Gel Mixture Research Articles

Strategic Synthesis to Disperse Zeolite NaY in Lead Tree Wood

The goal of this work is to synthesize zeolite NaY inside Lead tree wood. The wood is mixed with zeolite seed gel before mixing with feed gel and subsequent hydrothermal treatment. In the first trial, the dried and untreated Lead tree wood is mixed with the gel of zeolite NaY before the hydrothermal process. Only zeolite NaP is produced. Then, sonication is applied to the wood and zeolite gel mixture before the hydrothermal process. The product is mixed with the phase of NaP and NaY. In the next attempt, the wood is treated with acid reflux before mixing with the zeolite seed gel. NaY is successfully produced inside the wood. When sonication is also applied, the amount of NaY is increased. The presence of zeolites in the wood are confirmed by X-ray diffraction, scanning electron microscopy, nitrogen adsorption, and thermogravimetric analysis. Moreover, the composites are tested for the adsorption of nickel (II) ions from aqueous solutions. The novel Lead tree wood-zeolite NaY composite has the potential as an adsorbent which could be separated easily from the liquid media.

Comparison of visibility of iodinated hydrogel and gadolinium-modified hyaluronic acid spacer gels on computed tomography and onboard imaging.

Background and purposeIn accelerated partial breast irradiation (APBI), accurate definition of the tumour bed is crucial to reduce the risk of local recurrence and the volume of healthy tissue irradiated. Recently, hydrogels have been proposed to improve visibility of the lumpectomy cavity for APBI. The aim of this study was to alter two commercially available hyaluronic acid (HA) gels, with gadopentenate dimeglumine (GD), a magnetic resonance imaging (MRI) contrast agent. We hypothesize that after injection in the surgical cavity, the mixtures will be visible with computed tomography (CT) for improved treatment planning, cone-beam CT (CBCT) for improved patient setup and planar kilovoltage (kV) x-ray for real-time tracking during treatment.Materials and methodsIn this ex vivo study, GD was mixed with the two HA gels, and 1 mL of each mixture was injected into fatty and muscular tissue of a pork phantom. Visibility with CT, CBCT and planar x-ray imaging was assessed. Contrast-to-noise ratios (CNR) were measured and compared to commercially available iodinated polyethylene glycol (PEG).ResultsThe gel mixtures showed increased visibility over HA gels without GD. When comparing CNR of the gel mixtures to that of iodinated PEG on CT, there was a 4-fold increase in muscle for both mixtures and a 1.6-fold to 3.6-fold increase in fat, depending on the HA gel. Gel mixtures showed better visibility with planar kV imaging over iodinated PEG.ConclusionAddition of GD to HA gels increases visibility with CT, CBCT and planar x-ray imaging, indicating potential for improved delineation and positioning in APBI.

Thermodynamics predicts a stable microdroplet phase in polymer-gel mixtures undergoing elastic phase separation.

We study the thermodynamics of binary mixtures with the volume fraction of the minority component less than the amount required to form a flat interface and show that the surface tension dominated equilibrium phase of the mixture forms a single macroscopic droplet. Elastic interactions in gel-polymer mixtures stabilize a phase with multiple droplets. Using a mean-field free energy we compute the droplet size as a function of the interfacial tension, Flory parameter, and elastic moduli of the gel. Our results illustrate the role of elastic interactions in dictating the phase behavior of biopolymers undergoing liquid-liquid phase separation.

Intrauterine Injection of Umbilical Cord Mesenchymal Stem Cell Exosome Gel Significantly Improves the Pregnancy Rate in Thin Endometrium Rats

Human umbilical cord mesenchymal stem cell (HUMSC)-exosome gel played a significant role in promoting thin endometrial receptivity and improving the pregnancy rate by inhibiting endometrial fibrosis and accelerating subendometrial microangiogenesis. High-quality HUMSC-exosome were obtained by pretreating HUMSC with transforming growth factor-β1 (TGF-β1). Exosome gel mixture has good biocompatibility and physical rheological properties, stabilizing the structure of exosomes and prolonging the action of exosomes in the uterine cavity. HUMSC or HUMSC-derived exosomes were used to treat rat model of thin endometrium. In animal experiments, four groups, including the HUMSC, HUMSC-exosome, model (negative control), and sham operation groups, were designed. The therapeutic effects were evaluated by the thickness of the endometrium, the number of glands, the subendometrial vessel density, the markers of endometrial receptivity, and the pregnancy rate. In an in vivo study, three groups, involving HUMSC-coculture, HUMSC-exosome, and the control, were explored. The proliferation and migration of the human endometrial stromal cells (HESCs) were further determined by cell scratch and 5-ethynyl-2′-deoxyuridine (EdU) assays. The protein expression of the TGF-β1/smad2/3 signaling pathway was determined by Western blot. After treatment, the thickness of the endometrium, the number of glands, and the subendometrial microangiogenesis were obviously increased, and the level of inhibition of endometrial fibrosis, molecular markers of endometrial receptivity, and the pregnancy rate were also significantly improved. HUMSC-exosome and HUMSC significantly promoted the migration and proliferation of HESCs. And it was confirmed that HUMSC-exosome were superior to HUMSC in inhibiting HESCs fibrosis through TGF-β1/smad2/3 signaling pathway at the protein expression level.

Abstract 12597: Phenotypic Drug Screen Reveals That Lacidipine, a Calcium Channel Blocker, Enhances the Vascular Lumen Formation

Background: Vascular lumen formation is a critical process of angiogenesis towards establishing a functional circulatory system capable of delivering oxygen and nutrients to tissues. Targeting lumen formation is required for the development of efficient therapeutic angiogenesis. Objective: Perform a drug screen to identify compounds regulating the vascular lumen formation using a novel 2D angiogenesis assay that mimics the lumen formation of blood vessels and suitable for high throughput applications. Methods and Results: First, we optimized the phenotypic angiogenesis assay that captures the cellular process of lumen formation. Human Umbilical Vein Endothelial Cells (HUVEC) were seeded on Matrigel-coated wells. A mixture of matrix gel was added on top of adhered HUVEC. HUVECs form luminized vascular-like structures in 48 hours. To identify modulators of lumen formation, we conducted a high content screen of a library containing 150 FDA-approved cardiovascular drugs. The screening resulted in five calcium channel blockers being able to increase the lumen area compared to controls. Lacidipine was selected for further mechanistic studies. We found the cells in the luminal space stained positively for activated caspase-3 at 24 hours using immunofluorescence. Pharmacological inhibition of RAC1 or caspase activity abolished the Lacidipine-enhancing effect on lumen formation, suggesting the involvement of apoptosis and cell polarization. Next, we found that the addition of ML7, an MLCK inhibitor, enhances the lumen formation by inducing apoptosis. In contrast, the addition of the ROCK inhibitor GSK429286 or blebbistatin, an inhibitor of non-muscle myosin II ATPase, did not affect the lumen formation. Using a Ca2+ biosensor imaging, Lacipidine reduces the intracellular Ca2+ oscillations amplitude in the migrating cells at the early stage (6 hours), whereas Lacidipine blocked these Ca2+ oscillations completely at the late stages (24-48 hours). Conclusions: This study highlights a novel high throughput phenotypic assay to evaluate vascular lumen formation. Our findings suggest that calcium signaling plays a vital role during lumen morphogenesis, and calcium channel blockers could be used for more efficient angiogenesis-mediated therapies.

Hydrate‐Based CO2 Capture through Nano Dry Gels + Tetrahydrofuran – A Kinetic and Thermodynamic Study

AbstractThe synergic effects of four combinations of nano dry gels plus tetrahydrofuran (THF) on the CO2 capture and hydrate phase equilibrium were investigated. It was found that the hydrate phase equilibrium condition was almost identical with the mixture of nano dry gel + THF and THF solution. The gas storage capacity and CO2 uptake rate increased significantly by THF concentration increment up to 19.06 wt % in the dry gel structure compared to a similar THF solution. The hydrate induction time decreased at higher ratios of THF. The mixture of dry gel + THF acted as a stabilizer during the hydrate dissociation process. Considering the gas storage capacity, kinetics, and thermodynamic promoting effect, a mixture including 19.06 wt % THF was favorable for hydrate‐based CO2 capture compared to the other combinations investigated in this study.

An Overview of the Challenges and Progress of Synthesis, Characterization and Applications of Plugged SBA-15 Materials for Heterogeneous Catalysis.

A new generation of SBA-15, plugged SBA-15, was initially synthesized in 2002 using extra silica precursors (Si/organic template molar ratios ≈ 80–140) in the gel mixture. The plugged SBA-15 materials possess short cylinders (length ≈ 20–100 nm), which are connected to neighbors by constricted entrances (windows) through the central axis. The gas adsorption–desorption isotherms of plugged SBA-15 materials present unique hysteresis loop Type H5 classification identified by IUPAC in 2015, which is related to certain pore structures containing open and plugged mesopores. The plugged SBA-15 has been used to support various types of catalysts, including metal complexes, metal nanocatalysts, and active metals by the incorporation in their framework demonstrating excellent (enantio)selectivity, stability against coke, and thermal stability. The plugged SBA-15 materials bear the other unique properties of the ship-in-the-bottle synthesis of, e.g., metal complexes that confine homogeneous catalysts, which is not possible by conventional SBA-15 due to leaching. In this mini-review, the challenges and progress of the synthesis in controlling the plugging and incorporation of metals and organic moiety in their framework, characterizing the short mesochannel dimensions (window and length sizes) by several advanced techniques and applying plugged SBA-15 materials in heterogeneous catalysis for challenging reactions, has been discussed.

Local anesthetics versus systemic analgesics for reducing pain during Extracorporeal Shock Wave Lithotripsy (ESWL): A systematic review and meta-analysis.

Extracorporeal Shock Wave Lithotripsy (ESWL) is one of the treatment options for patients with renal and ureteral calculi. Even though the procedure is less invasive compared to others, pain caused by the procedure is a major concern. Several studies recommended the use of either local or systemic analgesia with varying results. We aimed to compare the use of local anesthetics and systemic analgesics from randomized controlled trials evaluating pain management during ESWL. A systematic search adhering to the Preferred Reporting Items for Systematic Review and Meta-Analysis protocol was performed in theMedline, ScienceDirect, and Cochrane library databases. The bias was evaluated using the Cochrane risk of bias tool. Mean difference (MD) was used to analyze continuous outcomes. A total of seven studies were obtained. The topical anesthesia used was eutectic mixture of local anesthetic cream and xylocaine gel. In contrast, the local injection anesthesia used was subcutaneous prilocaine and intracutaneous sterile water injection. The systemic analgesics used were intramuscular and oral forms of sodium diclofenac. There is no significant difference between the visual analogue scale results between the local and systemic groups (P> .05). The differences in ESWL frequency were also insignificant (P > .05). Additional analgesics supplementation (MD 8.44, 95% CI 2.28-14.61, P¼ .007) and the duration of the procedure (MD 1.39, 95% CI 0.21-2.56, P¼ .02) were significantly lower in the local group. Local anesthesia in ESWL shows a similar degree of pain and frequency but has a shorter duration and fewer analgesics supplementation than systemic analgesics.

Sulfate-bearing clay and Pietra Serena sludge: Raw materials for the development of alkali activated binders

The feasibility of transforming the residues of cultivation of two rocks into secondary raw materials through the alkali activation process has been assessed. Mixtures of a sulfate-bearing kaolinitic clay (L02-K) and a sludge derived by the sewing of Pietra Serena stone (sPS) have been investigated. These materials were preliminarily treated at high temperature to improve their reactivity (heat-treated samples are hereafter labelled as L02-MK and sPS-800). Pastes were prepared with mixtures of L02-MK and sPS-800 in different weight proportions by using 8 M NaOH solutions as alkaline activator and cured at 85 °C for 24 h. Mechanical strength was determined after 1, 7 and 28 days and the reaction products were characterized by XPRD, SEM/EDX and MAS-NMR. Sulfate solubility was quantified by leaching tests.The alkali activation of the sole sulfate-bearing clay gives a material with developed mechanical strength of 4(1) MPa. Some N-A-S-H gel forms together with gibbsite and thenardite, which can be easily leached. Better results are obtained by the activation of mixtures of the two precursors, and mixed alkali cements or hybrid cements are obtained. The presence of CaO from heat-treated Pietra Serena sludge improves the mechanical strength of the resulting pastes up to 11.8(9) MPa. In this case, a mixture of gels forms, specifically, a calcium-rich gel (C-A-S-H-type) co-exists with (N,C)-A-S-H-type gel. U-phase and CAN-type zeolites also form. They trap sulfate from the clay and considerably reduce sulfate solubility. In conclusion, L02-MK and sPS-800 are promising raw materials for alkaline cements, whose properties may suggest application in soil stabilization or in waste confinement.

Stability of Compounded Clozapine 25 mg/mL and 50 mg/mL Suspensions in Plastic Bottles.

Clozapine oral suspension is not commercially available in Canada but is required for administration to patients who cannot swallow intact tablets. To evaluate the stability of 25 mg/mL and 50 mg/mL clozapine suspensions prepared in a 50:50 mixture of methylcellulose gel 1% and Oral Syrup (flavoured syrup vehicle, Medisca Pharmaceutique Inc) and stored in amber glycol-modified polyethylene terephthalate (PET-G) bottles over 120 days at 4°C and 25°C. This study used a validated reverse-phase stability-indicating liquid chromatographic method capable of quantifying clozapine, 3 known degradation compounds, a known impurity, and an unknown compound. Three separate batches of 25 mg/mL and 50 mg/mL clozapine suspensions were prepared, divided into 100-mL aliquots, and stored in 120-mL PET-G bottles. Half of the bottles from each concentration were stored at room temperature (20°C to 25°C) and the other half were stored in the refrigerator (2°C to 8°C). On study days 0, 28, 60, 90, and 120, concentrations of clozapine, each of the 3 known clozapine degradation products, a known impurity, and an unknown compound were determined. When suspensions were stored in PET-G containers at room temperature or under refrigeration for 120 days, the concentration of clozapine remained above 95% of initial concentration, and the measured concentration of degradation products and impurities did not exceed the 0.5% limits set by regulatory authorities worldwide. The proportion of the initial concentration of clozapine remaining on day 120, based on fastest degradation rate with 95% confidence (1-sided), exceeded 92%, and the only degradation product found (clozapine lactam, 0.2%) and an unknown impurity (0.2%) also did not exceed allowable limits. Compounded clozapine suspensions of 25 mg/mL and 50 mg/mL can be stored in amber PET-G containers for up to 120 days after preparation with storage at room temperature or under refrigeration.

The rheological characteristics of soy protein isolate-glucose conjugate gel during simulated gastrointestinal digestion

• Gels were prepared using soy protein isolate-glucose conjugates cross-linked by transglutaminase. • The mechanical properties of gels were increased by glycation with limited reaction time. • The rheological properties of SPI-glc conjugate and mixture gels after in vitro gastrointestinal digestion have been studied. • Conjugate gels had slower gastric digestion kinetics than gel prepared by SPI-glc mixture. • There were no differences in simulated intestinal digestion among SPI-glc conjugate and mixture gels. In this study, soybean protein isolate (SPI) and glucose (glc) were conjugated by wet Maillard reaction at 95 °C for 0–6 h with a mass ratio of 1:2. The degree of grafting and SDS-PAGE of SPI-conjugates were studied and a highest degree of grafting (23.14 %) was achieved at reaction time of 4 h. Gels were then prepared by crosslinking SPI-glc mixture or conjugates using transglutaminase, and their mechanical properties were charactered by hardness and gumminess. To further study the impact of conjugation on the gastrointestinal digestion of gel, rheological properties of gels after in vitro gastric and intestinal digestions were evaluated through amplitude and frequency sweep tests. Compared with SPI and SPI-glc mixture, gels formed by conjugates with 1 h and 4 h reaction time showed significantly higher viscosity, storage modulus (G') and complex modulus (G*) values after gastric digestion, indicating that these conjugate gels had slower gastric digestion kinetics. There were no significant differences among these samples in simulated intestinal digestion. Therefore, the SPI-glc conjugate gels may have great potential to be used for gastric delivery.

Novel Colour-Based, Prototype Indicator for Use in High-Pressure Processing (HPP)

The preparation and testing of a colour-based prototype indicator for high-pressure processing (HPP) are described. The indicator is a layered structure comprising a pressed disc of a mixture of silica gel, which has been previously loaded with a set wt% of acidified water, and polytetrafluoroethylene, PTFE, powders, a water-permeable barrier layer, and a Congo-Red-based pH indicator layer, all vacuum-sealed in a water impermeable plastic film. The value of the wt% is calculated from the ratio of the mass of acidified water added to the mass of originally dry silica gel. The high pressures associated with HPP drive the release of the acidified water from the silica gel and its subsequent transport through the water-permeable barrier layer to the pH indicator, thereby producing a striking red-to-blue colour change. The response of the HPP indicator can be tuned to different HPP conditions by varying the wt% of acidified water used to load the silica gel powder. Indicators, with 61, 63, and 65 wt% acidified water loaded silica gel, are prepared and found to require, respectively, the application of at least, 600, 400, and 300 MPa pressure for 3 min to effect a change colour. To our knowledge, this is the first reported example of a prototype HPP indicator that can be tuned to respond to the very different pressure and time conditions used in HPP to sterilise such very different products as milk, apple and orange juice, and aloe vera gel.

Synthesis of amorphous nano-silica from recycled concrete fines by two-step wet carbonation

In this work, a two-step wet carbonation process was developed to synthesize amorphous nano-silica by extracting the silicon phase from recycled cement fines (RCF), aiming to convert RCF into value-added products and sequester CO2. The phases evolution and their microstructure during carbonation were investigated. The results indicated that the RCF was carbonated rapidly to form a mixture of calcite and amorphous silica gel, followed by the formation of silica bearing gel containing aluminosilicate gel and silica gel after two-step wet carbonation. An amorphous silica with a purity of 98.8% and in the form of aggregated nanoparticles (<10 nm) was successfully prepared, and another calcium carbonate-rich material was produced as a by-product. The proposed approach tackled several issues such as sequestration of CO2 (0.27 g CO2 per 1 g RCF), converting RCF into value-added nano-silica and promoting the recycling of RCF, which has good potential to be industrialized.

Modulating storage stability of binary gel by adjusting the ratios of starch and kappa-carrageenan

This study aimed to investigate the interaction mechanism of the waxy starch and kappa carrageenan (KC) gel with different ratios during co-gelatinization and storage. Water distributions, mobilities and rheological properties of the mixture gels were studied. When KC concentration was low (0.5%KC and 4% starch), the starch dominated the system, and the gel strength was the lowest. When KC concentration increased to 0.75%, the gel had the lowest change rate of fracture force, and the most homogeneous network of the freeze-dried gel was observed. When KC concentration increased to 1.0%, the gel strength was high, but the uneven structure led to the instability of the gel. Overall, the gel with 0.75%KC and 4% starch was the most stable during storage, and the exclusion of the two components to each other was the weakest, resulting in the uniform structure of the gel.

Evaluation of Acellular Dermal Matrix (ADM) as a Scaffold for Adipose-Derived Stem Cell Transfer in the Rat Model.

BACKGROUNDThis study was designed for the evaluation of Acellular Dermal Matrix (ADM) as a scaffold for adipose-derived stem cell transferring in the rat model. METHODSThis experimental study was done in the Burn Research Center of Iran University of Medical Sciences and Bonyakhteh Research Center, Tehran, Iran according to the standards of laboratory animals. Overall, 26 healthy Sprague-Dawley rats were used. Two of them were used to prepare ADM. In group one, the first wound on each, rat was spread with the mixture of fibrin gel and autologous stem cell. Only the stem cells combined with fibrinogen were spread on the other wound. In group two, the first wound on each rat was covered only with ADM, and the second wound was covered with gauze Vaseline. To perform sampling we used observation and photography at 7-30 days. Overall, 48 samples were taken of all the rats using skin punch biopsy on the 30th day for histopathology evaluation.RESULTSThere were significant differences in each group; however, the difference between different groups on days was not significant. In pathology, epithelialization, vascularization, the amount of collagen, collagen arrangement, the number of fibroblasts, and inflammation indices were investigated. The total score in each group was used for analysis. In statistical analysis, there was no pathology score difference among groups.CONCLUSION Using stem cells with or without ADM could not enhance the process of wound healing or improve pathology indices.

Preparation and gelation behaviors of poly(2-oxazoline)-grafted chitin nanofibers

Based on our previous work on successful gelation of poly(2-methyl-2-oxazoline)-grafted chitin nanofibers (ChNFs) with high polar media, in this study, we investigated the preparation and gelation behaviors of the ChNFs having different poly(2-alkyl-2-oxazoline) graft chains, that is, poly(2-methyl-2-oxazoline), poly(2-isopropyl-2-oxazoline), and poly(2-butyl-2-oxazoline), with various disperse media. The grafting was carried out by reactions of living propagating ends of poly(2-alkyl-2-oxazoline)s with amino groups present on the self-assembled ChNFs, which were obtained from a chitin ion gel. The products formed gels in the reaction mixtures, which could be converted into hydrogels. All the products with the three poly(2-alkyl-2-oxazoline) graft chains formed gels with high polar media. Besides, gelation of the product with poly(2-butyl-2-oxazoline) was observed by immersing it in relatively non-polar media such as benzyl alcohol, ethyl acetate, and toluene. The formation process of network structures by the grafting of poly(2-alkyl-2-oxazoline)s on ChNFs is proposed to induce gelation of the products.

Numerical study of polymer-ablation arc with polyacrylic acid + H2O mixture

As described in this paper, we proposed the adoption of polyacrylic acid (PAA) with H2O, which becomes PAA + H2O mixture gel, as an ablation medium for arc quenching in a low-voltage DC circuit breaker. It is well known that H2O is a highly arc-quenching medium, but it has been difficult to use H2O in liquid phase directly as an arc-quenching medium. The arc performance of PAA + H2O mixture gel was studied using numerical and experimental approaches. Numerical thermofluid simulation was conducted to obtain the arc temperature and gas flow distribution at different H2O mixing ratios in PAA + H2O gel. To consider ablation of PAA + H2O gel, a method of alternately arranging PAA and H2O in the ablation wall was also proposed. Calculation results demonstrate that increasing the H2O mixing ratio in PAA + H2O mixture gel makes the arc narrower in the temperature and electrical conductivity distributions. The experimentally obtained results also indicate that arcs confined in PAA + H2O mixture gel with higher H2O mixture become narrower than those in PAA or other materials. Moreover, arcs confined by PAA + H2O mixture gel with higher H2O mixing ratio enhance the arc resistance rapidly. The results suggest that PAA + H2O mixture gel can have higher arc-quenching performance than pure polymers.

New approaches to reduce sample processing times for the determination of polycyclic aromatic compounds in environmental samples

This study validates two approaches to streamlining the processing of sediment and biota for a suite of polycyclic aromatic compounds (PACs) with a wide range of chemical properties, including polycyclic aromatic hydrocarbons (PAHs) and alkyl-PAHs (APAHs), and a new class of environmental contaminants, halogenated PAHs (HPAHs). One method is based on one-step in situ extraction/cleanup using accelerated solvent extraction (ASE) in which a mixture of copper, deactivated alumina and silica gel were added directly to the ASE cell along with sample; the second technique is based on dispersive solid phase extraction (dSPE) using alumina/silica for cleanup of biota samples to augment conventional ASE extraction combined with gel permeation chromatography. Validation protocols were performed in accordance with the ISO/IEC 17025 guidelines, whereby method performance characteristics, i.e., accuracy, precision, linearity, limits of detection and ruggedness, were evaluated. Accuracies generally ranged from 70 to 120% for the in situ ASE method and 70–100% for the dSPE technique. Limits of detection/quantitation for the 45 target analytes for in situ ASE and dSPE methods were determined to be < 2.5/8 pg μL−1, and < 20/60 pg μL−1, respectively. Intra- and inter-day repeatability for both methods were < 25% except for 1 APAH which had an inter-day precision of 35% using the dSPE method. Neither method was affected by any of the purposeful changes attempted which implies that both methods are robust. Results of our validation studies showed excellent data quality for both methods in addition to achieving a reduction in sample processing times.

Treatment of Agate Dyeing Wastewater Using an Immobilized Gel Mixture with Nano-Fe3O4 Sulfate-Reducing Bacteria

To solve the problems of high Cr6+, Cr3+, SO42– and H+ concentrations, pollution and processing costs associated with agate dyeing industrial drainage, we prepared an immobilized gel mixture for the treatment of such drainage on the basis of microbial immobilization technology. The immobilized gel mixture was composed of sulfate-reducing bacteria (SRB), corn cob, and nano-Fe3O4 (nFe3O4). We used a single-factor experiment to determine the optimal dose of each matrix component. We analyzed the mechanism underlying the treatment of agate dyeing wastewater with an immobilized gel mixture by X-ray diffraction and scanning electron microscopy detection. The results of the single-factor test showed that the best treatment was obtained under the following conditions for each matrix component: SRB mass percentage of 30%, nFe3O4 dose of 3%, and corn cob mesh size of 100 and dose of 3%. On this basis, we conducted an L9(34 ) orthogonal experiment to determine the optimal proportion of each matrix component. The results showed that the best treatment was obtained when the gel mixture met the following conditions: SRB mass percentage of 40%, nFe3O4 dose of 4%, and corn cob dose of 1% and mesh size of 100. Accordingly, the SO42– , Cr6+ and Cr3+ removal rates from the agate dyeing drainage were 70.54%, 84.75%, and 73.80%, respectively; the total Fe and chemical oxygen demand releases were 1.086 mg·L–1 and 1104 mg·L–1 , respectively; and the pH was 6.27. The gel mixture had the best treatment effect on agate dyeing wastewater under this composition ratio.

Quantitative Correlation between the Degree of Reaction and Compressive Strength of Metakaolin-Based Geopolymers.

For geopolymers (usually composed of unreacted precursor and gel), the compressive strength is controlled by two factors. The first is the degree of reaction, or, equivalently, the amount of gel formed, including any calcium silicate hydrate gel in calcium-containing mixtures. The second factor is the gel composition, generally given by the Si/Al ratio. These two parameters are interrelated for typical silicate-activated metakaolin geopolymers. By separating out effects of Si/Al ratio and degree of reaction, this study quantitatively correlates the degree of reaction with the compressive strength of metakaolin-based geopolymers with and without calcium. Solid-state 29Si nuclear magnetic resonance (NMR) aided with chemical extractions was used to determine gel amounts and composition for several geopolymer mixtures. The compressive strength was also measured for each mixture at 7 days. Both the increase of Na/Al ratio in mixtures without calcium and addition of external calcium increased the degree of reaction, and compressive strength correlated linearly (R2 > 0.88) with the degree of reaction.