P. Le Cloirec

Application of Chitosan for the Removal of Metals From Wastewaters by Adsorption—Mechanisms and Models Review

Chitin is the worlds second most abundant naturally occurring polysaccharide. Much of this is disposed of as waste from seafood crustacean, mainly in shrimps, prawns, crabs, and lobsters, where it occurs as a significant component in the shells/exoskeletons of crustacea. Due to its widespread abundance, its chemical and physical versatility, and the problems of its disposal as a waste material, a wide range of value-added applications of chitin and chitosan is being initiated, investigated, and developed. The widely ranging value-added applications of chitin and chitosan are presented in this review. Chitin and its derivative, chitosan, both highly stable and difficult to degrade materials, can be obtained as 10–20% w/w from the waste seafood shells by suitable chemical processing. One of the significant developments in the new range of applications is the study of the ability of chitosan, as a potentially major environmental treatment material, to remove metal ions from wastewaters. Chitosan is the deacetylated form of chitin, and this process produces a chain of amino groups along the chitosan structure. Many researchers are now looking at the ability of this amino group to adsorb metal ions from industrial wastewaters and leachates. This review presents the developments in this area and identifies the defficiences in existing chitosan research by reviewing the equilibrium studies carried out to determine the capacity of chitosan for various metal ions. Then the kinetic studies are reviewed, as well as the solution methodologies adopted by various researchers to explain and model the rate of adsorption of the metal ions from solution. Both equilibrium knowledge and kinetic knowledge are required in order to design commercial treatment systems.

Analysis of endocrine disrupting compounds in wastewater and drinking water treatment plants at the nanogram per litre level.

Abstract The determination of steroid hormones, alkylphenolic compounds and bisphenol A at the ng l−1 level in environmental water samples (surface water and WasteWater Treatment Plant samples (WWTP)) is performed by a specific analytical procedure. Pre‐concentration by solid‐phase extraction conditions was optimized using C18 cartridges for steroid hormones and polymeric Oasis HLB cartridges for phenolic compounds. Identification and quantification were performed using a LC‐MS/MS system with electrospray ionization in the negative mode for both compound families. For steroid hormones, the need to have limits of detection lower than 0.5 ng l−1 in WWTP samples led to the improvement of a purification step on silica cartridges. In the case of the phenolic compounds, no purification was required because of their lower estrogenicity. The limits of detection in WWTP effluents ranged between 0.02 ng l−1 and 0.21 ng l−1 for steroid hormones and 0.4 and 10.2 ng l−1 for phenolic compounds. The method was then applied to determine concentrations of the target compounds at each step of a WWTP. The process efficiencies were evaluated. Finally, concentrations were measured in influents and effluents of a Drinking Water Treatment Plant showing the complete removal of estrogenicity.

La regeneration par echauffement intrinseque, de charbons actifs utiuses pour le traitement d'air

Abstract A procedure allowing an efficient regeneration by Joule effect, of activated carbons (granular or fibrous) used for the purification of hydrocarbon polluted air is proposed. This process was developped on pilot units feed. Optimal operation conditions (electrical power, temperature, air flow rate) were determined. Further, suggestions were made for the recovery of the desorbed solvents and potential applications of the procedure.

Biogas pre-upgrading by adsorption of trace compounds onto granular activated carbons and an activated carbon fiber-cloth.

The study assesses the adsorption onto activated carbon materials of selected volatile organic compounds -VOCs- (dichloromethane, 2-propanol, toluene, siloxane D4) in a biogas matrix composed of methane and carbon dioxide (55:45 v/v). Three different adsorbents are tested, two of them are granular activated carbon (GAC), and the last is an activated carbon fiber-cloth (ACFC). The adsorption isotherm data are fitted by different models by nonlinear regression. The Langmuir-Freundlich model appears to be the adequate one to describe the adsorption phenomena independently of the VOC considered or the adsorbent. The adsorbents present attractive adsorption capacity of the undesirable compounds in biogas atmosphere though the maximum adsorption capacities for a VOC are quite different from each other. The adsorption kinetics are characterized through three coefficients: the initial adsorption coefficient, the external film mass transfer coefficient and the internal diffusion coefficient of Weber. The ACFC demonstrates advanced kinetic yields compared to the granular activated carbon materials whatever VOC is considered. Therefore, pre-upgrading of biogas produced from wastewater sludge or co-digestion system by adsorption onto activated carbon appears worth investigating. Especially with ACFC material that presents correct adsorption capacities toward VOCs and concrete regeneration process opportunity to realize such process.

Visualization of the exothermal VOC adsorption in a fixed-bed activated carbon adsorber

Activated carbon fixed beds are classically used to remove volatile organic compounds (VOCs) present in gaseous emissions. In such use, an increase of local temperature due to exothermal adsorption has been reported; some accidental fires in the carbon bed due to the removal of high concentrations of ketones have been published. In this work, removal of VOCs was performed in a laboratory-scale pilot unit. In order to visualize the increase in local temperature, the adsorption front was tracked with a flame ionization detector and the thermal wave was simultaneously visualized with an infrared camera. In extreme conditions, fire in the adsorber and the combustion of activated carbon was achieved during ketone adsorption. Data have been extracted from these experiments, including local temperature, front velocity and carbon bed combustion conditions.

BIODEGRADATION OF ENDOCRINE DISRUPTERS: CASE OF 17BETA-ESTRADIOL AND BISPHENOL A.

Abstract The biodegradation of 17 β‐estradiol (E2) and bisphenol A (BPA) was compared to that of a reference pollutant, sodium benzoate (SB), known for its high biodegradability. The biodegradation was measured using the Sturm test (ISO 9439 modified Sturm test). The susceptibility of the target pollutants to be degraded by microorganisms of activated sludge from a wastewater treatment plant (WWTP) was evaluated by the production of carbon dioxide (CO2). Sorption experiments onto inactivated sludge were carried out to assess the contribution of sorption in E2 and BPA removal during biological treatment in a WWTP. E2 was more adsorbed than BPA onto inactivated sludge, probably making it less accessible to assimilation by microorganisms. In fact, E2 was less biodegradable than BPA with 66 % and 74 % of theoretical CO2 formation (ThCO2) in 28 days, respectively. However, E2 showed faster biodegradation than BPA due to the shorter adaptation time of the microorganisms to start the assimilation. Final concentrations were measured and revealed that, under Sturm test conditions, E2 was totally removed from the aqueous phase while some traces of BPA were detected. This result could be explained by the lower adsorbability of BPA observed in adsorption experiments onto inactivated sludge. To investigate competition in a bi‐component solution, Sturm tests were carried out with BPA/SB and E2/SB. Moreover, the biodegradation curves obtained did not indicate a toxicity of the target compounds towards microorganisms, which rapidly degraded SB. In the case of BPA/SB, an inflection in the curve confirmed the adaptation time of 4–5 days for BPA to be degraded.

Un modèle mathémathique de la dénitrification sur des filtres soufre-carbonate de calcium

Resume Sur la base de resultats obtenus au laboratoire et sur unite pilote, nous presentons un modele mathematique de denitrification par Thiobacillus denitrificans sur filtres garnis par du soufre et du carbonate de calcium (maerl). Les equations bilan du procede comprennent: la production de biomasse, lelimination des nitrates, lapparition puis la disparition des nitrites, la consummation du soufre. La resolution numerique du systeme dequations est basee sur une approche par variable. Pour chaque equation, la methode utilisee tient compte du comportement dans le temps du parametre considere. La vitesse dans la colonne est consideree comme une fonction du degre de vide dependant de la croissance bacterienne et de la consommation du soufre. Un traitement mathematique, par une methode Lagrange-Euler, de cette vitesse permet de simuler lecoulement dans le filtre. Nous obtenons une assez bonne correlation entre les valeurs experimentales et calculees.

ELECTRODEPOSITION OF COPPER AND IRON OXIDES ON TO ACTIVATED CARBON fibre CLOTHS: APPLICATION TO H2S AND NH3 REMOVAL FROM AIR

Abstract The present study concerns metal electrodeposition onto activated carbon fibre cloths (ACFC) for the treatment of odorous molecules such as hydrogen sulfide and ammonia. Characterizations of virgin, chemical impregnated and electro‐impregnated carbon fibre cloths allowed the determination of the physical and chemical properties of such materials. Adsorption kinetics and isotherms in a batch reactor were carried out with non‐impregnated and copper‐ or iron‐impregnated ACFC. It was observed that differences in the metal deposit directly influenced the porous structure and elimination kinetics and capacities towards both odorous molecules. Compared to non‐impregnated material, the adsorption velocities decrease in the case of chemically impregnated materials whereas they were similar when electrodeposition was used. Moreover, the maximal adsorption capacities were highest when metal was electrochemically deposited.

Membrane process treatment for greywater recycling: investigations on direct tubular nanofiltration.

On-site greywater recycling and reuse is one of the main ways to reduce potable water requirement in urban areas. Direct membrane filtration is a promising technology to recycle greywater on-site. This study aimed at selecting a tubular nanofiltration (NF) membrane and its operating conditions in order to treat and reuse greywater in buildings. To do so, a synthetic greywater (SGW) was reconstituted in order to conduct experiments on a reproducible effluent. Then, three PCI NF membranes (AFC30, AFC40 and AFC80) having distinct molecular weight cut-offs were tested to recycle this SGW with a constant concentration at 25°C at two different transmembrane pressures (20 and 35 bar). The best results were obtained with AFC80 at 35 bar: the flux was close to 50 L m⁻² u2009h⁻¹, retentions of 95% for chemical oxygen demand and anionic surfactants were observed, and no Enterococcus were detected in the permeate. The performances of AFC80 were also evaluated on a real greywater: fluxes and retentions were similar to those observed on SGW. These results demonstrate the effectiveness of direct nanofiltration to recycle and reuse greywater.

Modélisations des isothermes d'adsorption sur charbon actif de composés aromatiques en solution aqueuse

Resume De nombreux modeles ont ete proposes pour decrire ladsorption competitive. Dans cette etude, nous envisageons de decrire ladsorption competitive de composes aromatiques substitues, en solution aqueuse sur du charbon actif. Deux modeles disothermes de solutions complexes ont ete testes: le modele de Langmuir et le modele de lAIS (adsorption ideale de solutions). Pour chacun, les parametres des isothermes de solutions simples sont necessaires et doivent etre determines avec precision. Les coefficients trouves sont consideres comme constants dans des gammes de concentrations. Ceci permet une meilleure description des isothermes. Lapplication du modele de lAIS a des melanges binaires ou ternaires montre une bonne concordance entre les donnees experimentales et calculees. Ladaptation du modele de Langmuir par lintroduction de coefficients variables permet une valorisation de ce modele qui, par sa simplicite et sa qualite, reste un modele exploitable.