Copolyamides of nylon-4,6 and nylon-4,T

Copolyamides of nylon-4,6 and nylon-4,T were prepared by a two-step method: (1) a prepolymerization in an autoclave (40 min at 210°C) and (2) a postcondensation in the solid state (4 h, 260°C). On these materials was studied the melting behavior with DSC, the crystalline structure with WAXS, the water absorption, and the mechanical properties with a torsion pendulum. In these copolyamides the order was found to remain high, but the crystalline structures of -4,6 and -4,T were not isomorphous. The torsion moduli increased with -4,T content both at RT and at 140°C

Impact des éthers de cellulose sur l'hydratation du silicate tricalcique

National audienceLes mécanismes d'hydratation du ciment en présence de molécules organiques restent assez mal élucidés. Les éthers de cellulose sont systématiquement introduits dans les formulations des mortiers industriels. Leurs conséquences macroscopiques sur la réaction d'hydratation du ciment sont parfaitement connues, notamment en terme de ralentissement de la cinétique d'hydratation, mais elles n'en restent pas moins inexpliquées. Par conséquent, l'interaction des éthers de cellulose avec la matrice cimentaire a été examinée. Les résultats tendent à montrer que les éthers de cellulose ont un impact mineur sur la dissolution des différentes phases anhydres. Au contraire, ces adjuvants présentent un effet important sur la germination-croissance de certains hydrates comme l'hydrosilicate de calcium et la portlandite

Heavy Minerals In Placer Deposit In Singkawang Waters, West Kalimantan, Related To Felsic Source Rock Of Its Coastal Area

Placer deposits are physically accumulated by fluvial and marine processes in coastal area. Thirty six samples were selected from seventy seven samples of seafloor sediment of Singkawang waters. Those samples have been analyzed microscopically for heavy mineral contents. Based on this analysis, the heavy minerals can be divided into four groups: oxyde and hydroxyde, silicate, sulphide, and carbonate. The source of most heavy minerals in the study area is commonly formed by Felsic igneous rock and finally deposited on the seafloor sediments. Keywords: heavy minerals, placer deposit, felsic igneous rock, Singkawang Endapan letakan secara fisik umumnya terakumulasi oleh proses sungai dan laut. Sebanyak 36 contoh dipilih dari 77 contoh sedimen permukaan dasar laut di Perairan Singkawang. Contoh tersebut telah dilakukan analisis kandungan mineral berat secara mikroskopis. Berdasarkan hasil analisis mineral berat ini dapat dibedakan menjadi empat kelompok yaitu oksida dan hidroksida, silikat, sulfida, dan karbonat. Sebagian besar sumber mineral berat di daerah penelitian pada umumnya berasal dari batuan beku felsik yang akhirnya diendapkan di permukaan dasar laut. Kata kunci: mineral berat, endapan letakan, batuan beku felsik, Singkawang

Epoxy–amine/metal interphases: Influences from sharp needle-like crystal formation

When epoxy–amine liquid mixtures are applied onto metallic oxide layer, concomitant amine chemical sorption and metallic surface dissolution appear leading to the organo-metallic complex formation. We studied the interphase formation and used two different amines as hardener (isophoronediamine (IPDA) and diethylenetriamine (DETA)). If the complex concentration within the liquid amine or epoxy–amine prepolymer is higher than its solubility limit, complexes crystallize. Sharp needle-like crystals are observed only with modified IPDA. For Al-IPDA crystals, the melting point is about 78°C, but as the network is formed at this temperature, crystals remain present at the end of the polymerization cycle

Study on the toxicity of inhaled alumina nanoparticles: impact of physicochemical properties and adsorption artifacts on the measurement of biological responses

International audienceThis work aims at developping a multidisciplinary approach to highlight the correlation between the toxicity of alumina engineered nanoparticles (NP) and their physicochemical characteristics. Accuracy of measurements depends on cell production after contact with particles, but also depends on the ability of biomolecules to get adsorbed on the NP [1]. That's why, mechanisms of biomolecules adsorption on NP must be fully understood to avoid misinterpretation of data

Élimination des colorants des eaux résiduaires de l'industrie textile par la bentonite et des sels d'aluminium

L'industrie textile utilise des colorants de synthèse toxiques qui polluent ses eaux résiduaires avec, parfois, des flux importants. Les procédés traditionnels les éliminent mal : ils sont peu iodégradables et la seule floculation, par exemple par des sels de fer, donne des résultats insuffisants. Or, en Algérie, la réutilisation agricole des eaux usées même industrielles est devenue une impérieuse nécessité. Le procédé proposé repose sur l'utilisation de sels d'aluminium ou, mieux encore, un polyhydroxyaluminium, associés à une bentonite de forage très fine présentant l'avantage d'être localement disponible et peu coûteuse. Quatre colorants ont été testés. Ils appartiennent à deux grandes familles : les colorants acides d'une part, Jaune Supranol 4GL et Vert Nylomine C8B et les colorants dispersifs d'autre part, Rouge Foron RDGL et Violet Foron S3RL. Les essais montrent que, si la bentonite seule ou les sels d'aluminium seuls présentent des efficacités insuffisantes, ces derniers du fait d'une mauvaise décantabilité des microflocs formés, l'association bentonite-aluminium permet d'éliminer les colorants en quasi totalité avec une excellente décantabilité. Les concentrations optimales à mettre en oeuvre sont relativement basses, de l'ordre de 13 mg/l de Al3+ et 250 mg/l de bentonite. Les coûts d'exploitation sont donc très raisonnables. Sur un effluent industriel réel, le procédé permet de passer d'une DCO de 770 mg/l à moins de 30 mg/l.The textile industry uses synthetic dyes, most of them being toxic. In Algeria, the agricultural reuse of treated wastewater, even of industrial origin, is becoming commonplace. It is therefore compulsory to drastically reduce pollutant fluxes. The presently operated conventional processes cannot meet the water quality requirements: bioelimination of dyes is negligible and flocculation with iron salts, as currently carried out in the SOITEX plant located in Tlemcen, Algeria, is not effective enough. The use of aluminum salts in the flocculation of such wastewaters is well known (FIESSINGER AND BERSILLON, 1977; LAHAV et al., 1978) but the resulting microflocs are not easily settleable. Bentonite, locally available at a low cost, can also eliminate micropollutants (LAHAV et al., 1978). Associated with polyhydroxyaluminum, it can reduce such compounds as benzene or toluene, favoring simultaneously the liquid-solids separation. This paper evaluates the treatability of dyes by bentonite associated with aluminum salts.All the runs were carried out in a 200 cm3 batch reactor, mechanically stirred and thermoregulated at 20·C. The main physico-chemical characteristics of the bentonite are given in Table 1. The flocculant was aluminum chloride, previously neutralized with sodium hydroxide (mass ratio OH-/Al=1.85). The solutions were used immediately or left to polymerize during 6 days leading to polyhydroxyaluminum PHAl (LAHAV et al., 1978). When the reactor was operated with bentonite and aluminum, the mass ratio Al/bentonite was maintained at 53.10-3 (KACHA, 1994). Four dyes belonging to two main families were tested: Supranol Yellow 4GL and Nylomine Green (acid dyes) and Foron Red RDGL and Foron Violet S3RL (dispersive dyes). Their concentrations were obtained by spectrophotometry.Bentonite alone does not induce a significant abatement excepted for low pH values around 4 (Figs. 1 and 2). Dye elimination appears to require a previous protonation step followed by cation exchange. The equilibrium can be modeled by a Freundlich equation (Fig. 3 and Table 2). The dyes can also be eliminated by aluminum salts alone (Fig. 4). The efficiency is then better with polyhydroxyaluminum, i.e. more than 90 % of the initial concentration is removed. Nevertheless, the dyes abatement probably results from an adsorption or chemical reaction on microflocs which are not easily settleable. By assuming that all the aluminum ions are precipitated as aluminum hydroxide, the equilibrium is modeled by the Langmuir equation which would indicate a monolayer adsorption (Fig. 5). When the reactor is operated with bentonite and aluminum salts, dye abatement is nearly complete and the liquid-solids separation is particularly efficient (Figs. 6 and 7). The best results are obtained with PHAl but the use of the monomer can be sufficient. The required concentrations are relatively low and the process is then economically feasible (Table 3). However, the experimental data can no longer be modeled by the Freundlich equation nor by the Langmuir equation. When the aluminum salts react alone with the dyes, the conductance displayed against the aluminum concentration shows two straight lines of different slopes (Fig. 8). The abscissa of the points where the slopes change are proportional to the initial dye concentration, suggesting a chemical reaction between the dye and the aluminum salts (Fig. 9). However, the final pH value lies at the limit value of aluminum hydroxide precipitation; an adsorption on aluminum hydroxide or an aluminum salt precipitation cannot then be assumed. In presence of bentonite, such changes of slope are not observed and, moreover, the final pH value does not correspond either to a precipitation value (Figs. 11 and 12). At this stage, a comprehensive mechanism cannot thus be proposed. However, the process using bentonite/PHAl is particularly efficient and easy to operate (Fig. 13 and Table 3). The results were confirmed with a true industrial effluent, the Chemical Oxygen Demand (COD) of which was reduced from 770 mg/l to less than 30 mg/l (Fig. 14). As a matter of comparison, the actual process, which includes an activated sludge treatment followed by an iron sulfate/lime flocculation, leads to an effluent containing only 140 mgCOD/l