The conditions for synthesizing microtubes with a surface of "house of cards" structure via needlelike particles were examined in detail. Magnesium carbonate trihydrate was formed as a metastable phase in the reaction process using magnesium hydroxide and carbon dioxide as starting materials. Subsequently, in the formation of basic magnesium carbonate from magnesium carbonate trihydrate, microtubes with a surface of house of cards structure were obtained via needlelike particles of magnesium carbonate trihydrate under certain conditions where the temperature and added amount of sodium hydroxide were properly controlled. The pore size of the microtubes could be controlled within a range of 0.5-6 microm by adjusting the condition of needlelike particle formation. In addition, the sustainability of naphthalene release from the microtube was found to be about 6 times higher than that from naphthalene crystal.

14The ongoing development of new advanced technologies, created increasing demands for 15 rare earth elements (REEs) in the international market. The available conventional 16 technologies for concentration and recovery of REEs are expensive making biosorption an 17 efficient and low-cost technology for the recovery of REEs from aqueous solution. Thus, 18 the biosorption and desorption of multi-component solution containing Y(III), La(III), 19Sm(III), Dy(III), Pr(III), Nd(III), Gd(III) were investigated using dried or 250˚C and 350˚C 20 carbonized parachlorella. Evaluating the effect of pH with respect to contact time indicated 21 2 a dependency of the system with those parameters. The optimum pH for dried and 250˚C 22 carbonized parachlorella was 7 whereas 350˚C reaches it maximum uptake at pH 4. Rapid 23 adsorption within the first 5 min of contact followed by a slight variation the following 20 24 min characterized the sorption processes onto parachlorella by-products. The mechanism of 25 the biosorption is explained by a combination of complex reactions occurring 26 simultaneously in the biosorption process. 27 In addition, desorption process has been investigated using various concentrations of HCl, 28 HNO 3 , and H 2 SO 4 at different temperatures. It was found that the reversible process is rapid, 29 less temperature and pH dependent with high desorption percentage. Moreover, only light 30 REEs were desorbed regardless of the kind of acid and the solution temperature. 31Parachlorella is found to be good and low-cost biosorbent for the recovery of above REEs 32 from aqueous solutions. 33 34 35 36Rare earth elements (REEs) are often referred as the "seeds of technology" because 38 of their uses in high-tech strength permanent magnets, lasers, automotive catalytic 39 converters, fiber optics/superconductors, electronic devices, and green energy sectors [1, 2]. 40Due to the ongoing development of new advanced technologies, there is an over-increasing 41 demand for REEs in the international markets, with emphasis on identifying new resources 42 to ensure adequate supply for present and future use. 43 3The designation "rare earths" refers to the 15 elements of the periodic table known 44 as "lanthanides" with yttrium and scandium, further divided as a function of their atomic 45 number into two categories. Light rare earth elements (LREE), which accounted for 66.8% 46 of global demand in 2010 [2] referred to lanthanum, cerium, praseodymium, neodymium, 47 promethium and samarium. Heavy rare earths elements (HREE), less common and more 48 valuable, referred to the rest of lanthanides elements with yttrium. The 17 REEs are found 49 in all REE geological deposits because they share many similar properties but their 50 distribution and concentrations vary [2]. REE mineral deposits are usually rich in either 51 LREE or HREE, but rarely contain both in significant quantities [2]. The term "rare earth" 52 is actually a misnomer, because these elements are more abundant in the earth's crust 53 compared to silver, gold...

In the present study, REEs were leached from a Vietnamese ore, by using (NH 4 ) 2 SO 4 and REEs were adsorbed from this leachate by bluegreen algae (phormidium). In addition, the biosorption characteristics of phormidium for the adsorption of Nd has been studied.When the concentration of ammonium sulfide was 1%, leaching time was 3 h, and S/L ratio was 0.09, the leaching ratio of Nd was 67.3%. In the adsorption process, when dosage of phormidium was 0.2 kg/L, the contact time was 30 min, and the temperature was 298 K, while pH was kept at the initial value (i.e. pH 5.6), the adsorption density of Nd was 182 mg/kg. These results were similar with the adsorption density of other absorbents, such as: activated carbon, Fe-based absorbent, and calcinated dolomite. Moreover, the equilibrium sorption isotherm of Nd onto phormidium was described by the Langmuir isotherm equation and the pseudo-second-order kinetic model fits the experimental data well.

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The synthesis of basic magnesium carbonate was examined under ultrasonic irradiation and was performed by the soda ash method using magnesium sulfate and sodium carbonate as starting materials. The particulate product was evaluated using SEM observations. Ultrasonic irradiation in the preparation of basic magnesium carbonate was found to give fine petaloid microspheres of about 3 mum in primary particle size.