistema amb recirculació dels corrents de sortida del mòdul de la membrana. Un cop estudiats els efectes en la membrana dels diferents elements presents a l’eluat, es realitza un estudi amb una dissolució sintética a unes composicions determinades de metalls i àcid sulfúric, sense recirculació dels corrents de sortida, mitjançant un sistema de membranas de diàlisis per difusió comercial per avaluar la separació de l’àcid sufúric dels diferents metalls en condicions més properes a escala industrial. En aquest cas s’ha estudiat l’efecte del flux en la recuperación de l’àcid sulfúric. Basant-nos en els experiments realitzats, es conclou que el flux òptim d’operació es 2,08 L/m2·h aconseguint-se així un 78% de recuperació d’àcid sulfúric respecte a l’àcid total., The work carried out consists of the experimental study of the recovery and purification of sulfuric acid from waste streams by a separation process called diffusion dialysis with anion exchange membranes. The treated waste streams come from the elution of ion exchange resins and are characterized by containing a high concentration of sulfuric acid (to be recovered) and variable concentration of different metals ( Na, Mg, Al, Ca, Ni, Mn, and La and Y as examples of rare earth elements) as impurities. So it is proposed as an objective to obtain a current with the highest possible concentration of sulfuric acid and lowest possible concentration of metals. To carry out the experiments procedure, initially the experiments have been carried out using a diffusion dialysis equipment in recirculation at laboratory scale in order to study the characterstics of the anionic membrane used (“Fumasep FAQP-375-PP”) in the presence of different concentrations of acid and metals. For the development of the experiments have been used solutions previously prepared with variable concentrations of sulfuric acid and metals and operating the system with recirculation of the output currents of the membrane module. Once the efects on the membrane of the different elements presents in the eluate have been studied, a study is carried out with a synthetic solution with certain compositions of metals and sulfuric acid, without recirculation of the output currents, using of dialysis membranes by commercial diffusion to evaluate the separation of sulfuric acid from the different metals in conditions closer to industrial scale. In this case, the effect of flow on the recovery of sulfuric acid has been studied. Based on the experiments carried out, it is concluded that the optimal operating Flow us 2,08 L/m2·h, thus achieving a 78% recovery of sulfuric acid with respect to the total acid.

En este proyecto se ha realizado un estudio de tratamiento de las aguas ácidas de mina (AMW) de la mina de Los Frailes, Aznalcóllar (Sevilla) para la recuperación de tierras raras (REE). Para ello, se ha generado una solución sintética que simula el efluente resultante de la regeneración de las resinas de intercambio iónico de las propias AMW utilizando ácido sulfúrico (H2SO4) como regenerante. La recuperación se ha realizado por precipitación selectiva de las REE mediante la adición de ácido oxálico (H2C2O4) como agente precipitante. Se ha evaluado el efecto de la dosificación de H2C2O4, la concentración de H2SO4 en el agua a tratar, el volumen de disolución del agua a tratar y la velocidad de agitación durante el proceso de precipitación. Se han analizado las muestras de disolución mediante ICP y los precipitados mediante SEM y XRD para determinar el contenido del precipitado y su morfología. Los resultados obtenidos muestran como las REE ligeras (LREE) son las impulsoras de la nucleación necesaria para el proceso de precipitación mientras que las REE pesadas (HREE) no son capaces de iniciarla por si solas. Por otro lado, se ha deducido que las condiciones óptimas de proceso son la aplicación de oxalato en fase líquida con una concentración el doble de la estequiométrica, mientras que el volumen y la velocidad de agitación no afectan significativamente a la eficiencia del proceso., En aquest projecte s’ha realitzat un estudi de tractament de les aigües àcides de mina (AMW) de la mina Los Frailes, Aznalcóllar (Sevilla) per a la recuperació de les terres rares (REE). Per això, s’ha generat una solució sintètica que simula l’efluent resultant de la regeneració de les resines d’intercanvi iònic de les mateixes AMW utilitzant àcid sulfúric (H2SO4) com a regenerant. La recuperació s’ha realitzat per precipitació selectiva de les REE mitjançant l’addició d’àcid oxàlic (H2C2O4) com a agent precipitant. S’ha avaluat l’efecte de la dosificació de H2C2O4, la concentració de H2SO4 de l’aigua a tractar, el volum de dissolució de l’aigua a tractar y la velocitat d’agitació durant el procés de precipitació. S’han analitzat les mostres de dissolució mitjançant ICP i els precipitats mitjançant SEM y XRD per determinar el contingut del precipitat y la morfologia. Els resultats obtinguts mostren com les REE lleugeres (LREE) són les impulsores de la nucleació necessària per al procés de precipitació mentre que les REE pesades (HREE) no són capaces d’iniciar-la per elles mateixes. D’altra banda, s’ha deduït que les condicions òptimes de procés són l’aplicació d’oxalat en fase líquida amb una concentració el doble de l’estequiomètrica, mentre que el volum i la velocitat d’agitació no afecten significativament en l’eficiència del procés., In this project, a study has been carried out on the treatment of acid mine water (AMW) from the Los Frailes mine, Aznalcóllar (Seville) for the recovery of rare earths (REE). For this purpose, a synthetic solution has been generated that simulates the effluent resulting from the regeneration of the ion exchange resins of the AMW using sulphuric acid (H2SO4) as regenerant. The recovery has been performed by selective precipitation of the REE by the addition of oxalic acid (H2C2O4) as precipitating agent. The effect of the dosage of H2C2O4, the concentration of H2SO4 in the water to be treated, the dissolution volume of the water to be treated and the agitation speed during the precipitation process were evaluated. The dissolution samples have been analysed by ICP and the precipitates by SEM and XRD to determine the precipitate content and morphology. The results obtained show that light REE (LREE) are the nucleation drivers necessary for the precipitation process while heavy REE (HREE) are not able to initiate it on their own. On the other hand, it has been deduced that the optimal process conditions are the application of oxalate in liquid phase with a concentration twice the stoichiometric concentration, while the volume and stirring speed do not significantly affect the efficiency of the process.

Desde el siglo XX, las tierras raras (REE) se han posicionado como materias decisivas para el avance tecnológico con el objetivo de implementar esquemas circulares y valorizar los residuos. Pero el acceso a una fuente confiable de REE para la Unión Europea supone un desafío debido a la falta de minas, lo que conlleva a una relación de dependencia con China. El país oriental tiene la mayor producción y reserves de REE en el mundo siendo el principal exportar a nivel global. Actualmente, la UE investiga y estudia recursos secundarios de suministro sostenible, como son las aguas ácidas de mina (AMW de sus siglas en inglés). El abandono de las explotaciones mineras favorece la formación de las AMW mediante la oxidación de sulfuros metálicos en presencia del oxígeno y la humedad atmosférica, dando lugar a la formación de ácido sulfúrico, metales de transición y REE. Estos drenajes resultan tóxicos para el hombre, la fauna y la vegetación, pero a su vez se ha identificado como singularidad la presencia de REE en concentraciones que plantean la posibilidad de convertirse en una fuente secundaria. Este Trabajo de Final de Grado se ha centrado en el estudio de un tren de tratamiento de AMW que permita su recuperación mediante precipitación selectiva con H2C2O4. En etapas previas no incluidas en el alcance de este TFG, las REE son extraídas y concentradas mediante intercambio iónico. La regeneración de las resinas de intercambio iónico con H2SO4 0,4M, genera unas disoluciones de REE de la cuales el objetivo perseguido es su recuperación en forma de oxalatos de REE. El objetivo de este estudio es identificar las dos condiciones más importantes de operación: pH y concentración de H2C2O4necesaria para conseguir la máxima recuperación de las REE, evitando la presencia de otros elementos alcalinotérreos de transición y post-transición para conseguir la mayor pureza de los oxalatos precipitados en REE. Para ello, se han evaluado diferentes condiciones experimentales: i) a diferente, Since the 20th century, rare earths (REE) have been positioned as decisive materials for technological advancement with the aim of implementing circular schemes and valorizing waste. But access to a reliable REE source for the European Union is a challenge due to the lack of mines, leading to a dependency relationship with China. The eastern country has the largest production and reserves of REE in the world being the main export globally. The EU is currently researching and studying sustainable secondary supply resources, such as acidic mine water (AMW). The abandonment of mining operations favors the formation of AMW by oxidation of metal sulfides in the presence of oxygen and atmospheric humidity, leading to the formation of sulphuric acid, transition metals and REE. These drains are toxic to man, fauna and vegetation, but the presence of REE in concentrations that pose the possibility of becoming a secondary source has been identified as a singularity. This Final Grade Study focused on the study of an AMW treatment train that allows its recovery by selective precipitation with H2C2O4. In previous stages not included in the scope of this work, REE are extracted and concentrated by ion exchange. The regeneration of ion exchange resins with H2SO4 0,4M generates REE solutions from which the objective is their recovery in the form of REE oxalates. The objective of this study is to identify the two most important operating conditions: pH and oxalic acid concentration necessary to achieve maximum recovery of REE, avoiding the presence of other alkaline elements transition and post-transition to achieve the highest purity of REE precipitated oxalates. For this purpose, different conditions have been evaluated with different experimental conditions: i) at different pH values found in the range of 0.5-3.0, ii) with different methods of adding H2C2O4: direct addition and addition with peristaltic pump, iii) to different stoichiometric ratios that influence the dosing volum

Ion-exchange (IX) resins incorporating single functional groups (sulfonic or amino-phosphonic) and two functional groups (sulfonic and phosphonic) were evaluated for selective recovery of Rare Earth Elements (REEs) from acidic mine waters (AMW). The composition of AMW solution, complexing properties of the functional group, and acidity were investigated as key parameters for concentration and separation of REEs from transition elements (TEs). Fe has to be removed from AMW to enable REE recovery and here the AMW was treated with NaOH solutions to reach pH 3.9 where Fe(III) was selectively removed (≤99%) by precipitation of schwertmannite. Single functional IX resin containing a sulfonic group displayed a higher REE recovery efficiency and separation ratio than observed for the bi-functional resin (sulfonic/phosphonic). Concentration factors for REEs between 30 and 40 were achieved using regeneration cycles with H2SO4. The performance of the aminophosphonic resin showed lower separation factors for REEs from TEs than the two resins containing sulfonic groups. IX resins performance was improved by tuning the acidity to match the functional group reactivity, where pH adjustment to the range of 0.5–2.0 provided the highest REE/TE separation factor for the single sulfonic resin followed by the bifunctional resin. The integration of an elution cycle using Na2-EDTA/NH4Cl mixtures strongly increases the concentration factors of REE and Light REE (LREE) concentration factors of up to 260 were achieved for the single functional sulfonic resin.

Acidic mine Drainage (AMD) is still considered one of the greatest mining sustainability challenges due to the large volumes of wastes generated and the high associated treatment cost. New regulation initiatives on sustainable development, circular economy and the need for strategic elements as Rare Earth Elements (REE) may overcome the traditional research initiatives directed to developing low cost treatment options and to develop research initiatives to identify the potential benefit of considering such AMD as a potential secondary resource. As an example, this study develops the integration of a three-stage process where REE are selectively separated from base metals (e.g. Fe, Al, Mn, Ca, Mg, Cd, Pb) and then concentrate to produce a rich REE by-product recovered as REE-phosphates. Selective separation of Fe (>99%) was achieved by total oxidation to Fe(III) and subsequent precipitation as schwertmannite at pH 3,6 ± 0.2. REE were then extracted from AMD using a sulfonic ion-exchange resin to produce concentrated REE sulfuric solutions up to 0.25 gREE/L. In a final stage selective separation of REE from Al(III), Ca(II) and Mg(II) and transitions elements (Cu, Zn, Ni) was achieved by precipitation with phosphate solutions under optimized pH control and total phosphate concentration. XRD analysis identified low-crystalline minerals. By using a thermal treatment the presence of PrPO4(s) and Cheralite (CePO4(s)) where Ce is substituted by La and Ca and Xenotime (YPO4(s)) were found as main minerals AlPO4(s) Ca,MgYPO4(s) were also identified., Peer Reviewed, Objectius de Desenvolupament Sostenible::13 - Acció per al Clima, Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura, Postprint (published version)

Ion-exchange (IX) resins incorporating single functional groups (sulfonic or amino-phosphonic) and two functional groups (sulfonic and phosphonic) were evaluated for selective recovery of Rare Earth Elements (REEs) from acidic mine waters (AMW). The composition of AMW solution, complexing properties of the functional group, and acidity were investigated as key parameters for concentration and separation of REEs from transition elements (TEs). Fe has to be removed from AMW to enable REE recovery and here the AMW was treated with NaOH solutions to reach pH 3.9 where Fe(III) was selectively removed (=99%) by precipitation of schwertmannite. Single functional IX resin containing a sulfonic group displayed a higher REE recovery efficiency and separation ratio than observed for the bi-functional resin (sulfonic/phosphonic). Concentration factors for REEs between 30 and 40 were achieved using regeneration cycles with H2SO4. The performance of the aminophosphonic resin showed lower separation factors for REEs from TEs than the two resins containing sulfonic groups. IX resins performance was improved by tuning the acidity to match the functional group reactivity, where pH adjustment to the range of 0.5–2.0 provided the highest REE/TE separation factor for the single sulfonic resin followed by the bifunctional resin. The integration of an elution cycle using Na2-EDTA/NH4Cl mixtures strongly increases the concentration factors of REE and Light REE (LREE) concentration factors of up to 260 were achieved for the single functional sulfonic resin., Peer Reviewed, Postprint (published version)

A polymeric ion-exchange resin, incorporating methyl-amino-phosphonic (TP260) functionalities, and a solvent impregnated resin (SIR) incorporating tri-methylpentylphosphinic acid (TP272), were evaluated for the selective separation of Rare Earth Elements (REE) from Transition (TE), post -Transition (PTE), and Alkaline Earth (AE) Elements in acidic mine waters (AMW). The influence of the functional groups nature and the acidity dependence were studied and their effects on efficiencies for REE removal and separation from TE/PTE were analysed Both resins provided good separation factors of REE from TE/PTE by acidity control of the treated effluent once Fe (III), the major component in AMW, had been removed by precipitation. The TP272 resin, containing trimethylpentylphosphinic acid (Cyanex 272) onto the polymeric network, showed higher affinity towards Heavy REE (HRRE) than for Light REE (LRRE) by acidity control (pH > 4). Higher pre-concentration factors were achieved for TP272 impregnated resin (e.g., 20-30) in comparison with the TP260 phosphonic resin (2-5), as the pH extraction window is in the moderate pH region (1-5). The integration in series of both resins could be used to separate and recover HREE and LREE from TE/PTE from AMW generated concentrates could be used to recover REE as secondary resources for the clean energy technology industry.

A polymeric ion-exchange resin, incorporating methyl-amino-phosphonic (TP260) functionalities, and a solvent impregnated resin (SIR) incorporating tri-methylpentylphosphinic acid (TP272), were evaluated for the selective separation of Rare Earth Elements (REE) from Transition (TE), post -Transition (PTE), and Alkaline Earth (AE) Elements in acidic mine waters (AMW). The influence of the functional groups nature and the acidity dependence were studied and their effects on efficiencies for REE removal and separation from TE/PTE were analysed Both resins provided good separation factors of REE from TE/PTE by acidity control of the treated effluent once Fe(III), the major component in AMW, had been removed by precipitation. The TP272 resin, containing tri-methylpentylphosphinic acid (Cyanex 272) onto the polymeric network, showed higher affinity towards Heavy REE (HRRE) than for Light REE (LRRE) by acidity control (pH > 4). Higher pre-concentration factors were achieved for TP272 impregnated resin (e.g., 20–30) in comparison with the TP260 phosphonic resin (2-5), as the pH extraction window is in the moderate pH region (1-5). The integration in series of both resins could be used to separate and recover HREE and LREE from TE/PTE from AMW generated concentrates could be used to recover REE as secondary resources for the clean energy technology industry., Peer Reviewed, Objectius de Desenvolupament Sostenible::9 - Indústria, Innovació i Infraestructura, Objectius de Desenvolupament Sostenible::13 - Acció per al Clima, Postprint (author's final draft)

En els últims anys, la producció d’acer ha fet augmentar la quantitat de residus generats en la industria del acer. Com a conseqüència, han desenvolupat noves tecnologies per millorar les taxes de recuperació d’aquests residus. Una de les tècniques que s’està valorant, es la utilització de les cendres obtingudes en els Forns d’Arc Elèctric (EAF), com a fertilitzants en l’agricultura. Si es separen els elements claus per la fertilització dels elements tòxics que presenten aquestes cendres, es poden valoritzar i obtenir un benefici econòmic, a més de reduir els residus i beneficiar al medi ambient. Dins el projecte “Steel Slag Greening: From waste to fertilizer/remineralizers” es vol estudiar el mètode per a que les cendres obtingudes en els EAF puguin ser valoritzades com a fertilitzants en l’agricultura. Per això es necessita realitzar una caracterització de les mostres, estudiar quins mètodes son efectius per la separació dels elements tòxics presents en les cendres, valorar les propietats de les cendres en els sòls i millorar-ne les propietats per finalment utilitzar-les com a material fertilitzant. En aquest treball, s’estudiarà la caracterització de les cendres y la extracció dels compostos tòxics que estiguin presents en elles., En los últimos años, la producción de acero ha hecho aumentar la cantidad de residuos generados en la industria de acería. En consecuencia, las industrias han desarrollado nuevas tecnologías para mejorar las tasas de recuperación de estos residuos. Una de las técnicas que se está valorando, es la utilización de las cenizas obtenidas en los Hornos de Arco Eléctrico, como fertilizantes en la agricultura. Si se separan los elementos claves para la fertilización de los elementos tóxicos que presentan las cenizas, se pueden valorizar y obtener un beneficio económico, además de reducir los residuos y beneficiar al medioambiente. Dentro del proyecto “Steel Slag Greening: From waste to fertilizer/remineralizers” se quiere estudiar el método para que las cenizas obtenidas en los EAF puedan ser valorizados como fertilizantes en la agricultura. Para ello se necesita realizar una caracterización de las muestras, estudiar que métodos son efectivos para la separación de los elementos tóxicos presentes en las cenizas, valorar las propiedades de las escorias en los suelos y mejorar las propiedades para finalmente utilizarlas como material fertilizante. En este trabajo, se estudiará la caracterización de las cenizas y la extracción de los compuestos tóxicos que estén presentes en ellas., In recent years, steel production has increased the amount of by-products generated in the steelmaking industry. As a result, industries have developed new technologies to improve the recovery rates of these slags. One of the techniques that is being evaluated is the use of the ashes obtained from Electric Arc Furnaces as fertilisers in agriculture. If the key elements for fertilisation are separated from the toxic elements present in the ashes, they can be valorised and an economic benefit can be obtained, as well as reducing waste and benefiting the environment. Within the project "Steel Slag Greening: From waste to fertilizer/remineralizers", the aim is to study the method by which the ashes obtained in EAF can be valorised as fertilisers in agriculture. For this purpose, it is necessary to characterise the samples, study which methods are effective for the separation of the toxic elements present in the ashes, evaluate the properties of the slag in soils and improve their properties in order to finally use them as a fertiliser material. In this work, the characterisation of the ashes and the extraction of the toxic compounds present in them will be studied.

Peer Reviewed, Postprint (published version)

The sorption of phosphate by K-zeolites synthesized from fly ash (FA) by hydrothermal conversion is investigated in this study. The aim is the synthesis of Ca bearing K-zeolites to recover phosphate from urban and industrial wastewater effluents. The loaded zeolites are considered as a by-products rich in essential nutrients such K and P (KP1) with a potential use as slow release fertilizer. A number of synthesis conditions (temperature, KOH-solution/FA ratio, KOH concentration, and activation time) were applied on two FA samples (FA-TE and FA-LB) with similar glass content but different content of crystalline phases, to optimize the synthesis of a zeolitic sorbent suitable for the subsequent phosphate uptake. Merlinoite and W rich zeolitic products synthesized from FA-LB and FA-TE were found to have sorption properties for phosphate removal. A maximum phosphate sorption capacity of 250 mgP-PO4/g and 142 mgP-PO4/g for the zeolitic products selected (KP1-LB and KP1-TE, respectively) was achieved. The dominant phosphate sorption mechanism, in the pH range (6–9) of treated wastewater effluents, indicated that sorption proceeds via a diffusion-controlled process involving phosphate ions coupled with calcium supply dissolution from K-zeolitic products and subsequent formation of brushite (CaHPO4 2H2O(s)). The phosphate loaded sorbent containing a relatively soluble phosphate mineral is appropriate for its use as a synthetic slow release fertilizer. The simultaneous valorisation of fly ash waste and the P recovery from treated wastewaters effluents, (a nutrient with scarce natural resources and low supply) by obtaining a product with high potential for land restoration and agriculture will contribute to develop one example of circularity.

The sorption of phosphate by K-zeolites synthesized from fly ash (FA) by hydrothermal conversion is investigated in this study. The aim is the synthesis of Ca bearing K-zeolites to recover phosphate from urban and industrial wastewater effluents. The loaded zeolites are considered as a by-products rich in essential nutrients such K and P (KP1) with a potential use as slow release fertilizer. A number of synthesis conditions (temperature, KOH-solution/FA ratio, KOH concentration, and activation time) were applied on two FA samples (FA-TE and FA-LB) with similar glass content but different content of crystalline phases, to optimize the synthesis of a zeolitic sorbent suitable for the subsequent phosphate uptake. Merlinoite and W rich zeolitic products synthesized from FA-LB and FA-TE were found to have sorption properties for phosphate removal. A maximum phosphate sorption capacity of 250 mgP-PO4/g and 142 mgP-PO4/g for the zeolitic products selected (KP1-LB and KP1-TE, respectively) was achieved. The dominant phosphate sorption mechanism, in the pH range (6–9) of treated wastewater effluents, indicated that sorption proceeds via a diffusion-controlled process involving phosphate ions coupled with calcium supply dissolution from K-zeolitic products and subsequent formation of brushite (CaHPO4 2H2O(s)). The phosphate loaded sorbent containing a relatively soluble phosphate mineral is appropriate for its use as a synthetic slow release fertilizer. The simultaneous valorisation of fly ash waste and the P recovery from treated wastewaters effluents, (a nutrient with scarce natural resources and low supply) by obtaining a product with high potential for land restoration and agriculture will contribute to develop one example of circularity, Peer Reviewed, Postprint (author's final draft)

The main challenge for copper smelters is to ensure product quality under the constant increase in impurities (As, Se, Mo, Co, Zn, Sb, and Pb) in copper ores that has occurred over the years. The presence of toxic elements, such as As(V), in acidic streams rich Cu(II) and Zn(II) (pH 2.0–2.5) limits the valorisation of both metals. In this study, a novel combination of the following two ion-exchange-based processes were proposed: i) membrane selectrodialysis (SED) for the selective separation of Zn(II)/Cu(II) from As(V) and ii) solvent-impregnated ion-exchange (IX) resins for the selective separation of Zn(II) from Cu(II). The selective separation of As(V), which is present in solution as H3AsO4/H2AsO4–, is achieved using a combination of monocharge and non-monocharge selective cation-exchange membranes to avoid the co-precipitation of As(V) when IX resins are used for Cu(II)/Zn(II) recovery. This combination of processes represents the novelty of the present study since it could be used in hydrometallurgical industries to remove As(V) and, at the same time, to valorize two value-added metals [Cu(II) and Zn(II)]. At the moment, only single-stage processes have been proposed. Using SED, a Cu(II)/Zn(II)-rich stream [97¿±¿2% Cu(II) and 82¿±¿3% Zn(II)] was obtained, and 60¿±¿4% of As(V) was removed from the initial feed stream. Then, the separation of Zn(II) from Cu(II) was proposed using Lewatit VP OC 1026 resin at pH¿=¿2.2 and 4.3, respectively. In this IX resin process, it was possible to recover 70¿±¿3% of Zn(II) and 98¿±¿2% of Cu(II) and to concentrate Zn(II) and Cu(II) around 30- and 23-times, respectively., Postprint (author's final draft)

Postprint (published version)

Postprint (author's final draft)

The use of low-cost inorganic sorbents as a new sustainable strategy to enhance the valorization of nutrients (N-P-K), from the urban water cycle (e.g., side streams from sewage sludge anaerobic digestion), in agriculture applications is presented. The simultaneous recovery and stabilization of ammonium and phosphate by using a mixture of two reactive sorbents (Na and K zeolites and magnesium oxide) was evaluated. The nutrients stabilization process, favoured at alkaline pH values, is carried out by a) the precipitation of phosphate ions with magnesium and/or ammonium ions and b) the sorption of ammonium by Na- and K-zeolites. MgO(s) promoted the stabilization of phosphate as bobierrite (Mg3(PO4)2(s)) or struvite (MgNH4PO4(s)) depending on the applied dose. Doses with the stoichiometric molar ratio of Mg/P promote the formation of bobierrite, while molar ratios higher than 3 favour the formation of struvite. Na zeolites (NaP1-NA, NaP1-IQE) demonstrated efficiency on ammonium stabilization between 60 ± 2 (for 15 gZ/L) to 90 ± 3% (for 50 gZ/L). The ammonium recovery efficiency is limited by the zeolite sorption capacity. If the target of the fertilizing criteria should include K, then the use of a K-zeolite (e.g., 5AH-IQE) provides a good solution. The optimum pH for the precipitation of struvite and bobierrite is 9.5 and the optimum pH for ammonium removal is between 4 and 8.5. N is present in higher concentrations (up 0.7–1 g NH4+/L) when pH is ranged between 8.2 and 8.6. The ammonium recovery ratios were better than those previously reported using only magnesium oxide or even a more expensive reagent as newberrite (MgHPO4(s)). The recovery mechanisms described generate low-solubility stabilized nutrients forms that potentially can be applied as slow-release fertilizers in agriculture. Thus, the use in agriculture of blends of digested sludge with low-solubility stabilized nutrients forms will improve soils quality properties in terms of organic matter and nutrients, Peer Reviewed, Postprint (author's final draft)

BACKGROUND In this study three natural Yemeni zeolites (NZ1, NZ2 and NZ3) having major minerals such as clinoptilolite and mordenite, were evaluated as low cost sorbents for the removal and recovery of ammonium ions. RESULTS The zeolite samples, with pHPZC =¿9.1¿±¿0.2, 7.9¿±¿0.2 and 7.4¿±¿0.2 for NZ1, NZ2 and NZ3, respectively, showed high ammonium sorption capacities. At pH¿8, for treated waste waters: (i) with low NH4+ levels (from 25 to 100 mgNH4/L); and (ii) for concentrated NH4+ side streams generated from the anaerobic digestion of sewage sludge (from 400 up to 1500¿mg L-1), maximum loading capacities of 27 to 51 mgNH4 g-1 were measured for the studied zeolites. Measured sorption isotherms, in the concentration range 0.05 to 5¿g L-1, were well described by the Langmuir isotherm. The ammonium sorption kinetics was controlled by particle diffusion and was well described by both the homogeneous diffusion (HPDM) and shell progressive (SPM) models. CONCLUSION Comparison of the equilibrium data with results for natural and synthetic zeolites demonstrate the higher performance of the studied zeolites providing low residual ammonium values <1 mgNH4 g-1 and <10 mgNH4 g-1 when treating both diluted and concentrated-NH4+ streams, respectively., Preprint

Here, an alternative nutrient (N-P-K) recovery route from potassium-rich sludge anaerobic digestion side-streams using powder reactive sorbents (PRSs) is presented. In the first step, the optimum PRS system was determined in batch experiments with mixtures of: a) a sodium zeolite (NaP1) to facilitate the NH4+ and K+ sorption; b) a Ca-zeolite (CaP1) to facilitate the removal of P by formation of Ca-phosphates (e.g., CaHPO4(s)), and c) caustic magnesia containing mixtures of MgO to facilitate the formation of Mg/NH4/PO4 minerals (e.g., struvite and magnesium phosphates). Evaluation of the continuous and simultaneous N-P-K removal with mixtures of PRSs was carried out using a hybrid sorption/filtration system with ultrafiltration (UF) hollow-fibre membranes. The dosing ratios of the PRS mixtures were optimised on the basis of the equilibrium and kinetic sorption data, and a PRS dose (< 2–5 g PRS/L) was selected to ensure the hydraulic performance of the system. Under such conditions, and with synthetic anaerobic side-stream removal capacities (qt) of 220 ± 10 mg N-NH4/g, 35 ± 5 mg P-PO4/g, and 8 ± 2 mg K/g, removal efficiencies of 32 ± 3, 78 ± 5, and 26 ± 3% for ammonium, phosphate, and potassium, respectively, were obtained for the binary mixtures of NaP1/CaP1 zeolites. Contrary to the batch results, the use of tertiary mixtures of NaP1/CaP1/MgO only improved the K removal capacity and efficiency to 18 ± 2 mg K/g and 55 ± 4%, respectively, while the phosphate removal capacity and efficiency remained unchanged (ca. 35 ± 3 mg P-PO4/g; 80 ± 5%) and the ammonium capacity and efficiency were reduced to 185 ± 12 mg N-NH4/g and 20 ± 2%, respectively, due to the competing Mg2 + ion effect. Nutrient removal trials with real anaerobic side-streams using binary mixtures of Na/Ca zeolites showed a reduction of both the hydraulic performance and the nutrient removal ratios due to the presence of dissolved organic matter. However, constant removal ratios of N, P, and K were recorde, Preprint

There is interest in recovering phosphate (P(V)) from secondary sources, such as waste water streams for potential use as fertilizers reducing the environmental impacts of P(V) discharges and providing alternative phosphorus sources. The goal of this work was to provide an understanding of P(V) removal by fly ash (FA) from coal power plants. Phosphate removal using Ca(II) rich FA was evaluated in terms of i) sorption equilibrium, ii) sorption kinetics under the expected pH values and P(V) concentrations in wastewaters effluents, and iii) P(V) availability of the FAs in agricultural applications. At the pH values (6–9) expected for wastewater effluents, P(V) removal proceeds as a combination of CaO(s) dissolution and brushite (CaHPO4(s)) formation on the FA particles. This process avoids the formation of relatively insoluble Ca–phosphates, such as, hydroxyapatite (Hap) with limited fertilizing properties. High P-loadings were achieved (up to 50 mgP-PO4/g FA (5% P(V) by weight)) at a pH of 8. The removal kinetics data were well described as a diffusion-based process of phosphate ions (H2PO4- and HPO42-) on FA particles, and the CaO(s) dissolution process was discarded as the rate controlling step. The P(V) availability from loaded samples was determined via an agronomical assay with NaHCO3 solutions with P(V) release ratios of 10–30 mgP-PO4/g in FA, confirming the appropriateness of this material as a potential fertilizer, even in calcareous soils., Peer Reviewed, Postprint (author's final draft)

A natural clinoptilolite in its potassium form (KNC) was modified by impregnation of hydrated metal oxides (HMO) of aluminium (III) (KAlC), iron (III) (KFeC) and manganese (IV) (KMnC) for the simultaneous ammonium and phosphate recovery from urban wastewaters. The resulting pHpzc of the HMOs on the modified zeolites (7.3 ± 0.3 for KAlC, 6.4 ± 0.4 for KFeC and 6.9 ± 0.3 for KMnC) are suitable for phosphate sorption at pH of treated urban wastewaters (6–8). The sorption capacity for phosphate for KAlC and KFeC zeolites is higher at the lower pH range while for KMnC is higher at the upper pH range. Differences were associated to the intrinsic complexing properties of the MOH groups to form outer and inner sphere MOH-phosphate complexes. The maximum phosphate sorption capacity for the three zeolites were 6.8 mg-P/g for KAlC, 7.2 mg-P/g for KFeC and 8.2 mg-P/g for KMnC. Contrary maximum ammonium sorption capacity is kept constant between pH 4–9 for the tree zeolites as the main sorption mechanism is the ion-exchange reaction with K+ ions of the zeolite. The maximum ammonium sorption capacity for the three zeolites ranged from 29 to 33 mg-N/g. These differences on the nature of the sorption processes are also reflected in a much faster sorption kinetic for ammonium than for phosphate although for both species the rate determining step was ions diffusion on the zeolite particles. Modified zeolites shown high selectivity towards ammonium and phosphate in the presence of the dissolved organic matter as well as other ionic species present in the treated wastewaters. Finally, phosphorous (P) fractionation assays of the loaded zeolites confirmed a high phosphate bioavailability if these are applied as phosphate slow release fertilizers in soil applications, Postprint (author's final draft)

The influence of Mg(II) on phosphorous recovery as hydroxyapatite (Hap) from alkaline phosphate concentrates using desalinated industrial brines as the calcium source in a batch reactor was evaluated. Two synthetic brines with Mg/Ca molar ratios of 2.2 and 3.3 were continuously fed to reach a Ca/P molar ratio of ~1.67 to promote Hap formation under different constant pH values (8, 9.5, 10.5, 11.5 and 12). For both brines, inhibition of Hap precipitation and formation of the amorphous mineral phases of Ca-, Mg- and Ca/Mg-phosphates were observed at pH > 9.5. Mg(II) severely inhibited phosphate precipitation, allowing the formation of amorphous calcium phosphate from meta-stable clusters due to Mg(II) incorporation into Ca-phosphate. For the Mg/Ca (3.3) brine, a more soluble Mg-phosphate mineral (cattiite) was formed at pH 11.5. Thermal treatment of the amorphous solids to increase crystallinity confirmed the presence of Hap and chlorapatite as Ca-phosphate, stanfieldite as Ca–Mg-phosphate and farringtonite as Mg-phosphate. In the experiments at pH 8, the formation of stable nanometer-sized pre-nucleation clusters promoted nucleation inhibition, even in supersaturated solutions, and no solids were recovered after filtration. Although sulfate was involved in some of the precipitation reactions, its role in the inhibition of Hap formation is not clearly elucidated, Postprint (author's final draft)

Background: A powdered zeolitic material synthesised from fly ash (FA) (NaP1-FA) and its calcium modified form (CaP1-NA) were studied as sorbent materials for the recovery of phosphate from treated waste-water effluents. Phosphate-sorption equilibrium experiments were performed by varying the experimental conditions, including solution pH, phosphate concentration, and the presence of competing ions. Results: The maximum phosphate-sorption capacities were 57 ± 5 and 203 ± 11 mgP–PO4g-1 for NaP1-FA and CaP1-NA, respectively. The sorption capacities of both zeolites in the pH range expected for waste-water effluents (pH 7 to 9) were slightly dependent on pH, exhibiting maxima at pH 8. Phosphate removal proceeds through two main mechanisms: (a) surface complexation with ≅AlOH and ≅FeOH groups of the zeolitic structure or unreacted minerals from the FA; and (b) the formation of Ca–phosphate phases, mainly brushite. Conclusions: The removal mechanisms were confirmed by XRD analyses and P speciation. The stabilities of the phosphate-loaded zeolite samples evaluated by the extraction experiments confirmed their potential availabilities in soil applications. Finally, the higher solubility of brushite compared with that of Hap makes this zeolitic material promising as a novel inorganic zeolite/CaP1-NA/brushite fertiliser, Postprint (author's final draft)

The feasibility of continuous phosphate recovery, by adsorption on powdered Ca-activated zeolite (PAZ), was assessed in a hybrid sorption membrane ultrafiltration (UF) system. The objective was to explore the influence of process parameters such as initial P(V) concentration, pH, and PAZ dose on P(V) recovery from a tertiary treatment effluent. The hydrodynamic parameters of the UF operation were also evaluated as a function of the PAZ dose. The P(V) recovery profiles as a function of the initial P(V) concentrations, at pH 8 and 2.5 gpAz/L, indicated that the sorbent was not saturated, and recoveries reported were 1.8 +/- 0.2, 5.7 +/- 0.3, and 47.2 +/- 2 mg P(V)/gpAz for 10 +/- 1, 25 2, and 100 +/- 6 mg P(V)/L, respectively. The increase of the pH of the feed solution from 8 to 9 increased the P(V) recovery up to 70 4%. A P(V) fractionation protocol of the loaded samples confirmed that the phosphate -sorption process involves the formation of calcium phosphate mineral forms, Peer Reviewed, Postprint (author's final draft)