RESUMEN
Detailed adsorption experiments of Cd from aqueous solution on NiO were conducted under batch process with different concentrations of Cd, time and temperature of the suspension. The solution pH is found to play a decisive role in the metal ions precipitation, surface dissolution and adsorption of metal ions onto the NiO. Preliminary adsorption experiments show that the selectivity of NiO towards different divalent metal ions follows the trend Pb>Zn>Co>Cd, which is related to their first hydrolysis equilibrium constant. The exchange between the proton from the NiO surface and the metal from solution is responsible for the adsorption. The cation/exchange mechanism essentially remains the same for Pb, Zn, Co and Cd ions. The sorption of Cd on NiO particles is described by the modified Langmuir adsorption isotherms. The isosteric heat of adsorption (ΔH) indicates the endothermic nature of the cation exchange process. Spectroscopic analyses provide evidence that Cd is chemisorbed onto the surface of NiO.
Asunto(s)
Cadmio/aislamiento & purificación , Resinas de Intercambio de Catión , Níquel/química , Adsorción , Concentración de Iones de Hidrógeno , Solubilidad , Soluciones , Agua , Difracción de Rayos XRESUMEN
Batch adsorption technique was used to study the adsorption of cobalt on NiO. The aim of this work was to examine the effect of pH, concentration and temperature on the ion exchange removal of Co2+ from aqueous solution by the NiO surface. We used Langmuir model to interpret the adsorption data. The Kurbatov-type plots were tested to determine the adsorption mechanism. The kinetics of Co2+ adsorption on NiO was best described by film diffusion model. A well-known thermodynamic equation was used to assess the enthalpy and entropy of the system. The thermodynamic data were indicative of the spontaneous nature of the endothermic sorption process of Co2+ onto the NiO.
Asunto(s)
Cobalto/aislamiento & purificación , Iones , Níquel/química , Purificación del Agua/métodos , Adsorción , Cromatografía por Intercambio Iónico/métodos , Cobalto/análisis , Cobalto/química , Difusión , Relación Dosis-Respuesta a Droga , Calor , Concentración de Iones de Hidrógeno , Cinética , Modelos Químicos , Óxidos/química , Temperatura , Termodinámica , Contaminantes Químicos del Agua/química , Contaminantes Químicos del Agua/aislamiento & purificaciónRESUMEN
This paper reports NiO as a novel and an efficient adsorbent for the removal of Pb from aqueous solutions. In the present investigation, Pb adsorption experiments on NiO were conducted on aqueous solution at different initial Pb concentration, pH of the solution and adsorption temperature. The mechanism of adsorption was observed to be an ion exchange between the surface proton and Pb in aqueous solution. Experimental data were best described by the Langmuir isotherms. The surface structure of the NiO before and after adsorption of Pb was analyzed by using FTIR spectroscopy, scanning electron microscopy (SEM) coupled with energy dispersive X-ray analyses (EDX).