La pollution des eaux constitue actuellement une préoccupation majeure aussi bien d’un point de vue sanitaire qu’environnemental. Afin d’y remédier, des procédés de dépollution efficaces, économiques et durables sont constamment développés et l’adsorption reste une méthode largement utilisée dans le traitement des eaux usées. De nombreux travaux sont consacrés à l’adsorption des polluants cationiques, mais le développement de supports adaptés pour interagir avec les contaminants anioniques est moins abordé. L’objectif principal de ce travail de thèse est de mettre en forme deux adsorbants anioniques : l’HDL (hydroxyde double lamellaire) Mg/Al et la ferrihydrite deux-lignes, et les associant à un gel d’alginate pour produire des matériaux composites pouvant être mis en oeuvre dans des réacteurs spécialisés pour l’élimination de contaminants anioniques. Les résultats de l’adsorption en réacteur batch sur les HDL et la ferrihydrite ont montré une bonne efficacité pour l’élimination de certains anions. La ferrihydrite possède une capacité plus importante que les HDL pour l’élimination des anions inorganiques. L’augmentation du rapport Mg/Al dans l’HDL a favorisé l’adsorption du méthyl orange (MO) ; un rapport Mg/Al de 3 (L3) a été séléctionné pour la suite du travail. Deux protocoles ont été évalués pour associer les solides à un gel d’alginate : l’encapsulation et la synthèse interne dans le gel. La nature des cations réticulant et la création de la macroporosité ont été étudiées. L’encapsulation du solide a diminué légèrement la capacité d’adsorption des anions, cependant, la création de la macroporosité permet de compenser cet effet du gel d’alginate. Les études sur l’adsorption du MO avec les billes encapsulées ont montré que l’augmentation de la taille des billes et de la quantité du solide L3 encapsulée a été accompagnée par une diminution de la capacité d’adsorption du MO. Le remplacement du réticulant Ca2+ par Ba2+ a permis de renforcer la structure du gel et améliorer la cinétique d’adsorption du MO, mais a entrainé une diminution de la capacité d’adsorption. La caractérisation des supports préparés par synthèse interne a montré une structure des solides différente des matériaux attendus (L3 ou ferrihydrite) avec par conséquence une réactivité différente. Des mécanismes d’élimination des anions organiques et inorganiques ont été proposés selon les différents adsorbants étudiés. Les billes ferrihydrite/alginate préparées par encapsulation ont présentés globalement une bonne capacité de rétention des anions notamment pour les anions inorganiques (phosphate, chromate et arséniate). Tandis que celles préparées par synthèse interne ne fixent que les arséniates et les phosphates par différents mécanismes essentiellement la précipitation des anions à la surface des oxyde et oxy-hydroxydes de fer. L’adsorption du MO en réacteur filtrant ouvert a montré que l’augmentation du débit d’alimentation a un effet négatif sur l’adsorption alors qu’une concentration initiale plus grande favorise l’adsorption ce qui est en concordance avec les résultats obtenus en réacteur batch. Un taux de régénération de 30% des billes ferrihydrite/alginate macroporeuse (BPENFh-Ba) a été observé en réacteur batch en utilisant une solution de chlorure d’ammonium avec la possibilité de réutiliser l’adsorbant plusieurs fois.Ce travail confirme les performances et la possibilité d’utiliser des matériaux composite d’HDL ou ferrihydrite dans un gel d’alginate pour l’élimination de composés anioniques contenus dans des eaux usées. / Water pollution is currently a major concern from both health and environmental point of view. In order to solve this problem, efficient decontamination processes, economic and sustainable are constantly being developed and adsorption process remains a widely used method in the wastewater treatment. Many studies are devoted to the adsorption of cationic pollutants, but the development of suitable supports able to interact with the anionic contaminants is less discussed. The main objective of this work is to form two anionic adsorbents: the LDH (Layered Double Hydroxide) Mg/Al and two-line ferrihydrite. These adsorbents were associated with an alginate gel in order to produce composite materials that can be implemented in continuous reactors for the removal of anionic contaminants. The adsorption studies in batch reactor on LDH and ferrihydrite confirmed good removal efficiency for some anions. Ferrihydrite showed a higher adsorption capacity than LDH for the removal of inorganic anions. Increasing the Mg/Al ratio was favorable for the methyl orange (MO) adsorption, and an Mg/Al ratio of 3 (L3) was selected for the following work. Two protocols were evaluated for the integration of adsorbent into alginate gel: encapsulation and direct synthesis in the gel structure. The effect of crosslinking cation and the making of macroporosity were studied. The encapsulation of solids decreased slightly the adsorption ability of anions; however, the macroporosity counterbalances this negative effect of alginate gel. The MO adsorption studies with encapsulated beads showed that the increase of the bead size and the amount of solid in the beads were accompanied with a decrease in the adsorption capacity. The replacement of Ca2+ by Ba2+ strengthened the gel structure and improved the adsorption kinetics but decreased the adsorption capacity. The characterization of the support material prepared by direct synthesis in alginate gel showed a different structure from the expected materials (L3 or ferrihydrite), and therefore a different reactivity. The sorption mechanisms of various organic and inorganic anions were proposed for the studied adsorbents. The ferrihydrite/alginate beads prepared by encapsulation showed a good adsorption for all the anions used in this work, especially for inorganic anions (phosphate, chromate and arsenate); while those produced by direct synthesis in alginate gel removed only arsenate and phosphate essentially by a precipitation mechanism of the anions at the surface of the iron oxides and oxy-hydroxides. The sorption of MO in a continuous reactor showed that the increasing of the flow rate had a negative effect on sorption while higher initial concentration presented a favorable effect on the sorption, which is in accordance with results obtained in batch reactor. A desorption ratio of 30% for ferrihydrite/alginate macroporous beads (BPENFh-Ba) was observed in batch reactor with the possibility of reusing the adsorbent.This study confirms the performance and the possibility to use the composite materials of LDH or ferrihydrite in an alginate gel for the removal of anionic compounds contained in wastewater.

Au cours de la dernière décennie, le procédé de fabrication additive par fusion sélective d'un lit de poudre SLM a attiré une grande attention dans le domaine de l'industrie, car il permet de produire rapidement des pièces de formes complexes. Le but de ce travail est d'étendre les performances des procédés SLM en étudiant la possibilité d'élaborer des pièces en atmosphère raréfiée. Pour atteindre cet objectif, une approche théorique et expérimentale a été développée, avec la mise en place d'une machine de fusion sélective par laser capable de travailler dans le domaine de pression de 1 à 10-2 mbar.Le travail sous vide permet d'éviter la formation du "bouclier" de plasma généré à partir de l'atmosphère de gaz ionisé par l'énergie du laser. Ceci permet d'une part d'éviter la contamination chimique du matériau (oxydation, nitruration,...) au cours des processus de fusion et d'autre part de réduire le taux de porosité. L'effet des paramètres du laser et des variables d'environnement sur la qualité de pièces a été étudié en considérant le cas du fer pur, de l'acier Inox 316L et du titane.Par ailleurs nous avons étudié la possibilité d'obtenir des alliages in-situ au cours de la fabrication par la technique SLM à partir de mélanges de poudres.Des essais ont été conduits à partir de mélanges Mg/Al, Fe/Ni et Ti/Ni. Dans tous les cas nous avons pu obtenir des alliages in-situ pour les domaines de composition visés qui correspondent à des applications pratiques (structures légères, alliage magnétique à faible coercivité, alliage à mémoire de forme). Les propriétés des matériaux obtenus, d'après les premières caractérisations effectuées, se comparent de façon favorable par rapport aux techniques classiques d'élaboration et de mise en œuvre. / During the last decade, selective laser melting attracted attention in industry because it could allow producing parts with complex shapes rapidly and accurately. The aim of this work is to obtain parts with desired properties by SLM technology. To achieve this point, a theoretical and experimental approach was developed concerning a new process which carries out the selective laser melting process at pressures in the range 1 to 1×10-2 mbar.Vacuum operating under allows avoiding the plasma shield generated from the gas atmosphere ionized by the high laser energy, which on the one hand avoids the chemical contamination (oxidizing, nitriding…) during the melting process and on the other hand reduces the porosity rate. The effect of laser parameters and environment variables on the quality of parts was studied by considering the case of pure iron, stainless steel 316L and titanium.Moreover, we studied the possibility of obtaining in-situ alloys during the SLM manufacturing technique from mixtures of powders.Tests were conducted from mixtures Mg/Al, Fe/Ni and Ti/Ni. In all cases we were able to obtain in-situ alloys for areas covered composition corresponding to practical applications (lightweight structures, low coercivity magnetic alloy, shape memory alloy). The properties of material obtained from the characterizations performed, which are comparable with the conventional development and implementation.

The kinetics of incongruent reduction between sapphire and oxygen-controlled Mg-Al melts was studied by measuring spinel-layer thickness, sample-weight change and sample-thickness change as a function of time at various temperatures. To eliminate the crucible contamination caused by impurities in commercial MgO crucibles, self-made high-purity MgO crucibles were achieved by gelcasting method, which is an attractive ceramic-forming technique for making high-purity ceramic parts. The oxygen-controlled alloys were obtained by the three-phase-equilibrium experiments at various temperatures. To avoid MgO formation, the oxygen-controlled alloys prepared at relatively lower temperatures were used for incongruent reaction at relatively higher temperatures. That is to say, the oxygen-controlled alloys prepared at 900°C, 1000°C, and 1100°C were used for spinel formation at 1000°C, 1100°C, and 1200°C, respectively. The experiments were conducted in a vertical furnace, and sapphire wafers were hung vertically in high-purity MgO crucibles so that the natural convection induced by the density change in the melt could be investigated. Experimental results obtained at 1000°C, 1100°C, and 1200°C showed that the spinel layer thickness on two kinds of sapphire wafers, namely {0001} and , followed orientation-independent parabolic kinetics, indicating the diffusion in spinel was one of the rate-limiting steps. In addition, the spinel layer thickness was not a function of position. The results of sample-thickness- change measurements also indicated that the effect of natural convection could be neglected. XPS, XRD, and TEM were also employed to characterize some samples in this study. Based on a simple model where the diffusion in spinel was the only rate-limiting step, the governing partial differential equations for diffusion and fluid dynamics were solved by the finite element method. The calculated theoretical parabolic constants at various temperatures were compared with these experimental results, and a good agreement was obtained. Some preliminary studies were also made on the morphologies of spinel particles at the nucleation stage. It was found that the triangular {111} faces of spinel particles were parallel to the surface of {0001} sapphire substrate. The product shape was consistent with the tetrahedron composed of {111} faces. The morphology of spinel particles on a sapphire substrate was more complicated in that the triangular {111} faces of spinel had to be inclined at a certain angle to the substrate in order to maintain the orientation relationship.

The square-planar tetracyanonickelate(II) anion was intercalated into 2:1 and 3:1 Mg-Al layered double hydroxide systems (LDHs). In the 2:1 material, the anion holds itself at an angle of about 30° to the layers, whereas in the 3:1 material it lies more or less parallel to the layers. This is confirmed by orientation effects in the infrared spectra of the intercalated materials and by X-ray diffraction (XRD) data. The measured basal spacings for the intercalated LDH hosts are approximately 11 Å for the 2:1 and approximately 8 Å for the 3:1. The IR of the 2:1 material shows a slight splitting in the ν(CN) peak, which is suppressed in that compound's oriented IR spectrum, indicating that at least some of the intercalated anion's polarization is along the z-axis. This effect is not seen in the 3:1 material. A comparison between chloride LDHs and nitrate LDHs was made with respect to intercalation of tetracyanonickelate(II) anions. Both XRD data and atomic absorption spectroscopy (AAS) data of the LDH tetracyanonickelates confirms that there are no significant differences between the products from the two types of starting materials. The presence of a weak ν(NO) peak in the IR spectra of those samples made from nitrate parents indicates the presence of small amounts of residual [NO3]- in those systems. Small amounts of Cl- present in the chloride-derived samples, while perhaps detectable using AAS, would not be detectable in this manner. An attempted synthesis of Mg-Al LDH carbonates starting from reduced Mg and Al was unsuccessful due to pH constraints on hydroxide solubility in the solvent system used (water). The pH required to precipitate Al(OH)3 in the system was too high to allow precipitation of Mg(OH)2. Consequently, we found it impossible to have both of the required metal hydroxides present simultaneously in the system. An additional synthesis using a halogen as an oxidizing agent also failed to produce material of any characterizable quality.

Magnesium (Mg) is a light-weight metal that has extraordinary physical and chemical properties for many potential applications in automobile, military, and electronics. Aluminum alloys, because of its light-weight, high strength and corrosion resistance have a wide range of commercial applications. Given these two, sometime competing, alloy systems, there are now many applications where the metallurgical compatibility of Mg- and Al-alloys are required for engineering applications. One such case is the development of diffusion barrier for U-Mo metallic fuel in Al-alloy cladding, where Mg, with its complete immiscibility with U and Mo is being considered as the diffusion barrier. While negligible diffusional interaction between Mg and U-Mo alloys have been reported, diffusional interaction between the Mg and Al-alloy cladding has not been investigated. In this study, solid-to-solid diffusion couples were assembled using discs of pure Mg (99.999 %) and AA6061 Al-alloy. After preparation, Mg was diffusion bonded to AA6061 in sealed quartz capsule at 300°, 350°, and 400°C for 720, 360, and 240 hours, respectively. Scanning electron microscopy was used to inspect the interdiffusion zone, while phase identification was performed using X-ray energy dispersive spectroscopy. One specific phase that exists in the binary Mg-Al system, labeled “ε” was observed and characterized by transmission electron microscopy. From the preceding data, the growth rates as well as interdiffusion coefficients of the intermetallic phases were extracted and compared to previous investigations using pure Mg and Al.

Submitted by Cássio da Cruz Nogueira (cassionogueirakk@gmail.com) on 2017-07-11T15:25:33Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Tese_IntercalacaoIbuprofenoHidroxidos.pdf: 4225191 bytes, checksum: f534a7785ef5d7832ed27d9e670fbdb7 (MD5) / Approved for entry into archive by Irvana Coutinho (irvana@ufpa.br) on 2017-07-18T12:35:42Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Tese_IntercalacaoIbuprofenoHidroxidos.pdf: 4225191 bytes, checksum: f534a7785ef5d7832ed27d9e670fbdb7 (MD5) / Made available in DSpace on 2017-07-18T12:35:44Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Tese_IntercalacaoIbuprofenoHidroxidos.pdf: 4225191 bytes, checksum: f534a7785ef5d7832ed27d9e670fbdb7 (MD5) Previous issue date: 2016-10-14 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico / Ibuprofeno intercalado em hidroxidos duplos lamelares (IBU-HDL) foi sintetizado com sucesso via método da co-precipitação com uma razão nominal de [Al3+]/[Mg2+] 0,5 e uma relação molar variável de IBU/([Al3+] + [Mg2+]) de 0, 0,15, 0,18, 0,24, 0,36 e 0,72. Após uma determinação precisa da composição, natureza das espécies intercaladas e do efetivo rendimento de intercalação dos NO3 – pelos IBU, verificou-se que a rota de síntese utilizada permite um bom controle da quantidade de IBU intercalado dentro da estrutura do HDL. Isto resulta em diferentes amostras com a completa ou parcial intercalação do IBU no espaço interlamelar na troca dos ânions nitrato. A análise das reflexões basais de difração de raios X revelam que a intercalação do IBU na estrutura apenas aumenta as distâncias basais sem alteração das lamelas do tipo brucita. Além disso, um estudo computacional utilizado para modelar as posições e formas das reflexões basais mostrou que a estrutura dos compostos não totalmente intercalado segue um esquema de interstratificação aleatória. Finalmente, foram selecionadas três amostras que variam desde galerias ligeiramente a totlamente intercaladas com IBU para ensaios in vivo preliminares. Estes testes mostraram uma forte tendência que após 24 horas, o baixo rendimento de compostos intercalados com IBU é quase tão eficiente como a amostra completamente intercalada. / Ibuprofen-intercalated layered double hydroxides (LDH-IBU) have been successfully synthesized via a co-precipitation method with a nominal [Al3+]/[Mg2+] ratio of 0.5 and a variable molar IBU/([Al3+]+[Mg2+]) ratio of 0, 0.15, 0.18, 0.24, 0.36 and 0.72. After an accurate determination of the composition, the nature of the intercalated species and the effective intercalation yield from NO3 - to IBU, it is shown that the synthesis route used allows a good control of the quantity of intercalated IBU within the LDH framework. This results in different samples with full or partial IBU intercalation in the interlayer space in exchange of nitrate anions. The analysis of the X-ray diffraction basal reflections reveals that the intercalation of IBU in the framework only increases the basal distances with no alteration of the brucite-type layers. Also, a computational study used to model the positions and shapes of the basal reflections showed that the structure of the non-fully intercalated compounds follows a random interstratification scheme. Finally three samples ranging from slightly to fully IBU-intercalated galleries were selected for preliminary in vivo assays. These tests showed a strong tendency that after 24 hours the low yield of IBUintercalated compounds are almost as efficient as the fully intercalated sample.

Les Hydroxydes Doubles Lamellaires (HDL) présentent de nombreux domaines d'application en rapport avec leur structure lamellaire et la diversité de leur de composition. Ce travail souligne les potentialités des HDL lorsqu'ils sont utilisés comme précurseurs d'oxydes mixtes pouvant intervenir en catalyse hétérogène acido-basique ou d'oxydo-réduction.<br />La première partie du mémoire concerne l'étude d'une série d'oxydes à base de nickel, cuivre, magnésium et aluminium, obtenus par calcination des HDL précurseurs à 450°C. La caractérisation structurale et l'étude de l'acido-basicité des oxydes mixtes en fonction de leur composition ont été réalisées. Elles s'appuient sur l'utilisation complémentaire de différentes méthodes analytiques physico-chimiques donnant accès à des informations concernant à la fois la structure, la composition et la morphologie des cristaux obtenus(DRX, ATG, analyse chimique, SPX...), ou permettant la caractérisation de leurs propriétés acido-basiques (adsorption de molécules sondes suivie par microcalorimétrie et SPX).<br />La seconde partie du travail est consacrée à l'utilisation des oxydes mixtes obtenus après calcination à 800°C pour la synthèse de nanofilaments de carbone à partir de la décomposition catalytique du méthane. Après une étude détaillée des oxydes mixtes, les nanofilaments produits ont été caractérisés à l'aide de différentes techniques, notamment la microscopie électronique à transmission. Les données physico-chimiques obtenues ont mis en évidence les relations entre les caractéristiques du catalyseur (composition, mode de synthèse, propriétés...) et le type des nanofilaments (tubes, fibres) obtenus.

Au cours de la dernière décennie, le procédé de fabrication additive par fusion sélective d'un lit de poudre SLM a attiré une grande attention dans le domaine de l'industrie, car il permet de produire rapidement des pièces de formes complexes. Le but de ce travail est d'étendre les performances des procédés SLM en étudiant la possibilité d'élaborer des pièces en atmosphère raréfiée. Pour atteindre cet objectif, une approche théorique et expérimentale a été développée, avec la mise en place d'une machine de fusion sélective par laser capable de travailler dans le domaine de pression de 1 à 10-2 mbar.Le travail sous vide permet d'éviter la formation du "bouclier" de plasma généré à partir de l'atmosphère de gaz ionisé par l'énergie du laser. Ceci permet d'une part d'éviter la contamination chimique du matériau (oxydation, nitruration,...) au cours des processus de fusion et d'autre part de réduire le taux de porosité. L'effet des paramètres du laser et des variables d'environnement sur la qualité de pièces a été étudié en considérant le cas du fer pur, de l'acier Inox 316L et du titane.Par ailleurs nous avons étudié la possibilité d'obtenir des alliages in-situ au cours de la fabrication par la technique SLM à partir de mélanges de poudres.Des essais ont été conduits à partir de mélanges Mg/Al, Fe/Ni et Ti/Ni. Dans tous les cas nous avons pu obtenir des alliages in-situ pour les domaines de composition visés qui correspondent à des applications pratiques (structures légères, alliage magnétique à faible coercivité, alliage à mémoire de forme). Les propriétés des matériaux obtenus, d'après les premières caractérisations effectuées, se comparent de façon favorable par rapport aux techniques classiques d'élaboration et de mise en œuvre.

No description available.

Arsenic (As) contamination is a worldwide problem, and millions of people are suffering from it. There are two major inorganic forms of As in waters: arsenate(V) and arsenite(III), and adsorption to a sorbent material may be an efficient method to handle them. In this study, we focused on As(III), the more toxic form, which predominates under reducing conditions. The As(III) removal properties of four sorbent materials: hydrotalcite, Mg−Al layered double hydroxide, amorphous aluminium hydroxide and amorphous titanium oxide, are examined from the following viewpoints: As(III) adsorption, the effects of pH, the effects of adsorbent concentration, adsorption as a function of dissolved As(III), and the effect of co-existing anions (HCO3− and PO43−). The maximum adsorption of As(III) to HT (0.1 mmol As(III)/g adsorbent), Mg-Al LDH (0.1 mmol As(III)/g adsorbent), am-Al(OH)3 (0.22 mmol As(III)/g adsorbent), and am-TiO2 (0.21 mmol As(III)/g adsorbent) occurred at pH 7.5, 7, 7, 8, respectively. At this pH, approximately 20%, 62%, 35%, and 98.3%, respectively, of the added As(III) was adsorbed. When the As(III) to sorbent ratio was increased, the adsorption was instead around 7% to am-Al(OH)3 (2.2 mmol As(III)/g adsorbent), and 46.3% to am-TiO2 (2.1 mmol As(III)/g adsorbent). These figures show that am-TiO2is the most efficient sorbent for As(III) adsorption of the four materials tested, Mg-Al LDH is second best, while HT and am-Al(OH)3 are not suitable for As(III) removal. The adsorption of As(III) to Mg-Al LDH as a function of dissolved As(III) could be adequately described by a linear equation, suggesting that As(III) adsorption to Mg-Al LDH was governed by anion exchange. As a result, the co-existing anions (HCO3- and PO43-) showed a significant influence on As(III) adsorption to Mg-Al LDH. Considering the interfering effects of co-existing anions on am-TiO2, HCO3− did not influence As(III) adsorption, while PO43- caused a slight but clear competition effect. Overall, am-TiO2 would be the best choice of these four materials in contact with As-contaminated groundwater due to its superior As(III) removal properties and the limited competition from co-existing anions on As(III) adsorption. / Alltför höga halter av arsenik (As) i vatten är ett världsomspännande problem som orsakar hälsoproblem för miljontals människor. Det finns två huvudsakliga oorganiska former av As i vatten: arsenat(V) och arsenit(III), och adsorption till ett material (s.k. ”sorbent”) kan vara eneffektiv metod för att avlägsna dem från vatten. I denna studie fokuserade vi på arsenit(III), den mer giftiga formen, vilken dominerar under reducerande förhållanden. Vi undersökte adsorptionsegenskaperna för arsenit(III) för fyra sorbentmaterial som kan vara tänkbara när det gäller arsenikrening av förorenade vatten: hydrotalkit, s.k. Mg-Al LDH (Mg-Al-skiktad dubbelhydroxid), am-Al(OH)3 (amorf aluminiumhydroxid), och am-TiO2 (amorf titandioxid). Dessa material undersöktes när det gäller följande: adsorption av arsenit(III) som funktion av pH,betydelsen av sorbentkoncentration, adsorption som funktion av löst arsenit(III) (”isoterm”), och konkurrens från samexisterande anjoner (HCO3− och PO43−). Den maximala adsorptionen av As (III) till HT (0,1 mmol As(III)/g sorbent), Mg-Al LDH (0,1 mmol As(III)/g sorbent), am-Al(OH)3 (0,22 mmol As(III)/g sorbent) och am-TiO2(0,21 mmol As(III)/g sorbent) inträffade vid pH 7,5, 7, 7, respektive 8. Vid dessa pH-värden adsorberades ungefär 20%, 62%, 35% respektive 98,3% tillsatt As(III). När kvoten mellan As(III) till sorbent ökades blev adsorptionen istället cirka 7% till am-Al(OH)3 (2,2 mmol As(III)/g sorbent) och 46,3% till am-Ti02(2,1mmol As(III)/g sorbent). Dock var adsorptionsmängden per viktsenhetsorbenthögre över hela pH-området. Dessa siffror visar att am-TiO2 är det mest effektiva av de fyra testade materialen för As(III)-adsorption, Mg-Al LDH det näst bästa, medan HT och am-Al(OH)3 är olämpliga för detta ändamål. Adsorptionen av As(III) till Mg-Al LDH som funktion av löst As(III) kunde beskrivas väl med en linjär ekvation, vilket antyder att adsorptionen av As(III) till Mg-Al LDH styrdes av anjonbyte. I konsekvens med detta hade de samexisterande anjonerna (HCO3- och PO43-) ett betydande inflytande på As(III)-adsorptionen till Mg-Al LDH. För am-TiO2 påverkade HCO3− inte As(III)-adsorptionen, medan PO43- orsakade en liten men tydlig konkurrenseffekt. Sammantaget är am-TiO2 det bästa valet av dessa fyra material i kontakt med As- kontaminerat grundvatten på grund av dess betydligt bättre förmåga att avskilja arsenit(III) och den förhållandevis blygsamma konkurrensen från andra anjoner.