RESUMO
The CH4 storage by adsorption on activated carbons for natural gas handling has gained interest due to the appearance of lightweight materials with large surface areas and pore volumes. Consequently, kinetic parameters estimation of the adsorptive process can play a crucial role in understanding and scaling up the system. Concerning its versatility, banana peel (BP) is a biomass with potential for obtaining different products, such as biochar, a solid residue from the biomass' thermal decomposition of difficult disposal, where through an activation process, the material porous features are taken advantage to application as adsorbent of gaseous substances. This research reported data for the CH4 adsorption kinetic modeling by biochar from BP pyrolysis. The activated biochar textural characterization showed particles with fine mesoporous structure (pore diameter ranging between 29.39 and 55.62 Å). Adsorption kinetic analysis indicated that a modified pseudo-first-order model was the most suitable to represent the experimental data, with equilibrium adsorption of 28 mg g-1 for the samples activated with 20.0% vol wt.-1 of H3PO4 and pyrolysis at 500 °C. The equilibrium constant was consistent with the Freundlich isotherm model, suggesting a physisorption mechanism, and led to a non-ideal, reversible, and not limited to monolayer CH4 adsorption.
Assuntos
Carvão Vegetal , Metano , Metano/química , Adsorção , Carvão Vegetal/química , Cinética , Biomassa , Musa/químicaRESUMO
The minimum set of parameters that can be used to assess the adsorption capacity of activated carbon (AC) produced from termite bio-waste was determined. Three types of AC were prepared: AC600 at 600 °C, MAC600 at the same temperature and impregnated with FeCl3, and AC800 at 800 °C. The influence of the solution pH on the adsorption, adsorption kinetics, isotherms and thermodynamic parameters was considered to characterize the amoxicillin (AMX) adsorption process. The AC materials had surface areas (m2 g-1) of approximately 248.8 for AC600, 501.6 for AC800 and 269.5 for MAC600, with point of zero charge (pHPZC) values of 8.3, 7.5 and 1.7, respectively. A time period of 30 min was chosen for the adsorption kinetics, which was best represented by the pseudo-first-order model for AC600, the intraparticle diffusion model for AC800 and the pseudo-second-order model for MAC600. Regarding the isotherms, a maximum adsorption of 23.4 mg g-1 was found for AC800. In general, the thermodynamic parameters demonstrated a non-spontaneous process. It seems that the medium conditions, the adsorbate and adsorbent characteristics, and the Gibbs free energy are the most important parameters to be considered in a preliminary assessment of the adsorption efficiency of specific adsorbent/adsorbate pairs.
Assuntos
Amoxicilina/análise , Carvão Vegetal/química , Resíduos , Poluentes Químicos da Água/análise , Adsorção , Animais , Concentração de Íons de Hidrogênio , Isópteros/química , Cinética , Temperatura , TermodinâmicaRESUMO
OBJECTIVE: The aim of the present investigation was to evaluate the use of spray-dried O-carboxymethyl chitosan (OCMCS) as potential hydrophilic matrix excipient for sustained release of drug. METHODS: The polymer was synthesized from chitosan, then spray-dried and characterized. Tablets with different OCMCS concentrations (80, 50, 30, 5 and 2% w/w), containing diltiazem (DTZ) as model drug, were prepared for direct compression (DC) and after the wet granulation method (WG). RESULTS: The spray-dried OCMCS powder was spherical, with a smooth surface and an average size of 2.2 µm. The tablets prepared for WG disintegrated in time less than 30 min. The tablets obtained for DC presented high retention of the drug, with zero order or Higuchi release kinetic. There was a direct relationship between the OCMCS concentration and the release ratio, swelling degree and water uptake behavior. DC tablets containing 80% OCMCS presented behavior as an effective swelling-control system. The DC tablets with 5% OCMCS showed a similar release profile at formulations with 30% HPMC. CONCLUSION: Spray-dried OCMCS showed great potential as hydrophilic matrices for drug-sustained release.
Assuntos
Quitosana/análogos & derivados , Diltiazem/administração & dosagem , Excipientes/química , Química Farmacêutica/métodos , Quitosana/química , Preparações de Ação Retardada , Interações Hidrofóbicas e Hidrofílicas , Derivados da Hipromelose , Metilcelulose/análogos & derivados , Metilcelulose/química , Propriedades de Superfície , ComprimidosRESUMO
This study evaluates the effect of complex cross-linked chitosan iron-(III) (CH-FeCL) polymer as phosphate binder in renal failure induced by alloxan (150 mg/kg, i.p.) in rats. The animals (male and female) were divided into four groups and received the treatment once a day for 15 days: (i) control group, which received a single injection of saline (3 ml/kg, i.p.) and normal diet; (ii) alloxan group, which received only a dose of alloxan and normal diet; (iii) phosphate (PO4) group, which received diet supplemented with phosphate 1.2%; and (iv) CH-FeCL group, which received diet supplemented with phosphate 1.2% + CH-FeCL 0.5% (0.054% Fe elemental). It was observed that the CH-FeCL treatment did not alter body-weight, relative weight of the organs and haematological parameters in the treated and control groups for both sexes. However, a decrease in serum phosphorus level of the CH-FeCL group was observed after 15 days, compared with the phosphate group in both sexes. The serum iron concentration of the CH-FeCL group did not differ from the control group in either sex. CH-FeCL polymer decreases intestinal phosphate absorption in rats with renal failure and is promising for the treatment of phosphate retention in patients with renal failure.