Adsorption of Textile Dyes on the Shells of Snails <i>Achatina achatina</i>and <i>Lanistes varicus</i>Acclimatized in Benin: Influence of Their Heating Treatment

The characterization of the shells of snails Achatina achatina and Lanistes varicus indicates that they contain calcium carbonate (98%) essentially aragonite, and organic matter (2%). The heating at 500°C during three hours (3 h) has destroyed their constitutive organic matter, converted the aragonite form completely into the calcite and reduced their specific surfaces. The effects of these modifications have been revealed in the adsorption in aqueous environment of methylene blue (MB) and methyl orange (MO) which are respectively cationic and anionic dyes. The results showed that the sorption of these dyes on the raw shells is more important than the heated shells. The methylene blue has more affinity for shells than methyl orange. Between these two types of snails, the shells of Lanistes varicus have a higher capacity of adsorption. This sorption of the methylene blue is more in relationship with the Freundlich model ( for EG and for EA) comparatively to Langmuir model If the shells of these snails were calcined before using for the cicatrizing of the human cutaneous wounds in Benin. In the case of the sorption of organic molecule, it will be necessary to avoid submitting them to a preliminary heat treatment.

Use of Natural Coagulants in Removing Organic Matter, Turbidity and Fecal Bacteria from Hospital Wastewater by Coagulation-Flocculation Process

Hospital wastewater represents an infectious and toxic risk to human health and the environment due to its contents. Most hospitals in developing countries, including Benin, do not have a wastewater treatment plant. In this study, the wastewater from two hospitals in northern Benin was characterized and then treated with Azadirachta indica leaves, Moringa oleifera and Luffa cylindrica seeds by coagulation/flocculation process. The wastewater characteristics showed that the collected samples are greatly polluted by organic matter and fecal bacteria such as Escherichia coli, Enterococcus fecal and Total coliforms. Jar-test results revealed that 95.74%, 78%, 49.19% of turbidity, 51.35%, 38.32%, 22.19% of COD, 93.16%, 85.26%, 83.30% against Escherichia coli, 92.11%, 90.93%, 94.60% against total Coliforms and 99.37%, 91%, 99%, 55.07% against Enterococcus were removed from hospital wastewater using Moringa oleifera, Luffa cylindrica seed and Azadirachta indica leaves respectively at dose of 100 mg/L. The results highlighted that the natural coagulants could be successfully used for the removal of turbidity and fecal bacteria from hospital wastewater.

Negative Impacts of the Practices of Acadjas on the Aheme Lake in Benin

The objective of this study is to reveal the negative impacts of the practices of acadjas on the Aheme lake in Benin. Various material and methods were used for the measures of the physicochemical parameters such as: colorimetric HACH DR/890, the multiparameter WTW 340i and specific kits for the dosage of minerals. Also, the investigations were made with the resources by persons. It emerges from this study that the practices of acadjas asphyxiate and disturb the lake species. In fact, the concentrations in dissolved oxygen became very weak (1595 mg/L to 3740 mg/L), and the contents of nitrites (2, 25 mg/L to 14, 5 mg/L), suspension materials and turbidity are raised. The consequences both on the aquatic fauna and on the vegetation of the bank are worrying. The waterside populations are also threatened. Some actions in an attempt to regulate the practice of acadjas and promote reforestation of the lagoon bank need to be put in place.

Structural studies and conductivity of [Fe(O₃C₄)(COO)]·H₂O based H₄btec (H₄btec = 1,2,4,5-benzenetetracarboxylic acid)

A new metal-organic hybrid compound?[Fe(O3C4)(COO)]·H2O I has been hydrothermally synthesized and characterized by single-crystal X-ray diffraction. Rust crystals crystallize in the monoclinic system, space group I2/a, a = 6.9651(2) A, b = 8.12630(10) A, c = 19.4245(2) A, β = 92.6600(10)°;V = 1098.25(4) A3;Z = 2 and Dx =3.63g/cm3. The refinement converged into R = 0.042;Rw = 0.058. The structure, determined by single crystal X-ray diffraction, consists of a network of FeO6 centers, octahedral coordinated by btec (btec = 1,2,4,5-benzenetetracarboxylic acid) anions giving rise to a two-dimensional sheet structure. In the compound I,?[Fe(O3C4)(COO)]·H2O, the FeO6 group bridged by the 1,2,4,5-benzenetetracarboxyl anion exist in a unit cell, with each anion lying about an inversion centre. One of the FeO2 adistance [1.965(2)] significantly corresponds to the shortest distance as the other and the distances found in the axial direction of compound I.

Structure, Thermal Behavior and Characterization of a New Hybrid Iron Fluoride FeF4（2,2′-bipyridine）（H2O）2

New crystal of FeF4（2,2′-bipyridine）（H2O）2 was prepared by hydrothermal synthesis. Crystalline structure determination is performed from single crystal X-ray diffraction data. The unit cell is monoclinic space group P21/n, with cell parameters a=0.9046（5） nm, b=0.7502（5） nm, c=1.9539（5） nm,β=93.307（5）°, V=1.3238（12） nm^3 and Z=4. The structure of FeF4（2,2＇-bipyridine）（H2O）2 is built up from FeF4N2 octahedra coordinated by two nitrogen atoms of the 2,2＇-bipyridine molecules, and four fluorine atoms as well as uncoordinated H2O molecules. Thermal analysis of the title compound showed that the decomposition introduced four steps. IR spectra confirmed the presence of 2,2＇-bipyridine molecules. The optical absorption was measured at the corresponding 2max using UV-Vis diffuse reflectance spectrum.

Synthesis, Structural Study and Phase Transitions Characterization by Thermal Analysis and Vibrational Spectroscopy of an Ammonium Rubidium Arsenate Tellurate

The Rb2.42（NH4）0.58（HAsO4）（H2AsO4）. Te（OH）6 crystals（denoted by RbNAsTe） crystallize in the monoc-linic system, space group P21/n with the following parameters： a=1.3059（5） nm, b=0.6755（3） nm, c=1.6675（6） rim,β=94.126（4）°, Z=4 and V=1.46733（10） nm^3. Thermal analyses（DSC, DTA and TG） confirm the presence of the phasetransition and the temperatttre of the decomposition. The vibrational spectroscopy study at room temperature showthe presence and the independence of anionic groups, cationic groups, and give more importance to the hydrogenbonds. Raman spectra were recorded in the temperature range of 298--503 K. The temperature dependence of theRaman line shift, intensity reduction and the half width detects the phase transitions and confirms their nature. So, thephase transition at 453 K corresponds to the superprotonic-ionic conduction phase transition, and those at 483 and491 K correspond to the decomposition of our material.

Synthesis,structural study,thermal,optical properties and characterization of the new compound[C6H7N2O2]3TeCl5·2Cl

The new organic-inorganic compound, [C_6H_7N_2O_2]_3TeCl_5·2Cl was synthesized and its structure was determined at room temperature in the triclinic system （P^-1） with the following parameters： a = 10.5330（11） ？, b = 10.6663（11） ？, c = 15.9751（16）？, α = 82.090（2）°, β = 71.193（2）°, γ = 68.284（2）°and Z = 2. The final cycle of refinement led to R = 0.057 and Rw = 0.149. The crystal structure was stabilized by an extensive network of N--H···Cl and non-classical C--H···Cl hydrogen bonds between the cation and the anionic group. Several thermal analysis techniques such as thermogravimetric analysis, differential scanning calorimetric analysis and evolved gas analysis were used. We used isoconversional kinetics methods to determine the kinetics parameters. We observe that the decomposition of [C_6H_7N_2O_2]_3TeCl_5·2Cl entails the formation hydrochloric acid of nitroaniline as volatiles. The infrared spectra were recorded in the4000–400 cm^（-1）frequency region. The Raman spectra were recorded in the external region of the anionic sublattice vibration 50–1500 cm^（-1）. The optical band gap was calculated from the UV-Vis absorbance spectra using classical Tauc relation which was found to be 3.12 and 3.67 eV.