Gh. Eshaq

Ultrasonic assisted-Fenton-like degradation of nitrobenzene at neutral pH using nanosized oxides of Fe and Cu.

Ultrasonic-assisted heterogeneous Fenton reaction was used for degradation of nitrobenzene (NB) at neutral pH conditions. Nano-sized oxides of α-Fe2O3 and CuO were prepared, characterized and tested in degradation of NB (10 mg L(-1)) under sonication of 20 kHz at 25 °C. Complete degradation of NB was effected at pH 7 in presence of 10 mM H2O2 after 10 min of sonication in presence of α-Fe2O3 (1.0 g L(-1)), (k=0.58 min(-1)) and after 25 min in case of CuO (k=0.126 min(-1)). α-Fe2O3 showed also effective degradation under the conditions of 0.1 g L(-1) oxide and 5.0 mM of H2O2, even though with a lower rate constant (0.346 min(-1)). Sonication plays a major role in enhancing the production of hydroxyl radicals in presence of solid oxides. Hydroxyl radicals-degradation pathway is suggested and adopted to explain the differences noted in rate constants recorded on using different oxides.

Preparation and characterization of chitosan-clay nanocomposites for the removal of Cu(II) from aqueous solution

In the present study, chitosan assembled on gold and silver nanoparticles were prepared and characterized by UV-vis, TEM, EDX and DLS techniques. The nanocomposites chitosan (Ch)/clay, chitosan (Ch)/AgNPs/clay and chitosan (Ch)/AuNPs/clay were prepared by solution mixing method and characterized by FTIR, XRD, and SEM techniques. The adsorption of copper(II) ions onto the prepared hybrid composites from an aqueous solution using batch adsorption was examined. The results showed that benefiting from the surface property of clay, the abundant amino and hydroxyl functional groups of chitosan, the adsorbent provides adequate and versatile adsorption for the Cu(II) ions under investigation. The batch adsorption experiments showed that the adsorption of the Cu(II) is considerably dependent on pH of milieu, the amount of adsorbent, and contact time. Batch adsorption studies revealed that the adsorption capacity of Cu(II) increased with increase in initial concentration and contact time with optimum pH in the range around neutral. The maximum uptake of Cu(II) ions by (Ch)/AgNPs/clay composite was found to be 181.5mg/g. The adsorption efficiency of Cu(II) ions by prepared (Ch)/AgNPs/clay and (Ch)/AuNPs/clay is bigger than that the individual chitosan (Ch)/clay composite which clarifies the role of metal nanoparticles in enhancement the adsorption characters. The study suggests that the (Ch)/AgNPs/clay hybrid composite is a promising nano-adsorbent for the removal of Cu(II) ions from aqueous solution.

Extending the working pH of nitrobenzene degradation using ultrasonic/heterogeneous Fenton to the alkaline range via amino acid modification.

Oxides of iron, α-Fe2O3 (I), and copper, CuO (II) prepared by usual precipitation method without surfactant were used at room temperature in the process of nitrobenzene (10mgL(-1)) degradation at different pH values with ultrasonic at 20kHz. The degradation was complete in 20 and 30min for (I) and (II), respectively in the pH range 2-7 using1.0gL(-1) of solids and 10mM of H2O2. A remarkable decrease in degradation efficiency was recorded on increasing the pH to values higher than the neutral range. This loss in efficiency was cancelled to a great extent through modifying the used oxides with amino acids. Arginine showed higher improving effect to (II) (1:1 weight ration) than glycine or glutamic acid. Modification of both oxides with increasing amounts of arginine increased the degradation efficiency of (I) in a more regular way than in case of (II). However, the extent of improvement due to amino acid modification was higher in case of (II) because of its originally low degradation efficiency in strongly alkaline media.

Remediation of distilleries wastewater using chitosan immobilized Bentonite and Bentonite based organoclays

Organic-inorganic nanocomposite, namely chitosan immobilized Bentonite (CIB) with chitosan content of 5% was synthesized in an acetic acid solution (2%). Organically modified CIB and Bentonite (mbent.) were prepared by intercalating cetyl trimethylammonium bromide (CTAB) as a cationic surfactant at doses equivalent to 1.5 and 3 times the cation exchange capacity (CEC) of clay. The prepared samples were characterized using FTIR, XRD and SEM to explore the interlayer structure and morphology of the resultant nanocomposites. The remediation of distilleries (vinasse) wastewater process was carried out using different adsorbents including CIB, modified CIB (mCIB), Bentonite (bent.), modified Bentonite (mbent.) and chitosan at different contact time. The results showed that the packing density of surfactant used in the synthesis of organoclays strongly affects the sorption capacity of the clay mineral and also showed that (mCIB)3 was found to be the most effective sorbent in the purification of distilleries wastewater with 83% chemical oxygen demand (COD) reduction and 78% color removal.

Fe3O4-boosted MWCNT as an efficient sustainable catalyst for PET glycolysis

This study focuses on the utilization of Fe3O4-boosted multiwalled carbon nanotubes (MWCNT) as a sustainable, easily recoverable and a robust catalyst in the glycolysis of PET. A maximum yield (100%) of bis(2-hydroxyethyl)terephthalate (BHET) was achieved using Fe3O4-boosted MWCNT, which was higher than any other catalyst used in PET glycolysis with regard to the BHET yield. The extraordinary performance of the prepared Fe3O4-boosted MWCNT is attributed to the synergetic effect induced by both magnetite and MWCNT in the catalytic glycolysis of PET. With regard to sustainability, the catalyst endures the glycolysis process conditions for at least eight sequential runs. The reaction mechanism of PET glycolysis using Fe3O4-boosted MWCNT has also been proposed.

Kinetics of uptake of Fe(II) from aqueous solutions by Co/Mo layered double hydroxide (Part 2)

AbstractThe kinetics of the Fe(II) uptake by Co/Mo layered double hydroxide (Co/Mo-LDH) intercalated with carbonate (CO3)2− as an interlayer anion was studied. The results revealed that the maximum adsorption capacities were 29.5, 59.1, and 77.9 mg/g when the initial ferrous ion concentration was 25 mg/l at 298, 308, and 318 K, respectively. These results displayed a high efficiency of the Fe(II) uptake from aqueous solution at higher temperature. The adsorption isotherms were seen to be consistent with Langmuir’s adsorption isotherm. The equilibrium adsorption contact time was determined for Co/Mo-LDH. This suggested that the pseudo-first-order equation might not be sufficient to depict the kinetics of Fe(II) onto the Co/Mo-LDH, and the kinetics of adsorption of Fe(II) onto Co/Mo-LDH were best described by the pseudo-second-order model. Also, the paper discussed the thermodynamic parameters of the adsorption (Gibbs free energy, entropy, and enthalpy). Our results demonstrated that the adsorption process ...

Role of surface modification of some metal oxides with amino acids in upgrading the sonocatalytic degradation of nitrobenzene

AbstractThe influence of surface modification of some metal oxides (Fe2O3, CuO, NiO, and CO3O4) with amino acids was investigated in the sonocatalytic degradation of nitrobenzene (NB). Glycine, arginine, and glutamic acid were used as surface modifiers. This modification resulted in a considerable enhancement of sonochemical degradation of NB at pH higher than 7 with respect to the pristine catalysts before modification. Catalysts modified with arginine exhibited the highest degradation extent. The enhanced degradation efficiency was attributed to the promoted coupling via electrostatic attraction between the negatively charged NB molecules and the positively charged arginine layer on the surface of Fe2O3, CuO, NiO, and Co3O4. The attraction capability at all modified metal oxides increased via secondary forces such as hydrogen bonding, n–π and π–π interactions.

Novel Co/Mo layered double hydroxide: synthesis and uptake of Fe(II) from aqueous solutions (Part 1)

AbstractA new type of M2+/M6+-LDH was prepared by the intercalation of Co/Mo-LDH with carbonate (CO3)2− as an interlayer anion through a precise control of the titration rate of the alkaline solution into the cobalt and molybdenum cations. From the analytical results, the structure, composition and morphology of the prepared material were approved by XPS, XRD, FT-IR, N2 adsorption–desorption isotherm, SEM, and DSC-TGA. The synthesized Co/Mo-LDH was applied to the removal of ferrous ions from aqueous solutions at ambient temperature, different pH, constant stirring at 160 rpm and different iron/adsorbent ratios. According to the experimental data, we have succeeded to prepare a novel adsorbent for Fe(II) uptake and at pH 5, stirring at 160 rpm, and after 60 min the uptake reached a maximum value of 10 mg/g of Co/Mo-LDH. Hence, the higher adsorption capacity of the Co/Mo-LDH was explained by the formation of 4+ surface charges between Co2+ and Mo6+ which produced a highly energetic surface layers as detecte...

Studies of Ni/Kaolinite Catalysts for the Hydrogenation of Toluene

No mention appears to have been made in the literature to the use of kaolinite as a support for nickel catalysts in the hydrogenation of toluene. In this study, kaolinite-supported Ni catalysts (1–7 wt%) were prepared and characterized, and their activity in the catalytic hydrogenation of toluene at atmospheric pressure established. XRD, DSC, N2 adsorption and TPR methods were used as characterization techniques. XRD revealed that interaction occurs between the Ni species and the support at low Ni content (up to 3 wt%) but decreases as the Ni loading increases. This results in an increase in the number of Ni active sites with increased Ni loading and is reflected in the catalytic activity towards toluene conversion into methylcyclohexane, which increased as the Ni content of the catalyst increased. Modification by post-impregnation with KNO3 or Zn(NO3)2 (2–6 wt% K or Zn) affected the extent of interaction between the Ni species and the support. Thus, the catalytic activity increased in the presence of 2 wt% modifier (K or Zn). However, at higher levels of modification (4 and 6 wt%), the catalytic activity decreased relative to that for the unmodified sample containing the same Ni loading. This loss in catalytic activity increased as the modifier content increased. Furthermore, in the presence of K as a modifier, the decrease in toluene conversion was accompanied by a shift in the temperature of maximum conversion from 200°C for the unmodified sample to a value of 250°C. This was attributed to the covering of the Ni active sites by some incompletely decomposed KNO3.