In this paper, the evolution of structural, textural and surface properties of attapulgite after treatment with increasing concentrations of hydrochloric acid (0.5, 1, 3 and 5 M) is reported. The solids obtained were characterized by SEM, XRD, FTIR and BET analysis. The surface properties were also evaluated using inverse gas chromatography at infinite dilution (IGC-ID) and finite concentration (IGC-FC). The IGC analysis permitted us to reach several parameters such as: specific surface area, BET constant with organic probes and the distribution functions of the adsorption energy sites on the solid surface. At dilute concentrations of acid, carbonates are eliminated and the specific surface area increases. However, the morphology and crystal structure of attapulgite are preserved. At higher concentrations of acid, dissolution of octahedral sheets and at the same time formation of an amorphous silica from the tetrahedral sheets occur. However, the fibrous morphology is still preserved. The calculation of distribution functions reveals a clear evolution in the heterogeneity of the surface during the acid treatment, the appearance of shoulders is attributed to the development of strong specific interactions between the injected polar probe and silanol groups on the surface of amorphous silica formed during the acid treatment.

The effect of dry milling processes on the surface properties of an attapulgite clay, also called palygorskite, was investigated by carrying out experiments with different types of grinding devices. Ground products were then characterized by size measurement, scanning electron microscopy, X-ray diffraction, adsorption-desorption of N 2 and inverse gas chromatography at infinite dilution (IGC-ID) as well as finite concentration conditions (IGC-FC). These analyses were performed to evaluate the changes in particle size distribution, morphology, crystallinity and surface properties of attapulgite powder, respectively. Among the tested dry grinding devices, grinding in an air jet mill (Alpine 50 AS) and a vibratory ball mill (Pulverisette 0) led to the most significant particle size reduction. SEM photomicrographs showed that a breakage of the fibrous structure took place during dry grinding. Moreover, long grinding in Pulverisette 0 resulted in the complete destruction of fibre morphology followed by agglomeration. XRD analysis showed that whatever the grinding process, the microstructure of the attapulgite was not affected. IGC confirmed that only grinding in Pulverisette 0 affected the surface properties notably. In this case, the most significant decreases were observed in the dispersive component of the surface energy (164 to 116 mJ/m 2) and in the specific surface area obtained with the octane probe (114.5 m 2 /g to 62.6 m 2 /g) by IGC-ID and IGC-FC, respectively. At the same time, a modification of the distribution functions of the adsorption energies (DFAE), giving information about surface heterogeneity, was noticed.

At low temperatures, thermal treatment of attapulgite clay causes a loss of mass due to the elimination of linked, zeolitic and crystallized water molecules. At high temperatures, there is a junction of particles until total melting of the attapulgite fibers. This transformation reduces significantly the volume of the porous network resulting in the drop in the value of specific surface area and causing important changes in the textural, structural and surface properties of the raw attapulgite. The inverse gas chromatography shows sensitivity of the attapulgite sample to the effect of temperature through the decrease of the dispersive component of the surface energy d s. The evolution of the nanomorphological index, a measurement of the surface nanorugosity, follows the appearance of surface roughness on carbonates with the increase of the temperature. The surface heterogeneity, determined by calculating the distribution functions of adsorption energies also underlines the morphology changes and the formation of new phases under the effect of temperature.

The distinctive extra-virgin olive oil aroma consists of a complex mixture of volatile compounds. We comparatively studied the volatiles of eight autochthonous monovarietal extra-virgin olive oils from the north-east part of Algeria via headspace solid-phase microextraction GC-MS. We determined the effect of ripening of Chemlal olive fruit on aroma compounds. Twenty volatile analytes belonging to different chemical classes were identified and quantified. Both quantitative and qualitative differences were found among cultivars, indicating a close dependence of the composition of the volatile profile on the enzymatic pool, directly related to genetic characteristics. Moreover, differences in volatiles composition were observed for Chemlal oils during maturation.

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The most common means of reducing the particle size of solids is by grinding, a process which can affect the surface properties and the behavior of the solid in later stages (granulation, compaction, etc.), and which can influence the end-use properties of the final product. Inverse gas chromatography (IGC) measurements were used here to evaluate the influence of grinding, in a ball mill, on attapulgite. The milling experiments were performed in dry media for various periods. After 30 min of grinding, significant decreases in the particle size and specific surface areas were observed when calculated using different probes. No noticeable variation in the surface properties was observed by IGC either at infinite dilution or at finite concentration, however. In particular, the distribution functions of the adsorption energies (DFAE), giving information about the surface heterogeneity for both an apolar probe (octane) and a polar probe (isopropanol), remained unchanged, regardless of the grinding time. The stability of the surface energy with respect to the grinding process was seen to be related to the particular fibrous structure of the attapulgite clay.

BACKGROUND This study aims at evaluating the degradation of the antibiotic ciprofloxacin (CIP) in urban wastewater effluents using a UV‐C‐driven oxidation processes in the presence of hydrogen peroxide. Under the optimum experimental conditions, the phytotoxicity and ecotoxicity of the treated samples were investigated against one plant species (Sinapis alba) and a crustacean (Daphnia magna), respectively. The efficiency of the process to remove E. coli and ciprofloxacin‐resistant E. coli was also assessed. RESULTS Complete degradation of CIP was achieved within 15 min of treatment under the optimum concentration of the oxidant ([H2O2] = 10 mg L−1). The degradation rate of the antibiotic fitted pseudo‐first‐order kinetics. An increase in both shoot inhibition and root inhibition was observed, until 60 min of treatment, beyond which, the phytotoxic effect was eliminated. The results demonstrated the ability of the UV‐C process to reduce the toxicity towards D. magna by 40%, comparatively, to the untreated wastewater. The inactivation of E. coli and CIP‐resistant E. coli was achieved within 2 min of treatment. CONCLUSIONS The UV‐C/H2O2 process was successfully applied for the removal of CIP at low environmental concentration level. The treatment process was able to achieve a significant reduction of phyto‐ and eco‐toxic effects, as well as E. coli harbouring resistance to CIP. © 2016 Society of Chemical Industry

With its unique structure, graphene exhibits a number of outstanding mechanical, optical, and electronic properties, thus promising several potential applications. In the current work, graphene sheets were prepared from graphite and surface‐modified via an acid treatment. The synthesized material physicochemical properties were assessed using X‐ray diffraction, nitrogen adsorption and BET analysis, transmission electron microscopy, and Raman as well as X‐ray photoelectron spectroscopy techniques. The ability of the surface‐modified graphene in the adsorptive elimination of Pb(II) and Cd(II) cations from aqueous solutions was investigated batchwise under numerous experimental conditions. A pseudo‐second order kinetic model described adequately the adsorption kinetic profiles. The adsorption isotherms were compared to the Langmuir and Freundlich models. It was found that for both heavy metal cations, adsorption isotherms were reasonably described by Langmuir model equation. Maximum adsorption capacities reached 0.946 and 1.779 mmol ion/g for Pb(II) and Cd(II), respectively.