Étude de la biosorption du chrome (VI) par une biomasse méditerranéenne : Posidonia oceanica (L.) delile

Les fibres du végétal marin Posidonia oceanica (L.) ont été utilisées en tant que nouvel adsorbant biologique pour l’élimination du chrome hexavalent des solutions aqueuses artificiellement contaminées. Les expériences ont été effectuées en lots aussi bien pour les cinétiques que pour les isothermes d’adsorption. Les variables expérimentales étudiées sont le pH, la température, la quantité de biomasse et la concentration initiale de Cr(VI). Le maximum de biosorption a été observé pour un pH 2. La capacité de biosorption semble être optimisée par une augmentation de la température, de la quantité de biosorbant et de la concentration initiale. Les isothermes d’adsorption sont en accord avec les modèles de Redlich-Peterson et Langmuir. De plus, l’analyse thermodynamique a révélé que le présent processus d’adsorption est un phénomène favorable, endothermique et spontané.The marine biomass Posidonia oceanica (L.) fibres were used as a novel low cost biological adsorbent for the removal of hexavalent chromium from artificially contaminated aqueous solutions. Experiments were carried out for sorption kinetics and isotherms in a batch system. The operating variables studied were pH, temperature, biomass quantity and initial chrome concentration. The maximum adsorption removal was observed at pH 2. The biosorption capacity of P. oceanica fibres for Cr(VI) was enhanced by increasing the temperature, the biosorbent amount and initial chromium concentration. The isotherm adsorption data were satisfactorily found to be described by both Redlich-Peterson and Langmuir. Besides, the thermodynamic studies revealed that the present adsorption process is a favourable, endothermic and spontaneous phenomenon

Nutrients Enrichment and Process Repercussions in Hybrid Microfiltration Osmotic Membrane Bioreactor:A Guideline for Forward Osmosis Development Based on Lab-Scale Experience

The effects of reverse salt diffusion through a forward osmosis membrane were studied in a microfiltration osmotic membrane bioreactor. The reactor was used to treat and simultaneously concentrate nutrients from wastewater. The system was operated at different draw solution concentrations, leading to varying salinity conditions. A relatively low, yet stable forward osmosis flux was observed regardless of increasing draw solution conductivities from 10 to 50 mS cm−1. A substantial increase in sludge conductivity from 5.7 to 19.8 mS cm−1 was observed during the operation. Batch transmembrane pressure-step experiments showed a decline in sludge filtration properties with increasing salinity buildup in sludge due to increasing deflocculation and associated release of protein and carbohydrate fractions of extracellular polymeric substances. Mathematical simulations showed that accumulation of total dissolved solids could mainly be attributed to reverse flux of salts from the draw solution rather than by the enrichment of incoming nutrients when forward osmosis membrane’s salt permeability was high and water permeability low. Ideally, salt permeability below 0.010 L m−2 h−1 and effective water permeability above 0.13 L m−2 h−1 bar−1 are crucial to ensure enhanced nutrient enrichment and reduce sludge osmotic pressure, microbial inactivation, sludge deflocculation and membrane fouling

Intercomparison study on commonly used methods to determine microplastics in wastewater and sludge samples

The harmonized procedures in terms of the sampling, sample treatment and identification of microplastics in different environmental samples are missing, which poses challenges to researchers to compare the results or to adopt ‘the most effective’ monitoring approach. Furthermore, in the related literature, the used procedures are rarely tested with spiked microplastics to predetermine their recovery rates. Without this knowledge, results should only be discussed as rough estimations of the real environmental concentrations of microplastics. In this study, six different methods previously used in microplastic studies of different media were tested with municipal wastewater and digested sludge samples, spiked with seven different types of plastic particles and fibres. Recovery rates, time consumption, advantages and disadvantages were assessed and most suitable treatment procedures (i.e. high recovery rates in short amount of time) were chosen for both wastewater and sludge. Suitability of staining with Rose Bengal was examined together with most efficient methods, but it did not improve the recovery of microplastics. In addition, the possible impacts of the treatments for identification with micro-Raman and FTIR microscope were assessed. Filtration with size fractioning was found to be the best method for both wastewater and sludge samples, with recovery rates of spiked microplastics around 91.4% and 92.9%, respectively

Élimination du chrome hexavalent des solutions aqueuses par adsorption sur feuilles brutes de Posidonia oceanica (L.) : cinétiques, équilibres et modélisation

Les feuilles du végétal marin Posidonia oceanica (L.) ont été utilisées en tant que nouvel adsorbant biologique pour l’élimination du chrome hexavalent des solutions aqueuses artificiellement contaminées. Les expériences ont été effectuées en batch aussi bien pour les cinétiques que pour les isothermes d’adsorption. Les variables expérimentales étudiées sont le pH, la température, la quantité de biomasse et la concentration initiale de Cr(VI). Le maximum de biosorption a été observé pour un pH = 2. La capacité de biosorption semble être optimisée par une augmentation de la température, de la quantité de biosorbant et de la concentration initiale. La modélisation des données expérimentales a montré que le modèle du pseudo-second ordre décrit les cinétiques d’adsorption d’une façon adéquate. De même, les isothermes d’adsorption sont en accord avec le modèle de Redlich-Peterson et notamment celui de Langmuir. De plus, l’analyse thermodynamique a révélé que le processus d’adsorption étudié est un phénomène favorable, endothermique et spontané

Studies on the Biosorption of Textile Dyes from Aqueous Solutions Using (L.) Leaf Sheath Fibres

The adsorption of two textile dyes onto a low-cost and unexploited marine biomass, Posidonia oceanica (L.), was investigated in batch mode. The biosorption process was studied as a function of contact time, initial pH and temperature. The highest dye adsorption capacities attained at 30°C were 3.081 mg/g at pH 2 for the Direct dye and 4.252 mg/g at pH 5 for the Reactive dye. The Freundlich, Langmuir and Redlich–Peterson adsorption models were used to determine the parameters of the equilibrium data and, under the operating conditions studied, the best fit to the experimental curves was obtained using the Freundlich model. The thermodynamic constants of the adsorption process (i.e. ΔG 0 , ΔH 0 and ΔS 9 ) were evaluated as −6.36 kJ/mol, 57.80 kJ/mol and −103.45 J/(mol K), respectively, for the Direct dye and as −3.22 kJ/mol, 84.10 kJ/mol and −225.55 J/(mol K), respectively, for the Reactive dye. Consequently, the adsorption of dyes onto P. oceanica biomass was favourable, endothermic and spontaneous

Adsorptive removal of cadmium from aqueous solution by cork biomass: Equilibrium, dynamic and thermodynamic studies

The removal of toxic metal, cadmium, by using adsorption into Algerian cork biomass was investigated. The biosorption process was studied with respect to contact time, particle size, pH and temperature. The results showed that equilibrium was reached within 1 h. The used biosorbent gave the highest adsorption capacity at pH 6. The experimental isotherm data were analyzed and modeled. The maximum adsorption capacity, Langmuir’s qmax, improved from 9.65 to 14.77 mg/g as the temperature increased from 20 to 40 °C. The enthalpy ΔH° and entropy ΔS° values were respectively estimated at 110.47 kJ mol−1 and 0.3795 kJ K−1 mol−1 for the process, which reflects the endothermic nature and the spontaneous feasibility of the present sorption system. Besides, the adsorption kinetics was found to follow the second-order model, suggesting therefore a possible chemisorption process

On the adsorption mechanisms of diethylamine by medically-certified activated carbons: Investigation of critical parameters controlling sorption properties

International audienceThis study investigates the adsorption mechanisms and reaction pathways involved in the adsorption ofdiethylamine (DEA) by medically-certified activated carbons (ACs). DEA is used as a model of aminessecreted during healing process of chronic wounds. DEA adsorption kinetics/isotherms were performedin liquid phase. Based on a preliminary assumption of a sorption favoured by surface chemical functions,it was found that the sorption kinetics followed accurately a pseudo-second order model. In addition, ouranalysis revealed that surface diffusion strongly influenced DEA sorption. If Langmuir and Redlich–Peterson models provided the most accurate fit of the adsorption isotherms, the Freundlich isothermgave a fair representation of experimental data as well. L-type isotherms supported the occurrence ofstrong surface interactions. Also, a negative correlation was drawn between the micropore volumepercentage and adsorption capacity at equilibrium. Further, acid/base reactions were believed to occur,along with the establishment of numerous H-bonds between the sorbent and DEA. This study is ended bya discussion of the effect of AC entrapment within a polymeric matrix on the adsorption properties. IfDEA removal was still observed, a serious decrease of sorption properties was measured. We concludedthat AC must be treated during the activation process in order to possess a high BET surface, an importantmesopore/macropore content and a high content of acidic surface functions, in order to balance thedecreasing of adsorption properties owed to its entrapment