scholarly journals Differential Precipitation of Mg(OH)2 from CaSO4·2H2O Using Citrate as Inhibitor—A Promising Concept for Reagent Recovery from MgSO4 Waste Streams

Molecules ◽  
2020 ◽  
Vol 25 (21) ◽  
pp. 5012
Author(s):  
Szilveszter Ziegenheim ◽  
Márton Szabados ◽  
Zoltán Kónya ◽  
Ákos Kukovecz ◽  
István Pálinkó ◽  
...  
Keyword(s):  
Reaction Times ◽  
Precipitation Reaction ◽  
Organic Additives ◽  
Waste Streams ◽  
Solution Ph ◽  
Hydrometallurgical Processing ◽  
Gypsum Precipitation ◽  
Acidic Wastewater ◽  
Differential Precipitation

In hydrometallurgical processing and acidic wastewater treatment, one of the neutralizing agents employed is MgO or Mg(OH)2. At the end of this process, the resulting solution, which is rich in SO42− and Mg2+ is treated with lime to remove (or minimize the amount) of these ions via the precipitation of Mg(OH)2 and CaSO4·2H2O (gypsum). In our work, an attempt was made to separate the two solids by increasing the induction time of the gypsum precipitation, thus regenerating relatively pure Mg(OH)2 which could be reused in wastewater treatments or hydrometallurgical processing circuits, and in this way, significantly enhancing the economic viability of the process. During our experiments, the reaction of an MgSO4 solution with milk of lime prepared from quicklime was studied. The effects of a range of organic additives, which can slow down the precipitation of gypsum have been assessed. The process was optimized for the most promising inhibiting agent—that is, the citrate ion. The reactions were continuously monitored in situ by conductometric measurements with parallel monitoring of solution pH and temperature. ICP-OES measurements were also carried out on samples taken from the reaction slurry. The composition of the precipitating solids at different reaction times was established by powder XRD and their morphology by SEM. Finally, experiments were carried out to locate the additive after the completion of the precipitation reaction to get information about its potential reuse.

scholarly journals Diffusion-induced in situ growth of covalent organic frameworks for composite membranes

2019 ◽  
Vol 7 (45) ◽  
pp. 25802-25807 ◽  
Author(s):  
Priyanka Manchanda ◽  
Stefan Chisca ◽  
Lakshmeesha Upadhyaya ◽  
Valentina-Elena Musteata ◽  
Mark Carrington ◽  
...  
Keyword(s):  
Reaction Times ◽  
Composite Membranes ◽  
Thin Layers ◽  
In Situ Growth ◽  
Covalent Organic Frameworks ◽  
Polymeric Support ◽  
Ambient Conditions ◽  
Induction Method ◽  
Covalent Organic Framework

Thin layers of a covalent organic framework (COF) have been synthesized on a flexible polymeric support using a new diffusion-induction method under ambient conditions in reaction times as short as 3 hours.

SELF-HEALING OF WOVEN COMPOSITE LAMINATES VIA IN SITU THERMAL REMENDING

2021 ◽  
Author(s):  
ALEXANDER D. SNYDER ◽  
ZACHARY J. PHILLIPS ◽  
JASON F. PATRICK
Keyword(s):  
Composite Laminates ◽  
Composite Laminate ◽  
Laminated Composites ◽  
Reaction Times ◽  
Carbon Fiber Composites ◽  
Self Healing ◽  
Damage Mode ◽  
Woven Composite ◽  
Internal Damage

Fiber-reinforced polymer composites are attractive structural materials due to their high specific strength/stiffness and excellent corrosion resistance. However, the lack of through-thickness reinforcement in laminated composites creates inherent susceptibility to fiber-matrix debonding, i.e., interlaminar delamination. This internal damage mode has proven difficult to detect and nearly impossible to repair via conventional methods, and therefore, remains a significant factor limiting the reliability of composite laminates in lightweight structures. Thus, novel approaches for mitigation (e.g., self-healing) of this incessant damage mode are of tremendous interest. Self-healing strategies involving sequestration of reactive liquids, i.e. microcapsule and microvascular systems, show promise for the extending service- life of laminated composites. However, limited heal cycles, long reaction times (hours/days), and variable stability of chemical agents under changing environmental conditions remain formidable research challenges. Intrinsic self- healing approaches that utilize reversible bonds in the host material circumvent many of these limitations and offer the potential for unlimited heal cycles. Here we detail the development of an intrinsic self-healing woven composite laminate based on thermally-induced dynamic bond re-association of 3D-printed polymer interlayers. In contrast to prior work, self-repair of the laminate occurs in situ and below the glass-transition temperature of the epoxy matrix, and maintains >85% of the elastic modulus during healing. This new platform has been deployed in both glass and carbon-fiber composites, demonstrating application versatility. Remarkably, up to 20 rapid (minute-scale) self-healing cycles have been achieved with healing efficiencies hovering 100% of the interlayer toughened (4-5x) composite laminate. This latest self-healing advancement exhibits unprecedented potential for perpetual in-service repair along with material multi-functionality (e.g., deicing ability) to meet modern application demands.

scholarly journals A Theoretical and Experimental Study of Electrochemical pH Control at Gold Interdigitated Microband Arrays

2021 ◽  
Author(s):  
Bernardo Patella ◽  
Robert Daly ◽  
Ian Seymour ◽  
Pierre Lovera ◽  
James Rohan ◽  
...  
Keyword(s):  
Electrode Array ◽  
Ph Control ◽  
Reduction Peak ◽  
Solution Ph ◽  
Ph Indicator ◽  
Ph Change ◽  
Initial Ph ◽  
The Impact ◽  
Strong Acids

In electroanalysis, solution pH is a critical parameter that often needs to be adjusted and controlled for the detection of particular analytes. This is most commonly performed by the addition of chemicals, such as strong acids or bases. Electrochemical in-situ pH control offers the possibility for the local adjustment of pH at the point of detection, without additional reagents. FEA simulations have been performed to guide experimental design for both electroanalysis and in-situ control of solution pH. No previous model exists that describes the generation of protons at an interdigitated electrode array in buffered solution with one comb acting as a protonator, and the other as the sensor. In this work, FEA models are developed to provide insight into the optimum conditions necessary for electrochemical pH control. The magnitude of applied galvanostatic current has a direct relation to the flux of protons generated and subsequent change in pH. Increasing the separation between the electrodes increases the time taken for protons to diffuse across the gap. The final pH achieved at both, protonators and sensor electrodes, after 1 second, was shown to be largely uninfluenced by the initial pH of the solution. The impact of buffer concentration was modelled and investigated. In practice, the pH at the electrode surface was probed by means of cyclic voltammetry, i.e., by cycling a gold electrode in solution and identifying the potential of the gold oxide reduction peak. A pH indicator, methyl red, was used to visualise the solution pH change at the electrodes, comparing well with the model’s prediction

scholarly journals Evaluation of active sludge and aquatic ferns usage for removal of zinc in a biological wastewater treatment system

2019 ◽  
pp. 39-44
Author(s):  
Amir Hajiali ◽  
Lacramioara Diana Robescu
Keyword(s):  
Ph Value ◽  
Reaction Times ◽  
Treatment Method ◽  
Operating Conditions ◽  
Industrial Scale ◽  
Reactor Performance ◽  
Solution Ph ◽  
Active Sludge ◽  
Simple Method ◽  
Aquatic Fern

In this research capability of biological treatment method via active sludge and aquatic fern evaluated in different operating conditions and they were optimized in order to remove Zn (II). A simple reactor performance for treatment of model and real wastewater on laboratory and semi-industrial scale was investigated. This refining process proceeded with special attention to the effect of solution pH-value, pollutant concentration, absorbent concentration and reaction time. The batch semi-industrial scale reactor represented over 90 % removal efficiency under pH-value of 6 and 5-5.5 for aquatic ferns and active sludge, respectively. Effective reaction times represented various durations for aquatic ferns and active sludge with respect of 120 minutes and 90 minutes. The two biological masses had the best performances with 6 g/l for aquatic ferns and 5 g/l for active sludge. In the presence of 5 ppm of Zn (II) as the objective heavy metal, both absorbents had over 93.2 % removal efficiencies. While obviously laboratory-scale attempts introduced higher acceptable reduction efficiencies via this economic applicable treatment method. Additionally, economic considerations clarified feasibility of this recommended simple method.

scholarly journals Flame-Retardant and Smoke Suppression Properties of Nano MgAl-LDH Coating on Bamboo Prepared by an In Situ Reaction

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Xiaoling Yao ◽  
Chungui Du ◽  
Yating Hua ◽  
Jingjing Zhang ◽  
Rui Peng ◽  
...  
Keyword(s):  
Reaction Time ◽  
Flame Retardant ◽  
Building Materials ◽  
Reaction Times ◽  
Step Method ◽  
In Situ Reaction ◽  
One Step ◽  
Double Hydroxide ◽  
Optimal Reaction

In recent years, bamboo has been widely used for building materials and household goods. However, bamboo is flammable, so a flame-retardant treatment for bamboo is urgently needed. In this work, nano MgAl-layered double hydroxide (MgAl-LDH) coated on bamboo, which was called MgAl-LB, was synthesized by an in situ one-step method. To determine the optimal in situ time, the effects of different reaction times on LDH growth on the bamboo surface and the flame retardancy of the MgAl-LBs were investigated. The SEM observations show that LDH growth on the surface of bamboo was basically saturated when the in situ reaction time was 24 h. Abrasion experiments show that MgAl-LDH coating has good abrasion resistance. The fire performance of the MgAl-LBs was evaluated by cone calorimeter tests, which indicated that the THR and TSP of the MgAl-LBs were significantly lower than those of untreated bamboo. Taking into account the energy consumption problem, determining the reaction time of 24 h is the optimal reaction time. Compared with untreated bamboo, the THR and TSP of MgAl-LB prepared at 24 h decreased by 33.3% and 88.9%, respectively.

Heterogeneous Catalysis with Basic Compounds to Achieve the Synthesis and C–N Cleavage of Azetidin-2-ones under Microwave Irradiation

Synthesis ◽  
2019 ◽  
Vol 51 (19) ◽  
pp. 3625-3637 ◽  
Author(s):  
Adriana Galván ◽  
Fabiola N. de la Cruz ◽  
Francisco Cruz ◽  
Merced Martínez ◽  
Clarisa Villegas Gomez ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Heterogeneous Catalysis ◽  
Microwave Irradiation ◽  
Bond Cleavage ◽  
Reaction Times ◽  
Organic Additives ◽  
Acyl Chlorides ◽  
Solid Catalysts ◽  
Basic Compounds ◽  
High Yields

The synthesis of azetidin-2-ones with a completely heterogeneous catalysis is reported. The use of basic compounds as solid catalysts allowed for the synthesis of azetidin-2-ones under microwave irradiation without organic additives such as triethylamine. An excellent catalyst for this transformation was Mg-Al hydroxide (MAH). The present methodology offers the advantages of non-hazardous reaction conditions, short reaction times, high yields, and catalyst reusability. Different substitution groups were tested on the imines and acyl chlorides to explore the scope of the reaction. Unconventional N–C4 bond cleavage was detected in azetidin-2-ones. MAH was characterized by N2 adsorption–desorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM).

Production of Personalized Thyroid Cartilage Scaffold and Histological Analysis

2014 ◽  
Vol 881-883 ◽  
pp. 473-478
Author(s):  
Wei Xia ◽  
Gao Xiang Cao ◽  
Long Cheng Zhang ◽  
Jie Liao ◽  
Jian Min Zeng
Keyword(s):  
Histological Analysis ◽  
In Situ Polymerization ◽  
Thyroid Cartilage ◽  
Biological Properties ◽  
Bone Morphogenetic Protein 2 ◽  
Cartilage Defects ◽  
Organic Additives ◽  
Morphogenetic Protein ◽  
Specimen Density

To meet the bone defect on the personalized needs of implantation, this study presents the manufacture of personalized thyroid cartilage hydroxyapatite (HA) scaffold by the rapid prototyping(RP) technique combined with CT image reconstruction and employs the foaming of suspensions prior to the in situ polymerization of organic monomers contained in the compositions. The organic additives are eliminated at temperatures above 300°C, and sintering is carried out for consolidation of the ceramic matrix. Spherical interconnected cells with sizes ranging from 100μm to 250μm characterize the porous structure, depending on the specimen density. The biological properties of porous personalized scaffolds loaded with bone morphogenetic protein 2 (rhBMP-2) were evaluated, by which a simulated surgical method of thyroid cartilage defects in rabbits and repairing with artificial scaffolds, and compared with rhBMP-2 loaded dense personalized or porous non-personalized scaffolds. The results of the histological analysis and the electronic laryngoscope inspection of airway indicate that rhBMP-2/HA/ porous personalized scaffolds is a promising composite having osteogenic efficient enough for repairing thyroid cartilage defects.

scholarly journals Effect of Soil Solution pH during the Tetracycline Intercalation on the Structural Properties of a Dioctahedral Smectite: Microstructural Analysis

2019 ◽  
Vol 2019 ◽  
pp. 1-17
Author(s):  
Walid Oueslati
Keyword(s):  
Soil Solution ◽  
Structural Changes ◽  
Ph Value ◽  
Microstructural Analysis ◽  
Xrd Analysis ◽  
Deformation Bands ◽  
Solution Ph ◽  
Hydration Properties ◽  
In Situ Xrd

The aim of this work is to quantitatively characterize the structural response to a chemical disruption of saturated montmorillonite crystallites by organic molecules (tetracycline (TC)), derived from pharmaceutical waste. The chemical disturbance is performed by varying the surrounding soil solution pH. To show the effect of this chemical perturbation on the interlamellar space (IS) configuration and the hydration properties, an “in situ” XRD analysis, based on the modeling of the 00l reflections, is carried out. The “in situ” XRD analysis is performed by varying the relative humidity conditions (%RH). FTIR SEM and BET- (Brunauer-Emmett-Teller-) BJH (Barrett-Joyner-Halenda) analyses are used as complementary techniques to confirm the structural changes accompanying the intercalation process. Results showed a dependence between solution acid character and the TC adsorption mechanism. From pH values close to 7, the deprotonation of the TC molecule within IS is accelerated by an increasing %RH rate. IR spectroscopy shows that the structure is preserved versus pH value and only a shift of the water deformation bands ascribed to interlamellar water molecule abundance and TC conformation is observed. The surface morphology studied by SEM shows the increase in the surface porosity by increasing the pH value. BET-specific surface area and BJH pore size distribution (PSD) analyses confirm the SEM observations.

Mono Dispersable Water-Soluble Iron Sulfide Nanoclusters: Synthesis, Characterization and Catalytic Application for Highly Efficient Synthesis of Xanthene Derivatives

2020 ◽  
Vol 12 (5) ◽  
pp. 603-611
Author(s):  
Kumar Karitkey Yadav ◽  
Hemant Kumar ◽  
Balaram Pani ◽  
Indrajit Roy ◽  
Pramod Kumar
Keyword(s):  
Electron Microscopy ◽  
Iron Sulfide ◽  
Reaction Times ◽  
Current Method ◽  
Nitrogen Adsorption ◽  
Significant Loss ◽  
Water Soluble ◽  
Precipitation Reaction ◽  
Transmission Electron ◽  
Xanthene Derivatives

In this manuscript, we have synthesized Iron sulfide nanoclusters (FeSNCs) by precipitation reaction between ferric chloride (FeCl3 · 6H2O) and thiourea with sodium borohydride (NaBH4) as a reducing agent at room temperature in water. These nanoclusters are synthesized within two minutes. The morphology and size of these synthesized FeSNCs were confirmed from transmission electron microscopy (TEM) and scanning electron microscopy (SEM). TEM and SEM data showed that the average diameters of these FeSNCs are around 70 nm. The Power X-ray diffraction (XRD) patten of the FeSNCs clearly showed the crystalline nature of these nanoclusters. Vibrating sample magnetometer (VSM) experiment showed that these nanoclusters are ferromagnetic in nature having high magnetization (20 emu/g). The nitrogen adsorption isotherm of FeSNCs confirmed the porous nature. These well characterized FeSNCs were further utilized as a catalyst for the synthesis of 9-aryl-1,8-dioxooctahydroxanthenes and 14-substituted-14H-dibenzo[a, j] xanthene derivatives. It is observed that the catalytic activities of FeSNCs are much better than the other reported heterogeneous and homogeneous catalysts. After completion of the reaction, FeSNCs are separated from the reaction mixture with the help bar magnet, washed and reused for the next catalytic reaction. Current method offers several advantages over other reported methods such as excellent yields, short reaction times, simple reaction procedure, and reusability of the catalyst upto five times without any significant loss in its activity.

Sign in / Sign up

Export Citation Format

Share Document