Innovative applications of biomass gasification char in adsorption and catalysis

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Sustainable Conversion of Agriculture and Food Waste into Activated Carbons Devoted to Fluoride Removal from Drinking Water in Senegal

International audienceThe objective of this study was to investigate the production of activated carbons (AC) from cashew shells, and millet stalks and their efficiency in fluoride retention. These agricultural residues are collected from Senegal. It is known that some regions of Sénégal, commonly called the groundnut basin, are affected by a public health problem caused by an excess of fluoride in drinking water used by these populations. The activated carbons were produced by a combined pyrolysis and activation with water steam; no other chemical compounds were added. Then, activated carbonaceous materials obtained from cashew shells and millet stalks were called CS-H2O and MS-H2O respectively. CS-H2O and MS-H2O show very good adsorbent features, and present carbon content ranges between 71 % and 86 %. The BET surface areas are 942 m² g-1 and 1234 m².g-1 for CS-H2O and MS-H2O respectively. A third activated carbon produced from food wastes and coagulation-flocculation sludge (FW/CFS-H2O) was produced in the same conditions. Carbon and calcium content of FW/CFS-H2O are 32.6 and 39.3 % respectively. The kinetics sorption were performed with all these activated carbons, then the pseudo-first equation was used to describe the kinetics sorption. Fluoride adsorption isotherms were performed with synthetic and natural water with the best activated carbon from kinetics sorption, Langmuir and Freundlich models were used to describe the experimental data. The results showed that carbonaceous materials obtained from CS-H2O and MS-H2O were weakly efficient for fluoride removal. With FW/CFS-H2O, the adsorption capacity is 28.48 mg.g-1 with r² = 0.99 with synthetic water

Activated char produced from chontaduro seeds: a new potential precursor

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Application of sludge-based carbonaceous materials in a hybrid water treatment process based on adsorption and catalytic wet air oxidation

This paper describes a preliminary evaluation of the performance of carbonaceous materials prepared from sewage sludges (SBCMs) in a hybrid water treatment process based on adsorption and catalytic wet air oxidation; phenol was used as the model pollutant. Three different sewage sludges were treated by either carbonisation or steam activation, and the physico-chemical properties of the resultant carbonaceous materials (e.g. hardness, BET surface area, ash and elemental content, surface chemistry) were evaluated and compared with a commercial reference activated carbon (PICA F22). The adsorption capacity for phenol of the SBCMs was greater than suggested by their BET surface area, but less than F22; a steam activated, dewatered raw sludge (SA_DRAW) had the greatest adsorption capacity of the SBCMs in the investigated range of concentrations (<0.05 mol L−1). In batch oxidation tests, the SBCMs demonstrated catalytic behaviour arising from their substrate adsorptivity and metal content. Recycling of SA_DRAW in successive oxidations led to significant structural attrition and a hardened SA_DRAW was evaluated, but found to be unsatisfactory during the oxidation step. In a combined adsorption–oxidation sequence, both the PICA carbon and a selected SBCM showed deterioration in phenol adsorption after oxidative regeneration, but a steady state performance was reached after 2 or 3 cycles

Study of possibility to foresee the activated chars properties knowing the intrinsic characteristics of raw biomass

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Fixation de l'arsenic (V) sur le chitosane (étude des mécanismes et procédé)

Ce travail a pour objectif de développer un procédé d'adsorption de l'arsenic (V) sur du chitosane. Une caractérisation physico-chimique du matériau a été réalisée. L'étude des cinétiques de fixation a ensuite montré que le modèle cinétique de pseudo ordre un décrivait correctement les données expérimentales. L'analyse de différents modèles d'adsorption, et l'étude des anions compétiteurs confirment un mécanisme de fixation, par attraction électrostatique et échange d'ions. La température, le pH et la présence d'anions divalents sont les paramètres les plus influents. L'étude en système dynamique consiste à coupler un réacteur d'adsorption parfaitement agité à un module de microfiltration frontale. A partir de ces résultats, la possibilité d'utiliser du chitosane en flocon, pour le traitement d'eau chargée en arsenic (V) est clairement démontrée.The aim of this work is to perform a dynamic treatment process with chitosan, for arsenic removal. After a physico-chemical characterisation of the material, the kinetic study has shown that experimental data could be described by the pseudo first-order model. Then, the analysis of different adsorption models confirm that the mechanism of sorption is an electrostatic attraction and ion exchange. Temperature, pH and the presence of divalent anions are the main influencing parameters. The dynamic study involves a continuous stirred tank reactor coupled with a microfiltration membrane. A mass balance model based on the Langmuir equilibrium isotherm is used to describe the adsorption process and the breakthrough curves are well simulated. Based on these results, it is demonstrated that chitosan is an interesting biomaterial for the treatment of water contaminated with arsenic (V).NANTES-BU Sciences (441092104) / SudocNANTES-ENS Mines (441092314) / SudocSudocFranceF

Valorization of millet and buckwheat husks chars and activated carbons in H2S removal from biogas

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Characterization techniques of packing material colonization in gas biofiltration processes

Conference on Biological Air Treatment, Quebec City, CANADA, MAY 05-09, 2008International audienceno abstrac

Uranium removal onto chitosan : competition with organics substances

International audienceOrganic materials and especially humic substances are often present in natural waters. The influence of organic compounds on uranium removal onto chitosan is studied. The pH of the media is fixed at 6. In operating conditions, uranium major species present in solution are : (UO2)(3)(OH)(5)(+) and (UO2)(4)(OH)(7)(+). Capacity of fixation is found to be 450 mg g(-1), considering precipitation phenomena. Experimental results show that chitosan offers a selective adsorption depending on the different organics used: the adsorption capacity is maximum with benzaldehyde, average with humic acids, limited with phenol and insignificant with benzoic acid. Phenol does not affect the fixation capacity of uranium significantly whereas benzoic add and benzaldehyde have an average effect upon it and humic acids decrease it to 200 mg g(-1) and less as the concentration of the acid increases

Sustainable Activated Carbons from Agricultural Residues Dedicated to Antibiotic Removal by Adsorption

International audienceThe objectives of this study are to convert at laboratory scale agricultural residues into activated carbons (AC) with specific properties, to characterize them and to test them in adsorption reactor for tetracycline removal, a common antibiotic. Two new ACs were produced by direct activation with steam from beet pulp (BP-H2O) and peanut hulls (PH-H2O) in environmental friendly conditions. BP-H2O and PH-H2O present carbon content ranged between 78% and 91%, similar BET surface areas (821 and 829 m(2).g(-1) respectively) and pH(PZC) values (9.8). Their porosities are different: PH-H2O is mainly microporous (84%) with 0.403 cm(3).g(-1) of total porous volume, whereas BP-H2O develops a mesoporous volume of 0.361 cm(3).g-(1) representing 50% of the total porous volume. Two other commercial granular AC carbons (GAC1 and GAC2) were also characterised and used for comparison. The adsorption study is conducted in batch reactors. Two parts can be observed from kinetic decay curves: a very fast concentration decrease during the first 12 h, followed by a slow adsorption. An optimal contact time of 120 h is also deduced from these curves. It is shown as well that adsorption decreases with an increase of pH, indicating that the form preferentially adsorbed is probably the zwitterion form of the tetracycline. From equilibrium isotherms data, two adsorption models have been used: Langmuir and Freundlich. Both of them lead to a very good description of the experimental data. Maximum adsorption capacities deduced from the Langmuir equation follow the sequence: GAC2 (817 mg.g(-1))>BP-H2O (288 mg.g(-1))>GAC1 (133 mg.g(-1))>PH-H2O (28 mg.g(-1)). In real spring waters spiked with TC (tetracyclines), adsorption isotherms show that the maximum adsorption capacity of BP-H2O is slightly increased to 309 mg.g(-1) while it is decreased by one third to 550 mg.g(-1) in the case of GAC2. This study demonstrates that the production of AC from agricultural residues, at lab-scale, is feasible and leads to genuine activated carbons with different intrinsic properties