VOLUME 38, NO3, JUNE-2016
Kinetics and Mechanism of [Fe (bipy) 3]2+ and [BrO3–] System in Aqueous Acidic Medium

Shazia Summer, Iftikhar Imam Naqvi, Rozina Khattak, Shagufta Gulzar and Fayeza Reyaz

The kinetics of the oxidation of tris (2,2-bipyridine)iron(II) ([Fe(bipy)3]2+) by bromate ion (BrO3–) in aqueous medium have been investigated. The reaction was probed spectrophotometrically in the pH range 3.5-5.0, and from 0.01 to 0.1 mol/dm3 ionic strength. The kinetic runs were pursued to more than two half lives of the reaction. The pseudo first order rate constant was found independent of the concentration of tris (2, 2-bipyridine) iron (II), and increases with increasing concentration of bromate ion in the reaction mixture. Protonation of BrO3– in the acidic medium yields monoprotonated (HBrO3) and diprotonated (H2BrO3+) species. The rising figure of the rate constant upon lowering the pH refers to the involvement of protonated species in the rate-determining step. A rise in the value of the rate constant with increasing ionic strength implies, however, the diprotonated species, H2BrO3+, as the reactive species among the two competing. Involvement of the other Br(V) species results in a complex reaction pathway, consequently.
Coke Suppression by Holmium Promoter in Dry Reforming of Methane

A. H. Fakeeha, M. A. Naeem, A. E. Abasaeed, A. A. Ibrahim, W. U. Khan and Ahmed Sadeq Al Fatesh

The present research mainly focused on the development of highly coke resistant catalysts. In this context, Ni/ZrO2 novel catalysts with holmium (Ho) promoter were prepared using the polyol method and investigated, for CH4-CO2 reforming, at atmospheric pressure in the temperature range of 500–700 °C. For each catalyst, the Ni loading was fixed at 5 wt.%, while Ho loading was varied from 0.0–1.5 wt.%. Various techniques such as BET, H2-TPR, CO2-TPD, XRD, TGA and FESEM were used to characterize the prepared catalysts. The results demonstrated that the addition of Ho in Ni/ZrO2 catalyst had a notable effect on carbon suppression. Moreover, CO2-TPD results revealed that the incorporation of Ho in Ni/ZrO2 catalyst fairly enhanced its Lewis basicity. These improvements in basicity favored the chemisorption and activation of CO2 over the catalyst surface which in turn minimized coke deposition. Carbon deposition on the 1.5 wt.% Ho promoted catalyst (Ni-1.5Ho-Zr) was reduced about 92.7% compared to the un-promoted catalyst.
Sonic and Microwaves Assisted Redox Reactions of the Hydrolysates of Protein for the Preparation of Rechargeable Battery

Zahid Hussain, Karishma Khatak, Anila Sardar, Khalid Mohammed Khan and Shahnaz Perveen

Long recharging time is one of the serious limitations of batteries. One of the best solutions for quick redox reactions via the use of microwave and sound-assisted reversible redox reaction is presented in this work. A wireless charged prototype battery based on the redox reactions of hydrolyzed waste protein was designed. The effect of experimental conditions like time of charging, nature of media and strength of the acid on the voltage of this prototype battery was investigated. The experimental data was explained on the basis of the previous work on protein peptides and amino acids by various workers.
Computational Study on the Effect of Axial Ligation Upon the Electronic Structure of Copper (II) Porphyrinate (CuTPPs = [5,10,15,20-tetrakis(N-methylpyridyl-4)porhinato]copper(II)tetratosylate)) - Electronic Structure with Different Axial Ligands

Roxana-Viruca Ţolan, Alexandru Lupan and Radu Silaghi-Dumitrescu

Copper porphyrins are generally known to show a less diverse reactivity as compared to their iron counterparts, both redox-wise and in terms of axial ligation. Reported here are density functional theory (DFT) results on models of copper (II)-porphyrins (models of [5,10,15,20-tetrakis(N-methylpyridyl-4)porhinato]copper(II)tetratosylate) with a set of axial ligands – nitrite (both the nitrogen-bound isomer and the oxygen-bound isomer, i.e., nitro and nitrito), imidazole, two forms of phenol (neutral and anionic), and water - related to an unexpected range of electronic structures detectable in electron paramagnetic resonance (EPR) spectra of a water-soluble copper porphyrin with water, nitrite, imidazole, dithionite, 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) and guaiacol. Computed spin densities and atomic charges reveal various degrees of influence of the axial ligands on the Cu-porphyrin electronic structure, which may be related to the notably different changes induced by each ligand (imidazole, nitrite, guaiacol and ABTS) on the EPR superhyperfine splitting, but with an unexpectedly strong dependence on choice of the computational methodology. Thus, at the B3LYP/6-31G** level the copper spin densities are predicted to range from 0.69 to 0.73 depending on the axial ligand, this contribution being located on the dx2-y2 orbital in a range from 65% to 100%. BP86/DN** results tend to favor a distinctly larger spread of these values.
Transition Metal Complexes of S-Propyl-L-Cysteine

Shahbaz Nazir, Jamil Anwar, Munawar Ali Munawar, Stephen Peter Best, Michael Cheah, waqar Nasir, Amjad Ayub Bhatti and Peter Wichta

Four transition metal complexes of the type M(L)2 ( M= Co, Ni, Cu, Zn and L= S-Propyl-L-cysteine) were synthesized and characterized by elemental analysis, spectral studies, thermo-gravimetric analysis, magnetic moment measurement and EPR. The complexes are proposed to have octahedral geometry around the metal atoms due to nitrogen and oxygen atoms. The ligand acts as a bridging ligand between two adjacent metal atoms leading to the formation of polymeric complexes. The carboxylate group in the ligand acts as bridging moiety between the two metal atoms. The polymeric nature of these complexes is also confirmed by the fact that they are insoluble in ordinary solvents. XAFS was used as confirmatory technique and it also shows octahedral environment around the central metal atom due to nitrogen and oxygen and clearly rejects the involvement of sulphur in the coordination sphere. EPR and XAFS show Jahn-Teller distortion around copper in the complex.
Metal Doped Green Zeolites for Waste Water Treatment: A Sustainable Remediation Model

Noshabah Tabassum, Uzaira Rafique and Muhammad Aqeel Ashraf

The synthesis of zeolites from refused materials presents a greener model for environmental remediation. The present study offers a novel procedure to synthesize not only the basic framework but also Vanadium modified polymeric zeolites. The spent polythene bags, lunch boxes, and packaging are used as raw material for synthesis of zeolites. Characterization through EDX showed incorporation of vanadium is more than 35%, exhibiting FTIR frequencies in the range 601-995cm-1. Thermogravimetric (TG) analysis revealed a stabilizing effect of zeolites on addition of dopant upto 320°C as determined by higher residue percentage (> 98%). Vanadium doped synthesized zeolites (MP1, MP2, MP3) were applied in batch adsorption experiments for in-situ (synthetic metal salt solution) and ex-situ (industrial effluents) removal of metals (Pb, Cr, and Cd). Adsorption results indicated the successful metal removal of more than 90% in the sequence Pb > Cd > Cr. The sequence follows, higher is the ionic radius of the metal cation, more is the adsorption on zeolites. Application of adsorption isotherms demonstrated fitness of Freundlich and Temkin models, whereas pseudo first order kinetics depicts metal removal. The study concludes that synthesized zeolites are suitable candidates with improvised green economy for industrial sector to treat effectively industrial discharges.
A Simple Method for Simultaneous Spectrophotometric Determination of Brilliant Blue FCF and Sunset Yellow FCF in Food Samples after Cloud Point Extraction

Rouhollah Heydari, Mohammad Hosseini, Mohammad Alimoradi and Sanaz Zarabi

In this study, a simple and low-cost method for extraction and pre-concentration of brilliant blue FCF and sunset yellow FCF in food samples using cloud point extraction (CPE) and spectrophotometric detection was developed. The effects of main factors such as solution pH, surfactant concentration, salt and its concentration, incubation time and temperature on the CPE of both dyes were investigated and optimized. Linear range of calibration graphs were obtained in the range of 16.0–1300 ng mL−1 for brilliant blue FCF and 25.0–1300 ng mL−1 for sunset yellow FCFunder the optimum conditions. Limit of detection values for brilliant blue FCF and sunset yellow FCFwere 3 and 6 ng mL−1, respectively. The relative standard deviation (RSD) values of both dyes for repeated measurements (n=6) were less than 4.57 %. The obtained results were demonstrated the proposed method can be applied satisfactory to determine these dyes in different food samples.
Investigating the Conformation of Polymeric Dispersant Molecules on Nanoparticle Surface

Saima Yasin, Paul F. Luckham and Tanveer Iqbal

Block copolymers are widely used as stabilizers in industrial dispersions. These polymers adsorb on surfaces by an anchor chain and extend by a hydrophilic chain. Scaling model or de Gennes theory has been used to determine the grafting density of the block copolymers. By implementing this theory to the block copolymers, conformation of the polymer molecules as a function of distance between adjacent anchor chains can be determined. The scaling model was applied to a selection of block copolymers (PE/F 103, PE/F 108, NPE1800, Triton X100, Triton X405, Lugalvan BNO12, Hypermer LP1, Hypermer B246 and OLOA 11000) in this study. The cross sectional area σc, distance s (square root of σc) and the Flory radius (end to end dimension of polymer), Rf, for all the polymers was determined. The cross sectional area per PEO (Poly Ethylene Oxide) chain (nm2) was found to be increasing with the size of stabilizing chain. Triton X100 and Lugalvan BNO12 has the smaller stabilizing chains so occupy smaller cross sectional areas whereas PE/F108 and triton X405 have larger number of PEO units and occupy a larger cross sectional area. This shows that stabilizing chain regulates the adsorption amounts that are lower in case of lower number of EO units. The application of de Gennes theory to experimental results suggested brush configuration of adsorbed polymer molecules in case of PE/F 103, PE/F 108, Triton X100, Triton X405, NPE1800, Lugalvan BNO12, Hypermer B246 and OLOA 11000. Whereas, Hypermer LP1 is more likely found to be adsorbed on graphitic carbon black in loops and trains.
Synthesis, Characterization and Catalytic Activity of Pd Supported Zirconia for the Oxidation of Benzyl Alcohol in Liquid Phase Solvent Free Conditions

Mohsin Siddique, Mohammad Ilyas and Muhammad Saeed

Selective oxidation of benzyl alcohol was carried out using molecular oxygen under mild conditions at high turnover frequency [TOF] over palladium supported on zirconia. Zirconia was synthesized by co-precipitation of zirconyl chloride with dilute ammonia solution. Palladium supported zirconia was synthesized by incipient wet impregnation method. The high surface area of zirconia was responsible for the better dispersion of palladium metal over the support which improved the accessibility of the relatively large molecules to the active sites, leading to an improved catalytic performance for alcohol oxidation. The catalyst was characterized by different physical and analytical techniques. The catalyst was found to be active and selective towards the formation of benzaldehyde. The TOF was found to be > 6000/hour, which was amongst the highest reported in literature. Langmuir-Hinshelwood kinetic model was found to be applicable to the solvent free oxidation of benzyl alcohol oxidation.
Effect of Citric Acid on the Synthesis of MoP Catalyst for CO2 Reforming of CH4

Hui-Rui Guo, Xian-Cai Li, Ai-Jun Yang, Yi-Feng Yang and Li-Li Yu

A new molybdenum phosphide (MoP) catalyst was successfully synthesized for CO2 reforming of CH4 reaction. The catalysts were prepared by temperature-programmed reduction (TPR) of phosphomolybdate precursors which were modified by citric acid (CA) at the molar ratio of MoP:CA = 1: x (x = 0, 1.0, 2.0, 3.0), which were characterized by means of X-ray diffraction(XRD), N2 adsorption-desorption and CO2-TPD techniques. The results showed that the addition of citric acid can affect the catalytic activity and that the MoP catalyst had the highest catalytic activity at 1073 K and X=1. After reduced in H2 flow at 923 K, the activity of the post-reaction catalyst can be well restored, while its structure remains unchanged. In higher temperatures, the samples exhibit good anti-sintering ability and stability.


Browse By Issue