Enhancement of aragonite mineralization with a chelating agent for CO2 storage and utilization at low to moderate temperatures

Among the CaCO3 polymorphs, aragonite demonstrates a better performance as a filler material in the paper and plastic industries. Despite being ideal from the environmental protection perspective, the production of aragonite particles via CO2 mineralization of rocks is hindered by the difficulty in achieving high production efficiencies and purities, which, however, can be mitigated by exploiting the potential ability of chelating agents on metal ions extraction and carbonation controlling. Herein, chelating agent N,N-dicarboxymethyl glutamic acid (GLDA) was used to enhance the extraction of Ca from calcium silicate and facilitate the production of aragonite particles during the subsequent Ca carbonation. CO2 mineralization was promoted in the presence of 0.01–0.1 M GLDA at ≤ 80 °C, with the maximal CaCO3 production efficiency reached 308 g/kg of calcium silicate in 60 min using 0.03 M GLDA, which is 15.5 times higher than that without GLDA. In addition, GLDA showed excellent effects on promoting aragonite precipitation, e.g., the content of aragonite was only 5.1% in the absence of GLDA at 50 °C, whereas highly pure (> 90%, increased by a factor of 18) and morphologically uniform aragonite was obtained using ≥ 0.05 M GLDA under identical conditions. Aragonite particle morphologies could also be controlled by varying the GLDA concentration and carbonation temperature. This study proposed a carbon-negative aragonite production method, demonstrated the possibility of enhanced and controlled aragonite particle production during the CO2 mineralization of calcium silicates in the presence of chelating agents.

A method for selective separation of scandium (III) from yttrium and a number of rare-earth elements for its subsequent determination

The possibility of using an aqueous stratified system of antipyrine — sulfosalicylic acid — water for the selective isolation of scandium macro- and microquantities for subsequent determination is studied. The proposed extraction system eliminates the usage of toxic organic solvents. The organic phase with a volume of 1.2 to 2.0 ml, resulting from delamination of the aqueous phase containing antipyrine and sulfosalicylic acid is analysed to assess the possibility of using such systems for metal ions extraction. Condition necessary for the formation of such a phase were specified: the ratio of the initial components, their concentration, presence of inorganic salting out agents. The optimum ratio of antipyrine to sulfosalicylic acid is 2:1 at concentrations of 0.6 and 0.3 mol/liter in a volume of the aqueous phase of 10 ml. The obtained phase which consists of antipyrinium sulfosalicylate, free antipyrine and water, quantitatively extracts macro- and microquantities of scandium at pH = 1.54. Macro- and microquantities of yttrium, terbium, lanthanum, ytterbium and gadolinium are not extracted under the aforementioned conditions thus providing selective isolation of scandium from the bases containing yttrium, ytterbium, terbium, lanthanum, and gadolinium.

Sintesis Asam-Asam Lemak Hidroksamik dari Minyak Kelapa Menggunakan Lipase sebagai Katalis

Fatty hydroxamic acids (FHAs) have been successfully synthesized from coconut oil by a one-step lipase catalyzed reaction. FHAs are theacids that are based on fatty acids. Their hydrophobicity can be use for some applications such as surfactant and metal ions extraction fromaqueous media. This paper describes enzymatic synthesis of FHAs from coconut oil by reacting hydroxylamine with the substrate catalyzedby a lipase. The lipase used was Lipozyme, a commercially lipase of Mucor meihe fixed on a polymer anion exchange resin. The use ofimmobilized lipase as the catalyst for the preparation reaction provides an easy isolation of the enzyme from the products and othercomponents in the reaction mixture. In addition, it also allows the reaction to be carried out under mild conditions, which reduces thereaction’s side products. The optimum preparation conditions obtained were as follows; the reaction temperature was 30 oC, the reactiontime was 30 h, the ratio of coconut oil : lipozyme (g : g) was 29.5, and the ratio of hydroxylamine : coconut oil (mmol : mmol) was 6. Thesolvent used was hexane. The purified products were characterized by qualitative test, such as FTIR spectroscopy and HPLC.