pH Of Suspension Research Articles

Application of some cationic pullulan and curdlan derivatives as flocculants in fungicides-containing wastewater purification

The ability of some cationic pullulan (TMAPx-P) and curdlan (TMAP0.4-C) derivative to remove different fungicide particles from synthetic wastewater has been studied. Commercial fungicides formulations of different type, Bordeaux mixture (BM), Dithan M45 (Dt) and Melody Compact49 WG (MC) have been used. The influence of some parameters related to the dispersion characteristics (suspension pH and salinity) and the polysaccharide derivatives (polymer dose, the ionic groups content, flexibility) on the separation process have been assessed. All the polysaccharide samples revealed a good removal efficiency (RE%) for the fungicide formulations prepared in saltless aqueous solutions, namely between 94 and 98 % for BM, 81.5–85 % for Dt, 88–91 % for MC. Slightly higher residual fungicides absorbance percent values for the suspensions prepared in the presence of salts (up to 7 %) than those prepared in water have been noticed. Less amount of BM and MC particles were removed in acidic pH than in water and basic pH, while contrary results were recorded in case of Dt ones, irrespective of the flocculant used. However, the RE% values were located between 79 % and 98 % over the entirely suspension pH investigated. Both zeta potential and floc size measurements indicated the charge patch flocculation mechanism for the fungicide particles separation.

Quality and safety of fresh Spirulina (Arthrospira platensis) maintained by bubbling plasma-activated air

Spirulina (Arthrospira platensis) is a blue-green alga valued for its protein, phycocyanin, and other bioactive compounds. However, its commercial outdoor cultivation makes it susceptible to microbial contamination, affecting both biomass productivity and quality. Additionally, most commercial Spirulina is sold in dried forms such as powder, flakes, and tablets, which can degrade these bioactive components. To address these issues, non-thermal techniques, such as cold plasma, offer a promising solution by effectively reducing microbial contamination while preserving product quality without the need for drying. This study investigated the potential of bubbling cold plasma-activated (BCPA) air through freshly grown Spirulina to reduce microbial contamination and maintain quality during storage. Spirulina grown in an outdoor paddle-wheel driven pond was harvested in paste form, resuspended in deionized water, treated with plasma-activated air and stored at 4 °C for 28 days. The treatment significantly reduced microbial contamination and maintained Spirulina biomass and pigment contents compared to untreated control. The cellular structure remained intact, and colour changes were minimal in the treated samples when compared to the controls. Moreover, the Spirulina suspension pH became acidic (pH = 4), and oxidation-reduction potential was significantly higher (>150 mV) in treated samples compared to controls throughout the storage period. The results demonstrate the potential for BCPA air to maintain the quality of fresh Spirulina. This finding may have significant applications in the Spirulina industry for offering customers fresh products rather than dried Spirulina.

Formulation and Evaluation of Glipizide-loaded Mucoadhesive Microparticle Using Salvia hispanica Seeds Mucilage as Co-polymer

Aims: Chia seed (Salvia hispanica L.) gum is a mucoadhesive, biodegradable polymer with sustained release properties. Objective: The objective of this study was to compare different formulations of glipizide-loaded microparticles using chia seed mucilage and sodium alginate, focusing on sustained release and mucoadhesive properties. Background: The present study aimed to comparatively evaluate various eco-friendly formulations of glipizide-loaded microparticles prepared using chia seed mucilage and sodium alginate. Materials and Methods: Gum was extracted from chia seeds and lyophilized, and preformulation studies were performed according to established protocols. Microparticles were formulated using the ionic gelation method, with sodium alginate as a copolymer and zinc chloride as a cross-linking agent. The prepared microparticles were evaluated using scanning electron microscopy (SEM) for size and particle aggregation, and Fourier Transform infrared spectroscopy (FTIR) for drug-polymer interaction, entrapment efficiency, swelling index, and in vitro drug release. Results: The % yield of chia seed mucilage was 27.35%. The pH of the mucilaginous suspension was 4.67 ± 0.50. The moisture content value was 14.56 % ± 0.50. The values of Carr's index and Hausner's ratio were 22.58 ± 1.89 and 1.38 ± 0.05, respectively. FTIR spectra showed no interaction between pure glipizide and chia seed mucilage, confirming no possible change in glipizide's pharmacology. SEM studies have confirmed the shape of the microparticles to be spherical, with average sizes ranging from 1235.18 ± 8.7 to 1423.25 ± 9.5 µm, and the drug entrapment efficiency ranged from 64.25 ± 2.52 to 81.82 ± 7.56%. The release of glipizide from the microparticles was sustained, and the Higuchi and Korsmeyer-Peppas models were found to be the best-fit kinetic models. Conclusion: The promising copolymer blend of chia seed mucilage and sodium alginate was used for the development of sustained-release dosage forms. A copolymer blend with a ratio of 1:1 produced glipizide-loaded microparticles with sustained release profiles and good mucoadhesive ability, along with a high percentage of drug entrapment efficiency.

A recyclable dispersant based on carbomer utilizing controllable viscosity for high-efficiency dispersion of carbon fibers

Good dispersion of carbon fibers is important for the carbon paper production, which is usually achieved using low carbon fiber concentrations and disposable dispersants. In this study, we developed carbomer as a recyclable and high-efficiency dispersant for carbon fibers. When the carbon fiber concentration was 0.1 wt%, carbon fiber suspension showed improved dispersion performance as increasing the carbomer dosage. It exhibited low Turbiscan Stability Index (TSI) of 0.41 and small change of delta backscattering between −0.5 to 0.8 % when using 0.5 wt% carbomer. However, the good dispersibility fade away when increasing the concentration of carbon fibers. Subsequently, the pH of the carbon fiber suspension was adjusted to 7.0 to improve the dispersibility by increasing the viscosity, but causing a worse flowability. Then the pH was further adjusted to 13.0 to ensure good flowability in the wet-forming process and good dispersibility at carbon fiber concentration of 0.5 wt%. More importantly, the dispersant was successfully recycled and still exhibited excellent dispersion effects for carbon fibers after 5 cycles. Notably, the high-efficiency dispersion of carbon fibers and the recyclability of dispersant were achieved simultaneously for the first time, which is suitable for the eco-friendly and sustainable production of carbon paper.

Inhibitory Effects of Surface Pre-Reacted Glass Ionomer Filler Eluate on Streptococcus mutans in the Presence of Sucrose.

The surface pre-reacted glass ionomer (S-PRG) filler is a type of bioactive functional glass that releases six different ions. This study examined the effects of the S-PRG filler eluate on Streptococcus mutans in the presence of sucrose. In a solution containing S. mutans, the concentrations of BO33-, Al3+, Sr2+, and F- were significantly higher in the presence of the S-PRG filler eluate than in its absence (p < 0.001). The concentrations of these ions further increased in the presence of sucrose. Additionally, the S-PRG filler eluate significantly reduced glucan formation by S. mutans (p < 0.001) and significantly increased the pH of the bacterial suspension (p < 0.001). Bioinformatic analyses revealed that the S-PRG filler eluate downregulated genes involved in purine biosynthesis (purC, purF, purL, purM, and purN) and upregulated genes involved in osmotic pressure (opuAa and opuAb). At a low pH (5.0), the S-PRG filler eluate completely inhibited the growth of S. mutans in the presence of sucrose and significantly increased the osmotic pressure of the bacterial suspension compared with the control (p < 0.001). These findings suggest that ions released from the S-PRG filler induce gene expression changes and exert an inhibitory effect on S. mutans in the presence of sucrose.

Microbially controlled colloidal shaping of advanced ceramics

Advanced ceramics find applications in aerospace, energy harvesting and medical technologies. Despite their unique properties, the controlled manufacturing of ceramics with complex geometries is a recurring challenge in the field. Here, a novel manufacturing platform is reported for the colloidal shaping of advanced ceramics using the metabolism of living microorganisms. In this method, bacteria are employed to change the pH of colloidal suspensions in situ, thus enabling casting and time-delayed coagulation of ceramic wet parts in complex-shaped molds. Two distinct bacteria, S. pasteurii and E. coli, are used to investigate the coagulation kinetics of the fabrication process using alumina and zirconia as representative examples of ceramic particles with distinct surface chemistries. The experimental results reveal that the metabolism of bacteria provide an effective mechanism to generate strong ceramic parts with controllable coagulation speed combined with the cost-effective recovery of the microorganisms. These unique features illustrate the potential of engineered living materials for the manufacturing of advanced ceramics.

Electroosmotic coupled with particle-assisted deep eutectic solvent flotation for the enrichment of eugenol from clove

Eugenol has many biological and pharmacological activities such as antioxidant, anticancer, anti-inflammatory, antibacterial and anesthetic.In view of its wide range of beneficial activities, it is crucial to establish a method for the separation and purification of active components from clove. In this study, an electroosmotic coupled with particle-assisted deep eutectic solvent flotation method was established for the enrichment of eugenol from clove. Ten deep eutectic solvent (DES) extraction systems based on menthol as the hydrogen bond acceptor (HBA) were screened, and butanol was determined as the hydrogen bond donor (HBD) to prepare the optimal DES as extractant for extracting eugenol. Under the optimum operating conditions including solid–liquid ratio of 1:30, flotation time of 50 min, nitrogen flow rate of 55 mL/min, salt content of 20 g, pH of the clove suspension of 5.2, applied voltage of 15 V, copper electrode at the bottom, the yield of eugenol was 45.89 ± 1.61 mg/g. Compared with other extraction methods, the extraction rate was greatly improved. The electroosmotic coupled with particle-assisted deep eutectic solvent flotation method provides a green and efficient enrichment strategy for natural product, which has broad application prospects.

Preparation of zwitterionically charged chitin nanofibers through one step chemical modification and their application for antireflective coatings

Chitin nanofibers are widely used in many fields because of their biocompatibility, renewability and excellent mechanical properties. Herein, zwitterionically charged chitin nanofibers (ZC-ChNFs) were prepared from chitin via one step chemical modification (oxalic acid pretreatment) and subsequent ultrasound treatment. Effects of pretreatment time on size of the ZC-ChNFs and pH of ZC-ChNF suspensions on the thickness, porosity, refractive index and antireflective capacity of ZC-ChNF coatings were investigated. It was found that, by adjusting pH of the ZC-ChNF suspension, porosity and refractive index of the ZC-ChNF coatings could be controlled. The ZC-ChNF coatings fabricated with smaller ZC-ChNFs had higher antireflective performance and the transmittance gain of a glass with a ZC-ChNF coating was about 3.5 % at a wavelength of 550 nm compared to the bare glass. The results of this work provide a promising pathway to fabricate antireflective coating with ZC-ChNFs just by controlling the pH of ZC-ChNF suspensions.

Structurability of microalgae, soy and pea protein for extruded high-moisture meat analogues

Despite ecological and nutritional benefits, food ingredients derived from microalgae remain a niche market. A contributing factor to this is the lack of knowledge to exploit their techno-functional properties. This research investigated the structurability of Auxenochlorella protothecoides microalgal biomass during high moisture extrusion cooking for meat analogues. The fibrous extrudate structure weakened with increasing A. protothecoides content in the recipe. To scrutinise reasons for this phenomenon, a thorough compositional comparison of microalgal biomass and conventional raw materials from soy and pea was performed. The identified macrocompositional differences were shown to exert only a minor impact on fibrous structure formation. Thus, structurability appears to be predominately influenced by protein composition, protein properties and electrolyte environment. The proteins of the analysed microalgal biomass were 20 % smaller in molecular weight, had 18–68 % higher solubility and contained 15–50 % less hydrophobic sidechains, all of which may impede protein interaction potential and thereby network formation. Additionally, the pH of microalgae suspensions was lower, which has a negative impact on disulfide bridge formation. Moreover, the analysed microalgal biomass contained considerable amounts of kosmotropic ions that stabilise individual proteins. Denaturation, pH shift, addition of cysteine, transglutaminase and polyvalent cations were proposed as measures to improve structurability of the microalgae A. protothecoides.

Modulating Nonlinear Acoustic Response of Phospholipid-Coated Microbubbles with pH for Ultrasound Imaging.

Activatable microbubble contrast agents for contrast-enhanced ultrasound have a potential role for measuring physiologic and pathologic states in deep tissues, including tumor acidosis. In this study, we describe a novel observation of increased harmonic oscillation of phosphatidylcholine microbubbles (PC-MBs) in response to lower ambient pH using a clinical ultrasound scanner. MB echogenicity and nonlinear echoes were monitored at neutral and acidic pH using B-mode and Cadence contrast pulse sequencing (CPS), a harmonic imaging technique at 7.0 and 1.5 MHz. A 3-fold increase in harmonic signal intensity was observed when the pH of PC-MB suspensions was decreased from 7.4 to 5.5 to mimic normal and pathophysiological levels that can be encountered in vivo. This pH-mediated activation is tunable based on the chemical structure and length of phospholipids composing the MB shell. It is also reliant on the presence of phosphate groups, as the use of lipids without phosphate instead of phospholipids completely abrogated this phenomenon. The increased harmonic signal likely is the result of increased MB oscillation caused by a decrease of the interfacial tension induced at a lower pH, altering the lipid conformation. While relative signal changes are interpreted clinically as mostly related to blood flow, pH effects could be significant contributors, particularly when imaging tumors. While our observation can be used clinically, it requires further research to isolate the effect of pH from other variables. These findings could pave the way toward for the development of new smart ultrasound contrast agents that expand the clinical utility of contrast-enhanced ultrasound.

Effect of Stabilized nZVI Nanoparticles on the Reduction and Immobilization of Cr in Contaminated Soil: Column Experiment and Transport Modeling.

Batch and transport experiments were used to investigate the remediation of loamy sand soil contaminated with Cr(VI) using zero-valent iron nanoparticles (nZVI) stabilized by carboxymethylcellulose (CMC-nZVI). The effect of pH, ionic strength (IS), and flow rate on the removal efficiency of Cr(VI) were investigated under equilibrium (uniform transport) and non-equilibrium (two-site sorption) transport using the Hydrus-1D model. The overall removal efficiency ranged from 70 to over 90% based on the chemical characteristics of the CMC-nZVI suspension and the transport conditions. The concentration and pH of the CMC-nZVI suspension had the most significant effect on the removal efficiency and transport of Cr(VI) in the soil. The average removal efficiency of Cr(VI) was increased from 24.1 to 75.5% when the concentration of CMC-nZVI nanoparticles was increased from 10 to 250 mg L-1, mainly because of the increased total surface area at a larger particle concentration. Batch experiments showed that the removal efficiency of Cr(VI) was much larger under acidic conditions. The average removal efficiency of Cr(VI) reached 90.1 and 60.5% at pH 5 and 7, respectively. The two-site sorption model described (r2 = 0.96-0.98) the transport of Cr(VI) in soil quite well as compared to the uniform transport model (r2 = 0.81-0.98). The average retardation of Cr(VI) was 3.51 and 1.61 at pH 5 and 7, respectively, indicating earlier arrival for the breakthrough curves and a shorter time to reach maximum relative concentration at lower pH. The methodology presented in this study, combining column experiment and modeling transport using the Hydrus-1D model, successfully assessed the removal of Cr(VI) from polluted soils, offering innovative, cost-effective, and environmentally friendly remediation methodologies.

Investigation on the early proceeding of cement hydration containing dispersed nano Calcium Silicate Hydrated (CSH) seeds

Steam curing process is a traditional method for accelerating the progression of cement hydration to satisfy the rapid development of compressive strength in precast concrete industry. However, steam curing would release significant amount of CO2 into the atmosphere. In order to avoid the serious environmental pollution caused by the steam curing process, Calcium Silicate Hydrate (CSH) dispersed by comb-like polycarboxylate superplasticizer (PCE), shorted as dispersed nano CSH seed, was utilized to promote the early cement hydration at normal temperature. This investigation aims at disclosing the hydration process of cement and the microstructure evolution of cement paste in the presence of dispersed nano CSH seed during the early stage via setting time, ultrasonic pulse velocity (UPV), compressive strength, conductivity, pH, thermogravimetric (TG), 29Si NMR and nitrogen adsorption/desorption. The results demonstrated that with the dispersed nano CSH seed increasing, the setting process of cement paste was shortened dramatically, the compressive strength and UPV of cement mortar increased significantly especially at 12 h. The variation of conductivity and pH of cement suspension indicated that the ion dissolution process was promoted by dispersed nano CSH seed, which therefore conducive to the precipitation of cement hydration products. TG curves exhibited that the formation of cement hydration products, including CH (Calcium Hydrated), AFt and CSH gel were accelerated by dispersed nano CSH seed. The 29Si NMR (Nuclear Magnetic Resonance) and nitrogen adsorption/desorption results validated that the incorporating dispersed nano CSH seed promoted considerably the polymerization of CSH gel. The aforementioned results are correlated well with the fast formation of microstructure and in turn the rapid development of compressive strength at early age.

Environmentally Friendly UV-C Excimer Light Source with Advanced Oxidation Process for Rapid Mineralization of Azo Dye in Wastewater.

Wastewater discharged from the textile industry contains approximately 15% unfixed dyes, predominantly 60-70% azo dyes. These unfixed dyes are a major environmental concern due to their persistence and potential toxicity. In this paper, an environmentally friendly mercury-free XeI* excilamp emitting 253 nm UV light is reported, and the same has been utilized for the degradation of azo dyes using the advanced oxidation process (AOP) with TiO2/H2O2. A new process is developed in which one electrode of excilamp is coated with TiO2 nanoparticles that improves the efficiency of the dye degradation. Additionally, the effects of varying TiO2 loading concentrations, XeI*-excimer light intensity, starting dye concentration, suspension pH, and H2O2 addition are examined. The outcomes of this study confirm 13 times faster degradation in XeI*-excimer/H2O2 than in XeI*-excimer/TiO2, attributed to an abundance of hydroxyl radicals generated by the modified XeI*-excimer/H2O2. Also, the degradation of RB5 in the modified XeI*-excimer/H2O2 is 2.3 times faster as compared to that of the bare electrode XeI*-excimer/H2O2. A more than 95% reduction in chemical oxygen demand has been achieved in 40 min in the case of XeI*-excimer/H2O2. In this study, a maximum energy yield of 5712 mg/kWh is reported. Furthermore, a high degree of degradation is found in the alkaline medium (pH 10). Because textile effluent is highly alkaline, this result is significant, and direct treatment of azo dyes is possible. The use of the developed source in industrial applications appears to be highly promising based on testing on a real wastewater matrix. The treated effluent has been utilized to study its reusability for agricultural purposes on the germination of radish seeds in soil, and ∼26% enhanced germination has been observed compared to dye wastewater.

Colloidal Stability of PFSA-Ionomer Dispersions Part II: Determination of Suspension pH Using Single-Ion Potential Energies.

Perfluorosulfonic acid (PFSA) ionomers serve a vital role in the performance and stability of fuel-cell catalyst layers. These properties, in turn, depend on the colloidal processing of precursor inks. To understand the colloidal structure of fuel-cell catalyst layers, we explore the aggregation of PFSA ionomers dissolved in water/alcohol solutions and relate the predicted aggregation to experimental measurements of solution pH. Not all side chains contribute to measured pH because of burying inside particle aggregates. To account for the measured degree of dissociation, a new description is developed for how PFSA aggregates interact with each other. The developed single-counterion electrostatic repulsive pair potential from Part I is incorporated into the Smoluchowski collision-based kinetics of interacting aggregates with buried side chains. We demonstrate that the surrounding solvent mixture affects the degree of aggregation as well as the pH of the system primarily through the solution dielectric permittivity, which drives the strength of the interparticle repulsive energies. Successful pH prediction of Nafion ionomer dispersions in water/n-propanol solutions validates the numerical calculations. Nafion-dispersion pH measurements serve as a surrogate for Nafion particle-size distributions. The model and framework can be leveraged to explore different ink formulations.

Isolation of Decomposing Bacteria from Humus Sample and their Application

An investigation was carried out to study the activity of decomposing bacteria on plastic and leaves. To isolate bacteria that effectively degrade waste, a sample of humus soil was collected from the ground of Shri Guru Ram Rai medical college. Three bacterial strains, namely IsoA, IsoB, and IsoC, were obtained and cultured on Nutrient agar medium (NAM). The characteristics of these strains were examined through visual observation of colonies, assessment of their cultural properties, microscopic examination, and biochemical tests for identification. A bacterial suspension was prepared to observe the impact of these bacteria on plant leaves and plastic waste. During the degradation process, noticeable changes were observed in the odour, weight, and pH of the bacterial suspension. The findings of this study suggest that beneficial bacteria can be isolated from the surrounding environment, such as humus soil, to facilitate the eco-friendly conversion of waste materials.

Benzopyrene elimination from the environment using graphitic carbon nitride-SnS nanocomposites

Benzopyrene (BaP) stands as a potent polycyclic aromatic hydrocarbon (PAH) molecule, boasting five fused aromatic rings, making its way into the human food chain through soil contamination. The persistent environmental presence of PAHs in soil, attributed to industrial exposure, is primarily due to their low molecular weight and hydrophobic nature. To preemptively address the entry of BaP into the food chain, the application of nanocomposites was identified as an effective remediation strategy. Post-synthesis, comprehensive characterization tests employing techniques such as UV-DRS, XRD, SEM-EDX, FTIR, and DLS unveiled the distinctive features of the g–C3N4–SnS nanocomposites. These nanocomposites exhibited spherical shapes embedded on layers of nanosheets, boasting particle diameters measuring 88.9 nm. Subsequent tests were conducted to assess the efficacy of eliminating benzopyrene from a combination of PAH molecules and g–C3N4–SnS nanocomposites. Varied parameters, including PAH concentration, adsorbent dosage, and suspension pH, were systematically explored. The optimized conditions for the efficient removal of BaP utilizing the g–C3N4–SnS nanocomposite involved 2 μg/mL of benzopyrene, 10 μg/mL of the nanocomposite, and a pH of 5, considering UV light as the irradiation source. The investigation into the mechanism governing BaP elimination closely aligned with batch adsorption results involved a thorough exploration of adsorption kinetics and isotherms. Photocatalytic degradation of benzopyrene was achieved, reaching a maximum of 86 % in 4 h and 36 % in 2 h, with g–C3N4–SnS nanocomposite acting as the catalyst. Further validation through HPLC data confirmed the successful removal of BaP from the soil matrix.

Evaluation of Okra Pectin from Different Genotypes as Effective Suspending Agents in Pharmaceutical Formulations

Introduction: Natural suspending agents are increasingly being investigated because of their relative non-toxicity, lesser cost, availability and biocompatibility compared to the currently utilised synthetic and semi-synthetic suspending agents. Pectin, a biopolymer found naturally in plants is gaining increased application in the pharmaceutical and biotechnology industry following its successful functional application as gelling agents, emulsifying agents and fat substitutes in the food industry. This study aimed at evaluating the suspending properties of pectin obtained from five okra (Abelmoschus esculentus L.) genotypes; PL1 (Penkrumah), PL2 (Agbagoma), PL3 (Asha), PL4 (Sengavi) and PL5 (Balabi). Materials and methods: The pectin was extracted using standard protocols and characterised by investigating properties such as degree of esterification. A 5% w/v paracetamol suspension was formulated utilising okra pectin as a suspending agent at concentrations of 0.5%, 1% and 2%w/v and compared to Tragacanth gum suspensions at the same concentrations (0.5%, 1% and 2%w/v). Results: All the extracted pectins had low degrees of esterification (?50 %). The pH, redispersibility, apparent viscosity, sedimentation rate and sedimentation volume of the formulated suspensions were investigated over a 4-week period. The suspensions were stable as evidenced by no significant (p?0.05) fluctuations in pH during the period of study. Compared to when tragacanth was used as a suspending agent, the sedimentation rates, the flow rates of suspensions and redispersibility of the paracetamol suspensions utilising okra pectin were lower while the sedimentation volumes were higher at all the concentrations utilized and met standard requirements. Conclusion: The evidence suggests that all five okra genotypes exhibit better suspending properties when compared to tragacanth gum and thus may be used as an alternative suspending agent.

Continuous ammonia synthesis from water and nitrogen via contact electrification

We synthesized ammonia (NH3) by bubbling nitrogen (N2) gas into bulk liquid water (200 mL) containing 50 mg polytetrafluoroethylene (PTFE) particles (~5 µm in diameter) suspended with the help of a surfactant (Tween 20, ~0.05 vol.%) at room temperature (25 °C). Electron spin resonance spectroscopy and density functional theory calculations reveal that water acts as the proton donor for the reduction of N2. Moreover, isotopic labeling of the N2 gas shows that it is the source of nitrogen in the ammonia. We propose a mechanism for ammonia generation based on the activation of N2 caused by electron transfer and reduction processes driven by contact electrification. We optimized the pH of the PTFE suspension at 6.5 to 7.0 and employed ultrasonic mixing. We found an ammonia production rate of ~420 μmol L-1 h-1 per gram of PTFE particles for the conditions described above. This rate did not change more than 10% over an 8-h period of sustained reaction.

Extraction of Caffeine from Spent Coffee Ground by Solid-liquid Extraction

The current research aims to utilize the spent coffee ground as a feedstock which is a waste material with a negative effect on the environment to extract natural bioactive valuable caffeine and determine the effective parameters of the extraction process efficiency in terms of caffeine concentration. The key studied parameters included extraction time 0- 150 min, temperature 25-55˚C, mixing speed (180-450 rpm), pH of suspension (4-9), and solvent type. The results of the experimental work showed that changing the pH of the suspension has a significant impact on the recovery rate of caffeine. When only water was used as a solvent, the concentration of caffeine increased from 135.061 (mg/L) to 2478.179 (mg/L) by increasing the pH of the suspension to 9. Another promising finding is that by changing the solvent type to an aqueous organic solvent, where the recovery of caffeine augmented remarkably. When 20% ethanol-water was utilized as a solvent and at the pH of 6 (the original pH) of the suspension, the concentration of obtained caffeine increased from 135 mg/L to 213 mg/L. Furthermore, increasing the ethanol percentage to 80%, rising the caffeine concentration to 464 mg/L at the same pH. adjusting the pH of the suspension to 7, resulted in rising the obtained caffeine concentration to 2386.13 mg/l with a solvent concentration of 80% ethanol.

INTERACTION OF GLYCEROL WITH ACETONE IN THE PRESENCE OF ACID-MODIFIED CLINOPTILOLITE

Despite its wide application in industry, the effective use of glycerol growing volumes is very relevant, since «technical» glycerol with an acceptably high content of main substance can become an available and promising raw material for obtaining valuable chemical compounds, in particular cyclic glycerol ketals. Glycerol reaction with acetone in the presence of acid-modified clinoptilolite (CLI) as a catalyst for formation of cyclic ketals was studied. It was found that technology of acid modification doesn’t significantly affect the acidity of catalyst. For samples prepared by first method, with increasing time of acid modification, pH suspensions increase, namely the acidity decreases. As for catalysts prepared by second method, no such tendency is observed. The influence of modification time CLI samples has different effects on activity of prepared catalysts with different diameters. For CLI with a larger diameter (dav. = 1.5 mm) a minimum of activity is observed with increasing modification time (τH), namely the dependence of glycerol conversion (ZGL) on τH is extreme. For CLI of smaller dav. (0.05 mm and 0.75 mm) change of this factor has little effect on their activity. Comparing catalysts with same τH, but different dav. and method of preparation, it can be noted that the activity of catalyst with a higher d av. is higher than in samples with less. At the same time, two catalysts of same dav. (0.05 mm), but different methods of preparation practically don’t differ in their catalytic properties. CLI belongs to sorbents with a heterogeneous porous structure, catalytic activity of which depends on acidity, pore structure, and availability for diffusion of reagents. By method of planning two series experiments, according to a complete three-factor analysis, adequate models were obtained, according to which the pH of suspension and d av. are factors that have little influence on response function – ZGL. A linear (sympathetic) dependence is observed between glycerol conversion and initial rate of its loss, which is characteristic for most «families» of studied acid-modified CLI samples.