Pardeep Singh; Sourav Gautam; Pooja Shandilya; Bhanu Priya; Virender P. Singh; Pankaj Raizada
Abstract
The supported photocatalysis is emerging as an effective technology to overcome of inherent drawbacks of bare magnetic photocatalysts. Herein, ZnFe2O4 was immobilized over graphene sand composite (GSC) and bentonite (BT) to report ZnFe2O4/GSC and ZnFe2O4/BT photocatalyst. The size of ZnFe2O4/GSC and ...
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The supported photocatalysis is emerging as an effective technology to overcome of inherent drawbacks of bare magnetic photocatalysts. Herein, ZnFe2O4 was immobilized over graphene sand composite (GSC) and bentonite (BT) to report ZnFe2O4/GSC and ZnFe2O4/BT photocatalyst. The size of ZnFe2O4/GSC and ZnFe2O4/BT was obtained as 100 and 50 nm, respectively. Both photocatalysts exhibited band gap of 1.95 eV. ZnFe2O4/GSC and ZnFe2O4/BT had BET surface area of 15.6 and 14.5 cm 2 , respectively. The appearance of D and G band in Raman spectra indicated the formation of graphene sand composites. The superparamagnetic property of photocatalyst resulted in quick separation photocatalyst form reaction solution. The adsorption and photocatalytic capability of ZnFe2O4/GSC and ZnFe2O4/BT was evaluated for photo-mineralization of ampicillin and oxytetracycline antibiotics. The adsorption process showed significant effect on mineralization of selected antibiotics. Simultaneous adsorption and degradation (A+P) process was highly effective for antibiotic degradation. More than 90% of antibiotic mineralization was obtained in 10 hours. The power law model authorized the complex nature of degradation process. Magnetically recoverable photocatalyst exhibited significant recycling efficiency due to easier recovery of photocatalysts.
Aida Mohammadi; Abolghasem Ataie; Saeed Sheibani
Abstract
Barium hexaferrite (BaFe12O19) magnetic nano-powder was prepared by co-precipitation method. The effectiveness of different chemical synthesis variables such as solvent and mechanical milling on the adsorption efficiency of barium hexaferrite nano-particles to remove Cr (VI) ions from aqueous solutions ...
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Barium hexaferrite (BaFe12O19) magnetic nano-powder was prepared by co-precipitation method. The effectiveness of different chemical synthesis variables such as solvent and mechanical milling on the adsorption efficiency of barium hexaferrite nano-particles to remove Cr (VI) ions from aqueous solutions was examined. Structural, magnetic, and adsorption properties of the powders are investigated by different techniques. X-ray diffraction analysis revealed that barium hexaferrite formed at a relatively low temperature of 700?C in the sample prepared with a mixture of water/alcohol as a solvent. The FESEM and VSM studies confirmed that all samples had a plate like structure with a particle size in the range of 87-145 nm and high magnetic properties. It was demonstrated that nanometer barium hexaferrite was produced to be an operative adsorbent for removal of Cr (VI) ions from solutions. Different Cr (VI) adsorption experiments were carried out by controlling effective adsorption factors. It was revealed that the sample calcined at a temperature of 700°C and then milled for 5 h (owing themaximum surface area 13 m2/g) showed the highest removal efficiency of 99.5% at pH 3.0, amount of nano adsorbent 1.5 g, initial chromium concentration 133 mg/l, and contact time 1 h. FTIR analysis showed that due to the existence of Cr-O stretching band on the surface of nano-particles, the electrostatic reaction between Cr (VI) ions and nano-adsorbent is possible. The adsorption data were best fitted with the pseudo-second-order kinetic model. Also, the equilibrium adsorption capacity of Cr (VI) calculated from adsorption experiments was found to be 13.25 mg/g. Adsorption studies indicated that the potential use of barium hexaferrite nano-adsorbents for the removal of the other heavy metal ions without sacrificing adsorption capacity can be practical.
Ahmed Fawzy; Refat M. Hassan; Ismail Althagafi; Moataz Morad
Abstract
The kinetics of oxidation of iota- and lambda-carrageenans as sulfated polysaccharides by cerium(IV) was studied spectrophotometrically in aqueous perchlorate solutions at a fixed ionic strength of 2.0 mol dm -3 and a temperature of 25 o C. The reactions showed a first order dependence on [Ce IV ], whereas ...
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The kinetics of oxidation of iota- and lambda-carrageenans as sulfated polysaccharides by cerium(IV) was studied spectrophotometrically in aqueous perchlorate solutions at a fixed ionic strength of 2.0 mol dm -3 and a temperature of 25 o C. The reactions showed a first order dependence on [Ce IV ], whereas the orders with respect to each carrageenan concentration were less than unity. The reactions exhibited fractional-first order kinetics with respect to [H + ]. Increasing ionic strength increased the oxidation rates. The oxidation products of carrageenans were characterized by elemental analysis and IR spectra as their diketo-acid derivatives. The oxidation products were found to have high tendencies to form coordination polymer complexes with some metal cations such as Ba II , Cd II , Pb II and Ag I . Kinetic evidences for the formation of 1:1 complexes were revealed. Plausible mechanistic scheme for cerium(IV) oxidations of carrageenans were proposed. The activation parameters with respect to the slow step of the reactions were evaluated and discussed. The rate laws have been derived and the reaction constants involved in the different steps of the mechanisms were calculated. The activation parameters associated with the rate-determining step of the mechanism along with thermodynamic quantities of the equilibrium constants were computed and discussed.
Asha H. Gedam; Rajendra S. Dongre; Amit K. Bansiwal
Abstract
The adsorption of poisonous lead (II) from aqueous solution using graphite doped chitosan composite as an adsorbent has been carried out. The characterizations of graphite doped chitosan composite were studied by using instrumental techniques like X-ray diffraction, Fourier Transform Infrared Spectroscopy ...
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The adsorption of poisonous lead (II) from aqueous solution using graphite doped chitosan composite as an adsorbent has been carried out. The characterizations of graphite doped chitosan composite were studied by using instrumental techniques like X-ray diffraction, Fourier Transform Infrared Spectroscopy and Scanning Electron Microscopy. The XRD study showed the crystalline nature of synthesized graphite doped chitosan composite with sharp and symmetric peaks. SEM morphology showed wide range of porosity that could achieve high lead (II) sorption. FTIR investigation evidenced that the presence of C=O and –OH functionalities participated in lead (II) adsorption from aqueous solution. The influence of pH, contact time, dose of adsorbent and initial metal ion concentration on removal of lead (II) was investigated. The adsorption efficiency was found to be pH dependent and the maximum 98% lead (II) removal observed at optimum pH 6. Results showed that the maximum adsorbent capacity was at dosage of 1g/L and equilibrium time achieved at 120 min. Equilibrium adsorption experiments were studied at room temperature and data obtained fitted to Langmuir and Freundlich adsorption isotherm. Langmuir model had higher R 2 values of 0.943 with sorption capacity of 6.711 mg of adsorbate/g of adsorbent which fitted the equilibrium adsorption process more than the Freundlich model. The adsorption kinetics was analyzed using pseudo first order, pseudo-second order and intraparticle diffusion models. Experimental data better fitted with pseudo second order kinetics model. The results illustrated that graphite doped chitosan composite has the potential to remove lead (II) ions from aqueous solution.
Ankur Jain; Pragya Jain; Shivani Agarwal; Paola Gislon; Pier Paolo Prosini; I.P. Jain
Abstract
Magnesium hydride is a promising material for hydrogen storage due to its high storage capacity i.e.7.6wt%. But its high stability i.e. high desorption temperature (~350? o C) limits its practical application towards hydrogen economy. Moreover the kinetics is also too slow even at high temperatures. ...
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Magnesium hydride is a promising material for hydrogen storage due to its high storage capacity i.e.7.6wt%. But its high stability i.e. high desorption temperature (~350? o C) limits its practical application towards hydrogen economy. Moreover the kinetics is also too slow even at high temperatures. Composite formation with Zr based laves phase alloys, especially ZrCr2 family, is an effective method to improve the hydriding properties of MgH2. This work presents the synthesis, structural, morphological, and hydrogenation properties of Mg-x wt% ZrCrMn composites. Both phases i.e. Mg & ZrCrMn remain their presence after milling and several hydriding cycles as well. SEM results suggest the homogeneous distribution of alloy particles on Mg matrix. Pressure composition temperature (PCT) analysis shows a reduction in desorption temperature down to 250 o C for these composites. TG experiments suggest a total hydrogen capacity of 5.9% and 4.35% for x =25, 50 in Mg-x wt% ZrCrMn composites respectively. The enthalpy of hydride formation is also calculated using Van’t Hoff plots, which is found similar to the parent material i.e. MgH2. A remarkable enhancement in the kinetics of hydrogen absorption / desorption is reported here by forming these composites.
Narender Kumar; J. B. Dahiya
Abstract
Thermal degradation and stability of polypropylene-nanoclay composites containing organic phosphinate (OP) and ammonium polyphosphate (AP) flame retardants with maximum total 20 per cent loading was carried out using thermogravimetry (TG) and differential scanning calorimetry (DSC) analyses in inert ...
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Thermal degradation and stability of polypropylene-nanoclay composites containing organic phosphinate (OP) and ammonium polyphosphate (AP) flame retardants with maximum total 20 per cent loading was carried out using thermogravimetry (TG) and differential scanning calorimetry (DSC) analyses in inert atmosphere. Kinetic methods such as Broido, Horowitz-Metzger and Coats-Redfern were applied to study the mechanism of degradation of materials. The thermal stability of PP/PPgMA/AP/15A nanocomposite containing total 20 per cent loading is increased by 20 o C in comparison to that of control sample and also gives high char yield (14.4 %) due to presence of exfoliated clay and phosphorylating effect of AP in condensed phase. The random nucleation (first order) mechanism is found the most probable mechanism for PP composites degradation from kinetic study. The future prospective of the study is to develop superior fire safe polymeric materials.
Neha Gupta; Atul K. Kushwaha;M.C. Chattopadhyaya
Abstract
The Hydroxyapatite/Zeolite (HApZ) composite were synthesized by precipitation method and used as an adsorbent for the removal of cobalt ions from the aqueous solution. The materials were characterized by scanning electron microscope (SEM) and Fourier transform infrared (FTIR) spectroscopy. It has been ...
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The Hydroxyapatite/Zeolite (HApZ) composite were synthesized by precipitation method and used as an adsorbent for the removal of cobalt ions from the aqueous solution. The materials were characterized by scanning electron microscope (SEM) and Fourier transform infrared (FTIR) spectroscopy. It has been observed that there was slight enhancement in the % removal of cobalt ions from aqueous solution by HApZ (63%) than HAp (58%) and zeolite (47%). Batch experiments were performed to observe the effect of pH, adsorbent dose, contact time and initial cobalt (II) concentration. Kinetic study shows that the adsorption process follow pseudo-second order kinetic model. Equilibrium data were well fitted to Langmuir and Freundlich isotherm model.