Weak Alkaline Research Articles

An Ultra‐Small Osmium Clusters‐Loaded Organosilica‐Based Antibacterial Nanoagent for Efficient Infected‐Wound Healing

AbstractRecently, nanomaterials with natural enzymatic activity and photothermal effect offer an alternative pathway to combat bacterial infections and the abuse of antibiotics. Unfortunately, the development of these reported antibacterial nanoagents is always hampered by insufficient enzymatic activity and low photothermal conversion efficiency. To address these issues, herein, novel ultra‐small osmium clusters‐loaded F127‐organosilica micelles (Os@FOMs) are developed as antibacterial nanoagents for efficient infected‐wound healing. The preparation of nanoagents mainly involves the confined sol‐gel transition of thiol‐containing silane coupling agent in the hydrophobic region of F127 micelles and subsequent self‐reduction process of osmium salt in the thiols/disulfides‐doped organosilica framework. As a promising candidate for bacterial‐infected wound healing, Os@FOMs exhibit not only high photothermal conversion efficiency of 70% under 808 nm near infrared (NIR) irradiation, but also display peroxidase (POD)‐like activity in acidic conditions, which together contribute excellent antibacterial ability in acidic bacterial infectious microenvironment. On the other hand, Os@FOMs possess good catalase‐like effect in neutral or weak alkaline conditions, thus protecting normal tissues from the POD‐like protocol with exogenous H2O2 damage for efficient wound healing. It is highly expected that the new noble metal@organosilica‐based nanoagents present a promising paradigm to fight antibiotic‐resistant pathogens.

A Red-Emitting Fluorescence Probe for Rapid Detecting Exogenous and Endogenous Peroxynitrite in Living Cells with High Sensitivity and Selectivity

Peroxynitrite (ONOO−) has been revealed to play crucial roles in many physiological and pathological processes, and many diseases were proven to be associated with its misregulated production. The development of fluorescent probes meets the need for tracking ONOO− and gives a better understanding of its diverse mechanisms. In this work, a red-emitting fluorescent probe BP-ONOO was synthesized via functionalization of the rhodol-like fluorophore with a reactive site of hydrazide. The probe BP-ONOO exhibited high sensitivity, excellent selectivity, and short response time (less than 4 s) towards ONOO− under neutral or weak alkaline conditions. These attractive properties favor its application in real-time imaging of ONOO− in living cells, and the probe has been successfully applied for imaging the concentration levels of ONOO− in RAW 264.7 macrophage cells under drug stimulation.

Valorization of calcium hypochlorite precipitate as a new source of heterogeneous catalyst development for biodiesel production: A preliminary experiment

One of the main problem related with liquid bleach production from calcium hypochlorite is the amount of precipitates generated and its consequent management. As a result, academic and industrial communities have been challenged with searching of a means for its valorization. Therefore, this research explores the application of the precipitate as a viable source of Ca-based heterogeneous catalyst development for the production of waste cooking oil methyl esters for the first-time. The catalyst was prepared by dividing the precipitates into three forms, viz. raw untreated (RC), heat treated (RC-TB), and NaOH impregnated plus thermally activated (RC-ITB). The prepared catalysts were efficiently characterized by XRF, XRD, FTIR, SEM, and BET techniques. The characterization results indicated that the catalysts are mainly composed of calcium metal in the form of oxides (CaO), calcite (CaCO3) and Portlandite (Ca(OH)2), which are the promising constituents of basic catalysts. The BET inspection of RC, RC-TB, and RC-ITB revealed the specific surface area of 8.509, 9.089, and 9.312 m2/g, respectively. At the same reaction conditions, the maximum biodiesel yield of 76.05 % was achieved by RC-ITB compared to RC-TB (62.57 %) and RC (19.74 %), because it's larger specific surface area and highest basic nature (pH = 12.65 at 1:5 w/v) improves the reaction catalysis through better catalyst-substrates interactions. The lower biodiesel yield was attained through the RC catalyst due to its untreated surface, lower specific area, and weak alkaline nature (pH value = 10.66 at 1:5 w/v). Furthermore, regardless of the amount of yield, almost similar fuel properties and functional groups of the products over the coded catalysts were observed. Generally, the possibility of calcium hypochlorite precipitate as a precursor of Ca-based heterogeneous catalyst has been effectively proven in this research, which could be very important for environmental safety and industrial resource integration.

Optimization of the in vitro biodegradability, cytocompatibility, and wear resistance of the AZ31B alloy by micro-arc oxidation coatings doped with zinc phosphate

As implanted bone fixation materials, magnesium (Mg) alloys have significant advantages because the density and elastic modulus are closest to those of the human bone and they can bio-degrade in the physiological environment. However, Mg alloys degrade too rapidly and uncontrollably thus hampering clinical adoption. In this study, a highly corrosion-resistant zinc-phosphate-doped micro-arc oxidation (MAO) coating is prepared on the AZ31B alloy, and the degradation process is assessed in vitro. With increasing zinc phosphate concentrations, both the corrosion potentials and charge transfer resistance of the AZ31B alloy coated with MAO coatings increase gradually, while the corrosion current densities diminish gradually. Immersion tests in the simulated body fluid (SBF) reveal that the increased zinc phosphate concentration in MAO coating decreases the degradation rate, consequently reducing the release rates of Mg2+ and OH– in the physiological micro-environment, which obtains the lowest weight loss of only 5.22% after immersion for 56 days. Effective regulation of degradation provides a weak alkaline environment that is suitable for long-term cell growth and subsequent promotion of bone proliferation, differentiation, mineralization, and cytocompatibility. In addition, the zinc-phosphate-doped MAO coatings show an improved wear resistance as manifested by a wear rate of only 3.81 × 10–5 mm3 N–1 m–1. The results reveal a suitable strategy to improve the properties of biodegradable Mg alloys to balance tissue healing with mechanical degradation.

Interactive Effects of Inorganic–Organic Compounds on Passivation of Cadmium in Weakly Alkaline Soil

The availability of cadmium (Cd) in soils is an important factor affecting the safe production of crops. The application of certain soil amendments could reduce the soil Cd availability via the passivation of Cd. However, the passivation of Cd in alkaline soils is limited. Thus, different inorganic and organic amendments and their compound treatments were selected as passivators for reducing the Cd availability in a weakly alkaline farmland soil. The effects of different single and compound amendments on the soil pH and Cd availability, as well as the interactions between inorganic and organic components in immobilizing Cd, were evaluated. The results showed that the inorganic–organic compound amendments can considerably improve the Cd passivation efficiency in the weakly alkaline soil. Moreover, the inorganic and organic components in the compound amendments exerted different synergistic effects in Cd passivation. The manganese dioxide-based compound amendments showed the most remarkable synergistic effects, while the calcium–magnesium–phosphate fertilizer-based compound amendments displayed the weakest synergistic effects. The underlying mechanisms regarding the synergistic effects may be that the compound amendments enhanced the adsorption/specific adsorption, co-precipitation, and surface complexation of Cd in the alkaline soil. A more balanced recommendation for Cd immobilization in the weakly alkaline soil may be manganese dioxide-based compound amendments, given the synergistic effects and Cd immobilization capabilities of various compound materials. This study may provide a theoretical foundation for the passivation remediation of alkaline Cd-contaminated farmland soils by using inorganic–organic compound amendments.

Efficient and Selective Recovery of Gold from Thiosulfate Leaching Solution Using Functionalized β‐Cyclodextrins Synthesized by a Steric Hindrance Strategy

AbstractDesigning suitable adsorbents is a key challenge in the recovery of Au(I) from thiosulfate gold‐leaching solutions as the ideal adsorbent not only possesses abundant active sites with high affinities and selectivities toward Au(I), but also demonstrates fast recovery of Au(I) at high purity and large capacity. Herein, guided by theoretical calculations, a water‐insoluble inclusion complex is synthesized using β‐cyclodextrin (β‐CD) and diphenylphosphine (DPP) as host and guest molecules, respectively, by a steric hindrance strategy for highly efficient and selective Au(I) recovery. The prepared β‐CD@DPP exhibits outstanding Au(I) adsorption performance, with a saturated loading capacity of 146.28 mg g−1. The excellent adsorption performance of β‐CD@DPP for Au(I) is mainly attributed to the full exposure of the adsorption site and the weakly alkaline adsorption environment. Furthermore, β‐CD@DPP demonstrates outstanding selectivity for Au(I) in a Cu─NH3─thiosulfate gold‐leaching solution, and the Au(I) recovery rate is higher than 99%. Synthesis of β‐CD@DPP primarily depends on the weak interactions between DPP and β‐CD. Mechanism of adsorption of Au(I) on β‐CD@DPP involves ligand exchange between PPh2− and [Au(S2O3)2]3−. This study provides a new idea and material preparation method for highly efficient, selective, and large‐capacity recovery of Au(I) from thiosulfate leaching solution.

Preparation and performance testing of clad aluminum pigments

The organic pigment permanent red F3RK was precipitated on the surface of aluminum pigment by precipitating agent BaCl2·2H2O, and then carbon black was added to produce the organic pigment with metallic luster and strong covering power, and the performance of the coated aluminum pigment was analyzed by testing. Experiments show that the organic pigment firstly forms a uniform and dense coating layer on the surface of aluminum pigment, and the amount of hydrogen precipitation is stable at 30 mL after 48 h compared with that of unwrapped aluminum pigment under the weak alkaline environment of 40 °C, pH = 9. Test analysis showed that F3RK was oxidized and condensed during the reaction process, and bonded to the surface of the aluminum pigment, introducing new amino groups, attached to the surface of the aluminum pigment, and possessing better alkali resistance.

Dextranase Production Using Marine Microbacterium sp. XD05 and Its Application.

Dextranase, also known as glucanase, is a hydrolase enzyme that cleaves α-1,6 glycosidic bonds. In this study, a dextranase-producing strain was isolated from water samples of the Qingdao Sea and identified as Microbacterium sp. This strain was further evaluated for growth conditions, enzyme-producing conditions, enzymatic properties, and hydrolysates. Yeast extract and sodium chloride were found to be the most suitable carbon and nitrogen sources for strain growth, while sucrose and ammonium sodium were found to be suitable carbon and nitrogen sources for fermentation. The optimal pH was 7.5, with a culture temperature of 40 °C and a culture time of 48 h. Dextranase produced by strain XD05 showed good thermal stability at 40 °C by retaining more than 70% relative enzyme activity. The pH stability of the enzyme was better under a weak alkaline condition (pH 6.0-8.0). The addition of NH4+ increased dextranase activity, while Co2+ and Mn2+ had slight inhibitory effects on dextranase activity. In addition, high-performance liquid chromatography showed that dextran is mainly hydrolyzed to maltoheptanose, maltohexanose, maltopentose, and maltootriose. Moreover, it can form corn porous starch. Dextranase can be used in various fields, such as food, medicine, chemical industry, cosmetics, and agriculture.

Investigation of the Degradation Mechanism of the Tensile Mechanical Properties of Sandstone under the Corrosion of Various pH Solutions.

The research aimed to examine the impact of different pH solutions on the tensile mechanical properties of saturated and natural sandstone specimens. The study utilized the WHY-300/10 microcomputer-controlled pressure testing machine to conduct Brazil splitting tests and employed acoustic emission and local dynamic strain testing techniques. The results indicated the tensile strength and split tensile modulus of the sandstone specimens gradually decreased with the polarisation of the solution pH, and the acoustic emission signal ring number monitoring values showed an increasing trend. The pH of the soaking solution followed an exponential decay pattern over time, eventually tending towards weak alkalinity. A new damage variable based on the cumulative ring count after chemical corrosion was defined to indirectly analyze the degree of corrosion degradation. It was discovered that in acidic or alkaline environments, the internal crystals of the rock are dissolved, weakening the mineral interconnections and causing a deterioration in tensile stress and strength. These findings can provide valuable insights for ensuring the safety and stability of the Denglou Mountain Tunnel in Yunnan Province.

Biomimetic hydrophilic modification of poly (vinylidene fluoride) membrane for efficient oil-in-water emulsions separation

Membrane separation is one of the simple and efficient methods for treating oily wastewater. To improve the efficiency of oil-in-water emulsion separation, alkali treatment was used to promote the deposition of Fe (III) on poly (vinylidene fluoride) (PVDF) membranes, and the tannic acid (TA)-glutathione (GSH) hydrophilic coating was produced on the membrane surface by biomimetic coating method under weak alkaline conditions. The PVDF membrane with hydrophilic coating and multi-layered surface structure showed hydrophilic/ underwater superoleophobic. Meanwhile, the permeability and antifouling properties were significantly enhanced. According to the experimental results, the optimized modified membrane (MF-3) had excellent pure water flux (3368.0 ± 94.2 L·m−2·h−1), and oil rejection was 99.3 ± 0.2 % for toluene-in-water emulsion. In addition, after simulated fouling and regeneration by bovine serum albumin (BSA) solution, the flux recovery rate reached 97.0 %. Excellent underwater anti-oil adhesion and antifouling properties help maintain high separation efficiency during multiple filtration cycles. The chemical stability of the modified membranes was demonstrated after 7 d immersion in acid, alkali, and salt solutions, respectively. The superior performances of the membrane are attributed to the constructed hydrophilic coating. This environmentally friendly PVDF membrane modification strategy has great potential for application in oil-in-water emulsion separation and provides a reliable solution for sustainable development.

Fabricating oleic acid-ovalbumin complexes using an ultrasonic-coupled weakly alkaline pH technique: Improving the dispersibility, stability, and bioaccessibility of lutein in water

This study constructed a self-assembly non-covalent oleic acid (OA) and ovalbumin (OVA) complex via an ultrasonic coupled pH-driven approach to simultaneously improve the water dispersibility, stability, and bioaccessibility of lutein (LUT). The results showed that homogeneous, stable hydrophilic OA-OVA particles were obtained in optimized conditions (an OVA concentration of 4.0 mg/mL, pH 9.0, ultrasonic conditions of 200 W for 2 min, and OA-OVA molar ratios of 2:1–20:1), with the LUT encapsulation efficiency (EE) exceeding 88.9%. Furthermore, Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM) confirmed complete LUT encapsulation in the OA-OVA particles, displaying spherical particle formation with smooth surfaces. The OA-OVA complexes effectively improved the thermal and storage stability of LUT and significantly enhanced its bioaccessibility. These findings suggest that fatty acid-protein complexes may have potential application value as carotenoid delivery vectors.

Increasing Chemotherapeutic Efficacy Using pH-Modulating and Doxorubicin-Releasing Injectable Chitosan-Poly(ethylene glycol) Hydrogels.

Modulation of pH is crucial to maintaining the chemical homeostasis of biological environments. The irregular metabolic pathways exhibited by cancer cells result in the production of acidic byproducts that are excreted and accumulate in the extracellular tumor microenvironment, reducing the pH. As a consequence of the lower pH in tumors, cancer cells increase the expression of metastatic phenotypes and chemotherapeutic resistance. A significant limitation in current cancer therapies is the inability to locally deliver chemotherapeutics, leading to significant damage to healthy cells in systemic administration. To overcome these challenges, we present an injectable chitosan-poly(ethylene glycol) hydrogel that is dual-loaded with doxorubicin and sodium bicarbonate providing alkaline buffering of extracellular acidity and simultaneous chemotherapeutic delivery to increase chemotherapeutic efficacy. We conducted in vitro studies of weak base chemotherapeutic and alkaline buffer release from the hydrogel. The release of doxorubicin from hydrogels increased in a low-pH environment and was dependent on the encapsulated sodium bicarbonate concentration. We investigated the influence of pH on the doxorubicin efficacy and viability of MCF-7 and MDA-MB-231 breast cancer cell lines. The results show a 2- to 3-fold increase in IC50 values from neutral pH to low pH, showing decreased cancer cell viability at neutral pH as compared to acidic pH. The IC50 results were shown to correlate with a decrease in intracellular uptake of doxorubicin at low pH. The proposed hydrogels were confirmed to be nontoxic to healthy MCF-10A mammary epithelial cells. Rheological studies were performed to verify that the dual-loaded hydrogels were injectable. The mechanical and release properties of the hydrogels were maintained after extended storage. The chemotherapeutic activity of doxorubicin was evaluated in the presence of the proposed pH-regulating hydrogels. The findings suggest a promising nontoxic, biodegradable hydrogel buffer delivery system that can achieve two simultaneous important goals of local acidosis neutralization and chemotherapeutic release.

Iron plaque formation and its influences on the properties of polyethylene plastic surfaces in coastal wetlands: Abiotic factors and bacterial community

Iron (Fe) plaques in coastal wetlands are widely recognized because of their strong adsorption affinity for natural particles, but their interaction behaviors and mechanisms with plastics remain unknown. Through laboratory incubation experiments, paired with multiple characterization methods and microbial analysis, this work focused on the characteristics of Fe plaques on low-density polyethylene plastic surfaces and their relationship with environmental factors in coastal wetlands (Mangrove and Spartina alterniflora soil). The results showed that iron plaques increased the adhesive force of the plastic surface from 65.25 to 300 nN and promoted the oxidation of the plastic surface. Fe plaque formation was stimulated by salinity, anaerobic conditions, natural organic matter, and a weak alkaline scenario (pH 8.0–8.3). The Fe content showed a stable positive correlation with heavy metals loading (i.e., As, Mn, Co, Cr, Pb, and Zn). Furthermore, we revealed that Fe plaque was positively regulated by Nitrospirae through 16S rRNA high-throughput sequencing analysis. Meanwhile, Verrucomicrobia and Kiritimatiellaeota. may act as depressants by consuming salt. This work illustrated that iron plaques could enhance the role of plastics in contaminant migration by altering their adsorption performance, providing new insights into plastic interface behavior and potential ecological effects in coastal wetlands.

Preparation and Degradation Performance Study of P(AM/GG/PEGDA) Nanocomposite Self-Degradation Gel Plugging Material.

Lost circulation is a world-class problem, and the contradiction between plugging and unplugging in reservoirs is a problem that needs to be solved urgently. The traditional LCM is not suitable for reservoirs and the complex subsequent operations. Currently, a self-degrading plugging material is proposed. In this paper, a new self-degradation plugging material, CKS-DPPG, was prepared by AM, GG, nano silica, and PEGDA. The effects of reactant concentration, pH, mineralization, etc., on the swelling and degradation performance of CKS-DPPG were investigated. The plugging capacity was tested by fracture plugging equipment, and the mechanism of self-degradation was revealed. The results show that the CKS-DPPG reached a 50% degradation rate in 54 h and complete degradation in 106 h at 80 °C and pH = 8. Low temperatures, high mineralization, and weak alkaline conditions prolong the complete degradation time of CKS-DPPG, which facilitates subsequent operations. The simulation of the 3 mm opening fracture plugging experiment showed that the pressure-bearing capacity reached 6.85 MPa and that a 0.16 MPa pressure difference could unplug after degradation. The ester bond of PEGDA is hydrolyzed under high-temperature conditions, and the spatial three-dimensional structure of CKS-DPPG becomes linear. The CKS-DPPG can effectively reduce subsequent unplugging operations and lower production costs.

Hydrogen production from Al catalytic hydrolysis using highly active Nano composite CaO-AlOOH/Graphene oxide (GO) catalysts derived from eggshell and cauliflower stems

The hydrolysis of lightweight Al-based materials to produce hydrogen is a promising technology for compact hydrogen fuel cell production. However, developing nanostructures on a wide scale and at a low cost remains a major challenge. Herein, the high catalytic effect of CaO-γ-AlOOH/Graphene Oxide (GO) Nanocomposites (NCs) catalyst for hydrogen generation from Al and H2O reaction is discussed. These γ-phase aluminum oxyhydroxide Nanorods (NRs) (γ-AlOOH) on GO were synthesized through a simple hydrothermal method. High crystalline CaO-γ-AlOOH/GO NCs prepared bya mechanical grainingwithCaO nanoparticles (NPs). Experimental results show that small amounts of GO and CaO composite into γ-AlOOH NRs have high catalytic performance on the Al/H2O reaction for hydrogen generation at 25℃. In the catalysis process, the presence of oxygen on the catalyst surface promotes the formation of hydroxyl groups through a chemisorption process, further enhancing the catalytic activity. Because of high OH– concentrations in the local domain with a rise in the amount of Al(OH)3 precipitate byproduct, Al corrodes quickly and totally in a weak alkaline solution (pH < 8) after several contributions of Al batches. Accordingly, this research developed an excellent prediction for considering the Al reaction rate with H2O using CaO and/or GO composite crystalline γ-AlOOH catalyst.

Surface Interaction Effect and Mechanism of Methionine Derivatives as Novel Inhibitors for Alkaline Copper CMP: Insights from Molecular Simulation and Experimental Analysis

To prevent excessive corrosion caused by the slurry in the copper (Cu) chemical mechanical polishing (CMP) process, a corrosion inhibitor is normally required. In this study, the methionine (Met) derivative FMOC-L-Methionine (Fmoc-Met-OH) was explored as a corrosion inhibitor for Cu film CMP in weak alkaline conditions (pH = 8.5). A comprehensive evaluation was conducted to confirm the efficiency of Fmoc-Met-OH as a corrosion inhibitor, combining experiments and theoretical calculations. The results showed that Fmoc-Met-OH could effectively inhibit the corrosion of Cu, with a high inhibition efficiency (IE) of 78.26% while maintaining a high removal rate (RR) of 5703 Å min−1, a low static etch rate (SER) of 676 Å min−1, and a low surface root mean square deviation (Sq) of 1.41 nm. Simultaneously, the results of X-ray photoelectron spectroscopy (XPS) tests and electrochemical analysis confirm that Fmoc-Met-OH molecules can form a dense and ordered adsorption film on the Cu surface. According to the density functional theory (DFT) calculations and molecular dynamics (MD) simulation, it was verified that Fmoc-Met-OH exhibited strong chemical adsorption on Cu substrates, as evidenced by the high binding energy (E Binding) value, low energy gap (ΔE), and radial distribution function (RDF) analysis. The findings provided theoretical evidence of the better inhibition effectiveness of Fmoc-Met-OH at a molecular or atomic level.

Environmental Effect of Al- Kut Dam on Tigris River Properties Which passed throw Wassit Province-Iraq

The physical and chemical parameters of Tigris River water at AL- Kut City have been investigated. Five stations at the river were chosen to perform the study. Monthly samples from all stations were collected during the period from January - December 2015. The result of turbidity values showed height in summer reached to 68 NTU, The decrease of turbidity and the total suspended solids was one of the positive results to the effect of AL-Kut Dam on the Tigris River after the dam. The river water was fresh with a good aerated water with height of the dissolved oxygen value has been reached to 81. 2mg/L. Over saturated Oxygen condition was noticed 878.42 mg/L but the biological demand of oxygen with variation in some values. The result of hydrogen ion concentration values on the weak alkaline side. The Higher values of total hardness were recorded 838mg/L, also the Calcium and magnesium were the main cause of hardness. The most alkaline was caused by carbonate and bicarbonate ions the sulphates were increased to 821 mg/L. The phosphate of the surface water in concentration from 0.12- 1.65 mg/L.

Survival of Bacteriophage T4 in Quasi-Pure Ionic Solutions.

The preservative qualities of individual ionic compounds impacting the infectivity of T4 virions were elucidated. T4 virions were immersed in quasi-pure ionic solutions prior to the adsorption process, and the plaque forming unit (pfu) values of these were measured following the conventional method. In neutral ionic solutions, the minimum and the optimum concentrations of preservative qualities corresponded with the results obtained from the multi-ionic media/buffers. In acid and alkali solutions, phages show tolerances at a pH range of 5-11 in multi-ionic media/buffers. T4 virions show no tolerance in quasi-pure acid, neutral, and weak alkaline conditions. The preservative quality of T4 virions increased in over 10-1 mM OH- solution, equivalent to a pH value over 10, which corresponds to the pKa of the deprotonation of the DNA bases G and T. Infectivity was lost below 10-1 mM OH- and higher than 10 mM OH-. These results imply that maintaining infectivity of a virion may need the flexibility of the intra-capsid DNA by deprotonation.

Effect of Acidified Sodium Silicate on the Flotation Separation of Microfine Apatite from Chlorite in Seawater

In this work, selective flotation separation of microfine apatite and chlorite was achieved by using sodium oleate (NaOL) as a collector with a low dosage of acidified sodium silicate (ASS) as a depressant. The optimum ratio of sodium silicate to sulfuric acid for ASS was 5:3, and a good separation effect was also achieved in the mixed ore system. Compared to the deionized water system, the ions of Na+, Ca2+ and Mg2+ in seawater adsorbed on the surfaces of apatite and chlorite, which made the zeta potential of the two minerals shift positively. This presented a challenge to the selection of reagents for mineral separation. The addition of ASS changed the pH value of the pulp from weak alkalinity caused by seawater to weak acidity, which allowed the metal ions adsorbed on the mineral surface to desorb. Meanwhile, ASS can selectively adsorb on the desorbed chlorite surface in the form of Si(OH)4, which hindered the action of NaOL, leading to the depression of chlorite. NaOL adsorbed well on the desorbed surface of apatite and increased the apatite particle size from 27 μm to 229 μm, with a hydrophobic agglomeration effect, thus enhancing the flotation of microfine apatite.

The effect of sodium citrate on the photolytic reaction of catechin following the addition of aluminum chloride under alkaline conditions

Tea has an abundance of aluminum and catechins. As a food additive, citrate is often added to tea. An aluminum ionic species, including its amphoteric Al3+, can be either neutral or negatively charged and exist as intermediates simultaneously in weak alkaline solutions. This study is undertaken to investigate the photolytic processes of 290 mg/L catechin hydrate (CH) upon the addition of 133 mg/L AlCl3 (CHA) and CHA in the presence of 294 mg/L sodium citrate dihydrate (CHAS) to determine the structural changes in catechin and analyze its photoproducts after blue light irradiation at 20 W/m2 in H2O at pH 8 (BLIH) via high-performance liquid chromatography equipped with a diode array detector and mass spectrometry (HPLC-DAD-MS) system. The photolytic effect of blue light on sodium citrate was also determined. When CH is treated with BLIH, A-type and B-type proanthocyanidin dimers, AtPA and BtPA, respectively, are formed by a photochemically driven redox reaction. Relative percentages of the resultant catechin are 46.3, 98.1, and 46.9 for CH, CHA, and CHAS, respectively, after BLIH treatment, suggesting that the photolysis of catechin after BLIH is suppressed by AlCl3 and that sodium citrate restores the process of the catechin-aluminum system under BLIH in alkaline conditions. The addition of AlCl3 reduces the generation of proanthocyanidins during the photolysis of catechin after the dimeric molecule is disconnected by AlCl3, which acts as a catalyst after BLIH. However, under the same conditions, the addition of sodium citrate inhibits the catalytic capacity of AlCl3, and more proanthocyanidins are generated by the catechin-aluminum system under BLIH. Sodium citrate features an inherent reducing potential to maintain the photostability of the catechin-aluminum system and inhibits the catalysis of aluminum ions in alkaline conditions under BLIH.