Dissolution Kinetics of Sepiolite in Hydrochloric Acid And Nitric Acid

Abstract

The dissolution kinetics of sepiolite in hydrochloric acid and nitric acid were studied in a batch reactor. The effects of reaction temperature, acid concentration, particle size and solid-to-liquid ratio on the dissolution process were investigated. Experimental studies were carried out in the ranges of 25À75ºC for reaction temperature, 0.25À1.00 mol/L for acid concentration, 0.00755À0.05020 cm for average particle size and 2.5 to 12.5 g of solid/100 mL of acid for solid-to-liquid ratio. It was determined that the dissolution process is controlled by resistance of the diffusion through the product layer. The activation energies of the process were determined to be 40.8 and 38.3 kJ/mol for hydrochloric and nitric acid, respectively. The apparent rate constants were expressed as a function of reaction temperature, acid concentration, particle radius and solid-to-liquid ratio: kae À4 9 1 0 ( 1 / T ) Cr À0 . 6 (s/l) À1 and kae À4606(1/T) Cr À0.5 (s/l) À1 for hydrochloric and nitric acid, respectively; k is the apparent rate constant in min À1 ; T, the reaction temperature (K); C, the acid concentration (mol/L); r, the initial particle radius (cm); s/l, the solid-to-liquid ratio (g of solid/100 mL of acid).

Chemical stability and dehydration behavior of a sepiolite/indigo Maya Blue pigment

“…Acid attack was performed with concentrated HNO 3 (65%) at room temperature, which applied on pure indigo immediately decomposes its molecule into isatin (C 8 H 5 NO 2 ), a yellowish-red precipitate. Such an attack showed the more pronounced intrinsic fragility of the structure of sepiolite compared to that of palygorskite, as already reported by several authors (Myriam et al, 1998;Özdemir and Kipçak, 2004;Yebra-Rodrìguez et al, 2003;Sanchez del Rìo et al, 2006;Kilislioglu and Aras, 2010). A prolonged acid treatment (4 days) almost completely destroyed the sepiolite lattice producing an amorphous phase, whereas an analogous treatment on palygorskite left the clay structure virtually unaltered (data not shown).…”

Microfibrous Chitosan−Sepiolite Nanocomposites

“…The preparation of chitosan−sepiolite nanocomposites is carried out in the acidic medium required to dissolve the biopolymer. It is known that the treatment of sepiolite by acids produces the magnesium extraction, and therefore a structural alteration could be significant in appropriated experimental conditions. , The extracted magnesium was measured (ICP/AES) in the supernatant obtained after centrifugation of the chitosan−sepiolite mixtures. For all the preparations the measured amount of lixiviated Mg was ca.…”

Sustainable preparation of a novel glycerol-free biofuel by using pig pancreatic lipase: Partial 1,3-regiospecific alcoholysis of sunflower oil

“…The extraction of the ions (i.e. Mg 2+ , Al 3+ ) by acid treatment significantly increases the size of the pores, making them comparable to those of amorphous silica [65][66][67][68] or even to a mesoporous MCM-41-like structure [69,70]. These big pores are able to trap some macromolecules including various enzymes [58,59].…”