Dynamics, Mechanistic and Equilibrium Studies for the Biosorption of Nickel on Palm Tree Leaves

Adsorption of heavy metals on biological sorbents, activated carbon and synthetic resin particles is a common separation technique. In this study, the biosorption of nickel ions from aqueous solution by palm tree leaves was investigated as a function of shaking time, nickel ions concentration and equilibrium pH. Competitive adsorption of nickel on palm tree leaves with EDTA and citric acid was also investigated. Batch adsorption experiments revealed that the biosorption of nickel on palm tree leaves was strongly pH dependent, and maximum nickel sorption was found to occur at equilibrium pH of 6.0. Dynamics studies showed that: the initial uptake of nickel on palm tree leaves was rapid, equilibrium was established within 30 minutes, and the data followed the pseudo-second order reaction. The equilibrium sorption data of nickel on palm tree leaves at solution pH 6.0 were described by two-parameter isotherm models such as the Langmuir, Freundlich, and D-R models and three-parameter models such as Redlich-Peterson and Sips isotherm models. Ion-exchange, adsorption-complexation and intraparticle diffusion mechanisms were found to be involved in the biosorption process. The Effect of ions interference on the biosorption of nickel on palm tree leaves showed that the sorption of nickel on palm tree leaves was adversely affected by the presence of chelating agents such as EDTA and citric acid

Povećanje oslobađanja gliklazida iz smjesa dobivenih geometrijskim miješanjem

The poorly water soluble antidiabetic drug gliclazide was selected to study the effect of excipients on dissolution rate enhancement. Ordered mixtures of micronized gliclazide with lactose, mannitol, sorbitol, maltitol and sodium chloride were prepared by manual shaking of glass vials containing the drug and excipient(s). Different water soluble excipients, addition of surfactant and superdisintegrant, drug concentration and carrier particle size influenced the dissolution rate of the drug. Dissolution rate studies of the prepared ordered mixtures revealed an increase in drug dissolution with all water soluble excipients. The order of dissolution rate improvement for gliclazide was mannitol > lactose > maltitol > sorbitol > sodium chloride. Composite granules of the particle size range 355-710 µm were superior in increasing the drug dissolution rate from ordered mixtures. Reducing the carrier particle size decreased the dissolution rate of the drug, as well as the increase in drug concentration. Kinetic modeling of drug release data fitted best the Hixson-Crowell model, which indicates that all the ordered mixture formulations followed the cube root law fairly well.Teško topljivi antidijabetik gliklazid izabran je za proučavanje utjecaja pomoćnih tvari na povećanje oslobađanja. Homogene smjese mikroniziranog gliklazida s laktozom, manitolom, sorbitolom, maltitolom i natrijevim kloridom pripravljene su ručnim tresenjem staklenih bočica s lijekom i pomoćnom tvari/tvarima. Na oslobađanje lijeka utjecali su vrsta vodotopljivog ekscipijensa, dodatak surfaktanta i superdezintegratora, udio lijeka i veličina čestica punila. Sve vodotopljive pomoćne tvari povećavale su oslobađanje ljekovite tvari i to sljedećim redom: manitol > laktoza > maltitol > sorbitol > natrijev klorid. Najbolje oslobađanje lijeka bilo je iz kompozitnih granula veličine 355 do 710 µm. Iz smjesa s manjom veličinom čestica punila i većim udjelom lijeka oslobađanje lijeka bilo je manje. Kinetičko modeliranje oslobađanja najbolje je odgovaralo Hixson-Crowellovom modelu, što ukazuje na to da sve formulacije prilično dobro slijede zakon trećeg korijena