Search

The present work deals with the investigation of the use of the elaborated aluminophosphate (AlPO$_{4}$-5) and silico-aluminophosphate (SAPO-5) materials, in uranium sorption from aqueous solution and real effluents obtained from Nuclear Research Center of Draria, Algiers, Algeria. The surface charge and acidic–basic character of AlPO$_{4}$-5 and SAPO-5 is investigated by the determination of point of zero charge. Batch adsorption experimental studies are carried out to evaluate the influence of initial uranium concentration, final solution pH, contact time, solid-to-liquid ratio and temperature. A maximum adsorption capacity of 61.96 and 74.10 mg/g was obtained for AlPO$_{4}$-5 and SAPO-5 respectively, at pH 7 with an adsorbent ratio of 0.1/150 g/ml and an equilibrium time of 120 min. Kinetic models (pseudo-first order, pseudo-second order and Weber–Morris) are applied to find the mechanism for the removal of uranium ions, experimental data are analyzed by equilibrium models (Langmuir, Freundlich, Dubinin–Radushkevich and Temkin). Modeling sorption results show that uranium sorption is a chemical and endothermic process. The results showed that AlPO$_{4}$-5 and SAPO-5 are effective materials for the removal of uranium (VI) ions.

BACKGROUND Studies on the degradation and mineralization of tetracycline by means of the electro-Fenton process are lacking in the available literature. Its relevance as a pre-treatment prior to a biological process for the removal of tetracycline was therefore examined. RESULTS Degradation followed pseudo-first-order kinetics and the optimal operating conditions were: 0.1 mmol L-1 catalyst (Fe2+) concentration, 300 mA applied current intensity and 25 mg L-1 tetracycline, leading to total degradation within only 5 min and a mineralization yield of 89 % after 6 h electrolysis. Biodegradability tests were realized with 100 mg L-1 tetracycline; BOD5/ COD ratio increased from 0.02 to 0.56 after 6 h electrolysis, showing the relevance of the electro-Fenton pre-treatment. However, to keep a significant residual organic content, 2 to 4 h electrolysis time may be more relevant, leading to BOD5/ COD ratio and mineralization yields of 0.33-0.44 and 46-72%, respectively. CONCLUSION Activated sludge cultures of pretreated and non-pretreated tetracycline solutions were carried out for 3 weeks. The overall TOC removal increased from 28% for the non-pretreated tetracycline to 68 and 86% after 2 and 4 h electrolysis, confirming the efficiency of the proposed combined process. © 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

A biodegradable solvent was used in a two-phase aqueous-organic system for hydrophobic VOC (volatile organic compounds) elimination by activated sludge. Unlike usual two-phase aqueous-organic systems where the organic phase is chosen nonbiodegradable in view of its recycling, in this study the solvent was assimilated by micro-organisms simultaneously with the VOC. The chosen solvent and VOC were hexadecane and toluene. Experiments showed in a first step that activated sludge were able to assimilate part of hexadecane at different phase ratios (5and 10% v/v) and a higher biomass growth was obtained for the lower ratio. Toluene was removed simultaneously with organic solvent elimination; cells were readily able to completely consume the toluene available at low and even at high concentrations within 48 h (0.2 and 4.3 g L−1 in the organic phase), even if they were not previously preadapted to these substrates. Consequently, a two-phase partitioning bioreactor conception with a biodegradable solvent can be envisaged. © 2010 American Institute of Chemical Engineers Environ Prog, 2011. [ABSTRACT FROM AUTHOR]