Solution Agitation Research Articles

Influence of Quenching Conditions on Microstructure Evolution and Hardness of 42CrMo4 Alloy Steel

Evolution of microstructure and hardness in 42CrMo4 steel during quenching under the different cooling conditions were investigated. Mineral oil, polymer solution and water were selected as quenchants to provide different cooling conditions. Quenching experiments were also conducted under magnetic stirring and ultrasonic agitation of polymer solution. Cooling conditions during quenching had significant effect on phase transformation and hardness of 42CrMo4 steel. The quench hardened samples show martensite microstructure along with other micro-constituents. Needle like/acicular ferrite was observed with water quenching due to diffusion less transformation. Sample quenched under ultrasonic agitated medium showed formation of network of carbides. Higher hardness values were obtained with water quenching and ultrasonic agitated polymer quenching.

Microwave-Assisted Hydrothermal Synthesis of Zinc-tin Based Nanoflower for the Adsorptive Removal of Cadmium from Synthetic Wastewater

The present study utilized zinc-tin nanoflowers (ZT-NFs) in a batch adsorption treatment process to effectively remove cadmium from synthetic wastewater. The batch adsorption strategy was optimized using the univariate approach to enhance the efficiency of the adsorption process. The dominant parameters examined in the optimization experiments were pH/volume of buffer solution, nanoflower amount, and sample agitation type/period. After determining the optimal batch adsorption conditions, equilibrium studies were performed by adding cadmium to synthetic wastewater at concentrations in the range of 1.0 – 40 mg/L. The quantification accuracy for cadmium was improved by developing the calibration plot with spiked sample matrix. The equilibrium data were subjected to mathematical modelling utilizing the Langmuir adsorption isotherm model. The calculated isotherm constants indicated a well-fitted isotherm model to the experimental data. The reported ZT-NFs-based adsorptive removal strategy was effectively employed to remove cadmium from synthetic wastewater.

Comparative evaluation of the effect of ultrasonic and rotary agitation of herbal irrigating solutions on smear layer: A SEM study.

Instrumentation and irrigation balance helps in effective removal of endodontic microbes housing inside the smear layer. This study aimed to (1) evaluate whether activation of the irrigating solutions with two different systems during the final irrigation step can lead to smear layer formation in the middle and apical third of the root canal and (2) evaluate and compare the smear layer removal ability of the aqueous extracts of Emblica officinalis and Morinda citrifolia. A total of 72 single-rooted teeth were prepared up to F4 ProTaper. The specimens were assigned into eight groups of nine teeth each, according to the final irrigant and activation techniques. Further, the teeth were evaluated under SEM for endodontic smear layer at the middle and apical third. Inferential statistics included Pearson's Chi-square. Level of significance was set at 0.05 at 95% confidence level. Ultrasonic activation system showed significant (P = 0.000) amount of smear layer compared to XP-Endo Finisher file. A significant difference (P = 0.00) in the smear layer removal was observed when 6% M. citrifolia was activated with XP-Endo Finisher file both in the middle and apical third. Within the limitations of this in vitro study, it can be concluded that smear layer formation was noted with ultrasonic and XP-Endo Finisher file when saline was used as an irrigant. 6% M. citrifolia when activated with XP-Endo Finisher file showed best results among all other experimental groups.

Synergistic effects of PVDF membrane surface functionalization with polydopamine and titanium dioxide for enhanced oil/water separation and photocatalytic behavior

This study investigates the surface modification of poly(vinylidene fluoride) (PVDF) membranes using polydopamine (PDA) and titanium dioxide (TiO2) for effective separation of oily compounds and self-cleaning photocatalytic behavior. The aim was to improve the antifouling properties of the membrane, which was modified by varied PDA and TiO2 concentrations and evaluated regarding the water permeance, total organic carbon (TOC) rejection, and photocatalytic degradation activity. The results demonstrated considerable improvements in the membrane's antifouling properties, achieving a water permeance of 781 kg h−1 bar−1 m−2, TOC rejection of 87%, and methylene blue photocatalytic degradation of 97%, using dopamine (DA) and TiO2 concentration of 0.92 g L−1 and 1.4% (w/w), respectively, and a solution agitation speed of 106 rpm. Additionally, flux recovery reached 86% after the photocatalytic self-cleaning process, indicating that TiO2 improved the membrane's antifouling properties. These findings highlight the potential of PDA and TiO2 as effective surface modifiers for enhancing oil/water separation, reducing fouling, and promoting self-cleaning effect in photocatalytic PVDF membranes. This study’s outcomes provide valuable insights for developing efficient and sustainable membrane-based separation processes for oily wastewater treatment applications.

Filling Material Bond Strength to Dentin Is Positively Influenced by the Agitation of Endodontic Final Irrigating Solutions.

The final step of irrigation has been considered to of increase the bonding strength of filling material to dentin. This study investigated the impact of three final-step irrigation methods on the endodontic sealer bond strength to dentin by using a micro push-out test. Palatal roots of human maxillary molars were cleaned and shaped and randomly divided in six groups (n=15) according to the final-step irrigation method and the type of root canal sealer used. The solutions used for the final-step irrigation were 17% ethylenediaminetetraacetic acid and 2.5% sodium hypochlorite, which underwent three methods: 1) syringe-needle irrigation/conventional, 2) passive ultrasonic irrigation, and 3) XP-endo Finisher agitation. The root canal sealers used were: EndoSequence BC Sealer, and AH-Plus sealer. Roots were obturated with the single cone technique and then, cross-sectioned in 2-mm-thick slices (3 slices from each root). Push-out test was performed on the sliced specimens (cervical, middle, and apical thirds) with a universal testing machine. Bond strength values were recorded in megapascal (MPa). Subsequently, each specimen was longitudinally split to verify the type of failure. Data analysis was performed using Johnson transformation, three-way analysis of variance, Tukey's post-hoc tests, and the partial Eta squared test. There were significant differences in bond strength between the sealers [AH: 4.46±2.24 and BC: 3.47±2.19 MPa (P<0.001)]; between final-step irrigation methods [passive ultrasonic irrigation: 4.52±2.25, XP-endo Finisher: 3.93±3.93 and syringe-needle irrigation/conventional: 3.37±2.51 MPa (P<0.001)], and between the root canal thirds represented by the sliced specimens [cervical: 5.45±2.39, middle: 4.14±1.99 and apical: 2.30±1.30 MPa (P<0.001)]. The interaction between the variables had no significance (P>0.05). Agitation of the final irrigating solution may improve the bonding of the sealer to canal walls. AH-Plus sealer had the highest bond strength. The bond strength reduced significantly towards the apical third.

Waste bamboo-derived magnetically separable bamboo-activated carbon: from characterization to effective remediation of fluoride (F-) ions from water.

An effective and affordable nanoadsorbent, magnetically separable magnetite-activated bamboo carbon (MABC), was obtained from waste bamboo biomass via pyrolysis of bamboo chunks and the co-precipitation method using ferrous and ferric chloride as iron precursors. The synthesized nanosorbents were characterised using XRD, SEM, and DLS techniques to study the surface characteristics and morphology. Chemical composition, optical absorption, and magnetic properties were studied using FTIR spectroscopy, UV-vis spectroscopy, and VSM, respectively. The BET surface area, porosity and surface charge were determined using N2 adsorption-desorption isotherm and zeta potential technique. The cytotoxicity and antimicrobial properties of BC, ABC and MABC were investigated against prokaryotes and eukaryotes. The result demonstrates the nontoxic nature of BC, ABC and MABC, indicating their significant potential for addressing water treatment using sustainable and eco-friendly nanosorbents. Comparative fluoride ion removal studies were performed using ABC and MABC NPs. About 99.6% of F- ions were adsorbed using MABC and 75.9% were adsorbed using ABC. Thus, MABC NPs were used as sorbents for the rest of the fluoride ion adsorption parameters. The batch fluoride ion sorption was performed at various sorption parameters, such as diverse solution pH (1.0-8.0), temperature (25-45 °C), agitation times (10-60 min), and adsorbent dose (0.01-0.04 g L-1). The pseudo-second-order kinetic model exhibited the best fit with F- ion adsorption (95.96 mg g-1) compared with the pseudo-first-order model (12.30 mg g-1), thereby indicating chemisorption adsorption. The exhausted MABC was recovered from the aqueous solution using a bar magnet. Regeneration studies of exhausted MABC were successfully performed using NaOH (0.1 M) as a desorbing agent.

IoT implemented Osmotic Dehydrator

Osmotic dehydration is a dehydration technique that allows the preservation of the organoleptic characteristics of the food and its nutritional properties compared to other preservation methods, such as hot air drying or solar drying. Studies on this dehydration process are usually carried out on a laboratory scale and with the constant presence of the evaluator, interrupting the process for sampling. That is why the main objective of this research was to build an automated osmotic dehydration equipment implementing the Internet of Things (IoT). The measurable factors involved in the process were determined, and the necessary sensors and actuators were chosen along with the best IoT alternative for the process. A prototype was built, which allows for controlling the agitation of the osmotic solution, temperature control, and remote monitoring of concentration and temperature variables. The equipment was tested by evaluating its performance in the dehydration of melon and apple, where the ANOVA tests demonstrated the significance (p &lt; 0.05) of the factors chosen as part of the equipment design and their interaction with the process. In the apple samples, a weight loss of up to 44.007% and a water loss of 53.234% were obtained. For melon, the process showed greater efficiency in dehydration, with values of 75.259% for weight loss and 75.979% for water loss.

The utilization of mechanical agitation of irrigation solution in endodontic treatment: case series

Aim. To evaluate the advantages of working with the Endoactivator device on the example of a series of clinical cases concerning the treatment of chronic apical periodontitis. Materials and methods. The series of clinical cases included five patients (two men and three women) who were treated for chronic apical periodontitis (diagnosis according to ICD-10 K04.5). The patients underwent endodontic treatment in two visits, namely, mechanical treatment with rotating nickel-titanium instruments, drug treatment using an Endoactivator device for sound activation of irrigation solutions and the introduction of calcium hydroxide between visits. Postoperative sensitivity was assessed according to the criteria: absent, low, medium and high. The patients informed the research doctors via messengers about the intensity of postoperative soreness. Results. Next results of postoperative sensitivity have been revealed: none of the patients noted high postoperative soreness, average soreness was noted by one patient, low soreness was noted by two patients and absence of soreness was noted by two patients. Conclusions: on the example of this series of clinical cases, convenient manipulation characteristics of the EndoActivator device were revealed. There were no cases of high postoperative sensitivity after operation of these devices in the presented series of cases. In all clinical cases, radiological methods confirm the positive dynamics of healing of periapical foci.

Adsorption of Basic Yellow 28 and Basic Blue 3 Dyes from Aqueous Solution Using Silybum Marianum Stem as a Low-Cost Adsorbent.

In the present study, the ability of an adsorbent (SLM Stem) obtained from the stem of the Silybum Marianum plant to treat wastewater containing the cationic dyes basic blue 3 (BB3) and basic yellow 28 (BY28) from aqueous solutions was investigated using a batch method. Then, the SLM Stem (SLM Stem-Natural) adsorbent was carbonized at different temperatures (200-900 °C) and the removal capacity of the products obtained for both dyes was examined again. The investigation continued with the product carbonized at 800 °C (SLM Stem-800 °C), the adsorbent with the highest removal capacity. The dyestuff removal studies were continued with the SLM Stem-Natural and SLM Stem-800 °C adsorbents because they had the highest removal values. The surface properties of these two adsorbents were investigated using IR, SEM, and XRD measurements. It was determined that the SLM Stem-Natural has mainly non-porous material, and the SLM Stem-800 °C has a microporous structure. The optimal values for various parameters, including adsorbent amount, initial dye solution concentration, contact time, temperature, pH, and agitation speed, were investigated for BY28 dye and were 0.05 g, 15 mg/L, 30 min, 40 °C, pH 6 and 100 rpm when SLM Stem-Natural adsorbent was used and, 0.15 g, 30 mg/L, 30 min, 40 °C, pH 10, and 150 rpm when SLM Stem-800 °C adsorbent was used. For BB3 dye, optimal parameter values of 0.20 g, 10 mg/L, 30 min, 25 °C, pH 7, and 100 rpm were obtained when SLM Stem-Natural adsorbent was used and 0.15 g, 15 mg/L, 40 min, 40 °C, pH 10, and 100 rpm when SLM Stem-800 °C adsorbent was used. The Langmuir isotherm described the adsorption process best, with a value of r2 = 0.9987. When SLM Stem-800 °C adsorbent was used for BY28 dye at 25 °C, the highest qm value in the Langmuir isotherm was 271.73 mg/g. When the study was repeated with actual water samples under optimum conditions, the highest removal for the BY28 dye was 99.9% in tap water with the SLM Stem-800 °C adsorbent. Furthermore, the reuse study showed the adsorbent's efficiency even after three repetitions.

Mechanical activation with Easy Clean device enhanced organic tissue removal from simulated internal root resorption in a laboratory evaluation

BackgroundConsidering the irregular shape of the root canal, removing inflamed pulp and granulation tissue completely from internal resorption cavities during chemomechanical preparation can be challenging. This study aimed to evaluate the effectiveness of passive ultrasonic irrigation (PUI) compared to mechanical activation with Easy Clean in the removal of organic tissue from simulated areas of internal root resorption.MethodsThe root canals of 72 extracted single-rooted teeth with oval canals were instrumented with Reciproc R25 instruments. After root canal preparations, the specimens were split longitudinally, and semicircular cavities were prepared using a round bur on each half of the roots. Samples obtained from bovine muscle tissue were weighed and adapted into semicircular cavities. The roots were reassembled and joined, and the teeth were divided into six groups (n = 12) according to the irrigation protocol: Sodium hypochlorite (NaOCl) without activation; NaOCl + PUI; NaOCl + Easy Clean; distilled water without activation; distilled water + PUI; and distilled water + Easy Clean. After irrigation protocols, the teeth were disassembled, and the remaining organic tissue was weighed. Data were analyzed by two-way ANOVA and Tukey’s post hoc test (p < 0.05).ResultsNone of the experimental protocols totally removed the bovine tissue from simulated cavities. Tissue weight reduction was significantly affected by the activation method (p < 0.05) and by irrigation solution (p < 0.05). Groups with NaOCl irrigation presented higher tissue weight loss when compared to distilled water, for all irrigation methods (p < 0.05). The use of Easy Clean resulted in the greatest tissue weight loss (42.0%—Distilled water/45.5%- NaOCl) compared to those of PUI (33.3%—Distilled water/37.7%- NaOCl) and no activation (33.4%—Distilled water/38.8%- NaOCl) (p < 0.05). However, no differences were observed between PUI and no activation groups (p > 0.05).ConclusionsMechanical activation with Easy Clean enhanced organic tissue removal from simulated internal resorption more effectively than PUI. Easy Clean for agitation of the irrigating solution is effective in removing simulated organic tissues from artificial internal resorption cavities, being an alternative to the use of PUI.

Analysis of aged refuse bio adsorbent for heavy metal removal in electroplating effluent

ABSTRACT The electroplating process is a common method in the surface-finishing process that produces toxic industrial discharges containing nickel, cobalt, cadmium, chromium, lead, cyanide, copper, zinc and other chemical reagents. Without adequate treatment, the release of these harmful compounds into an aquatic environment can have major negative repercussions for biota as well as humans. Heavy metal cationic pollutants in high concentrations can cause major health problems. As a result, it is critical to effectively remove heavy metal ion pollutants from electroplating effluents. Hence, in this research, at room temperature, aged refuse has been used as an adsorbent, which is a solid waste from landfills that have stabilised after several years of placement and are treated with concentrated sulphuric acid, was investigated for metal removal efficiency. Contact time, starting ion concentration, adsorbent dosage, aqueous solution pH and agitation speed were all changed and evaluated to depict the effect they had on removal efficiency. The BET isotherms, multipoint BET and BJH pore size distribution were determined for the adsorbent during the BET analysis. From that, the surface area for the adsorbent was found to be 4.6 /g. For the experimental results, the Langmuir and Freundlich isotherm models were compared and the Freundlich isotherm model agreed on good results. Finally, the adsorbent’s response surface methods for pH, time, dosage and agitation speed were compared, and the results indicated good agreement with the actual values.

Comparison of the Effect of Mechanical and Ultrasonic Agitation on the Properties of Electrodeposited Ni-Co/ZrO2 Composite Coatings

Ni-Co/ZrO2 composite coatings were fabricated by electrochemical deposition from sulfamate solutions containing zirconia nanoparticles. The main purpose of this research was to evaluate the effect of mechanical stirring and ultrasonic agitation in plating solutions on the structure and properties of Ni-Co/ZrO2 composite coatings. The morphology, microstructure, microhardness, anti-corrosion and wear resistance of the composites were investigated via scanning electron microscopy, X-ray diffraction, Vickers microhardness testing, electrochemical workstation utilization and friction wear testing. The hardness, friction coefficient, wear loss, corrosion rate of the composite coating prepared with mechanical stirring, and ultrasonic agitation were 533 and 680 HV; 0.40 ± 0.02 and 0.35 ± 0.02; 2.15 × 10−5; 0.85 × 10−5 g·m−1; and 0.36 and 0.07 mm/year, respectively. In comparison to mechanical stirring, ultrasonic agitation could more uniformly disperse the zirconia nanoparticles to obtain Ni-Co/ZrO2 composite coatings, which has simplicity and compactness.

Decoupling thermal effects and possible non-thermal effects of microwaves in vacuum evaporation of glucose solutions

Microwave vacuum evaporation (MVE) is a promising alternative to conventional methods. However, the mechanisms underlying its efficiency remain elusive. In this study, the effects of microwaves on glucose solutions were investigated via molecular dynamics (MD) simulations and experimental studies to elucidate possible microwave non-thermal and thermal effects, respectively. MD simulations on energy-related parameters, interfacial properties, and molecular migration indicated that a microwave electric field of 10 5 V/m could not influence water evaporation behavior at a constant temperature of 90 °C, validating the absence of non-thermal effects in the MVE of glucose solutions. Meanwhile, superheating was not observed in this study during microwave heating at atmospheric pressure or in vacuum. High-intensity microwaves enabled the solution to reach its boiling point rapidly and remarkably induced an intensified film boiling during MVE, thereby shortening the evaporation time. Therefore, the high efficiency of MVE may be attributed to the thermal effects of strong microwaves. • Thermal effects and possible non-thermal effects during MVE were studied. • Non-thermal effects were not observed during microwave evaporation at 10 5 V/m. • 10 9 V/m-z and 10 9 V/m-x microwaves accelerated and impeded evaporation, respectively. • Superheating did not occur during microwave heating with solution agitation.

Biofunctionalization of polyetheretherketone implant material by bone-forming peptide-2 immobilization

Polyetheretherketone (PEEK) has favorable biomechanical properties to be used as an implant material. Unfortunately, it is hydrophobic and does not promote cellular adhesion, which could result in poor integration with bone tissue. Bio-functionalization of PEEK surface with osteogenic peptides derived from bone extracellular matrix proteins is an excit-ing approach to encourage bone formation around the implant. In the current study, bone-forming peptide-2 was immo-bilized on PEEK surface using two different methods, using dopamine and a diglycidyl ether as conjugate compounds, respectively. Peptide quantification test revealed that the two strategies resulted in the most amount of peptides were attached with 0.5 mM concentration and no further peptides were grafted with a higher peptide concentration. Both methods showed good peptide stability after agitation in aqueous solution. Peptide grafting was confirmed with ATR-FTIR. Surface characterizations with AFM and wettability tests resulted in a significant increase in surface roughness and surface area ratio for the peptide-grafted PEEK compared to unmodified PEEK, which led to a signifi-cant enhancement in the wettability of the modified PEEK surface

Stereomicroscope Analysis of the Cleaning Capacity of an Abrasive-Expansive System in Oval Canals: A Laboratory Study

Background: The aim of this study was to evaluate, by means of a stereomicroscope, the influence on the removal of smear layer obtained by the XP-endo Finisher and Tornado Disinfection Kit systems during the final agitation of the irrigating solution, in conservative preparations. Materials and methods: Ten extracted human lower premolars were chemically-mechanically prepared with the ProDesign Logic 2 NiTi rotary system (25/.05) and 2.5% NaOCl. The same specimens were submitted to three different protocols of agitation of the irrigating solution: Conventional irrigation, XP-endo Finisher and Tornado Disinfection Kit. For this, a closed system was made, the roots were cleaved and three holes were made in each third of the root canal and filled with dentinal debris to take initial photos under a stereomicroscope. The amount of debris was rated using a 4-point scoring system. The data obtained were submitted to the Wilcoxon, Kruskal-Wallis and Dunn tests (p&lt;0.05). Results: In the analysis of the effectiveness of each protocol, it was possible to observe a statistically significant difference in the removal of debris in all thirds for all protocols (p&lt;0.05). Regarding the difference in score found before and after application of the protocol, a significant difference was observed between the apical and the middle third in the Tornado Disinfection Kit group (p&lt;0.05) and there was no difference between the same third for different groups (p&gt;0.05). Conclusion: Based on the methodology and the results presented, it was concluded that both evaluated protocols improved the cleaning of root canal recesses in all thirds, with no difference between them.

Biosorption kinetics of cerium(III) and cobalt(II) from liquid wastes using individual bacterial species isolated from low-level liquid radioactive wastes.

The existence of toxic heavy metals in the aquatic environment has emphasized a considerable exigency to develop several multifunctional biosorbents for their removal. Herein, three individual bacterial species of Cellulosimicrobium cellulans, Bacillus coagulans, and Microbacterium testaceum were successfully isolated from low-level liquid radioactive wastes. Their loading capacities towards cerium and cobalt metal ions were inclusivity inspected under variable operational parameters of pH, primary pollutant concentration, interaction time, temperature, stirring speed, and biosorbent dosage. By analyzing the influence of solution pH, concentration, temperature, biosorbent mass, and agitation speed on the biosorption kinetics, the biosorption process confirms pseudo-second-order kinetic, intraparticle diffusion, and Elovich equation. Remarkably, the isolated Microbacterium testaceum exhibited high loading capacities reaching 68.1mgg-1, and 49.6mgg-1 towards Ce(III), and Co(II) ions, respectively, at the initial concentration of 2.8mM, pH 4.5, and 25°C. Overall, the isolated bacterial species can potentially be offered up as a promising scavenger for Ce(III) and Co(II) from liquid waste effluents.

Effect of solution pH, precursor ratio, agitation and temperature on Ni-Mo and Ni-Mo-O electrodeposits from ammonium citrate baths.

The induced co-electrodeposition of Ni and Mo is a complex process, where metallic Ni-Mo alloys and Ni-Mo-O composites can originate from the complete and partial reduction of Mo respectively. By adjusting electrolyte compositions and electrodeposition parameters, various metallic, metal/oxide composite, and oxide thin films of Ni-Mo and Ni-Mo-O were electrodeposited from ammonium citrate baths. Ni-ammonia complexes, which play a critical role in promoting the deposition of metallic Ni-Mo alloys, were enhanced at alkaline pH (i.e., 8–10) and lower temperature (i.e., 25–45°C). Moreover, the electrochemical reduction of Ni is under mass transfer limitation, so the deposited Mo content decreased with increasing agitation. On the other hand, higher Mo content can be achieved by relatively higher citrate concentration and larger Mo-to-Ni precursor molar ratio. However, a critical molar ratio of metal precursor resulted in transition from alloy to composite due to Ni inducing the reduction of Mo.

The synergistic effects of additives on the micro vias copper filling

• N-(3-(5-Mercapto-1H-tetrazol-1-yl) phenyl) acetamide was investigated as leveler to develop the microvia with or without cracked plating. • An optimal plating solution was found and applied to carry out superfilling of microvias. • the cracked plating occur on the side and bottom of the microvia when without accelerator. A nitrogen-containing heterocyclic compound N-(3-(5-Mercapto-1H-tetrazol-1-yl) phenyl) acetamide (named L) was investigated as a new leveler to develop the microvias Cu filling with or without cracked plating in blind via. The synergistic effects of L with other plating additives were investigated by galvanostatic measurements (GMs) and cyclic voltammetry (CV) measurements. The GMs show that the Δη values (Potential difference at different speeds of Cu rotating disk electrode) are approximately 24 mV which usually suggests better Cu filling performance for the corresponding electrolyte additives. In addition, the optical microscope (OM) measurements indicated that microvias cracked plating was more likely to occur when there is no accelerator in the copper plating solution. The results of OM experiments also show that the microvia super-filling would not appear although the copper plating rate at the bottom of the blind hole is higher than that of the outer copper layer of the blind hole if there is no air agitation in the copper plating solution. The finest copper electroplating formula made up of the virgin acid solution (VAS) only added the PEP, L, SPS, Cl − was found and applied to carry out superfilling of microvias.

Critical evaluation of zeolite N synthesis parameters which influence process design

Zeolite N exhibits high selectivity and capacity for ammonium ions, which makes it attractive applications such as wastewater treatment. However, there is a lack of knowledge regarding process issues pertinent to zeolite synthesis scale-up. Therefore, this study addressed factors including agitation of reactant solution during zeolite N synthesis, the benefit of mother liquor recycling, zeolite washing strategies, influence of clay source, reactor geometry and materials of construction. Use of both stirred and static reactant solutions did not impact the rate of zeolite N formation when the reaction temperature was 120 oC; whereas at 100 oC stirring promoted the creation of zeolite N. Stirred solutions resulted in smaller zeolite crystals. Mother liquor recycling not only reduced the need for KOH and KCl but also enhanced the product quality (cation exchange capacity increased from 558 to 586 meq/100 g). Reuse of the first stage wash water was recommended as it comprised of a comparable potassium content as the mother liquor (c.f. 13.1–15.4 g, respectively). Addition of acid or salts to the wash water did not remarkably accelerate the reduction in effluent solution pH. Excessive quartz content in the clay feedstock inhibited the growth of zeolite N. It was necessary to adjust the SiO2/Al2O3 feed ratio to 2 by pre-dissolving Al(OH)3 in potassium hydroxide. Use of two different reactor types to make zeolite N suggested that reaction time was significantly faster if reactors were made of Inconel (4 h) and did not contain a teflon insert (8 h).

Al2O3/Fe3O4/ZrO2 ternary oxide sorbent: Synthesis, characterization and sorption behavior to fluoride and phosphate ions from aqueous solution

ABSTRACT. Excess quantities of fluoride and phosphate in water bodies can lead to fluorosis and eutrophication problems, respectively. In search of a promising adsorbent targeting these ions, Fe3O4/Al2O3/ZrO2 ternary oxide was synthesized via co-precipitation method and characterized by X-ray diffraction (XRD), Fourier transform-infrared (FTIR) and Brunauer-Emmer-Teller (BET). Its specific surface area was found to be 205 m2/g. The effects of solution pH, adsorbent dose, contact time, agitation speed and initial fluoride and phosphate concentrations were also investigated and the optimum values were 4, 0.5 g, 12 h, 100 rpm and 20 mg/L, respectively, for fluoride and 5, 0.1 g, 8 h, 100 rpm and 10 mg/L, respectively, for phosphate. Fluoride and phosphate adsorptions fitted well with Freundlich and Langmuir isotherm models, respectively and their kinetic data correlated well with the pseudo-second order model. Desorbability study revealed that maximum desorption was achieved at pH 12. Thermodynamics study on the other hand showed that adsorption of fluoride was nonspontaneous and endothermic whereas that of phosphate was spontaneous and exothermic. Application on real water sample decreased the concentration of fluoride from 4.92 to 1.97 mg/L in ground water and phosphate from 1.7 to 0.35 mg/L lake water showing its potential as a promising adsorbent.&#x0D; &#x0D; KEY WORDS: Adsorption, Fluoride, Phosphate, Ternary oxide sorbent, Isotherm models&#x0D; &#x0D; Bull. Chem. Soc. Ethiop. 2022, 36(3), 555-569. &#x0D; DOI: https://dx.doi.org/10.4314/bcse.v36i3.6 &#x0D;