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In the present study, indigo blue dye removal efficiency of activated carbon (AC) and natural clay (NC) was evaluated and compared, firstly in an adsorption unit, and then in an adsorption coupling ultrafiltration (A/UF) system. Effect of operating variables like pH, contact time, adsorbent dosage, initial dyes concentration during the adsorption was investigated and consequently optimised. The optimal conditions were employed for the adsorbents during the removal of the dye in the A/UF system. The optimal amount of NC and AC was 0.4 g/L and 0.3 g/L, respectively, and NC and AC displayed adsorption capacity of 57 mg/g and 53 mg/g, respectively, at this condition. Application of UF reveals a decrease of membrane fouling for both adsorbents in A/UF system. In addition, colour retention, when the adsorbents were used in A/UF, increased significantly from 90.5% to 99% as compared to using adsorption only. The efficiency of the membrane regeneration was estimated by the determination of the water permeability after rinsing. It is noteworthy to mention that a total regeneration of the membrane after the application of continous hybrid A/UF was achieved, however, the use of UF alone exhibited a fouling decrease by 40%. [ABSTRACT FROM AUTHOR]

In the present work, two Algerian clay samples, Djebel Debagh (DD3) and Tamazert (KT2), were used as adsorbents for the removal from the water of Derma Blue R67, which is an acid dye commonly used in the tanning industry. The two clay samples used were first treated by acid in order to enhance their retention capacities, and then characterized using X-ray diffraction, scanning electron microscopy, surface area measurements (Brunauer, Emmett et Teller method (BET)), surface charge (points of zero net proton charge), and electrophoretic mobility (Zetaphoremeter). Further, the adsorption experiments of the acid dye from water onto the clay surface were carried out by investigating various parameters such as, the contact time, the initial dye concentration, the aqueous phase pH, the clay amount and the temperature. The results indicate that the two adsorbents are efficient and that the anionic dye removal from water is mainly feasible at ambient temperature. Further, the comparison of the experimental adsorption data to the prediction models has shown that the Langmuir model gives the best fit, indicating the formation of a monolayer by the acid dye molecules on the clay surface. Finally, the adsorption kinetics follows a two-type process onto KT2 kaolinite, whereas onto DD3, it only follows the pseudo-second order model. From the overall data, it is concluded that the Algerian local kaolin clays are good adsorbent candidates for wastewater treatments [ABSTRACT FROM AUTHOR]

Abstract: One of the principal applications for bentonite is in drilling muds. Moreover it is widely used as a suspending and stabilizing agent, and as an adsorbent or clarifying agent, in many industries. Recently the bentonites have been proposed as engineered barriers for radioactive waste repository because these materials are supposed to build up a better impermeable zone around wastes by swelling. For these reasons, a textural characterization of bentonites in the laboratory is very important. The aim in this study was to estimate several textural properties of compacted and cation-exchanged bentonite by using Hg-porosimetry, N2-adsorption, water vapour adsorption, scanning electron microscopy (SEM) observations and environmental scanning electron microscopy-digital images analysis measurements. For that, bulk samples were mechanically compressed at atmospheric conditions by using a uniaxial system at four different pressures (21, 35, 49, and 63MPa) in order to obtain four physical densities. On the other hand, the bulk samples of bentonite were treated separately with four concentrated solutions (1N concentration) of sodium, potassium, magnesium and calcium chlorides in order to obtain a homoionic interlayer cation in the clay phase. The results showed that the macro-porosity (porous size>50nm) and eventually the mesoporosity (porous size 2–50nm) are affected by the uniaxial compaction. In this case, a transformation of the shape of the macro-pores network from tube to crack was observed. On the other hand, the swelling potential and water content are governed by the relative humidity and by the nature of interlayer cation. [Copyright &y& Elsevier]

Abstract: Soils of the semi-arid area of the El Melah coastal lagoon (NE Tunisia), with a closing evolution dynamic, were studied aiming: (1) the chemical and mineralogical characterization of surface and subsurface layers of soil profiles from locations previously submerged and of soils developed on dunes; (2) to evaluate the dependence on the environment conditions of the geochemical patterns of the soils; and (3) to determine chemical and mineralogical variations with the emersion of the sediments resulting from the decrease in the extent of the area permanently covered by water in the lagoon. The compositional results obtained showed significant differences depending on the environment (littoral plain, old dunes and sandy spit), but soils of the different environmental zones studied do not appear to be significantly polluted as far as trace elements are concerned. Among the elements studied, high element/Sc ratios and variations were found for As, Sb and Zn. Antimony is more concentrated in coarser samples suggesting its adsorption in Fe or Mn oxides coating quartz grain surfaces. Arsenic and zinc may be incorporated into the carbonates structure, as well as adsorbed on, or coprecipitated with, iron oxides. Zinc may also be significantly incorporated in clay minerals. Iron was found to be more oxidized in the cultivated soil from the old dune strand; and more reduced in the sandy spit where ankerite occurs suggesting the reduction of Fe3+ in oxide/hydroxides by microorganisms and incorporation of Fe2+ in carbonates. REE patterns, particularly the HREE/LREE are correlated with carbonates, indicating preferential incorporation of the HREE in carbonates, and of the LREE in clay minerals/iron oxides. High Ga contents were found in soils and sediments rich in clay minerals/Al, suggesting its incorporation in clay minerals structure. Therefore, Ga may be used as an indicator of the clay minerals proportion in sediments and soils. Carbonates, sulphates, besides Fe and/or Mn oxides and clay minerals, appear to play an important role on the trace elements distribution. [Copyright &y& Elsevier]