Introducing the theory of successful settling in order to evaluate and optimize the sedimentation tanks

A rectangular settling tank in full scale is investigated using the Fluent software to increase its efficiency. First, the pure water is simulated in the absence of particles. Then particles are injected into the flow field and tracked by means of the discrete phase model. Three methods are presented to optimize the settling tank: (1) adding a baffle which is mounted in the bottom and is extended up to the near of free surface, (2) adding a baffle which is mounted in the free surface and is extended up to the near of the tank bottom and (3) install a bi-directional baffle which is mounted in the free surface and is extended up to the near of the bottom. These three suggestions are checked using the short-circuiting phenomenon and the successful settling theory. The successful settling theory states that a particle can be accounted as a “trapped” particle if (1) settled particle stays static and stable in the tank bottom and (2) settled particle doesn’t return to purified sewage. Although the second method provided higher efficiency, the third method was selected as the most appropriate method in order to optimize the settling tank.     

New Correlative Models to Improve Prediction of Fracture Permeability and Inertial Resistance Coefficient

Presence of fracture roughness and occurrence of nonlinear flow complicate fluid flow through rock fractures. This paper presents a qualitative and quantitative study on the effects of fracture wall surface roughness on flow behavior using direct flow simulation on artificial fractures. Previous studies have highlighted the importance of roughness on linear and nonlinear flow through rock fractures. Therefore, considering fracture roughness to propose models for the linear and nonlinear flow parameters seems to be necessary. In the current report, lattice Boltzmann method is used to numerically simulate fluid flow through different fracture realizations. Flow simulations are conducted over a wide range of pressure gradients through each fracture. It is observed that creeping flow at lower pressure gradients can be described using Darcy’s law, while transition to inertial flow occurs at higher pressure gradients. By detecting the onset of inertial flow and regression analysis on the simulation results with Forchheimer equation, inertial resistance coefficients are determined for each fracture. Fracture permeability values are also determined from Darcy flow as well. According to simulation results through different fractures, two parametric expressions are proposed for permeability and inertial resistance coefficient. The proposed models are validated using 3D numerical simulations and experimental results. The results obtained from these two proposed models are further compared with those obtained from the conventional models. The calculated average absolute relative errors and correlation coefficients indicate that the proposed models, despite their simplicity, present acceptable outcomes; the models are also more accurate compared to the available methods in the literature.     

Phosphorus Fertilizers from Sewage Sludge Ash and Animal Blood as an Example of Biobased Environment-Friendly Agrochemicals: Findings from Field Experiments

Wastes of biological origin from wastewater treatment systems and slaughterhouses contain substantial amounts of phosphorus (P) with high recovery potential and can contribute to alleviating the global P supply problem. This paper presents the performance of fertilizer (AF) and biofertilizer (BF) from sewage sludge ash and animal blood under field conditions. BF is AF incorporated with lyophilized cells of P-solubilizing bacteria, Bacillus megaterium. In the experiments with spring or winter wheat, the biobased fertilizers were compared to commercial P fertilizer, superphosphate (SP). No P fertilization provided an additional reference. Fertilizer effects on wheat productivity and on selected properties of soil were studied. BF showed the same yield-forming efficiency as SP, and under poorer habitat conditions, performed slightly better than AF in increasing yield and soil available P. Biobased fertilizers applied at the P rate up to 35.2 kg ha^–1 did not affect the soil pH, did not increase As, Cd, Cr, Ni, and Pb content, and did not alter the abundance of heterotrophic bacteria and fungi in the soil. The findings indicate that biobased fertilizers could at least partially replace conventional P fertilizers. Research into strain selection and the proportion of P-solubilizing microorganisms introduced into fertilizers should be continued.     

Fabrication and Properties of Polycaprolactone Composites Containing Calcium Phosphate-Based Ceramics and Bioactive Glasses in Bone Tissue Engineering: A Review

Polycaprolactone (PCL) is a bioresorbable and biocompatible polymer that has been widely used in long-term implants and controlled drug release applications. However, when it comes to tissue engineering, PCL suffers from some shortcomings such as slow degradation rate, poor mechanical properties, and low cell adhesion. The incorporation of calcium phosphate-based ceramics and bioactive glasses into PCL has yielded a class of hybrid biomaterials with remarkably improved mechanical properties, controllable degradation rates, and enhanced bioactivity that are suitable for bone tissue engineering. This review presents a comprehensive study on recent advances in the fabrication and properties of PCL-based composite scaffolds containing calcium phosphate-based ceramics and bioglasses in terms of porosity, degradation rate, mechanical properties, in vitro and in vivo biocompatibility and bioactivity for bone regeneration applications. The fabrication routes range from traditional methods such as solvent casting and particulate leaching to novel approaches including solid free-form techniques.     

Synthesis,spectroscopic and magnetic properties of methoxo- bridged copper(II) complexes with 2-amino-4-methylpyridine as the ligand

Three new methoxo-bridged copper(II) complexes with 2-amino-4- methylpyridine as the ligand have been synthesized and characterized by elemental analyses, FTIR and electronic spectra, and by their magnetic properties. The complexes exhibit strong antiferromagnetic interactions at room temperature. The u.v.-vis spectra exhibits three absorption bands, which can attributed to d–d, L–M and –* transitions. The i.r. spectra indicates Cu2O2 ring vibrations in the 580–530cm–1 range. The magnetic properties of the [Cu2(2-amino-4-methylpyridine)4(O- Me)2](ClO4)2 complex has been investigated in the 5–270K range and a singlet-triplet energy gap (–2J) of 67cm–1 was observed. All complexes in the solid state are e.p.r.-silent and show no triplet spectrum; in fact a weak signal due to a monomeric impurity are observed. Frozen solution e.p.r. spectra suggest that the complexes dissociate when dissolved in DMF or DMSO.     

Synergistic flotation of U(VI)-alizarin complex with some diamines followed by spectrophotometric determination of U(VI) using 4,4′-diaminophenylmethane

In this work, synergistic flotation of U(VI)-alizarin complex at the presence of some diamine compounds was firstly investigated by the spectrophotometric method. The flotation process was carried out on aliquots of 100 ml of U(VI) solutions containing alizarin and the diamine at pH of 5.00 using n-heptane. The floated layer was then dissolved in acetonitrile and its absorbance was measured. Since the synergistic effect of 4,4′-diaminophenylmethane (dapm) was much more than the others, it was used for the determination of U(VI) by this method. Beer's law was obeyed (λ_max = 591 nm) in the range of 5 × 10⁻⁷ to 1 × 10⁻⁵ mol l⁻¹ with the apparent molar absorptivity of 1.12 × 10⁶ l mol⁻¹ cm⁻¹, and a correlation coefficient of 0.9991. The detection limit (n = 7) was 1 × 10⁻⁷ mol l⁻¹, and the R.S.D. (n = 7) obtained for 4 × 10⁻⁶ mol l⁻¹ of U(VI) was 2.23%. Except that only a few analogous cations, which could be masked by EDTA, no interference was observed at the presence of various conventional ions, even at high concentrations. The reliability and applicability of the method were confirmed using some geological standard reference materials and spiked synthetic water samples, respectively.     

Synthesis and characterization of chitosan coating of NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanoparticles for biomedical applications

Nickel ferrite nanoparticle is a soft magnetic material whose appealing properties as well as various technical applications have rendered it as one of the most attractive class of materials; its technical applications range from its utility as a sensor and catalyst to its utility in biomedical processes. The present paper focuses first on the synthesis of NiFe₂O₄ nanoparticles through co-precipitation method resulting in calcined nanoparticles that were achieved at different times and at a constant temperature (773 k). Afterward, they were dispersed in water that was mixed by chitosan. Chitosan was bonded on the surface of nanoparticles by controlling the pH of media. In order to assess the structural and magnetic properties of nanoparticles, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM) analyses were conducted at room temperature. As per the results of XRD analysis, the pure NiFe₂O₄ was synthesized. Additionally, nanoparticles grew in size by extending the calcination process duration. TEM micrographs were used to determine the size and shape of particle; the obtained results indicate that the particle size was in a range of 17–30 nm and of a circular shape. The proper chitosan covering was also indicated by FTIR results. The VSM analysis also revealed that the saturated magnetization of NiFe₂O₄ nanoparticles stood in a range of 29 emu/g and 45 Q_e. A stable maximum temperature ranging from 30 to 42 was successfully achieved within 10 min. Also, a specific absorption rate of up to 8.4 W/g was achieved. The study results revealed that the SAR parameter of the coated nickel ferrite nanoparticle is more than that of pure nickel ferrite or cobalt ferrite nanoparticles.     

Multiscale Computational Study on the Adsorption and Separation of CO2/CH4 and CO2/H2 on Li+‐Doped Mixed‐Ligand Metal–Organic Framework Zn2(NDC)2(diPyNI)

The quantum mechanics (QM) method and grand canonical Monte Carlo (GCMC) simulations are used to study the effect of lithium cation doping on the adsorption and separation of CO₂, CH₄, and H₂ on a twofold interwoven metal–organic framework (MOF), Zn₂(NDC)₂(diPyNI) (NDC=2,6‐naphthalenedicarboxylate; diPyNI=N,N′‐di‐(4‐pyridyl)‐1,4,5,8‐naphthalenetetracarboxydiimide). Second‐order Moller–Plesset (MP2) calculations on the (Li⁺–diPyNI) cluster model show that the energetically most favorable lithium binding site is above the pyridine ring side at a distance of 1.817 Å from the oxygen atom. The results reveal that the adsorption capacity of Zn₂(NDC)₂(diPyNI) for carbon dioxide is higher than those of hydrogen and methane at room temperature. Furthermore, GCMC simulations on the structures obtained from QM calculations predict that the Li⁺‐doped MOF has higher adsorption capacities than the nondoped MOF, especially at low pressures. In addition, the probability density distribution plots reveal that CO₂, CH₄, and H₂ molecules accumulate close to the Li cation site. The selectivity results indicate that CO₂/H₂ selectivity values in Zn₂(NDC)₂(diPyNI) are higher than those of CO₂/CH₄. The selectivity of CO₂ over CH₄ on Li⁺‐doped Zn₂(NDC)₂(diPyNI) is improved relative to the nondoped MOF.     

Preconcentration of valsartan by dispersive liquid–liquid microextraction based on solidification of floating organic drop and its determination in urine sample: Central composite design

In this work, a fast, easy, and efficient dispersive liquid–liquid microextraction method based on solidification of floating organic drop followed by high‐performance liquid chromatography with UV detection was developed for the separation/preconcentration and determination of the drug valsartan. Experimental design was applied for the optimization of the effective variables (such as volume of extracting and dispersing solvents, ionic strength, and pH) on the extraction efficiency of valsartan from urine samples. The optimized values were 250.0 μL ethanol, 65.0 μL 1‐dodecanol, 4.0% w/v NaCl, pH 3.8, 1.0 min extraction time, and 4.0 min centrifugation at 4000 rpm min^?1. The linear response (r² = 0.997) was obtained in the range of 0.013–10.0 μg mL^?1 with a limit of detection of 4.0 ng mL^?1 and relative standard deviations of less than 5.0 % (n = 6).