A Hypothesis Regarding the Origin of Additional Surface Acidity in Solid Complexes with Same Metal Cations

Based on the criteria for additional surface acidity generation in composite oxides and composite fluorides proposed by Tanabe and Kemnitz et al.A hypothesis for the origin of additional surface acidity in solid composites with the same metal cations is proposed.The surface acidsites of We analyze three types of solid composite systems,that is,CrF_(3)/Cr_(2)O_(3),MgF_(2)/MgO,and ZnF_(2)/ZnO,is systematically analyzed,which agrees with experimental results.Accordingly,the origin of additional surface acidity in these solid composites is reasonably explained,and the types of acidic sites are also predicted.

The Influence of Tartaric Acid in the Silver Nanoparticle Synthesis Using Response Surface Methodology

Silver nanoparticles(AgNPs)synthesized using tartaric acid as a capping agent have a great impact on the reaction kinetics and contribute significantly to the stability of AgNPs.The protective layer formed by tartaric acid is an important factor that protects the silver surface and reduces potential cytotoxicity problems.These attributes are critical for assessing the compatibility of AgNPs with biological systems and making them suitable for drug delivery applications.The aim of this research is to conduct a comprehensive study of the effect of tartaric acid concentration,sonication time and temperature on the formation of silver nanoparticles.Using Response Surface Methodology(RSM)with Face-Centered Central Composite Design(FCCD),the optimization process identifies the most favorable synthesis conditions.UV-Vis spectrum regression analysis shows that AgNPs stabilized with tartaric acid are more stable than AgNPs without tartaric acid.This highlights the increased stability that tartaric acid provides in AgNP ssssynthesis.Particle size distribution analysis showed a multimodal distribution for AgNPs with tartaric acid and showed the smallest size peak with an average size of 20.53 nm.The second peak with increasing intensity shows a dominant average size of 108.8 nm accompanied by one standard deviation of 4.225 nm and a zeta potential of−11.08 mV.In contrast,AgNPs synthesized with polyvinylpyrrolidone(PVP)showed a unimodal particle distribution with an average particle size of 81.62 nm and a zeta potential of−2.96 mV.The more negative zeta potential of AgNP-tartaric acid indicates its increased stability.Evaluation of antibacterial activity showed that AgNPs stabilized with tartaric acid showed better performance against E.coli and B.subtilis bacteria compared with AgNPs-PVP.In summary,this study highlights the potential of tartaric acid in AgNP synthesis and suggests an avenue for the development of stable AgNPs with versatile applications.

Dynamically-evolved surface heterojunction in iridium nanocrystals boosting acidic oxygen evolution and overall water splitting

Simultaneously realizing improved activity and stability of acidic oxygen evolution reaction(OER) electrocatalysts is highly promising for developing cost-effective sustainable energy in the splitting of water technique.Herein,we report iridium nanocrystals embedded into 3D conductive clothes(Ir-NCT/CC) as a low iridium electrocatalyst realizing ultrahigh acidic OER activity and robust stability.The well-designed Ir-NCT/CC requires a low overpotential of 202 mV to reach the current density of 10 mA cm^(-2)with a high mass activity of 1754 A g^(-1).Importantly,in acidic overall water splitting,Ir-NCT/CC merely delivers a cell voltage of 1.469 V at a typical current density of 10 mA cm^(-2)and also maintains robust durability under continuous operation.We identify that a low working voltage drives the formation of a highly stable amorphous IrOxactive phase over the surface of Ir nanocrystals(surface heterojunction IrOx/Ir-NCT) during operating conditions,which contributes to an effective and durable OER process.

Separation of galena and chalcopyrite using the difference in their surface acid corrosion characteristics

Galena(PbS)and chalcopyrite(CuFeS_(2))are sulfide minerals that exhibit good floatability characteristics.Thus,efficiently separating them via common flotation is challenging.Herein,a new method of surface sulfuric acid corrosion in conjunction with flotation separation was proposed,and the efficient separation of galena and chalcopyrite was successfully realized.Contact angle test results showed a substantial decrease in surface contact angle and a selective inhibition of surface floatability for corroded galena.Meanwhile,the contact angle and floatability of corroded chalcopyrite remained almost unaffected.Scanning electron microscope results confirmed that sulfuric acid corrosion led to the formation of a dense oxide layer on the galena surface,whereas the chalcopyrite surface remained unaltered.X-ray photoelectron spectroscopy results showed that the chemical state of S^(2-)on the surface of corroded galena was oxidized to SO_(4)^(2-).A layer of hydrophilic PbSO4was formed on the surface,leading to a sharp decrease in galena floatability.Meanwhile,new hydrophobic CuS_(2),CuS,and Cu_(1-x)Fe_(1-y)S_(2-z)species exhibiting good floatability were generated on the chalcopyrite surface.Finally,theoretical analysis results were further verified by corrosion–flotation separation experiments.The galena–chalcopyrite mixture was completely separated via flotation separation under appropriate corrosion acidity,corrosion temperature,and corrosion time.A novel approach has been outlined in this study,providing potential applications in the efficient separation of refractory copper–lead sulfide ore.

Theoretical Study on Dissociation Potential Energy Surface of Peroxynitric Acid

The lowest energy structures of peroxynitric acid have been studied with B3LYP/6-311＋ G（2d,2p） method. The potential energy surfaces （PES） along the O-N and O-O bonds have been scanned at CCSD（T）/aug-cc-pVDZ level, respectively. The calculated results show that on the O-N PES, the O3-N4 bond length of the loose transition state is 2.82A^° and the corresponding energy barrier is 25.6 kcal/mol, while on the O-O PES, the loose transition state with of O2-O3 bond length of 2.35A^° has the energy barrier of 37.4 kcal/mol. Thus the primary reaction path for peroxynitric acid is the dissociation into HO2 and NO2.

Response surface methodology for optimizing adsorption performance of gel-type weak acid resin for Eu(Ⅲ)

The conditions relating to enhanced adsorption procedure of earth element europium（Eu） onto gel-type weak acid resin（110-H） in aqueous solution were optimized by means of the response surface methodology（RSM）, which proved that 110-H owned satisfactory adsorption capacity（346.85 mg/g） in optimum conditions, belonging to one of the high adsorption capacity materials. Then, the adsorption and desorption behaviors were investigated by batch studies. The adsorption performance showed high agreement with the Lagergren-first-order model and Langmuir isotherm with thermodynamic adsorption parameters of ΔH= 36.1 k J/mol and ΔS=200 J/（mol·K）. Desorption study revealed that 110-H could be effectively eluted by a low concentration of HCl solution（0.1 mol/L） to regenerate and reuse. Finally, the 110-H and Eu（III） loaded 110-H were characterized by IR spectroscopy and scanning electron microscope（SEM） to analyze the mechanism of adsorption, which proved to be chemisorbed.

Surface Acidity of Amorphous Aluminum Hydroxide

The surface acidity of synthetic amorphous AI hydroxide was determined by acid/base titration with several complementary methods including solution analyses of the reacted solutions and XRD characterization of the reacted solids. The synthetic specimen was characterized to be the amorphous material showing four broad peaks in XRD pattern. XRD analyses of reacted solids after the titration experiments showed that amorphous AI hydroxide rapidly transformed to crystalline bayerite at the alkaline condition （pH〉10）. The solution analyses after and during the titration Ksp=^aAl^3＋/aH^＋^3 ,was 10^10.3. The amount of consumption of added acid or base during the titration experiment was attributed to both the protonation/deprotonation of dissolved AI species and surface hydroxyl group. The surface acidity constants, surface hydroxyl density and specific surface area were estimated by FITEQL 4.0.

Sorption of a triazol derivative by soils: importance of surface acidity

The sorption of a triazol derivative, 1-(4-chlorophenyl)- 4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)penten-3-ol with a common name of S3307D, on fifteen soils and three H_2O_2-treated soils was investigated. The sorption isotherm for each untreated and treated soil was non-linear, and was best fitted to Freundlich sorption equation. Soils containing high amount of clay content or organic matter or both sorbed much higher amounts of the chemical than soils that had low contents of these soil constituents. H_2O_2-treated soils showed considerable sorptive affinity for S3307D. It was concluded that both organic matter and mineral fraction in natural soils contributed to the sorption of the basic compound. Sorption by the H_2O_2 treated soils increased as suspension pH decreased, but all suspension pHs exceeded the pKa of the compound by more than two units. This implies that organic base protonation can occur on surfaces of soil components, and surface acidity (exchangeable acidity ) is important in sorption process of the organic base rather than suspension pH.

Application of response surface methodology in medium optimization for pyruvic acid production of Torulopsis glabrata TP19 in batch fermentation

Response surface methodology (RSM) was used to optimize the fermentation medium for enhancing pyruvic acid production by Torulopsis glabrata TP19. In the first step of optimization, with Plackett-Burman design, ammonium sulfate, glucose and nicotinic acid were found to be the important factors affecting pyruvic acid production significantly. In the second step, a 23 full factorial central composite design and RSM were applied to determine the optimal concentration of each significant variable. A second-order polynomial was determined by the multiple regression analysis of the experimental data. The optimum values for the critical components were obtained as follows: ammonium sulfate 0.7498 (10.75 g/L), glucose 0.9383 (109.38 g/L) and nicotinic acid 0.3633 (7.86 mg/L) with a predicted value of maximum pyruvic acid production of 42.2 g/L. Under the optimal conditions, the practical pyruvic acid production was 42.4 g/L. The determination coefficient (R2) was 0.9483, which ensures adequate credibility of the model. By scaling up fermentation from flask to jar fermentor, we obtained promising results.

Surface properties of superfine alumina trihydrate after surface modification with stearic acid

The surface properties of superfine alumina trihydrate （ATH） after surface modification were studied by measuring the contact angle, active ratio, oil adsorption, total organic carbon, adsorption ratio, and Fourier transform infrared （FTIR） spectrum. The contact angle increased initially and then slowly decreased with an increase of the amount of stearic acid. However, the surface flee energy decreased ini- tially and then increased. Surface modification with stearic acid or sodium stearate can benefit from elevating temperature. The base surface tension component and the free energy of Lewis acid-base both declined sharply following the surface modification. Excess stearic acid was physically adsorbed in the form of multilayer adsorption, and an interaction between oxygen on the ATH surface and hydroxyl in stearic acid was subsequently determined. Our results further indicated that the contact angle and adsorption ratio can be used as control indicators for surface modification compared with active ratio, oil adsorption and total organic carbon.

Optimization on the Conversion of Bamboo Shoot Shell to Levulinic Acid with Environmentally Benign Acidic Ionic Liquid and Response Surface Analysis

Levulinic acid（LA） has been identified as a promising green,biomass derived platform chemical.Response surface analysis（RSA） with a four-factor-five-level central composite design（CCD） was applied to optimize the hydrolysis conditions for the conversion of bamboo（Phyllostachys Praecox f.preveynalis） shoot shell（BSS） to LA catalyzed with ionic liquid [C4mim]HSO4.The effects of four main reaction parameters including temperature,time,C[C4mim]HSO4（initial [C4mim]HSO4 concentration） and XBSS（initial BSS intake） on the hydrolysis reaction for yield of LA were analyzed.A quadratic equation model for yield of LA was established and fitted to the data with an R2 of 0.9868,and effects of main factors and their corresponding relationships were obtained with RSA.Model validation and results of CCD showed good correspondence between actual and predicted values.The analysis of variance（ANOVA） of the results indicated that the yield of LA in the range studied was significantly（P＆lt;0.05） affected by the four factors.The optimized reaction conditions were as follows：temperature of 145 ℃,time of 103.8 min,C[C4mim]HSO4 of 0.9 mol.L-1 and XBSS of 2.04%（by mass）,respectively.A high yield [（71±0.41）%（by mol）,triplicate experiment] was obtained at the optimum conditions of temperature of 145 ℃,time of 104 min,C[C4mim]HSO4 of 0.9 mol.L-1 and XBSS of 2%（by mass）,which obtained from the real experiments,concurred with the model prediction [73.8%（by mol） based on available C6 sugars in BSS or 17.9%（by mass） based on the mass of BSS],indicating that the model was adequate for the hydrolysis process.

Densities and surface tensions of ionic liquids/sulfuric acid binary mixtures

The densities and surface tensions of [Bmim][TFO]/H2SO4, [Hmim][TFO]/H2SO4 and [Omim][TFO]/H2SO4 binary mixtures were measured by pycnometer and Wilhelmy plate method respectively. The results show that densities and surface tensions of the mixtures decreased monotonously with increasing temperatures and increasing ionic liquid （IL） molar fraction. IL with longer alkyl side-chain length brings a lower density and a smaller surface tension to the ILs/H2SO4 binary mixtures. The densities and surface tensions of the mixtures are fitted well by Jouyban-Acree （JAM） model and LWW model respectively. Redlich-Kister （R-K）equation and modified Redlich-Kister （R-K） equation describe the excess molar volumes and excess surface tensions of the mixtures well respectively. Adding a small amount of ILs （XIL 〈 0.1 ） into sulfuric acid brings an obvious decrease to the density and the surface tension. The results imply that the densities and surface tensions of IL5/H2SO4 binary mixtures can be modulated by changing the IL dosage or tailoring the IL structure.

Corrugated surface microparticles with chitosan and levofloxacin for improved aerodynamic performance

Corrugated surface microparticles comprising levofloxacin(LEV),chitosan and organic acid were prepared using the 3-combo spray drying method.The amount and the boiling point of the organic acid affected the degree of roughness.In this study,we tried to improve the aerodynamic performance and increase aerosolization by corrugated surface microparticle for lung drug delivery efficiency as dry powder inhaler.HMP175 L20 prepared with 175 mmol propionic acid solution was corrugated more than HMF175 L20 prepared with 175 mmol formic acid solution.The ACI and PIV results showed a significant increase in aerodynamic performance of corrugated microparticles.The FPF value of HMP175 L20 was 41.3%±3.9%compared with 25.6%±7.7%of HMF175 L20.Corrugated microparticles also showed better aerosolization,decreased x-axial velocity,and variable angle.Rapid dissolution of drug formulationswas observed in vivo.Lowdoses administered to the lungs achieved higher LEV concentrations in the lung fluid than high doses administered orally.Surface modification in the polymer-based formulation was achieved by controlling the evaporation rate and improving the inhalation efficiency of DPIs.

Optimization of Fermentation Medium for Producing α-Hydroxyphenylacetic Acid by Using Plackett-Burman Design and Response Surface Methodology

Plackett-Burman design and response surface methodology were applied in order to optimize the fermentation medium of (R)-α-hydroxyphenylacetic acid ((R)-HPA) producing Bacillus sp. HZG-19. The factors playing important roles in the production of (R)-HPA were selected based on Plackett-Burman design. The path of steepest ascent was undertaken to optimize said fermentation medium. Finally, the optimal levels of the factors with the greatest change in regard to product yield were further optimized using Box-Behnken and response surface analysis. The optimal conditions were found to be as follows: casein peptone 30.49 (g × L-1), glycerol 14.09 (g × L-1), KH2PO4 0.1345 (g × L-1), K2HPO4 0.01 (g × L-1), CaCl2 0.1 (g × L-1), MnSO4 0.01 (g × L-1). Under the optimal conditions described above, the yield of (R)-HPA reached 63.30%, which indicated an increase of 14.9%, as compared to the yield obtained before optimization.

SURFACE OF GELATIN MODIFIED POLY(L-LACTIC ACID)FILM

In this paper, the surface structure of poly(L-lactic acid) (PLLA) film modified with gelatin was investigated. ThePLLA film specimens were treated directly with aqueous alkali solution to provide their surfaces with carboxyl groups, sothat these functional groups could become the reactive sites for gelatin immobilization. The functional groups of the PLLAfilms were identified by ATR-FTIR spectra and XPS spectra, the changes in surface morphology were observed by usingenvironmental scanning electron microscopy (ESEM), and the hydrophilicity of modified PLLA films was examined bywater contact angle measurement. Experimental results showed that the gelatin was immobilized with water-solublecarbodiimide (EDC) onto the PLLA film's surfaces, and the gelatin content on the polymer surface was related to carboxylicgroup formed in the controlled hydrolysis process. Rough surfaces caused by hydrolysis will predominantly favor the adhesion and growth of cell; and the hydrophilicity of these surfaces after the modification procedure is enhanced.

Humic acid-mediated visible-light degradation of phenol on phosphate-modified and Nafion-modified TiO_2 surfaces

Although humic acid(HA)can inhibit TiO2photocatalysis,it can sensitize TiO2and induce significant visible‐light(VL)activity in phenol degradation.This favorable effect of HA was negligible on phosphate‐modified TiO2(P‐TiO2),but significantly stronger on Nafion‐modified TiO2(Nf‐TiO2).The reaction rate constants for phenol degradation on Nf‐TiO2increased from(0.003±0.001)to(0.025±0.003)min?1when the reaction was performed in the presence of20mg/L HA.The different effects of HA on P‐TiO2and Nf‐TiO2photocatalysis cannot be attributed to adsorption changes,because the adsorption capacities of P‐TiO2and Nf‐TiO2were only slightly lower than that of TiO2at an initial HA concentration of20mg/mL.Scavenger tests,electron paramagnetic resonance spectroscopy,and H2O2detection were taken to understand the low VL activity of the P‐TiO2/HA suspension.The main active species for phenol degradation in the TiO2and Nf‐TiO2suspensions were superoxide radicals.There were negligible amounts of superoxide radicals in the P‐TiO2/HA suspension,possibly because a direct four‐electron oxygen reduction reaction occurred.The better VL activity of Nf‐TiO2was rationalized on the basis of Mott–Schottky and electrochemical impedance plots.Nafion modification resulted in cathodic shifts of the energy band positions,increased electron density,and less resistance to electron transfer across the interface between TiO2and electrolytes.All these factors facilitated electron transfer and improved the production of active species.Phosphate modification therefore did not improve the VL response of HA sensitized TiO2,and low concentrations of HA can facilitate VL photocatalytic degradation of organic pollutants on Nafion surface‐modified TiO2.

Optimization of the Ultrasonic-assisted Extraction Process for Protocatechuic Acid from Emilia sonchifolia DC by Response Surface Methodology

[Objectives] This study was conducted to optimize the extraction process of protocatechuic acid from Emilia sonchifolia DC. [Methods] The optimal extraction conditions were determined by single factor,response surface analysis and variance analysis,and the content of protocatechuic acid was determined by HPLC. [Results] The protocatechuic acid standard curve equation was: y = 1 435 x + 8 403,R^2= 0. 999 8,indicating a good linear relationship. The optimal extraction conditions were as follows: a temperature at 80 ℃,an extraction time of 1 h,a material-to-liquid ratio at 1:10 and an ultrasonic power of 600 W,and the content of protocatechuic acid extracted was 1. 93 mg/g. The method showed a RSD of 0. 41%,less than 2%,and the detection limit was 0. 0000047261 g/ml.The experimental sample X1 was the low-level 0. 1 mg/ml standard solution,which showed recovery of protocatechuic acid between 100.8% and 105.2%,with a RSD of 0. 013%;and the sample X2 was the high-level 1. 0 mg/ml standard solution,which exhibited recovery between 100. 6% and 102. 2%,with a RSD of 0.076%. Thus,the recovery was high,and the requirements of the performance index were met. [Conclusions] The detection method is stable and reliable and can produce satisfactory results.

Scheimpflug imaged corneal changes on anterior and posterior surfaces after collagen cross-linking

AIM:To compare the anterior and posterior corneal parameters before and after collagen cross-linking therapy for keratoconus.METHODS:Collagen cross-linking was performed in31 eyes of 31 keratoconus patients(mean age 30.6±8.9y).Prior to treatment and an average 7mo after therapy,Scheimpflug analysis was performed using Pentacam HR.In addition to corneal thickness assessments,corneal radius,elevation,and aberrometric measurements were performed both on anterior and posterior corneal surfaces.Data obtained before and after surgery were statistically analyzed.RESULTS:In terms of horizontal and vertical corneal radius,and central corneal thickness no deviations were observed an average 7mo after operation.Corneal higher order aberration showed no difference neither on anterior nor on posterior corneal surfaces.During follow-up period,no significant deviation was detected regarding elevation values obtained by measurement in mm units between the 3.0-8.0 mm-zones.CONCLUSION:Corneal stabilization could be observed in terms of anterior and posterior corneal surfaces,elevation and higher order aberration values 7mo after collagen cross-linking therapy for keratoconus.

THE INTRINSIC ACIDITY CONSTANTS AND SPECIFIC SURFACE AREA OF MARINE SOLID PARTICLES I. A NEW METHOD

This paper proposes a new method for determining the intrinsic acidity constants K and K The new method is a great improvement over the modified Langmuir plot method generally adopted in that determination of these constants is not dependent on the specific surface area S of the marine solid particles. The new method was used to determine K, K and S for the main inorganic components of marine solid particles, including illite, montmorillonite, kaolinite, goethite, y-AlOOH. amorphous ferric oxide, MnO2, manganite, SiO 2 and calcium carbonate, and can facilitate the study on the effect of solution constituents, solution temperature, ionic strength, etc. on the value

The Studies on the Surface Organic Modification of Tourmaline Powder with Stearic Acid and Its Composite

Stearic acid modified tourmaline powder had been investigated to improve the compatibility and dispersed stability between tourmaline and polymer matrix. The experimental results indicated that the activation index was 100% and contact angle reached 120° when the ratio of the ore slurry is 5:50, the dosage of stearic acid and p-toluenesulfonic acid is 10% and 0.5% (of tourmaline powder’s quantity) respectively with reaction at 80°C for 6.0 h, and the modified tourmaline exhibited an excellent hydrophobic property. The introduction of stearic groups reduced the reunion of tourmaline particles clearly and improved the dispersivity in polymers, and the amount of negative ions released of modified tourmaline increased obviously for both modified tourmaline powders and its composite with polyamide-66 compared to the unmodified tourmaline. Moreover, the structure of modified tourmaline was also characterized by means of Fourier Transform infrared spectroscopy, X-ray diffraction, thermal gravimetric analysis, scanning electron microscope.