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Journal of Thermal Analysis and Calorimetry
Authors: Tomohito Kameda, Yuki Fubasami, and Toshiaki Yoshioka

Introduction Mg–Al layered double hydroxide (Mg–Al LDH) is represented by the formula [Mg 1− x 2+ Al x 3+ (OH) 2 ](A n − ) x / n · m H 2 O, where A n − is an anion, such as CO 3 2− or SO 4 2− , and x is the Al/(Mg + Al

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Abstract  

In the present study, Mg–Al layered double hydroxide intercalated with nitrate anions (LDH-NO3) was synthesized, modified with the anionic surfactant, sodium lauryl sulfate, and applied for the removal of 152+154Eu from aqueous solutions. Modification of the as-synthesized Mg–Al layered double hydroxide was carried out at surfactant concentration of 0.01 M (the organo-LDH produced denoted LDH-NaLS). The as-synthesized and surfactant-intercalated LDHs were characterized by FT-IR and energy-dispersive X-ray spectroscopy techniques. The effect of some variables such as solution pH, contact time and sorbate concentration on removal of 152+154Eu was investigated. The kinetic data obtained were well fitted by the pseudo-second-order kinetic model rather than the pseudo-first-order model. Intraparticle diffusion model showed that sorption of 152+154Eu proceed by intraparticle diffusion together with boundary layer diffusion. Experimental isotherm data were well described by Langmuir model. Organo-LDH was found to have higher capacity (156.45 mg g−1) for europium than the as-synthesized LDH-NO3 (119.56 mg g−1). Comparing LDHs capacities obtained for Eu(III) in the present work with other sorbents reported in literature indicated that LDHs have the highest capacities. Application of the developed process for removal of 152+154Eu(III) from radioactive process wastewaters was also studied and the obtained results revealed that these LDHs are promising materials for treatment of radioactive wastewaters.

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Abstract  

Mg-Al L(ayered) D(ouble) H(ydroxide) was prepared and its thermal behaviour was characterized by thermoanalytical methods (TG, DTG, DTA), 27Al M(agic) A(ngle) S(pinning) NMR spectroscopy, X-ray diffractometry (XRD) and S(canning) E(lectron) M(icroscopy). Heat treatment destroyed the layered structure, which could only be partially reconstituted by rehydration. On calcination mixed oxide with the predominance of basic sites were formed. Pillaring the LDH with Fe(CN)6 4- anions was also performed. The material was characterized by XRD and BET measurements. Heat stability of the pillared substance was investigated, too. Pillaring proved to be successful, however, decreased heat resistance was found in the intercalated material relative to the guest LDH.

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. Calistor , N , Everson , K , Wang , DY . 2008 . Flame-retarded polystyrene: Investigating chemical interactions between ammonium polyphosphate and Mg–Al layered double hydroxide . Polym Degrad Stab . 93 : 1656 – 1663 10.1016/j.polymdegradstab.2008

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. Ay AN . Synthesis and characterization of Mg-Al-layered double hydroxides intercalated by borate anions . PhD Thesis. Ankara; 2007 . 7. Lin , JT , Tsai

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oxide . J Therm Anal Cal 94 2 477 – 481 10.1007/s10973-008-9178-9 . 23. Kaneyoshi , M , Jones , W 1999 Formation of Mg–Al layered double hydroxides intercalated with nitrilotriacetate

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, AB 2008 Non-isothermal crystallization kinetics and activity of filler in polypropylene/Mg-Al layered double hydroxide nanocomposites . Thermochim Acta 479 : 45 – 52 10.1016/j.tca.2008.09.016 . 15

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layered double hydroxides intercalated with citrate, malate, and tartrate prepared by co-precipitation . Mater Res Bull . 44 : 840 – 845 10.1016/j.materresbull.2008.09.003 . 4. Smaihi , M

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.eurpolymj.2005.03.008 . 50. Costa , FR , Wagenknecht , U , Heinrich , G 2007 LDPE/Mg–Al layered double hydroxide nanocomposite: thermal and flammability properties . Polym Degrad Stab 92

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Reaction Kinetics, Mechanisms and Catalysis
Authors: Viorel Chihaia, Karl Sohlberg, Margarita Gabrovska, Rumeana Edreva-Kardjieva, Dorel Crişan, Peter Tzvetkov, Maya Shopska, and Iskra Shtereva

: 269 – 274 . 72. Lebedeva , O , Tichit , D , Coq , B 1999 Influence of the compensating anions of Ni/Al and Ni/Mg/Al layered double hydroxides on their activation under oxidizing and

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