Stirring Period Research Articles

Removal of malachite green from an aqueous environment using chitosan-xanthan gum coagulation system: A response surface methodology approach

Natural coagulants provide a safe and sustainable alternative for water treatment. Our study used shrimp shell-derived chitosan combined with xanthan gum to remove malachite green dye from water. Using a Box-Behnken design, we optimized parameters, achieving up to 99.7 % dye removal under optimal conditions: chitosan (1.75 mg/L), xanthan gum (1.73 %–3.0 %), dye (5–27.5 mg/L), pH 6.0, stirring period (5–7.5 min), and stirring rate (105 rpm). Key factors affecting sedimentation included xanthan gum dosage and its interactions with pH and stirring rate. SEM and FT-IR analyses characterized dye-polymer interactions. Pilot-scale tests on aquaculture wastewater showed significant turbidity reduction and enhanced dye removal in 15 L volumes. Toxicity assessments post remediation was performed on Artemia salina as a model organism and hatching efficiency and survival were essential parameters studied. Our findings highlight the potential for sustainable dye recovery and reuse in wastewater treatment.

Application of Placket Burman Design Analysis for Optimization of the Physico-Chemical Properties of Multispecies Surimi

ABSTRACT The application of Plackett–Burman design in investigating the effect of physicochemical attributes of multispecies surimi was performed. The surimi was made from five species, added with four types of cryoprotectant and two different gelling agents, thus constructing 11 processing variables. Surimi was observed for the physico-chemical parameters including moisture, salt-soluble protein, pH, hardness, whiteness degree, and water-holding capacity and sensory evaluation. The best formulation was obtained from consisting of threadfin bream, croaker, lattice monocle bream, tilapia, sorbitol, sucrose, sodium tripolyphosphate, k-carrageenan, sodium lactate, and konjac with 15 min stirring period.

Analysis of the Upshot of Heat Treatment on Properties of Magnesium Hybrid Composites

Magnesium-based materials are in superior demand in auto industries due to their improved properties and behavior. However, processing and further post-treatment of this kind of magnesium composite is a stimulating chore because of its characteristics. In particular, heat treatment of this kind of magnesium composites may induce a change in grain structure which in turn alters the properties according to the need. So, this article is chiefly focused on the fabrication of magnesium composites by filling with SiC and graphite. According to the Taguchi array, the composites were developed by altering the reinforcing material content, stirring period, and rate. Four samples were fabricated accordingly by employing the stir casting technique. The fabricated composites were exposed to diverse forms of heat treatment processes such as annealing, normalizing, tempering, and quenching to learn the upshot of the same on its behavior. The surface structure of the dispersions in the developed composites was analyzed using an optical microscope, and the mechanical and physical behavior like strength, density, wear, and tensile tests were done on the developed samples. The morphology and behavior of the fabricated composites were compared and analyzed pre and post-heat treatment. Keywords. Magnesium Hybrid Composites, Stir Casting, Heat Treatment.

Foamability and foam stability of oily mixtures

Lubricating oils consist of base oil, containing different hydrocarbons, and modifying components (additives) which improve the application performance. Some of these additives are able to stabilize entrained air bubbles, potentially causing serious problems for engines, transmissions and hydraulic systems. Here we evaluate the foamability and foam stability of model mineral oils (hexadecane, light oil, heavy oil and their mixtures) in the presence and in the absence of nanoparticles as additives, at several temperatures. The results allow us to categorize the systems studied into three groups: (1) Oils unable to entrap any air during the stirring period; (2) Oils able to entrap air during stirring, but unable to retain it after stopping the stirring; (3) Oils which form stable bubbles and foams. Hexadecane, with and without nanoparticles, falls into the first group. Heavy oil in the presence of nanoparticles falls into the third group, whereas all other mixtures are in the second group. The inability of hexadecane to entrain air is related to its low viscosity and very low foam film stability which leads to instantaneous coalescence of the bubbles formed. The increased foamability of heavy and light oils and their mixtures is explained by: (1) their higher viscosity as compared to hexadecane which leads to slower foam film thinning and (2) the presence of long chain alkanes in these oils which create weak steric repulsion between the foam film surfaces. The addition of nanoparticles increases the foamability and the foam stability of heavy oil, without changing significantly the foam properties of the light oil and hexadecane. The latter effect is explained by the inability of the particles to attach to the light oil-air and hexadecane-air interfaces, whereas the same particles adsorb on the heavy oil-air interface and create additional steric repulsion between the air bubbles, thus allowing the formation of stable foam.

The utilization of moringa (moringa oleifera) seed powder as a biocoagulant and flocculant in waste water treatment coal mining industry

Mineralogically, acid mine drainage consists of minerals such as silica, iron silicate, magnesium, sodium, potassium and sulfide. These minerals can undergo oxidation (especially pyrite oxidation) to form acidic salts with a pH of 2.8-3.4. Moringa seed powder activity test were performed by adding 30% H2O2 to coal waste water treatment; Moringa seed powder was added to 2 L of coal waste water and stirred for 50, 100, 150, 200, and 250 minutes. Observations were analyzed using the AAS (Atomic Absorption Spectofotometry) to measure the quality of degraded waste water and X-Ray Diffraction (XRD). The results showed that the pH value reached 7.6 in the addition of H2O2 at the mixing time of 250 minutes, the TSS level reached 0 at the stirring period of 250 minutes without the addition of Moringa oleifera powder, while the addition of H2O2 and Moringa oleifera seed powder decreased heavy metals with an average of 69.06%at the stirring period of 100 minutes. Â

Production and characterization of soft Sardaigne-type cheese by using almond gum as a functional additive.

The effect of almond gum (AG), as natural polysaccharide with high nutritional value and important functional properties, on physicochemical and textural characteristics of Sardaigne‐type cheese was investigated. Response surface methodology (RSM) using Box–Behnken design was applied to determine optimal levels of three selected processing variables such as coagulation temperature (25–45°C), stirring period (20–30 min), and AG concentration (0.25%–0.75%). A 3‐level factorial design was employed to evaluate physicochemical and rheological responses of Sardaigne‐type cheese with AG added. The P‐values of ANOVA indicated that the processing variables selected have significantly affected dry matter content (p = .002), cheese yield (p = .0172), syneresis level (p = .0135), hardness (p = .0103), and adhesiveness (p = .0410). However, pH, cohesiveness, and elasticity are not affected by the selected processing variables. Predictive regression equations with a high coefficient of (R 2 ≥ .686) determination are constructed. The addition of AG owing to its water retention property has improved yield cheese as well moisture level. Therefore, this additional moisture in Sardaigne‐type cheese will be responsible for softer and smoother textural. Indeed, fivefold drop of adhesiveness and fourfold reduction of hardness are observed in cheese formulated with AG at 0.75% and in same temperature and stirring period conditions that commercial cheese. RSM analysis showed that optimum levels of processing variables are reached at AG concentration of 0.57% (w/v), coagulation temperature of 42.57°C, and stirring period of 20 min. Results of sensory properties showed that AG incorporation in Sardaigne‐type cheese does not have an adverse impact on organoleptically characteristics and overall acceptability of product was better than commercial cheese.

Ceramic bricks containing Ni ions from contaminated biomass used as an adsorbent

This article shows how pine sawdust residues can be used to adsorb nickel ions from synthetic solutions and then to produce porous bricks for civil construction using a mixture of natural clay and biomass containing the adsorbed metals. The adsorption tests were performed by mixing NiCl2 solutions with pine sawdust during a fixed stirring period of 24 h. The set was filtered and the filtrate was analysed. Highest efficiency adsorbate/adsorbent ratio was 50 mL of 1 M NiCl2 solution and 20 g L− 1 of pine sawdust. This was the contaminated biomass sample used in the manufacture of the bricks. This paper analyses the properties of the bricks achieved and compares them with bricks without added biomass, porous bricks containing zinc and commercial bricks. The obtained values of bulk density, apparent specific weight, apparent porosity, water absorption, apparent volume, weight loss on ignition, compressive strength, flexural modulus of rupture and efficiency retention of metal in the brick, demonstrate that the ceramic pieces obtained are optimal for construction.

Experimental design and chemometric techniques applied in electronic nose analysis of wood-aged sugar cane spirit (cachaça)

Wood barrel aging distilled beverages corresponds to a process capable of aggregate flavor compounds that may change sensory profiles and improve distillates quality. The analysis of the flavor compounds to determine degree of maturation of distillate relies most on costly techniques such as chromatography, so that more affordable and less laborious technologies may be suitable for wood-derived flavor determination in beverages, such as digital olfactometry. An electronic nose system reliability may take into consideration appropriate sample preparation method in order to obtain optimal performance over detection of odor compounds. An optimized pre-injection method was established for cachaça analysis in an electronic nose system after an experimental Rotational Central Composite Design, considering the sample preparation factors: incubation temperature, samples ethanol content, stirring period and equilibrium period. Raw data underwent the chemometric technique Multiple Co-inertia Analysis for feature extraction in prior to optimization design. The chemometric approach for data pre-treatment and analysis demonstrated favorable performance for electronic nose application. The optimal sample preparation included dilution of the aged distillate to lower ethanol content (10% v/v), sample incubation at 49 °C and excluded stirring and equilibrium stages, leading to a simpler and less time-consuming protocol.

Recrystallization of Cu-30Zn brass during friction stir welding

The recrystallization process of Cu-30Zn brass during friction stir welding (FSW) was investigated. The microstructural evolution in the stirring period and the subsequent normal air-cooling period were separately studied by using stop-action technology, liquid nitrogen cooling, and subsequent heat treatment. During the stirring period, the initial large grains in the base material underwent serious shear deformation at elevated temperatures, resulting in the occurrence of dynamic recrystallization. The weld exhibited ultrafine grains with high dislocation density and a typical {111}<110> shear texture. The grain refinement mechanism was mainly attributed to discontinuous dynamic recrystallization, although several features of continuous dynamic recrystallization could also be found. In the subsequent normal air-cooling period, static restoration occurred and led to dislocation annihilation, selected grain growth, and appearance of annealing twins. The {111}<110> textural component partially changed into a {110}<001> Goss recrystallization texture. From these results, it was deduced that the brass experienced static restoration following dynamic recrystallization during FSW. The static restoration produced by the stirring remarkably influenced the microstructure. This study concluded that if the rapid cooling method is adopted during FSW, the static restoration process can be effectively restrained, and the microstructure of the joint can be significantly improved.

Increase of solidification rate to improve quality of productivity for xylitol/sorbitol crystalline candy products

When manufacturing crystalline candies, increase of the solidification rate is important to improve the quality of productivity. The effect of outer seed crystal specifications and stirring period in processing for food engineering on the solidification rate of molten sugar was investigated based on the concept of solid-state transformation of sugar melt crystallization. From experiments using outer seed crystals, we found that the solidification rate depended on the surface of the seed crystals and the stirring period before molten sugar was cast. This dependence was caused by shear nucleation where microcrystal fragments are generated by an attrition process based on shear force from the crystal surface. Without the proposed treatment, solidification required 106.0 h. However, we succeeded in increasing the solidification rate to 1.0 h, which is approximately 106 times faster. Thus, we proposed an operational strategy to improve the quality of productivity.

On the Alternate Stirring Mode of F-EMS for Bloom Continuous Castings

Local solute transportation behaviors under different alternate stirring parameters of final electromagnetic stirring (F-EMS) and their influences on the internal quality of the as-cast bloom are compared and evaluated based on a developed coupled model of electromagnetism, heat, and solute transport. To this end, plant trials were conducted in Shaoguan Steel, China. Under the action of F-EMS, a negative segregation band in an ellipse shape is observed at the central area of strand cross section, where the minimum carbon segregation degree is decreased from 0.98 to 0.84 as the stirring duration increases from 15 to 35 seconds in the alternate stirring mode, while it is reduced to 0.805 in the continuous stirring mode. The white band and shrinkage cavity are simultaneously observed at strand center under the conditions of continuous stirring mode, and alternate stirring mode with a stirring period of 35 seconds because of the local over-sustaining melt rotation. In contrast, the V-shape porosity belt width and strand center segregation fluctuation range increase from 60 to 90 mm and from 0.12 to 0.30, respectively, as the stirring duration is reduced from 25 to 15 seconds in the alternate stirring mode because of the poor mixing of the local melt at the strand center.

Nano-/Microfibrous Cotton-Wool-Like 3D Scaffold with Core-Shell Architecture by Emulsion Electrospinning for Skin Tissue Regeneration.

Electrospun nanofibrous scaffold has long been studied as skin substitutes for their structural resemblance to the dermal extracellular matrix. However, packed fibrous architecture with small pore size restricts cellular infiltration into nanofibrous mat. In this article, we report highly porous, nano-/microfibrous 3D structure using polycaprolactone-chitosan emulsion and its application in skin regeneration. Under the influence of electric field, the emulsion containing encapsulated charged chitosan droplets enhances charge of the spinning solution and residual charge in the core of the deposited fiber, thereby creating core-shell, cotton-like fluffy structure with average pore size 62 μm, fiber diameter ∼1.62 μm, contact angle of 72° and 80% water uptake capacity of the scaffold. Further, differential stirring period of the specific emulsion developed compact nanofibrous membrane with nanometer ranged pore size emphasizing the role played by emulsion droplet size and the charge carried thereafter. Presence of nanofibers with high-interconnected porosity promoted efficient cellular infiltration and proliferation from initial days of cell seeding. The scaffold supported extracellular matrix protein expression and stratified epithelialization in vitro. Effective integration and attachment of scaffold with margins of a full-thickness excision wound created in a rat model with accelerated healing within 3 weeks proved the efficiency of the scaffold as skin substitute. Additionally, gradual and prolong release of acidic chitosan from the core section benefitted wound healing by lowering the pH of wound environment. Simple technique with inexpensive raw materials endorsed the scaffold as a promising off-the-shelf matrix for skin tissue regeneration.

Adsorption of Cu(II) onto Cross-Linked Chitosan Coated Bentonite Beads: Kinetic and Isotherm Studies

In this study, cross-linked chitosan coated bentonite (CCB) beads were prepared as a potential adsorbent to adsorb Cu(II) from aqueous solution. As adsorption capacity was affected by several conditions such as initial Cu(II) concentrations, stirring period and temperature, these parameters were important to be investigated. Three different concentrations of Cu(II) were used in the kinetic study, which were 10, 25 and 50 mg/L. The experimental data was found fitted well with the pseudo-second-order model, an indication that chemisorption was the rate controlling mechanism. Isotherm study was done at different temperatures with concentration of Cu(II) was varied from 10 to 200 mg/L. The maximum monolayer adsorption of Cu(II) on CCB beads based on Langmuir isotherm model at 300, 310 and 320 K were 114.94, 119.05 and 77.52 mg/g, respectively. Therefore, adsorption of Cu(II) was preferred at lower temperatures. This work proved CCB beads as an effective adsorbent for fast removal of Cu(II) from wastewater solutions.

Research on magnetic separation for complex nickel deep removal and magnetic seed recycling.

This study investigated the deep removal of complex nickel from simulated wastewater using magnetic separation and magnetic seed recycling. Nano-magnetite (Fe3O4) was used as the magnetic seed. The flocculant applied was N,N-bis-(dithiocarboxy) ethanediamine (EDTC), a highly efficient heavy metal chelating agent included in dithiocarbamate (DTC). Important investigated parameters included hydraulic retention time, magnetic seed dosage, and magnetic field strength. The study also explored the magnetic flocculation mechanism involved in the reaction. The result indicated that the residual Ni concentration was reduced to less than 0.1mg/L from the initial concentration of 50mg/L under optimal conditions. Magnetic seed recovery reached 76.42% after a 3-h stirring period; recycled magnetic seeds were analyzed using scanning electron microscope (SEM) and X-ray diffraction (XRD). The zeta potential results illustrated that magnetic seeds firmly combined with flocs when the pH ranged from 6.5 to 7.5 due to the electrostatic attraction. When the pH was less than 7, magnetic seeds and EDTC were also combined due to electrostatic attraction. Particle size did affect microfloc size; it decreased microfloc size and increased floc volume through magnetic seed loading. The effective binding sites between flocs and magnetic seeds increased when adding the magnetic seeds. This led the majority of magnetic flocs to be integrated with the magnetic seeds, which served as a nucleus to enhance the flocculation property and ultimately improve the nickel complex removal rate.

Microstructural evolution and mechanical properties of rheocast Al-7.1WT%Si alloy

Effects of Semi-Solid Rheocasting (SSR) process on the structure and mechanical properties of Al-7.1wt%Si alloy were studied. The results showed that the non-dendritic structure could be formed by a short stirring period below liquidus temperature provided that stirring was combined with localized rapid heat extraction from the melt. The effect was examined by calculation of the time needed for detachment of dendrite arms at the initial stages of solidification and was associated with a large particle density in the rheocast slurry. Samples processed in semisolid state had lower porosity, higher tensile strength and higher elongation than that processed in fully-liquid state. The SSR- processed sample had a lower tensile strength but a higher elongation than the sample cooled without localized cooling and stirring. It was suggested that the lower strength of SSR-processed alloy was related to the inability of the α-particles to restrain crack propagation through the brittle eutectic matrix.

Removal of Cd(II) from Water System Using Novel Biosorbent Derived from Persimmon Fallen Leaves

A biosorbent was prepared by treating the persimmon (Diospyros kaki Thunb.) fallen leaves with sodium hydroxide (NaOH). The NaOH concentration and stirring period for the preparation of the biosorbent were adjusted to optimise the Cd(I) adsorption capacity of the biosorbents. Removal of highly toxic Cadmium metal ions from water system using the optimal biosorbent named ‘NPFL’ was investigated using a mimic industrial column. The result showed that NPFL could remove Cd(II) in large quantities from aqueous solution with coexisting metal ions. The raw material, NPFL and Cd(II) loaded NPFL were characterized by SEM-EDS. The reusability of NPFL was also studied by batch adsorption-desorption test.

Stir casting process for manufacture of Al–SiC composites

Stir casting is an economical process for the fabrication of aluminum matrix composites. There are many parameters in this process, which affect the final microstructure and mechanical properties of the composites. In this study, micron-sized SiC particles were used as reinforcement to fabricate Al-3 wt% SiC composites at two casting temperatures (680 and 850 °C) and stirring periods (2 and 6 min). Factors of reaction at matrix/ceramic interface, porosity, ceramic incorporation, and agglomeration of the particles were evaluated by scanning electron microscope (SEM) and high-resolution transition electron microscope (HRTEM) studies. From microstructural characterizations, it is concluded that the shorter stirring period is required for ceramic incorporation to achieve metal/ceramic bonding at the interface. The higher stirring temperature (850 °C) also leads to improved ceramic incorporation. In some cases, shrinkage porosity and intensive formation of Al4C3 at the metal/ceramic interface are also observed. Finally, the mechanical properties of the composites were evaluated, and their relation with the corresponding microstructure and processing parameters of the composites was discussed.

Karakteristik Mutu Biji Kakao Aceh Hasil Fermentasi Dengan Berbagai Cara Dan Interval Waktu Pengadukan

(Quality Characteristics Of Aceh Cacao Beans Resulted From Different Fermentation Methods)ABSTRACT. Response of cocoa beans to any fermentation treatment may vary according to crop variety, farming conditions and practices, and fermentation methods; including type of beans stirring methods and stirring frequencies applied during fermentation period. The objective of this research is to study quality characteristics of Aceh fermented cocoa beans treated with different stirring methods and stirring frequencies. The cocoa beans of 40 cm mass depth were kept in 53x40x50 cm rattan buckets and were fermented for 5 days. Beans stirring during fermentation was conducted either by in-place stirring andreplace-stirring to other rattan bucket. Stirring period was set for each 12 hours, 24 hours, and 48 hours of fermentation time. Beans temperature, pH, and total sugar content for each stirring period along five days-fermentationtime were recorded. The fermented beans were sundried for moisture content of approximately 6%. The results showed that the beans temperature during fermentation increased up to 45.7-46.6oC on the third-day and then decreased to 37.9-40.4oC on the fifth-day. The highest temperature (46.6oC) was recorded for in-place stirring with stirring period of 48 hours. The pH value of the beans decreased from 5.6-5.9 on the first-day to 3.2-3.4 on the fourth-day and then slightly increased to 3.4 in average on the fifth-day. The total sugar content decreased from 9.1-9.6% on the first-day to approximately 0.4% on the fifth-day. Quality analysis of the fermented beans showed that pH value varied 5.5-5.8 and fat content was 47.9-49.1%. The best quality of fermented beans was found for replace-stirring method with stirring period of 24 hours. This treatment resulted in fermented cocoa beans with 0.4% moldy, 17.5% partly purple, 3.0% slaty, and 76.7% fully fermented.

EFFECT OF MECHANICAL STIRRING ON BIOGAS PRODUCTION EFFICIENCY IN LARGE SCALE DIGESTERS

This research work aims to study the effect of mechanical stirring at different speeds and interval stirring periods on the biogas production yield and productivity and the energy balance in large scale biogas digesters. This investigation was conducted on two fixed dome digesters with 20 m3 total volume. The study includes three speeds of stirring (30, 45 and 60 rpm) and four stirring periods (15 min/hr, 15 min/2 hr, 15 min./3 hr and 15 min./4hr) ‘which equal to 6, 3, 2 and 1.5 hr/day, respectively. The obtained results showed that the stirring speed of 60 rpm was gave the high values of biogas production rate( 0.423 m3/m3/day), biogas productivity (0.423 m3/m3/day, 0.106 m3/kg TS add and 0.707 m3/kg VS consumed), energy production (9.379 MJ/m3/day), energy consumption in the stirring process (3.430 MJ/m3/day) and net energy gained (8.448 MJ/m3/day). However, the stirring period of 15 min./2 hr (3 hr/day) was gave the maximum biogas production rate and energy production at different stirring speeds and net energy gained at stirring speeds of 30 and 45 rpm. Meanwhile, the stirring period of 15 min./4 hr (1.5 hr/day) was gave the lowest energy consumption at different speeds and high net energy gained at stirring speeds of 60 rpm.

Superhydrophobic hybrid aerogel powders from waterglass with distinctive applications

Hybrid silica aerogel powders with enhanced superhydrophobicity and very high reaction yield were prepared by a fast co-precursor method at ambient pressure. An inexpensive aqueous sodium silicate solution was used as starting material (waterglass or WG), with hexamethyldisilazane (HMDZ) as organic co-precursor.The key for successfully achieving such high yields and superhydrophobicity was a systematic tuning of the synthesis parameters (co-precursors and acid catalyst molar ratios) and process conditions (stirring speed, stirring period, aging, washing and drying steps), in close correlation with the reaction mechanism. Using a minimum amount of organic co-precursor, a total yield of ∼80% in hybrid aerogels with high lipophilic/hydrophilic ratio, very high water contact angles (∼152±2°) and very low densities (∼0.120gcm−3) were obtained. The optimized synthesis conditions consist in HNO3:WG:HMDZ molar ratios of 1.5:1.0:1.5, stirring speed of 120rpm, only during addition of the catalyst and co-precursor, aging for 5min and washing with water before drying at atmospheric pressure.The minimization of the only costly precursor allows envisaging a low-cost large scale production and, moreover, the encapsulation of water droplets within aerogel powder allows proposing distinctive applications, such as water transport at a microscale level.