Adsorption Thermodynamics of Cr(VI) Removal by using Agro-Industrial Waste of Oil Palm Bagasse and Plantain Peels

The effect of temperature on the adsorption of Cr (VI) was determined with waste materials from the agroindustry, such as palm bagasse and plantain peels, by determining the thermodynamic parameters which allow to establish the mechanisms that control the process. The methodology included an initial preparation of the biomass, its characterization, and subsequent adsorption tests by setting the initial concentration of the metal to 100 ppm, a particle size of 0,5 mm, a biomass amount of 0,325 g, pH 2, and a volume of 100 mL. The process temperature varied between 303,15, and 352,15 K. The concentration of the remaining metal in the solution was performed using the diphenyl carbazide colorimetric method through a UVVis spectroscopy at a wavelength of 540 nm. The results show that the effect of temperature does not present a defined trend for palm bagasse, whereas it is linear for adsorption using plantain peels. Furthermore, the process of adsorption of Cr (VI) with palm bagasse is more favorable at higher temperatures, since it is a spontaneous process with a physical adsorption mechanism. On the other hand, the adsorption process with plantain peels is thermodynamically feasible at temperatures from 40 to 55 °C and not spontaneous at higher temperatures. Also, a physicochemical adsorption mechanism was evinced. It is concluded that the use of the studied materials is possible in the removal of the Cr (VI) ion in aqueous solutions.

Preparation and Charactreization Selective Electrode for Determination of CopperIon(II)

<span>Achemically modified carbon paste electrode with diphenyl carbazide the potentiometric determination of Cu(II) is demonstrated. The electrode exhibits linear response to Cu(II) over a wide concentration range (9.2×10−7-5.0×10−1) with Nernstian slope of 30±0.15 mV per decade. It has a response time of about 40 s and can be used for a period of two months with good reproducibility. The detection limit of this electrode was 7.0×10−7 M. The proposed electrode shows a very good selectivity for Cu(II) over a wide variety of metal ions. This chemically modified carbon paste electrode was successfully used for the determination of Cu(II) in various water samples solution and pharmaceutical formulation</span>