A Comparison of the Leaching Kinetics and Mechanism of Calcined Magnesite with an Organic Leach Reagent

The leaching kinetics of calcined magnesite in aqueous lactic acid solutions was investigated in a batch reactor by using parameters such as temperature, acid concentration, particle size, solid/liquid ratio, and stirring speed. A mathematical model was evaluated for the rate increased by decreasing particle size and by increasing temperature; and initially the leaching is increased in terms of acid concentration and then decreased by increasing concentration. It was determined that experimental data complies with shrinking core model for fluid-solid systems. It was also found that the stirring speed did not change the dissolution and that the dissolution rate was controlled by surface chemical reaction. Additionally, the fact that leaching was controlled by the chemical reaction was also supported by the relationship between the rate constant and the particle radius. The activation energy of the process was determined to be 30.61 kJ mol-1.read more

Feray Bakan, Oral Lacin and Hanifi Sarac

Removal of Pb(II) from Aqueous Solutions by D113 Resin Kinetics and Isotherms Study

In this study, the adsorption and desorption properties of Pb(II) on D113 resin have been investigated. The different variables affecting the adsorption capacity have been also studied, such as pH of the solution, contact time, Pb(II) concentrations, resin amounts and temperatures, which indicate that D113 resin could be used effectively for the removal of Pb(II) ions from aqueous solution. The results show that the optimal pH for the adsorption of Pb(II) is 5.73 and the maximum saturated adsorption capacity is 598.3 mg/g at 298K. The apparent activation energy Ea and adsorption rate constant k298K values are 16.5 kJ/mol and 1.89×10−5 s−1, respectively. The adsorption of Pb(II) follows the Langmuir isotherm and Freundlich isotherm, and the correlation coefficients have been evaluated. Thermodynamic parameters which ΔS value of 0.241 kJ/(mol K) and ΔH value of 55.18 kJ/mol indicate the endothermic nature of the adsorption process, and a decrease of Gibb's free energy (ΔG) with increasing temperature indicates the spontaneous nature of the adsorption process. The resin can be regenerated through desorption of the Pb(II) using 0.5 mol/L HCl solution and can be reused to adsorb again.read more

Jianjun Mo, Qian Jia, Chunhua Xiong and Caiping Yao

Effect of Thermal Treatment on Production of Graphene from Graphite via Exfoliation in Organic Solvent (Acetonitrile)

Graphite flakes were divided into two equal parts Part A and Part B. Part A was thermally shocked at 800oC under inert atmosphere of argon for two min before exfoliation under sonic tip while Part B was exfoliated as such using acetonitrile (ACN) as exfoliating media in both cases at 15-20oC. The concentration of the graphene as a result of exfoliation and centrifugation at 500 rpm for 45 min in both cases were determined. After ten hours of sonication the concentration of graphene in Part A is >12mg/ml with few layered thickness while that of Part B was <5mg/ml consisting of more layers than Part A. UV spectroscopy, Raman, Transmission Electron Microscopy and Scanning Electron Microscopy (SEM) were used for the study of these nanoflakes.read more

Khalid Nawaz, Muhammad Ayub, Arshad Hussain, Abdul Qadeer Malik, Muhammad Bilal Khan, Muhammad Bilal Khan Niazi, Muzammil Hussain, Asad Ullah Khan and Noaman Ul-Haq

Slow Manifolds in Chemical Kinetics

Modelling the chemical system, especially for complex and higher dimensional problems, gives an easy way to handle the ongoing reaction process with respect to time. Here, we will consider some of the newly developed computational methods commonly used for model reductions in a chemical reaction. An effective (simple) method is planned to measure the low dimensional manifold, which reduces the higher dimensional system in such a way that it may not affect the precision of the whole mechanism. The phase flow of the solution trajectories near the equilibrium point is observed while the initial approximation is measured with the spectral quasi equilibrium manifold, which starts from the equilibrium point. To make it an invariant curve, the approximated curve is first refined a certain number of times using the method of invariant grids. The other way of getting the reduced data in the low dimensional manifold is possible through the intrinsic low dimensional manifold. Then, we compare these two invariant curves given by both the methods. Finally, the idea is extended to the higher dimensional manifold, where more number of progress variables will be added.read more

Muhammad Shahzad, Ibrar ul Haq, Faisal Sultan, Abdul Wahab, Faiz Faizullah and Ghaus Ur Rahman

Kinetic and Equilibrium Studies of Neutral Red Adsorption onto Spent Ground Coffee from Aqueous Solution

In this study, the adsorption of neutral red (NR) on the spent ground coffee (SGC) was examined. The effect of various parameters such as pH and adsorbent dose on the removal of NR was investigated. The removal ratios of NR (25 and 40 mg/L) on SGC after 2 h were 95.6 and 90.2%, respectively. The removal ratio of NR is increased by increasing the pH value. Equilibrium data fitted very well in a Langmuir isotherm equation, the adsorption capacity of NR was 136.98 mg/g for SGC. The adsorption mechanisms can be contributed by hydrophobicity interaction at the interface occurs between NR and SGC. The present study shows that the SGC is an inexpensive and easily used NR adsorbent.read more

Yingjie Dai, Kexin Zhang, Danfeng Zhang and Yanjun Chen

Influence of Operating Parameters on the Arsenic and Boron Removal by Electrocoagulation

Despite their high boron contents, some boron deposits contain considerable amounts of arsenic. Its toxicology and health hazard also has been reported for many years. In this work arsenic and boron removal from synthetic water was studied on laboratory scale by electrocoagulation using aluminum electrodes. The influence of main operating parameters such as current density, stirring speed, supporting electrolyte type and concentration on the arsenic and boron removal was investigated. Waste water sample was prepared with initial arsenic concentration of 50 mg L-1 and boron concentration of 1000 mg L-1. Current density was varied from 0.18 to 4.28 mA cm-2, stirring speed was varied as 50, 150, 250, 350 rpm, NaCl, KCl and Na2SO4 were used as supporting electrolyte. The obtained experimental results showed that efficiency of arsenic and boron removal increased with increasing current density. As the current density increases, the potential difference applied to the system also increases the energy consumption. Increasing the supporting electrolyte concentration increased conductivity of solution and decreased energy consumption. The most favorable supporting electrolyte type was NaCl for arsenic and boron removal. The best stirring speed were 150 rpm for arsenic and boron removal.read more

Berrin Zeliha Can, Recep Boncukcuoğlu, Serkan BAYAR and Yalçın Kemal BAYHAN

Silver Nanoparticles Fabricated Hybrid Microgels for Optical and Catalytic Study

In this work different compositions of smart poly(N-isopropylacrylamide-vinylacetic acid-acrylamide) poly(NIPAM-VAA-AAm) microgels with different vinyl acetic acid (VAA) contents have been synthesized successfully by conventional free radical emulsion polymerization. Silver metal nanoparticles (NPs) were fabricated inside the microgels network by insitu reduction method using sodium borohydride (NaBH4) as reducing agent. The confirmation of polymerization and entrapment of metal NPs were carried out by FT-IR spectroscopy. Dynamic laser light scattering (DLLS) technique was used for calculating average hydrodynamic diameter of microgel particles. The optical properties of silver NPs were studied by UV-Visible spectroscopy at various conditions of pH and temperature. The hybrid microgels show red shift and increase in intensity of surface plasmon resonance (SPR) band with the increase in temperature and decrease in pH of the medium. The synthesized materials were used as catalysts in the reduction process and it was found that the catalyst composed of high amount of VAA shows enhanced catalytic activity. The apparent rate constant (kapp) for catalyst composed of 12% VAA was doubled (5.6×10-3sec-1) as compared to 4% VAA containing catalyst (2.8×10-3sec-1).read more

Luqman Ali Shah, Jaweria Ambreen, Iram Bibi, Murtaza Sayed and Mohammad Siddiq

Ammonium Hydrotribromide Salts as Convenient and Selective Brominating Agents of Aryl Methyl Ketones

A simple and improved protocol for the α-monobromination of acetophenone and acetyl carbazole derivatives using different ammonium hydrotribromide salts under mild reaction condition was described.read more

Mohammad Badali, Jabbar Khalafy, Elnaz Alidoost and Masomeh Aghazadeh

Antiurease, Antiphosphodiesterase and Antiglycation Studies of Pd(II) Complexes with Monodentate Hydrazides

The present study was aimed to synthesize and characterize a series of Pd(II)-benzohydrazide complexes with subsequent high throughput screening to seek their effects as enzyme inhibitors and antiglycating agents. Based on complete characterization via elemental (CHN, Pd) analysis, physical (conductivity, magnetic moment) measurements and spectral (FT-IR, 1H-NMR, 13C-NMR) techniques, all Pd(II) complexes were identified as diamagnetic, neutral and orienting in trans square planar geometry with general formula [PdL2Cl2]. The benzohydrazide (L) in these complexes depicts monodentate behavior, providing terminal amino nitrogen as a donor atom. Compared to inactive precursors (free benzohydrazides and Pd2+), almost all Pd(II) complexes showed in vitro antiglycation activity, illustrating the potential role of resulting complexes in the suppression of diabetes and related disorders. The presence of free carbonyl group in complexes has been recognized as possible cause of antiglycation. This study also indicated Pd(II) compounds as far more superior inhibitors of urease and phosphodiesterase-I than parent ligands; many of them exhibited inhibitions equivalent or even greater than the standard inhibitors (thiourea, urease; EDTA, phosphodiesterase), which shows their potential use in future in the control of peptic ulcer and arthritis, respectively. The structure activity relationship (SAR) study demonstrated that complexation, steric hindrance, position of substituents, electron density around metal centre, hydrogen bonding and coordination mode of complexed ligands play prime role in modulating the biological activities of complexes.read more

Qurrat-ul-Ain, Saima Rasheed, Mohammad Mahroof-Tahir, Uzma Ashiq, Rifat Ara Jamal, Sumaira Khurshid and Sana Mustafa

Flow Injection Potentiometric Determination of Silver(I) in Photographic Film Developing Solution Samples by Polyvinylchloride Membrane Silver(I) Selective Electrode

A polyvinylchloride (PVC) membrane silver(I) selective electrode was developed for the determination of silver(I) ions in photographic film developing solutions. The electrode was embedded into a home-made flow cell and successfully used as a potentiometric detector in a flow injection potentiometric (FIP) system. Under the optimized flow injection conditions, the electrode exhibited a non-Nernstian slope of 67.20±0.80 mV in the linear range from 1.0×10-5 to 1.0×10-1 mol/L (R2=0.9961) and the lowest value for limit of detection (LOD) was calculated as 7.1×10-6 mol/L. The electrode displayed good sensitivity, selectivity, repeatable and rapid response towards silver(I) ions. Lifetime of the electrode was determined as at least two months in FIP system. The electrode was also successfully applied for the potentiometric determination of silver(I) ions in photographic film developing solution samples in FIP system. The results attained from FIP system were compared with the atomic absorption spectrophotometry (AAS) results by using student’s t-test at 95 % confidence level and relative deviation (RD) between the two methods was < 8 %.read more

Cihan Topcu, Fatih Coldur, Muberra Andac, Osman Cubuk, Gulsah Saydan Kanberoglu, Bulent Caglar and Ibrahim Isildak