Mechanochemical sulfidization of a mixed oxide-sulphide copper ore by co-grinding with sulfur and its effect on the flotation efficiency

Mechanochemical sulfidization of a mixed sulfide/oxide copper ore by co-grinding with sulfur and additives including Mg(NO₃)₂ and Fe(NO₃)₃ salts and iron, aluminum and magnesium powders was investigated for the first time. Also, the influence of sulfidization during the wet-milling process was examined on the separation efficiency and recovery of copper in detail. The results demonstrated that co-grinding with sulfur solely had the best flotation performance at the value of 0.5 wt.% and it was attributed to the possible existence of S-O bonding on copper oxides surfaces. In addition, adding magnesium nitrate salt, magnesium powder, iron nitrate salt and aluminum powder as additive associated with 0.5 wt% sulfur into ball milling caused the flotation improvement at the amounts of 0.2 wt%, 0.2 wt%, 0.5 wt% and 0.5 wt%, respectively. Also, the effect of grinding time and sulfidization pH with 0.5 wt% sulfur solely was determined and pHs of 7.5 to 8.5 gave the best results. The highest recovery (75.76%) and separation efficiency (63.44%) were achieved at pH of 7.5 and 8.5, respectively.     

Formulation and Characterization of Human Milk Fat Substitutes Made from Blends of Refined Palm Olein,and Soybean,Olive, Fish,and Virgin Coconut Oils

The simplest and the most cost-effective way of human milk fat substitute (HMFS) production is formulating of suitable vegetable oils at proper ratios. To do this, the D-optimal mixture design was used to optimize the HMFS formulation. The design included 25 formulations made from refined palm olein (35–55%), soybean oil (5–25%), olive oil (5–20%), virgin coconut oil (5–15%), and fish oil (0–10%). Samples were produced in laboratory and characterized in terms of fatty acid and triacylglycerol (TAG) compositions, free fatty acid content, peroxide value, iodine value, and oxidative stability index (OSI). HMFS samples were also compared with Codex Alimentarius (CA) and Iran National Standards Organization (INSO) standards. Each characteristic of HMFS samples was then expressed as a function of ingredient ratio using regression models. Finally, using numerical optimization, four optimized blends (PB₁-PB₄) were selected, made in the laboratory (HMFS₁-HMFS₄), characterized, and compared with CA and INSO standards. The properties of all the optimized blends (except the palmitic acid content of HMFS₂ and the monounsaturated fatty acid [MUFA] content of HMFS₃) met the standards. HMFS₄ showed the highest OSI in Rancimat and the lowest oxidation rate in Schaal oven tests. POL (19.53–21.73%), PPO (20.77–21.73%), OOO (9.11–11.16%), and OPO (8.84–9.46%) were the main (totally about 60%) TAG species found in HMFS samples. In conclusion, the HMFS₄ formula (55% palm olein, 13.5% soybean oil, 16% refined olive oil, 15% virgin coconut oil, and 0.5% fish oil) was suggested as the best formula for HMFS production.     

Study and characterization of porous copper oxide produced by electrochemical anodization for radiometric heat absorber

The aim of this work is to optimize the different parameters for realization of an absorbing cavity to measure the incident absolute laser energy. Electrochemical oxidation is the background process that allowed the copper blackening. A study of the blackened surface quality was undertaken using atomic force microscopy (AFM) analysis and ultraviolet-visible-infrared spectrophotometry using a Shimadzu spectrophotometer. A two-dimensional and three-dimensional visualization by AFM of the formed oxide coating showed that the copper surfaces became porous after electrochemical etching with different roughness. This aspect is becoming more and more important with decreasing current density anodization. In a 2 mol L ^-1 of NaOH solution, at a temperature of 90°C, and using a 16 mA cm² constant density current, the copper oxide formed has a reflectivity of around 3% in the spectral range between 300 and 1,800 nm. Using the ‘mirage effect’ technique, the obtained Cu₂O diffusivity and thermal conductivity are respectively equal to (11.5 ± 0.5) 10 to 7 m² s^-1 and (370 ± 20) Wm^-1 K^-1. This allows us to consider that our Cu₂O coating is a good thermal conductor. The results of the optical and thermal studies dictate the choice of the cavity design. The absorbing cavity is a hollow cylinder machined to its base at an angle of 30°. If the included angle of the plane is 30° and the interior surface gives specular reflection, an incoming ray parallel to the axis will undergo five reflections before exit. So the absorption of the surface becomes closely near 0.999999.     

Surface and pore modification of tripolyphosphate-crosslinked chitosan/polyethersulfone composite nanofiltration membrane; characterization and performance evaluation

A PES-based composite nanofiltration membrane was prepared by spreading a thin layer of sodium tripolyphosphate (STPP)-modified chitosan (CS) on a PES membrane. Two approaches of modification were employed: coating, and injecting the chitosan solution into PES membrane by applying pressure. Physicochemical properties of the prepared membranes were characterized by FTIR-ATR, zeta potential, contact angle, AFM and FE-SEM methods. AFM images showed a denser and more compact surface for STPP-modified membranes compared to the unmodified one. The membranes prepared by the second approach illustrated favorable properties: the increase of both flux and rejection. Engaging of -NH₂ groups in CS with polyanionic phosphate groups of STPP resulted in less availability of functional groups. Furthermore, denser and relatively higher positively charged surface could be the main reasons for higher rejection of membrane composed of 0.05wt% STTP towards copper ions in comparison with the other membranes. Furthermore, the presence of SO ₄ ^2- ions in the CuSO₄ solution slightly changed the positive charge of the membrane surface, resulting in tangible variations in rejection. According to the Donnan exclusion theory, relative increase of the negative charge of the surface in the presence of the highest concentration of STTP caused less NaCl and CuSO₄ rejection compared to the other STPP modified membranes.     

Nanogrooved carbon microtubes for wet three‐dimensional printing of conductive composite structures

Recent advances in three‐dimensional (3D) printing have enabled the fabrication of interesting structures which are not achievable using traditional fabrication approaches. The 3D printing of carbon microtube composite inks allows fabrication of conductive structures for practical applications in soft robotics and tissue engineering. However, it is challenging to achieve 3D printed structures from solution‐based composite inks, which requires an additional process to solidify the ink. Here, we introduce a wet 3D printing technique which uses a coagulation bath to fabricate carbon microtube composite structures. We show that through a facile nanogrooving approach which introduces cavitation and channels on carbon microtubes, enhanced interfacial interactions with a chitosan polymer matrix are achieved. Consequently, the mechanical properties of the 3D printed composites improve when nanogrooved carbon microtubes are used, compared to untreated microtubes. We show that by carefully controlling the coagulation bath, extrusion pressure, printing distance and printed line distance, we can 3D print composite lattices which are composed of well‐defined and separated printed lines. The conductive composite 3D structures with highly customised design presented in this work provide a suitable platform for applications ranging from soft robotics to smart tissue engineering scaffolds. © 2019 Society of Chemical Industry     

Switching from Ethylene Trimerization to Ethylene Polymerization by Chromium Catalysts Bearing SNS Tridentate Ligands: Process Optimization Using Response Surface Methodology

Two types of chromium catalysts bearing pyridine and amine based SNS ligands under the title of (pyridine-SNS-alkyl/CrCl₃) and (amine-SNS-alkyl/CrCl₃) were synthesized. Different thiolates such as octyl, pentyl, butyl, cyclohexyl and cyclopentyl thiolates were reacted with 2,6-pyridine-dimethylene-ditosylate (PMT)/THF solution at room temperature. Then, the purified pyridine-based SNS ligands (1–5) were reacted with CrCl₃ (THF)₃ to obtain the pyridine-SNS-alkyl/CrCl₃ catalysts (6–10) in 50–70% yields. MMAO-activated pyridine-SNS-alkyl/CrCl₃ catalysts were capable of oligomerizing ethylene. Statistical experimental design was conducted using the central composite design method and surface methodology to study of the effect of important parameters such as ethylene pressure, Al/Cr ratio, catalyst concentration and the reaction temperature on 1-C₆ productivity of catalyst (7). A quadratic polynomial equation was developed to predict the 1-C₆ productivity. Ethylene oligomerization using the catalyst (7) was lead to a optimized reaction conditions, including the ethylene pressure of 19.5 bar, the temperature of 58.2 °C, the MMAO co-catalyst, Al/Cr?=?841 and the catalyst concentration of 8.7 µmol. The catalytic properties for ethylene oligomerization are strongly affected by reaction temperature. The experimental results indicated the reasonable agreement with the predicted values. The transformation from ethylene trimerization to ethylenev polymerization of catalyst system (7) was occurred by exchanging the reaction pressure. Influence of ligand structure with different substitutions on sulphur atom on productivity and selectivity was investigated. 1-C₆ with the high selectivity and productivity 4318 (g 1-C₆/g Cr h) was obtained for catalyst (7). In the second part, 1-C₆ was obtained with high selectivity and productivity around 141?×?10³ (g 1-C₆/g Cr h) for amine-based catalyst. All amine-based catalysts (14–16) showed considerably higher catalytic activities compared to pyridine-based catalysts. According to the TGA analysis the thermal stability of pyridine-based catalysts was found to be higher than the amine-based catalysts.

Graphical Abstract

Chromium complexes bearing pyridine and amine based SNS ligands have been synthesized and their catalytic performance in ethylene oligomerization has been investigated. A switching from ethylene trimerization to ethylene polymerization of the catalyst (7) was obtained utilizing exchanging of the ethylene pressure.

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MnO2 Nanoparticles as Efficient Oxidant for Ultrasound-Assisted Synthesis of 2-substituted Benzimidazoles under Mild Conditions

In this article, a novel method for synthesis of 2-substituted benzimidazoles using MnO₂ nanoparticles as a convenient oxidant agent in ethanol-water (1:1) as solvent under ultrasound irradiation was demonstrated. In this protocol the desired products were purely obtained in high yields. The main advantages of this research are: mild procedure, simplicity of method, easily work-up, high yields, and short reaction times. The MnO₂ nanoparticles were synthesized through a solid-state reaction route using simple strarting materials. Furthermore, their structure was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR).     

Magnetic solid phase extraction of copper from aquatic samples by Fe3O4/SiO2 nanoparticles followed by atomic absorption spectrometric determination

A magnetic solid phase extraction was developed for preconcentration of Cu(II) as a 4-bromo-2-(2,4-dichloro-phenylimino)-phenol complex on Fe₃O₄/SiO₂ nanoparticles prior to its determination by atomic absorption spectroscopy. The effect of different parameters influencing the formation of the Cu complex and the extraction efficiency of the Cu complex were studied. Under optimal conditions, the calibration graph showed linearity in the range of 0.946–700 µg L^?1 (R² = 0.9995) of Cu(II). The limit of detection and relative standard deviation of the method (n = 6) were 0.283 µg L^?1 and 3.0%, respectively. The method was successfully applied to determine copper (II) in water samples.     

Facile catalytic ring opening polymerization of lactic acid: Comparing the performance of Fe and Zn metal species

As a bio‐compatible/degradable polymer, poly(lactic acid) (PLA) has been widely noticed in tissue engineering and medical applications. Proper catalytic ring‐opening polymerization of lactic acid is pertinent to development of active metal species capable of producing high‐molecular‐weight polymers. In this work, ligand catalyst (2,4‐di‐tertio‐butyl‐6‐{[(2‐di‐methyl‐amino ethyl) methyl amino] methyl} phenol) was synthesized and then attached to Fe‐based and Zn‐based metal substitutes, and performance of metal species toward ring opening polymerization of lactic acid has been investigated. Regulation of reaction condition at 180°C for 36 h with Zn‐based catalyst allowed for late‐stage production of a high‐molecular‐weight PLA, while Fe‐based facilitated polymerization at early stages leading to PLAs with comparatively twofold higher molecular weight at lower time, monomer‐to‐initiator ratio, and temperature (at 170°C). A ratio of monomer to initiator of 5000 with Fe catalyst resulted in the highest molecular weight. Thus, polymerization has been facilitated by the use of Fe‐based catalyst. For this class of catalyst with Fe substitute, the product was characterized by means of ¹H‐NMR, Fourier transform infrared spectroscopy, and differential scanning calorimetry analyses. J. VINYL ADDIT. TECHNOL., 25:215–224, 2019. © 2018 Society of Plastics Engineers