RESUMEN
Trivalent chromium and iron are the products of the traditional reduction of hexavalent chromium by ferrous salts in industrial wastewater. Although there have been a few studies of Cr(III) adsorption, none have considered the effect of Fe(III) on Cr(III) adsorption in a binary system representing expected products of hexavalent chromium in industrial wastewater. The biosorption of Cr(III) and Fe(III) ions onto pretreated ground orange peel in single and binary systems was studied in batch experiments using a variety of techniques. The kinetic results showed a rapid rate of biosorption of Cr(III) and Fe(III) in single and binary systems and mutual interference effects in the competitive binary Cr(III)-Fe(III) system. Second order kinetic models showed the best fit for all systems. The behavior of competitive Cr(III)-Fe(III) biosorption were successfully described by the multicomponent Langmuir model, obtaining maximum capacities for Cr(III) and Fe(III) of 9.43 and 18.19 mg/g respectively. SEM/EDS results confirmed that the metals adsorb on the surface and FTIR identified the hydroxyl groups on the carboxylic acids as the active binding sites.
Asunto(s)
Cromo/química , Citrus sinensis/metabolismo , Compuestos Férricos/química , Adsorción , Concentración de Iones de Hidrógeno , Cinética , Microscopía Electrónica de Rastreo , Espectroscopía Infrarroja por Transformada de Fourier , TermodinámicaRESUMEN
A new adsorbent material for removing lead ions from aqueous solutions has been investigated. The residue of the allspice extraction process (De-Oiled Allspice Husk) was used on the removal of Pb(II) from water solutions. The lead sorption capacity of De-Olied Allspice Husk (DOAH) was studied in batch and continuous processes. It was found that percentage removals of Pb(II) depend on the pH and the initial lead concentrations. The Pb(II) uptake process was maximum at pH 5 in a range concentrations of 5-25 mg L(-1). The overall sorption process was well described by the pseudo-second-order kinetic model under conditions of pH 5 (0.1 g adsorbent per 100 mL of contaminated solution) 0.001 mass/volume ratio and 25 degrees C. The sorption capacity of lead(II) onto DOAH in batch process was 5.00, 8.02, 11.59, 15.23 and 20.07 mg g(-1), when the concentration solutions were 5, 10, 15, 20 and 25 mg L(-1) respectively. These values are lower than obtained in continuous process, where lead was removed by 95% and the experimental results were appropriately fitted by the Yoon-Nelson model. X-ray photoelectron spectroscopy (XPS) provides information regarding the interactions between lead ions and the adsorbent surface indicating that the formation of 2 complexes depends on the functional groups associated.
Asunto(s)
Plomo/aislamiento & purificación , Pimenta/química , Contaminantes Químicos del Agua/aislamiento & purificación , Adsorción , Concentración de Iones de Hidrógeno , Espectroscopía de Fotoelectrones , Soluciones , Contaminantes Químicos del Agua/química , Purificación del Agua/métodosRESUMEN
A continuous system electrocoagulation--active sludge was designed and built for the treatment of industrial wastewater. The system included an electrochemical reactor with aluminum electrodes, a clarifier and a biological reactor. The electrochemical reactor was tested under different flowrates (50, 100 and 200 mL/min). In the biological reactor, the performance of different cultures of active sludge was assessed: coliform bacterial, ciliate and flagellate protozoa and aquatic fungus. Overall treatment efficiencies of color, turbidity and COD removal were 94%, 92% and 80%, respectively, under optimal conditions of 50 mL/min flowrate and using ciliate and flagellate protozoa. It was concluded that the system was efficient for the treatment of industrial wastewater.
Asunto(s)
Residuos Industriales , Aguas del Alcantarillado , Aguas Residuales , Análisis de la Demanda Biológica de Oxígeno , Color , Técnicas Electroquímicas , Nefelometría y Turbidimetría , Contaminantes del Agua/aislamiento & purificaciónRESUMEN
The bioaccumulation of Cr(VI) and Cd(II) in Prosopis laevigata and the effect of these heavy metals on plant growth were assessed. P. laevigata seeds were cultured during 50 days on modified Murashige-Skoog medium supplemented with four different concentrations of Cr(VI) (0-3.4mM) and Cd(II) (0-2.2mM), respectively. Heavy metals did not stop germination, but smaller plants with fewer leaves and secondary roots were produced. Seedlings showed an accumulation of 8176 and 21,437 mg Cd kg(-1) and of 5461 and 8090 mg Cr kg(-1) dry weight, in shoot and root, when cultured with 0.65 mM Cd(II) and 3.4mM Cr(VI), respectively. These results indicated that significant translocation from the roots unto aerial parts took place. A bioaccumulation factor greater than 100 for Cd and 24 for Cr was exhibited by the seedlings. P. laevigata can be considered as a potential hyperaccumulator of Cd(II) and Cr(VI) species and considered as a promising candidate for phytoremediation purposes.
Asunto(s)
Cadmio/farmacocinética , Cromo/farmacocinética , Raíces de Plantas/metabolismo , Prosopis/metabolismo , Contaminantes del Suelo/farmacocinética , Biodegradación AmbientalRESUMEN
This paper presents the results of the investigation on the removal of Cr(VI) and the complex Cr(VI)-diphenylcarbazide from aqueous solutions using an electrochemical reactor, with iron electrodes. A maximum value of 99% Cr(VI) removal from aqueous solutions is observed for both Cr(VI) and Cr(VI)-diphenylcarbazide, at initial concentrations from 150 to 800 mg l(-1). Cyclic voltammetry experiments of water show the presence of electroactive species in the oxidation and reduction zones previous to the treatment and how this presence diminishes as the electrochemical treatment is applied to the wastewater. UV-Vis analyses corroborate the improvement on the quality of aqueous solutions treated. Finally, scanning electron microscopy and energy dispersion spectra show that Cr and Fe are present as constituents of the sludge formed during the electrochemical treatment. It was demonstrated that the use of electrochemical methods for the treatment of Cr(VI) and Cr(VI)-diphenylcarbazide aqueous solutions is an effective and economical method.