Defluoridation of water via Light Weight Expanded Clay Aggregate (LECA): Adsorbent characterization, competing ions, chemical regeneration, equilibrium and kinetic modeling

International audienceNatural, H2O2 and MgCl2 - modified Light Weight Expanded Clay Aggregate (LECA) were used as fluoride adsorbents. Characterization of LECA and its modified forms was done by infra-red, X-ray diffraction, scanning electron microscope and X-ray fluorescence studies. The specific surface area of HML and MGML was 3.34 and 3.97 times greater than that of NL (11.72 m2/g). Improved chemical composition of Magnesium (as oxide) to 15.6% by 2 M MgCl2 solution was ascertained through XRF results. The fluoride levels were reduced (within the safe limit of WHO: 0.5-1.5 mg/L−1) to 0.39 mg/L, 1.0 mg/L and 0.075 mg/L respectively using natural (NL), H2O2 (HML) and MgCl2 - modified LECA (MGML) at a pH of 6.0 and initial fluoride concentration of 10 g/L for an equilibrium time of 120 min. The sorption capacities of 8.53 mg/g, 17.83 mg/g and 23.86 mg/g were determined for NL, HML and MGML respectively. Validation of kinetic and isotherm models was checked for the present fluoride sorption dynamics. The thermodynamic data revealed that the present fluoride sorption was spontaneous, exothermic and ends up with decrease in randomness. Prediction of fluoride sorption mechanism for onto natural and modified LECA forms was also elucidated. Chloride and sulfate were the highly competing species against fluoride sorption. Regeneration efficiency of the spent LECA materials prompted the ability of MGML even after five cycles of adsorption-regeneration processes

Removal of hardness agents, calcium and magnesium, by natural and alkaline modified pumice stones in single and binary systems

International audienceNatural and alkaline modified pumice stones were used for the adsorption of water hardening cations, Ca2+ and Mg2+. The adsorbents were characterized using XRF, XRD, SEM and FTIR instrumental techniques. At equilibrium time and for 150 mg/L of a given cation, removal efficiencies were 83% and 94% for calcium and 48% and 73% for magnesium for raw and modified pumices, respectively. The optimal pH for raw and modified pumices were found to be 6.0, leading to the removal of 79 and 96% of calcium and 51 and 93% of magnesium by 10 g/L of raw and modified pumice adsorbents, respectively. Maximum adsorption capacities were 57.27 and 62.34 mg/g for Ca2+ and 44.53 and 56.11 mg/g for Mg2+ on the raw and modified pumices, respectively. Ca2+ and Mg2+ adsorption capacities of the pumice adsorbents decreased in the presence of competing cations. Less than 300 min were needed to achieve 99 and 92% desorption of the adsorbed Ca2+ and 100 and 89% of the adsorbed Mg2+ from the natural and modified pumices, respectively. After treating synthetic water solution simulating an actual water stream with the alkali-modified pumice, total hardness of the treated sample met the required standard for drinking water, namely below 300 mg/L of CaCO3 (297.5 mg/L). The studied pumice adsorbents, and especially the treated pumice, can be therefore considered as promising low cost adsorbents, suitable for the removal of hardness ions from drinking water

High frequency of methicillin-resistant Staphylococcus aureus (MRSA) with SCCmec type III and spa type t030 in Karaj’s teaching hospitals, Iran

Methicillin-resistant Staphylococcus aureus (MRSA) has been one of the most important antibiotic-resistant pathogen in many parts of the world over the past decades. This cross-sectional study was conducted to investigate MRSA isolated between July 2013 and July 2014 in Karaj, Iran. All tested isolates were collected in teaching hospitals from personnel, patients, and surfaces and each MRSA was analyzed by SCCmec and spa typing. Antibiotic susceptibility testing was accomplished by disk diffusion method. Out of 49 MRSA isolates from the Karaj’s teaching hospitals, 82%, 10%, and 6% of the isolates were SCCmec types III, II, and I, respectively. The main spa type in this study was spa t030 with frequency as high as 75.5% from intensive care unit (ICU) of the hospitals and high rate of resistance to rifampicin (53%) was found in MRSA isolates. In conclusion, high frequency of spa t030 with SCCmec type III and MRSA phenotype illustrated circulating of one of the antibiotic-resistant strains in ICU of Karaj’s teaching hospitals and emphasizes the need for ongoing molecular surveillance, antibiotic susceptibility monitoring, and infection control

Removal of CR (III) from model solutions by isolated Aspergillus niger and Aspergillus oryzae living microorganisms: Equilibrium and kinetic studies

International audienceBiosorption by fungi is a efficient method for removal of heavy metals which have been recently used by many researchers. The aim of the present work was the seeking and the isolation of sustainable microorganisms and their application for the removal of Cr (III) from simulated and real solutions. To isolate sustainable microorganisms, soil samples were taken from rawhide, tannery tanks and effluents discharged environment. Aspergillus niger and Aspergillus oryzae were the two types of isolated fungi from tanning factory environment. Fungal growth and chromium removal efficiency were studied as a function of maximum fungal tolerance to Cr (III) concentration, pH, temperature, contact time, agitation speed and nutrients addition. The optimal conditions for fungal growth were 30 h at pH 5.2, an agitation speed of 150 rpm and 30 °C in a medium containing yeast powder and di-hydrogen ammonium phosphate as nutrients. Maximum biomass concentration increased from 0.8 to 4 g/L for both fungi in the above mentioned conditions. Maximum fungal tolerance and chromium removal were found to be 600 mg/L and 95-98% of Cr (III). Equilibrium data were found to follow a Langmuir isotherm model and maximum sorption capacities were 185 and 208 mg/g for A. niger and A. oryzae, respectively. Experimental data was accurately fitted onto pseudo-second order kinetic model. Promissing results were also recorded on a real effluent, since in the above optimal conditions, chromium removal yields were 72 and 67% for A. niger and A. oryzae, respectively. However and owing to the high variability of the effluent, subsequent work is needed to confirm these positive results irrespective of the characteristics of the inlet effluent

EFFECT OF MEDIUM NUTRIENTS ON Cr(III) REMOVAL BY PHANEROCHAETE CHRYSOSPORIUM, Aspergillus niger AND A. oryzae

International audienceIn this work, the effect of the addition of some nutrients on fungal growth and removal of Cr(III) were investigated. The considered fungi, isolated from real tanning factory environment were Phanerochaete chrysosporium, Aspergillus niger and A. oryzae. Firstly, the optimal conditions for fungal growth were determined as a function of pH, contact time, temperature and agitation speed. Secondly, the effect of the addition of some nutrients on fungal growth was examined. Without the addition of any nutrient, the best growth conditions were found to be pH 5, 30oC temperature, 150 rpm agitation speed and 30 hours contact time. Except sodium nitrite, all tested nutrients, namely NH4Cl, (NH4)2SO4, NaNO2, NaNO3, NH4H2PO4, and KH2PO4, enhanced fungal growth, and hence Cr(III) removal which appeared clearly related to growth. NH4H2PO4 (in the range 4-6 g/L) was found to be the most efficient nitrogen source for fungal growth, resulting in an increase of fungal concentrations from an initial value of 0.8 g/L to maximum values of 4.8, 4.1 and 4.4 g/L for A. niger, A. oryzae and P. chrysosporium, respectively. Regarding phosphorus supply, 8 g/L KH2PO4 was found to be the optimum amount, leading to 5.7 g/L of biomass and hence an almost total chromium removal, showing the positive phosphorus effect on growth. Under the optimum conditions, chromium was almost totally removed (at least 99.8 %) for Aspergillus species, and especially A. niger, which appeared to be more efficient than P. chrysosporium. Maximum removal efficiencies on tanning effluent were 63, 52 and 43% for A. niger, A. oryzae and P. chrysosporium, respectively. These results are promising considering the high chromium content of the real effluent (1000 - 1300 mg/L)

Removal of Cr (III) from model solutions and a real effluent by Phanerochaete chrysosporium isolated living microorganism: equilibrium and kinetics

International audienceRemoval of Cr (III) was investigated using Phanerochaete chrysosporium-isolated living microorganism; pH, contact time, temperature and nutrients addition were examined. It was found that P. chrysosporium can tolerate up to 600 mg/L chromium solution. The optimal growth conditions of the biosorbent were found to be 35°C, 26 h contact time and pH = 5. In addition, a complex nitrogen substrate, yeast powder, was shown to be most efficient than a synthetic one, like di-hydrogen ammonium phosphate. High chromium removal (98%) was observed in these optimal growth conditions. Experimental data were found to follow a Langmuir isotherm model (r 2 > 0.99). Maximum sorption capacity for the present biosorbent was 213 mg/g according to the Langmuir isotherm model, namely significantly higher than the values reported in the literature, even for activated carbon. The fitting of experimental data onto kinetic models showed the relevance of the pseudo-second-order model (r 2 > 0.99) for Cr (III) sorption by P. chrysosporium. In addition, a real effluent was obtained from tanning factory and was treated to examine process feasibility on real effluents

Removal of phosphate from aqueous solutions by yellow and red soil from West Azerbaijan and its EDTA-modified form

Background & Objectives: Phosphorus is a common ion in wastewater treatment effluents, but excess amount of phosphate concentration in the effluent discharge accelerates eutrophication that affects many natural water bodies. Eutrophication of the water bodies is one of the most important environmental problems. Eutrophication can lead to abundant development of aquatic plants, growth of algae and disturbance to the balance of organisms present in the water. Therefore, in present work, natural and modified yellow and red soil with EDTA was used for removal of phosphorous from aqueous solution. Materials & Methods: All experiments were conducted in a batch system. Natural yellow and red soil and its modified one with EDTA were used as adsorbent for removal of phosphorous from aqueous solutions. Effect of various experimental parameters such as pH, initial phosphorus concentration, contact time and adsorbent mass were investigated. Results: Results showed that the removal efficiency was increased by increasing in contact time, adsorbent mass and initial phosphorus concentration. Higher removal efficiency was observed at 150 min contact time, 10 g/L adsorbent mass, 50 mg/L phosphorus concentration and pH 5. At these conditions, about 65 of phosphorus were removed by natural soils, while 78 was removed by modified adsorbents. Conclusion: The results of present work well demonstrate that, due to higher content of calcium, red and yellow soil is capable for adsorption of phosphorus and if they be modified with EDTA, their efficiency will be improved remarkably

Removal of acid black dye by pumice stone as a low cost adsorbent: kinetic, thermodynamic and equilibrium studies

International audienceThe removal of Acid Black 1 dye was investigated by acid treated pumice stone as a low cost adsorbent, since acidic modifications were expected to improve the sorption capacity. The main components of the considered adsorbent were SiO2 and Al2O3 and acid treated pumice shows irregular structure. The effect of various parameters such as the initial dye concentration, the contact time, the temperature and the pH were studied. An increase of the contact time, the initial dye concentration or an acidification of the medium had a positive impact of dye removal. Among the tested isotherms, linear regression analysis showed that the removal of Acid Black 1 dye follows a Temkin model (r2>0.93). The value of the separation factor (RL) was 0.17, showing a favorable adsorption. Despite a low specific area (54m2/g), pumice stone displayed a high sorption capacity (72.46 mg/g), which should be related to its high porosity (85 %). The fitting of experimental time-course data showed that kinetics followed a pseudo-second order model (r2>0.99). Mass transfer coefficient was determined at various initial dye concentrations and showed external mass transfer cofficient values in the range of 10-3-10-4 (cm/s), namely in agreement with the values reported in the available literature. Thermodynamic study demonstrated an exothermic adsorption, which however was not spontaneous. pH and heating methods were tested for dye desorption and confirmed the relevance of pumice stone for dye removal, since the heating method led to 83 % pumice regeneration

Removal of Cr (III) from tanning effluent by Aspergillus niger in airlift bioreactor.

International audienceIn this study, the removal of Cr (III) from tanning effluents by Aspergillus niger isolated from tanning environment was investigated in a bioreactor. Various experimental parameters such as initial Cr (III) concentration, pH, nutrients addition, air volume, inoculum size, contact time and temperature were investigated. The selected fungus exhibited a maximum tolerance to Cr (III) of 500 mg/L for 0.12% inoculum size. Optimal culture conditions for fungal growth and Cr (III) removal efficiency were observed to be pH 5.1, 30 C, 32 h contact time and 4 v/v aeration rate. In addition, the effect of some nitrogen nutrients was investigated. Among used nutrients, di-hydrogen ammonium phosphate (4 g/L) was found to be the more efficient compound on chromium removal efficiency and fungal growth. In addition, sodium nitrite showed a reverse effect on growth. Without any nutrients addition, Cr (III) removal efficiency and biomass were found to be 88% and 2.12 g/L, respectively; while in presence of additional nitrogen these parameters increased up to 96% and 5.03 g/L, respectively. These results appeared especially promising showing on the one hand the efficiency of the considered microorganism, A. niger, and on the other hand the relevance of the culture configuration, airlift reactor. Experimental equilibrium data were accurately fitted onto pseudo-first order, pseudo-second order and intra-particle diffusion kinetic models, even if the highest correlation coefficient was found for the pseudo-second kinetic order model. Contrarily the results of intra-particle diffusion kinetic model revealed that intra-particle diffusion was not the rate-controlling step

Removal of Tetracycline from Synthetic Solution by Natural LECA

Background: Antibiotic in environment can be accumulated in soil and sediment and then adversely affect the ecosystem function as well as decrease the natural degradation rate of pollutants by producing a antibiotic-resistant microorganisms. The antibiotic-resistant genes can also transfer to drinking water resources and then, leading untreatable human disease. Methods: Natural LECA was supported from rural resources and washed with deionized water for several time and then used as natural adsorbent. The adsorbents were characterized with a scanning electron microscope (SEM), Fourier Transform Infrared spectroscopy (FTIR), X-ray fluorescence spectroscopy (XRF) and X ray diffract meter (XRD). All experiments were conducted in a batch reactor. Various parameters such as initial adsorbent mass (2, 4, 6, 8 and 10 g/L), initial antibiotic concentration (50, 100, 150 and 200 mg/L), initial solution pH (3, 5, 7, 9, and 11) and contact time (1-210 min) were investigated. Results: The Results of present work showed the high removal efficiency of the adsorbent for adsorption of Tetracycline from aqueous solution. Higher removal efficiency was observed for Tetracycline at pH 3, 180 min contact time, 10 g/L of adsorbent dose and 200 mg/L of initial antibiotic concentration. In optimum condition, up to 49% of tetracycline was removed. Conclusion: Overall, the results of the present work well demonstrated that natural LECA as an inexpensive adsorbent could remove effectively the antibiotics namely Tetracycline from aqueous solution