Kinetic modeling of pyrolysis of three Iranian waste oils in a micro-fluidized bed

Different approaches have been used to convert the waste materials into a clean syngas or other chemicals such as methanol. Among them, pyrolysis is a good candidate to produce the synthesis gas and volatile matters for industrial and refinery applications. In this work, we studied the kinetic and chemical behavior of three Iranian waste oils through a kinetic model and an experimental study. The experiments carried out in a micro-FB reactor, which is a good option for low emissions. Results showed that the reaction temperature and reaction rate are two of the most important factors for maximum conversion level of fuel. Results also showed an optimum value for reaction rate. The modeling results validated against the experimental measurements and found to be in good agreements.     

Bimetallic dies with direct metal-deposited steel on Moldmax for high-pressure die casting application

In high-pressure die casting, cooling time greatly affects the total cycle time. As thermal conductivity is the main governing factor, a higher thermal conductive die material allows faster extraction of heat from the casting, thus resulting in shorter cycle time and higher productivity. This paper presents a novel approach to replace a conventional steel die by a bimetallic die made of Moldmax copper alloy coated with a protective layer of steel using laser cladding technology, direct metal deposition on the cavity surface for high-pressure die casting of aluminum alloys. Study includes the investigation of suitable steel layer thickness on Moldmax substrate in terms of porosity, hardness, presence of copper content, and copper particle. Results obtained from the scanning electron microscope and energy dispersive spectroscopy display a metallurgicallly sound and fully dense steel layer on copper alloy. Results of finite element heat transfer analysis also show that bimetallic die offers superior thermal performance compared with monolithic steel die.     

Glass transition kinetics and optical band gap in Se85−xSb15Snx (x = 10, 11, 12.5, and 13) chalcogenide glasses

Se_85−xSb₁₅Sn_x (10 ≤ x ≤ 13) chalcogenide glasses were prepared by melt quenching technique. The glass transition temperature T_g of the samples was recorded at different heating rates using differential scanning calorimeter DSC. From the heating rate dependence of T_g, the activation energy for thermal relaxation E_t was calculated using Moynihan model and Kissinger equation. It is found that T_g increases with Sn content due to enhancement of both the degree of cross-linking parameter D_cl and the mean bond energy of the average cross-linking per atom 〈E_cl〉. The observed increase in D_cl and 〈E_cl〉 is attributed to the formation of SnSe_4/2 structural units of energies higher than that of Se–Se and Se–Sb bond energies. The decreasing trend of E_t with the addition of Sn is an indication of improving thermal stability as it is also evident from the values of the temperature difference T_c − T_g. Correlation of T_g values with the physical parameters of the studied glasses (for instance, the average coordination number 〈Z〉, the average heat of atomization (H_s), the overall mean bond energy 〈E〉, and the optical band gap (E_g)) reveals that T_g increases linearly with 〈Z〉, H_s, and 〈E〉 but the behavior with E_g is opposite.     

Degradation of sulfamonomethoxine with Fe3O4 magnetic nanoparticles as heterogeneous activator of persulfate

The photocatalytic HCrO(4)(-) reduction was investigated in air equilibrated solution using the spinel CuFe(2)O(4) nanoparticles as sensitizers. The oxide is p-type semi conductor, prepared from nitrates decomposition. The catalytic performance increases with decreasing pH and the concomitant oxidation of salicylic acid contributes significantly to the photoactivity through the charges separation of electron/hole pairs (C(7)H(6)O(3)+6 O(2)+4h(+)+3 H(2)O → 7 CO(2)+4 H(3)O(+)). Evidence has been given to show the advantages of the hetero-system CuFe(2)O(4)/CdS in the chromate reduction. CuFe(2)O(4) acts as electrons pump and the electron transfer to chromate is mediated via CdS hexagonal variety (greenockite). A reduction of 60% occurs and the process is well described by a pseudo first order kinetic with a half life of ～2.8h and a quantum yield of ～0.12% for an initial HCrO(4)(-) concentration of 3 × 10(-4)M. An improvement up to 72% is obtained when the reaction occurs in a stirred reactor and no cadmium was detected after 6h illumination. The results indicate a competitive effect with the water reduction. The hydrogen evolutions are found to be 0.236 and 0.960 cm(3)mn(-1)g(-1) in presence and in absence of HCrO(4)(-), respectively.     

PAPR reduction in mobile WiMAX: a novel DST precoding based random interleaved OFDMA uplink system

Mobile WiMAX is a 3rd generation broadband wireless technology that enables the convergence of mobile and fixed broadband networks through a wide area radio-access. Since January 2007, the IEEE 802.16 working group has been developing a new amendment the IEEE 802.16 standard i.e. IEEE 802.16 m as an advanced air interface to meet the requirements of ITU-R/IMT-Advanced for 4G systems. The mobile WiMAX air interface adopts orthogonal frequency division multiple access (OFDMA) as multiple access technique for its uplink and downlink to improve signal performance affected by multipath distortion. All OFDMA based networks, including mobile WiMAX, experience the problem of high peak-to-average power ratio (PAPR). This paper presents a discrete-sine-transform precoding technique based random-interleaved OFDMA (RI-OFDMA) uplink system for PAPR reduction in mobile WiMAX. The PAPR of proposed system is analyzed with root-raised-cosine pulse shaping filter to keep out of band radiation low and to fulfill the spectrum mask requirements. Simulation results show that, the proposed system has low PAPR compared to the Hadamard transform precoded RI-OFDMA uplink systems and the conventional RI-OFDMA uplink systems.     

Simultaneous measurements of thermal conductivity and diffusivity of Se80Te20-xInx (x = 2, 4, 6 and 10) chalcogenide glasses at room temperature

Measurements of thermal conductivity and thermal diffusivity of twin pellets of Se₈₀Te_20-xIn_x (x = 2, 4, 6 and 10) glasses, prepared under a load of 5 tons were carried out at room temperature using transient plane source (TPS) technique. The measured values of both thermal conductivity and diffusivity were used to determine the specific heat per unit volume of the said materials in the composition range of investigation. Results indicated that both the values of thermal conductivity and thermal diffusivity increased with the addition of indium at the cost of tellurium whereas the specific heat remained almost constant. This compositional dependence behaviour of the thermal conductivity and diffusivity has been explained in terms of the iono-covalent type of bond which In makes with Se as it is incorporated in the Se-Te glass.     

Preparation, characterization, and stability of liposome-based formulations of mitoxantrone

The preparation, characterization, and stability of lyophilized liposome-based formulation of mitoxantrone was investigated. Mitoxantrone was entrapped inside small, unilamellar liposomes composed of dioleoylphosphocholine (DOPC), cholesterol, and cardiolipin. The mean vesicle size and drug entrapment efficiency of the liposomes were ~ 150 nm and ~ 99%, respectively. Less than 1% of drug was lost and mean vesicle size remained unchanged after sterile filtration. The pre-lyophilized (pre-lyo) formulations were characterized by a differential scanning calorimetric (DSC) method. Results showed that the glass transition temperatures (Tg') increased as the molar ratios of sucrose:lipid and trehalose:lipid in the formulations were increased. The maximum Tg' of the pre-lyo formulations containing 10:1 sucrose:lipid and trehalose:lipid molar ratios were - 37°C and - 41°C, respectively. After reconstitution of the lyophilized cake of the sucrose-containing formulation, the mean vesicle size was comparable to pre-lyo liposome size. In vitro release studies showed that less than 2% of mitoxantrone was released after an extensive dialysis against phosphate buffered saline (PBS) at 37°C, indicating that the mitoxantrone was highly associated and retained inside the liposomes. Short-term stability studies of the sucrose-containing formulations revealed that the reconstituted and eight-fold diluted formulations were stable for up to 8 hours at room temperature. Long-term stability studies of lyophilized liposomal mitoxantrone showed that the lyophilized formulation was stable for up to 13 months after storage at refrigerated condition.     

Degradation of methotrexate by UV/peroxymonosulfate: Kinetics,effect of operational parameters and mechanism

Methotrexate (MTX) is one of the most consumed anti-cancer drugs in the pharmaceutical market around the world. The widespread occurrence of MTX in aquatic environment through hospital effluent has attracted increasing concern due to its potential to induce water pollution. In the present study, the degradation of MTX in aqueous medium was investigated by UV-activated peroxymonosulfate (PMS). A significant improvement in degradation rate by increasing UV intensity and PMS concentration while the decrease in degradation efficiency with the increase of solution pH and initial concentration of MTX was observed. The proposed UV/PMS process could achieve more than 90% MTX degradation in 30 min with a good mineralization degree (65%). A pseudofirst order kinetic model was employed and successfully predicted the degradation of MTX. The effect of other operational parameters such as the initial concentration of the targeted compound, dosage of oxidant (PMS), solution pH and UV intensity on the degradation rate were investigated. At the last, the main transform intermediates were identified using LC-MS and possible degradation pathways were proposed. The results show that UV/ PMS can be used as an efficient technology to treat pharmaceuticals such as methotrexate containing water and wastewater.     

Development of antimicrobial edible coating based on modified chitosan for the improvement of strawberries shelf life

Food Science and Biotechnology - Edible antimicrobial coating produced from chitosan (CS) and its derivative was applied to improve the shelf life of fresh strawberries at 10 °C....     

Removal of lead and cadmium ions by single and binary systems using phytogenic magnetic nanoparticles functionalized by 3-marcaptopropanic acid

The present research study is focused on green fabrication of superparamagnetic Phytogenic Magnetic Nanoparticles(PMNPs), and then its surface functionalization with 3-Mercaptopropionic acid(3-MPA). The resulting material(i.e. 3-MPA@PMNPs) characterized by FTIR, powder XRD, SEM, TEM, EDX, VSM, BET and TGA techniques and then further employed for the investigation of the adsorptive removal of lead(Pb~(2+)) and cadmium(Cd~(2+)) ions from aqueous solutions in single and binary systems. The material showed fastest adsorptive rate(98.23%) for Pb~(2+) and(96.5%) Cd~(2+)within the contact time of 60 min at pH 6.5 in the single system. The experimental data were fitted well to Langmuir isotherm, indicated monolayer adsorption of both metal ions onto 3-MPA@PMNPs and an estimated comparable adsorptive capacity of 68.41 mg·g~(-1)(Pb~(2+)) and 79.8 mg·g~(-1)(Cd~(2+)) at p H 6.5. However, kinetic data agreed well with pseudo-second-order model, and indicated that the removal mainly supported chemisorption and/or ion-exchange mechanism. Thermodynamic parameters such asΔGo, ΔHo, and ΔSo, were-3259.20, 119.35 and 20.73 for Pb2+, and-1491.10, 45.441 and 7.87 for Cd~(2+) at temperature 298.15 K, confirmed that adsorption was endothermic, spontaneous and favorable. The material demonstrated higher selectivity of Pb~(2+) and its removal efficiency was(98.20 ± 0.3)% in binary system experiments. The material persisted performance up-to seven(07) consecutive treatment cycles without losing their stability and offered comparable fastest magnetic separation(35 s) from aqueous solutions. Therefore, it is recommended that the prepared material can be employed to remove toxic heavy metal ions from water/wastewaters and this "green" method can easily be implemented at large scale in low economy countries.