Abdeltif Amrane

Biodegradation by activated sludge and toxicity of tetracycline into a semi-industrial membrane bioreactor.

Much attention has been devoted recently to the fate of pharmaceutically active compounds such as tetracycline antibiotics in soil and water. Tetracycline (TC) biodegradability by activated sludge derived from membrane bioreactor (MBR) treating swine wastewater via CO(2)-evolution was evaluated by means of modified Sturm test, which was also used to evaluate its toxicity on carbon degradation. The impact of tetracycline on a semi-industrial MBR process was also examined and confronted to lab-scale experiments. After tetracycline injection in the pilot, no disturbance was detected on the elimination of organic matters and ammonium (nitrification), reaching after injection 88% and 99% respectively; only denitrification was slightly affected. Confirming the ruggedness and the superiority of membrane bioreactors over conventional bioreactors, no toxicity was observed at the considered level of TC in the pilot (20 mg TOC L(-1)), while at lab-scale sodium benzoate biodegradation was completely inhibited from 10 mg TOC L(-1) TC. The origin of the activated sludge showed a significant impact on the performances, since the ultimate biodegradation was in the range -50% to -53% for TC concentrations in the range 10-20 mg TOC L(-1) with conventional bioreactor sludge and increased to 18% for 40 mg TOC L(-1) of TC with activated sludge derived from the MBR pilot. This confirmed the higher resistance of activated sludge arising from membrane bioreactor.

Photocatalytic reduction of Cr(VI) on the new hetero-system CuAl2O4/TiO2.

Visible light driven HCrO(4)(-) reduction was successfully achieved over the new hetero-system CuAl(2)O(4)/TiO(2). The spinel, elaborated by nitrate route, was characterized photo electrochemically. The optical gap was found to be 1.70 eV and the transition is directly allowed. The conduction band (-1.05 V(SCE)) is located below that of TiO(2), more negative than the HCrO(4)(-)/Cr(3+) level (+0.58 V(SCE)) yielding a thermodynamically feasible chromate reduction upon visible illumination. CuAl(2)O(4) is stable against photo corrosion by holes consumption reaction involving salicylic acid which favors the charges separation. There is a direct correlation between the dark adsorption and the photo activity. A reduction of more than 95% of chromate was achieved after 3 h irradiation at pH 2 with an optimal mass ratio (CuAl(2)O(4)/TiO(2)) equal to 1/3. The reduction follows a first order kinetic with a half life of ∼1 h and a quantum yield of 0.11% under polychromatic light. Prolonged illumination was accompanied by a deceleration of the Cr(VI) reduction thanks to the competitive water discharge. The hydrogen evolution, an issue of energetic concern, took place with a rate of 3.75 cm(3) (g catalyst)(-1) h(-1).

Application of acidic treated pumice as an adsorbent for the removal of azo dye from aqueous solutions: kinetic, equilibrium and thermodynamic studies

Colored effluents are one of the important environment pollution sources since they contain unused dye compounds which are toxic and less-biodegradable. In this work removal of Acid Red 14 and Acid Red 18 azo dyes was investigated by acidic treated pumice stone as an efficient adsorbent at various experimental conditions. Removal of dye increased with increase in contact time and initial dye concentration, while decreased for increment in solution temperature and pH. Results of the equilibrium study showed that the removal of AR14 and AR18 followed Freundlich (r2>0.99) and Langmuir (r2>0.99) isotherm models. Maximum sorption capacities were 3.1 and 29.7 mg/g for AR 14 and AR18, namely significantly higher than those reported in the literature, even for activated carbon. Fitting of experimental data onto kinetic models showed the relevance of the pseudo-second order (r2>0.99) and intra-particle diffusion (r2>0.98) models for AR14 and AR18, respectively. For both dyes, the values of external mass transfer coefficient decreased for increasing initial dye concentrations, showing increasing external mass transfer resistance at solid/liquid layer. Desorption experiments confirmed the relevance of pumice stone for dye removal, since the pH regeneration method showed 86% and 89% regeneration for AR14 and AR18, respectively.

Absorption and biodegradation of hydrophobic volatile organic compounds: determination of Henry's constants and biodegradation levels.

Biodegradation of three volatile organic compounds (VOCs) was studied. Toluene, dimethylsulphide (DMS), and dimethyldisulphide (DMDS) were introduced into flasks filled with emulsions of Di-2-EthylHexylAdipate (DEHA) in water, containing biomass (activated sludge). The VOC concentrations were analysed in the gas, organic and aqueous phases, and compared to the initial VOC quantities introduced in order to deduce their consumption by biomass. Toluene and DMDS were completely consumed, and then removed from the gas and the organic phases, except when DEHA and water are in the same volume ratio, which appears to be extreme environmental conditions for bacterial growth. The high DMS volatility resulted in an important gas loss, leading to a lower amount of DMS available for activated sludge growth. For all the VOC experiments, some components, characteristics of the DEHA degradation, including 2-ethylhexanal, 2-ethylhexanol, 2-ethylhexanoic acid and adipic acid, were identified.

Competitive biosorption of heavy metals from aqueous solutions onto Streptomyces rimosus

The aim of this study is the simultaneous biosorption of Cd+2 and Ni+2 on a dead biomass, Streptomyces rimosus pretreated with NaOH (0,1 M). Kinetic tests were carried out for the binary mixture (cadmium-nickel) during 6 hours contact time to ensure that balance was reached. The amounts adsorbed at equilibrium were 22.8 mg Ni2+/g and 9.86 mg Cd2+/g biomass, respectively. The biosorption depends mainly by some parameters, such as the pH, the initial concentration of metal and the initial concentration of biomass. The isotherm of adsorption according to two models, Langmuir and Freundlich, was carried out in our study. The results of the kinetics of adsorption show that the experimental values are well represented by the kinetic model of pseudo-second order. This enables us to determine the behavior of these adsorbents with respect to a real industrial effluent.

Liquid–liquid extraction and quantitative determination of tungsten(VI) using macrocyclic reagent (DB-18-C-6) as a thiocyanate complex [WO (SCN)5]2−

AbstractIn recent years, the extraction using crown ethers has reached a resounding success in different scientific and technical fields. In this work, the authors report the results of the main steps of extraction and determination (proportioning) of the tungsten ion (VI) using a chloroformed solution of crown ether. The dibenzo–18–C-6(2,3,11,12-dibenzo-1,4,7,10,13,16-hexaoxacyclooctadeca-2,11-diene according to the IUPAC systematic nomenclature). The identification and quantification of W(VI) using the absorption spectrum, the influence of the necessary reagents, the needed acidity level for complete extraction and complexation of W(VI) using a crown ether, and the influence of multivalent metal ions were examined, considering that the sensitivity, selectivity, and detection limits have been determined. This system obeys Beer’s law in the range of 0.18–18.3 μg cm−3of tungsten with a molar absorption of 1.6 × 104 mol−1 cm−1 at 415 nm and the detection, quantification limits were, respectively, equal to 0...