Weak Alkaline Solution Research Articles

Simultaneous fabrication of superhydrophobic cathodic cobalt and anodic copper surfaces by a one-step electrodeposition process

Superhydrophobic cathodic cobalt and anodic copper surfaces were fabricated by one-step electrodeposition process. The superhydrophobicity properties, morphological features and chemical composition of the coatings were characterised. The results show that a short time of 0·5 minute is sufficient to render superhydrophobicity on the cathodic cobalt deposit. The cathodic cobalt surface exhibits a contact angle of 160° and a sliding angle of 6·2° when it is electrodeposited for 5 minutes. The corresponding anodic copper surface displays superhydrophobicity with a contact angle of 153° and a sliding angle of 6·8° after electrodeposition for 2 hours. Meanwhile, the cathodic cobalt surfaces show superhydrophobicity even for corrosive liquids with pH value ranging from 1 to 14. However, the anodic copper surfaces only have superhydrophobicity in the neutral, weak alkaline or acid aqueous solutions. The superhydrophobicity of the surfaces result from the formation of the myristate compounds on their surfaces and their special micro-/nanostructures.

Analysis of accumulation patterns and preliminary study on the condensation mechanism of proanthocyanidins in the tea plant [Camellia sinensis

In the present study, proanthocyanidins were qualitatively and quantitatively identified using hydrolysis and thiolysis assays, NP-HPLC, HPLC-ESI-MS, MALDI-TOF-MS, 1H-NMR, and 13C-NMR techniques in different organs of tea plants. The results showed that in leaves, the tri-hydroxyl, cis- and galloylated flavan-3-ols were the main monomeric catechins units, and (epi)catechin was found to be the major unit of polymeric flavan-3-ols when the degree of polymerization was greater than five. In roots, the PAs were found to be abundant, and epicatechin formed the predominant extension unit of oligomeric and polymeric PAs. In order to understand the mechanism of proanthocyanidins polymerization, auto-condensation of the flavan-3-ols was investigated. The results showed that the same trimers (m/z 865) were detected in the extracts of tea plants and in the non-enzymatic in vitro assay, in weak acid as well as weak alkaline solutions at room temperature, when the substrates used were either procyanidin B2 and monomeric flavan-3-ols (epicatechin or catechin), or only procyanidin B2. This suggested that procyanidin B2 not only released carbocation as electrophilic upper units, but also could be used as nucleophilic lower units directly itself, to form the procyanidin trimer in vitro or in vivo.

Efficient photocatalytic removal of aqueous NH4+–NH3 by palladium-modified nitrogen-doped titanium oxide nanoparticles under visible light illumination, even in weak alkaline solutions

Aqueous ammonium–ammonia (NH4+–NH3) is a commonly found pollutant in industrial and domestic wastewater, which poses a great threat to both the environment and the human health. Photocatalytic treatment had been proved to be an efficient approach to oxidize aqueous NH4+–NH3 for its removal. However, most current researches still suffer from the requirements of UV illumination and strong alkaline environment, low removal rates, and high ratios of toxic oxidation by-products of NO3− and NO2−. In this study, palladium-modified nitrogen-doped titanium oxide (TiO2−xNx/PdO) nanoparticles were synthesized by a simple sol–gel process, which demonstrated an effective photocatalytic removal of aqueous NH4+–NH3 under visible light illumination. By optimizing the reaction conditions, a high removal rate of over 90% could be achieved by TiO2−xNx/PdO nanoparticles under only visible light illumination with the major product of N2, and the production of toxic photocatalytic oxidation by-products of NO3− and NO2− was minimized. The real time solution pH was found to be critical for the photocatalytic oxidation of aqueous NH4+–NH3. By keeping the solution pH constantly at ∼8, the effective photocatalytic removal of aqueous NH4+–NH3 in a weak alkaline solution was achieved for the first time.

Characterization of hydroxypropyl-β-cyclodextrins with different substitution patterns via FTIR, GC-MS, and TG-DTA.

The structure and thermal properties of hydroxylpropyl-β-cyclodextrins (HPCDs) with different degrees of substitution (DS) and different substitution sites were evaluated via GC-MS, FTIR, and TG-DTA combined thermoanalytical techniques. The results of GC-MS provided the DS and substitution pattern of the HPCD samples. The IR spectra of HPCDs showed all characteristic peaks corresponding to cyclodextrin. Furthermore, the characteristic peaks for methyl in the hydroxypropyl group at 2960 and 1,375 cm(-1) were observed. The thermal decomposition temperature of HPCDs was about 300°C to 400°C and enhanced linearly as the molecular DS increased. The rate of DS rise of HPCDs prepared at a strong alkaline condition was higher than that prepared in a weak alkaline solution.

Chemical stability of basalt fiber in alkaline solution

The chemical stability of basalt fiber in alkaline solution is investigated by the means of weight retention and tensile strength retention. It has been observed that the basalt fiber immersed in weak alkaline solution is very stable whereas the basalt fiber immersed in strong alkaline solution shows poor weight retention due to the high dissociation constant. On the other hand, the tensile strength of basalt fiber in alkaline solutions is drastically decreased regardless of alkaline solution concentrations. Also basalt fiber in saturated Ca(OH)2 solution, which is similar to the alkaline environment of cement hydration, shows very low weight loss and high stability even after 3 months of immersion compared to glass fiber in the same condition.

Betaine ester-shell functionalized hyperbranched polymers for potential antimicrobial usage: Guest loading capability, pH controlled release and adjustable compatibility

Betaine ester-shell functionalized hyperbranched polyethylenimines (BEHPEI) were synthesized by Menschutkin reaction between per-N-methylated polyethylenimine (MeHPEI) and alkyl bromoacetate. BEHPEI could play dual antimicrobial roles that were, the betaine ester-shell acted as contact-based antibacterial polycations and the drug-loaded BEHPEI could controllably release the drugs due to the cleavage of the betaine ester groups under weak alkaline condition. The BEHPEI exhibited high transport capacities that per gram of BEHPEI could encapsulate 0.24–2.67 g of dyes or drugs. The model drug release experiment employing methyl orange (MO) showed that the drug release of MO-loaded BEHPEI complex occurred slowly in weak alkaline solutions and the release rate was controlled by varying pH, while the complex kept very stable under weak acid condition (pH = 3.0–7.0). BEHPEI generated from long chain alkyl bromoacetate was compatible with organic resins implying the possible usage in antimicrobial fibers and coatings. Another BEHPEI obtained from short-chain alkyl bromoacetate was water soluble and maybe used in lotion formula. The hydrolysis of BEHPEI afforded zwitterionic shell.

Comparison of electrochemical current noise signals arising from symmetrical and asymmetrical electrodes made of Al alloys at different pH values using statistical and wavelet analysis. Part II: Alkaline solutions

In this paper, the electrochemical current noise (ECN) signals arising from the symmetrical (both small and large) and asymmetrical electrodes made of AA6061 and AA2024 in 1.0M NaCl electrolyte adjusted to pH 9 and 12 were analyzed by statistical and wavelet methods. The asymmetrical electrodes (1–100mm2) retained their essential advantages in weak alkaline solutions as well as in the near-neutral solutions. However, their advantages were partly lost in the strong alkaline solutions. The use of statistical data made it possible to differentiate between the two symmetrical configurations. The statistical analysis of ECN signals arising from the symmetrical electrodes revealed that the small symmetrical electrodes (1–1mm2) were preferable for measuring ECN in near-neutral solutions, while the large symmetrical electrodes (100–100mm2) were preferable for measuring ECN in weak alkaline solutions. However, in strong alkaline solutions the large symmetrical electrodes were preferable for measuring ECN on AA6061, but the small symmetrical electrodes were preferable for measuring ECN on AA2024. The electrochemical behavior of intermetallic particles as a function of pH along with an earlier modeling of ECN transients were employed to interpret the ECN data of AA2024 asymmetrical electrodes at pH 9 in comparison with near-neutral pH. The SDPS values of the true timescale crystals of the ECN signals arising from asymmetrical electrodes increased with increasing pH value from 9 to 12 due to the enhanced corrosion severity. A recently presented model describing the process of EN generation has been employed to interpret all results obtained in near-neutral, acidic and alkaline solutions.

A new method to construct hierarchical ZSM-5 zeolites with excellent catalytic activity

Desilicication and dealuminzation with weak alkaline solution and acid liquor is an effective way to construct hierarchically mesoporous without damaging its crystallinity and preserving its acidity in ZSM-5 zeolites. We investigated the influence of the concentration of NaAlO2, treatment time, temperature and the concentration of HCl on the crystallinity of ZSM-5 and characterized the products with XRD, SEM, XRF, BET, NH3-TPD, etc. The results showed that the appropriate concentration of NaAlO2 solutions extract selectively silicon from the framework of the zeolites while a small portion of aluminum would patch some parts of vacancies produced by the removal of silicon, then the HCl would dealuminize to maintain the SiO2/Al2O3 ratios, which preserved the crystallinity of ZSM-5 perfectly. Furthermore, the micro-reaction activity tests displayed that the obtained products had higher catalytic than the parent zeolites because of their optimized hierarchical micro-mesoporous.

Removal of Chlorpheniramine from Water by Birnessite

With more and more emerging organic contaminants (EOCs) detected in the soil and groundwater, researches on interactions between these pollutants and soils or aquifer materials have attracted greater concerns. In this study, the removal of chlorpheniramine maleate (CP), an antihistamine drug used to treat rhinitis and urticaria, by birnessite, which is a common layered manganese oxide, in aqueous solution was investigated by batch studies, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses, and molecular simulations. The quantum mechanics simulation showed that the final energy of the interaction between CP and the (010) edge surfaces under a strong alkaline condition was much smaller than that under a neutral to slightly alkaline condition. A higher CP adsorption were achieved from neutral to weak alkaline solution, as the broken bond effect of birnessite was strongly influenced by solution pH by protonation and deprotonation of birnessite edges.

One-step synthesis of mussel-inspired molecularly imprinted magnetic polymer as stationary phase for chip-based open tubular capillary electrochromatography enantioseparation

A facile approach for preparation of molecularly imprinted polymers was developed and successfully used as chiral stationary phase for rapid enantioseparation by open tubular capillary electrochromatography (OT-CEC). In this work, molecularly imprinted polymers were one-step prepared employing Fe3O4 nanoparticles (NPs) as the supporting substrate and dopamine as the functional monomer. By simply mixing Fe3O4 NPs with template molecules in a weak alkaline solution of dopamine, a thin adherent polydopamine (PDA) film imprinted with template molecules was formed by the self-polymerization of dopamine on the surface of Fe3O4 NPs. After extracting the embedded template molecules, the produced imprinted Fe3O4@PDA NPs are of three dimensional shape of template molecules favoring high binding capacity and magnetism property for easy manipulation. The imprinted Fe3O4@PDA NPs prepared with l-tryptophan, l-tyrosine, Gly-l-Phe or s-ofloxacin as template molecules were packed in the PDMS microchannel via magnetic field as novel stationary phase for the successful enantioseparation of corresponding target analysts. In addition, the imprinted Fe3O4@PDA NPs-based OT-CEC system exhibited excellent reproducibility, stability and repeatability, which provides a powerful protocol for separation enantiomers within a short analytical time and opens up a promising avenue for high-throughput screening of chiral compounds.

Nanoparticle Electrocatalysts for the Oxidation of Waste Lignin

Lignin is a large organic molecule and a primary waste from the pulping industry and biorefineries [1, 2]. Currently, lignin has little value other than as a fuel to generate heat. Lignin can, however, be used as a renewable raw material for a variety of value-added chemicals. Unfortunately, catalytic processes are difficult to implement for the degradation of waste lignin because selective oxidation is difficult and these processes produce an unacceptable amount of solid residue like char [2, 3].Electrochemical processes, on the other hand, have several advantages over catalytic processes, including the use of mildly basic solvents as electrolytes, and control over the rate of reaction and the products. Thus, the electrochemical oxidation of waste lignin would be an ideal process to utilize this renewable raw material.While there have been efforts related to the electrochemical oxidation of lignin, most work has focused either on expensive platinum electrodes or on low surface area, large metal electrodes. However, nanoparticle electrocatalysts can be developed that enhance the rate of electrochemical reaction through enhancement of electrocatalyst surface area and porosity.We will report on our efforts to develop nanoparticle electrocatalysts with specific compositions and architectures for the electrochemical oxidation of lignin in weak alkaline solution. For example, Ni-Cu alloy nanoparticle electrocatalysts are suitable for the electro-oxidation of lignin in basic solution, as shown in Figure 1. Figure 1. Electrochemical oxidation of lignin on Ni-Cu alloy nanoparticle electrocatalysts. Baseline is 1 M NaOH in the absence of lignin. As shown in Figure 1, oxidation peaks in the presence of lignin occur around 0.03 V and 0.45 V vs. NHE that do not occur in the absence of lignin. Figure 1 indicates that lignin may undergo a complicated, multi-step oxidation process. For example, lignin may oxidize to one product at a lower potential, and that product may in turn oxidize to yet another product at higher potential. The oxidation potential and oxidation time (i.e., charge passed) affects the product distribution.One of the most important aspects of the electrochemical oxidation of lignin in alkaline solution is the identification of the oxidation products. We will present GC/MS data that identify lignin oxidation products. This process could provide an economic way of reducing the organic waste from the pulping and biorefinery industries. References. 1. A. French, “’Lignin’ May Be the Magic Word,” Innovation: America’s Journal of Technology Commercialization, June/July 2011.2. C. Grestini, “Conversion of Lignin: Chemical Technologies and Biotechnologies,” EuroBioRef Summer School, Universita Degli Studi di Roma, Castro Marina, Lecce, Italy, September 21, 2011.3. M. P. Pandey and C. S. Kim, “Lignin Depolymerization and Conversion: A Review of Thermochemical Methods,” Chemical Engineering and Technology, 34, 327-331 (1999)

Colourimetric and fluorometric substrates for measurement of pullulanase activity

Specific and highly sensitive colourimetric and fluorometric substrate mixtures have been prepared for the measurement of pullulanase and limit-dextrinase activity and assays employing these substrates have been developed. These mixtures comprise thermostable α- and β-glucosidases and either 4,6-O-benzylidene-2-chloro-4-nitrophenyl-β-maltotriosyl (1-6) α-maltotrioside (BzCNPG3G3, 1) as a colourimetric substrate or 4,6-O-benzylidene-4-methylumbelliferyl-β-maltotriosyl (1-6) α-maltotrioside (BzMUG3G3, 2) as a fluorometric substrate. Hydrolysis of substrates 1 and 2 by exo-acting enzymes such as amyloglucosidase, β-amylase and α-glucosidase is prevented by the presence of the 4,6-O-benzylidene group on the non-reducing end d-glucosyl residue. The substrates are not hydrolysed by any α-amylases studied, (including those from Aspergillus niger and porcine pancreas) and are resistant to hydrolysis by Pseudomonas sp. isoamylase. On hydrolysis by pullulanase, the 2-chloro-4-nitrophenyl-β-maltotrioside (3) or 4-methylumbelliferyl-β-maltotrioside (4) liberated is immediately hydrolysed to d-glucose and 2-chloro-4-nitrophenol or 4-methylumbelliferone. The reaction is terminated by the addition of a weak alkaline solution leading to the formation of phenolate ions in solution whose concentration can be determined using either spectrophotometric or fluorometric analysis. The assay procedure is simple to use, specific, accurate, robust and readily adapted to automation.

IGCC fly ash valorisation. Optimisation of Ge and Ga recovery for an industrial application

Fly ash (FA) disposal in landfills has a significant economic and environmental burden. A promising approach for FA valorisation aside from building purposes is the recovery of valuable elements since FA has a huge potential role as a source of valuable metals. In most cases, reported work in this area has been of theoretical research and further development work is needed. Germanium and gallium occur in relatively high proportions and mainly as water soluble and oxide species, respectively in the Puertollano Integrated Gasification Combined Cycle (IGCC) fly ash. Both the speciation and concentrations of Ge and Ga in this IGCC FA allowed starting research for developing extraction methods. High but not regular extraction yields were achieved in previous investigations. The aim of this research work is focused on the optimisation of Ge and Ga extraction conditions from IGCC FA for its feasible industrial application regardless the operational conditions of the IGCC plant. To this aim, first the daily, monthly, and yearly variability of Ge and Ga concentrations in IGCC fly ashes were determined. Samples were taken during almost 10years. Then a number of extraction tests were carried out using different extractants to cover a wide range of extraction conditions (acid, alkaline, complexant, reducing and oxidising), on IGCC FA samples produced under different operating conditions. High and regular Ge extraction yields (up to 83% after 2h leaching period) may be achieved using a weak acid solution. Gallium yielded up to 70 and 64% extraction after a 24h leaching period using a weak acid and alkaline solution, respectively.

Polydopamine-Based Simple and Versatile Surface Modification of Polymeric Nano Drug Carriers

The surface of a polymeric nanoparticle (NP) is often functionalized with cell-interactive ligands and/or additional polymeric layers to control NP interaction with cells and proteins. However, such modification is not always straightforward when the surface is not chemically reactive. For this reason, most NP functionalization processes employ reactive linkers or coupling agents or involve prefunctionalization of the polymer, which are complicated and inefficient. Moreover, prefunctionalized polymers can lose the ability to encapsulate and retain a drug if the added ligands change the chemical properties of the polymer. To overcome this challenge, we use dopamine polymerization as a way of functionalizing NP surfaces. This method includes brief incubation of the preformed NPs in a weak alkaline solution of dopamine, followed by secondary incubation with desired ligands. Using this method, we have functionalized poly(lactic-co-glycolic acid) (PLGA) NPs with three representative surface modifiers: a small molecule (folate), a peptide (Arg-Gly-Asp), and a polymer [poly(carboxybetaine methacrylate)]. We confirmed that the modified NPs showed the expected cellular interactions with no cytotoxicity or residual bioactivity of dopamine. The dopamine polymerization method is a simple and versatile surface modification method, applicable to a variety of NP drug carriers irrespective of their chemical reactivity and the types of ligands.

Binding sites of chlorpheniramine on 1:1 layered kaolinite from aqueous solution

Interactions between chlorpheniramine (CP), an antihistamine drug used to treat allergy, and kaolinite in aqueous solution were investigated under batch studies and molecular simulations. The CP adsorption was relatively fast with a large rate constant. The CP adsorption capacity on kaolinite was 25mmol/kg, about the same magnitude of the cation exchange capacity of kaolinite. Molecular dynamic simulation showed that the edges of kaolinite were responsible for the uptake of CP, while a net repulsive interaction between the basal plane and CP molecules was obtained. As the broken bond effect of kaolinite was strongly affected by solution pH via protonation–deprotonation of kaolinite edges, a higher CP adsorption was achieved under neutral to weak alkaline solution. It was the charge density, rather than the surface area, that ultimately controlled the amount of CP adsorption on kaolinite.

Study on the inclusion and solubilization processes of inclusion complex of carboxymethyl-β-cyclodextrin with CDOTP

The inclusion and solubilization processes of the inclusion complex between carboxymethyl-β-cyclodextrin and chloro1, 4-dibenzyl-1, 4-dinitrogen diheterocycly [2,2,2] octane tungstic peroxide were investigated using ultraviolet spectrophotometry characterization. Association constant KCD.Q=1.07×106L/mol and the inclusion ratio n=3 were determined by means of competitive inclusion method with phenolphthalein. Moreover, based on solubilization experiment of inclusion complex, it can be found that the solubility is improved vastly compared with the guest without inclusion, especially in the condition of normal atmospheric temperature and weak alkaline solutions. Additionally, thermodynamic analysis of this inclusion process and relevant evaluation of thermodynamic parameters, such as ΔS, ΔH and ΔG have been investigated, which indicates that this process is unprompted, thermodynamically sustained and driven by both enthalpy and entropy, and especially depends on entropy. The possible prediction of inclusion structure has also been investigated.

Novel substrates for the measurement of endo-1,4-β-glucanase (endo-cellulase)

A specific and sensitive substrate for the assay of endo-1,4-β-glucanase (cellulase) has been prepared. The substrate mixture comprises benzylidene end-blocked 2-chloro-4-nitrophenyl-β-cellotrioside (BzCNPG3) in the presence of thermostable β-glucosidase. Hydrolysis by exo-acting enzymes such as β-glucosidase and exo-β-glucanase is prevented by the presence of the benzylidene group on the non-reducing end d-glucosyl residue. On hydrolysis by cellulase, the 2-chloro-4-nitrophenyl-β-glycoside is immediately hydrolysed to 2-chloro-4-nitrophenol and free d-glucose by the β-glucosidase in the substrate mixture. The reaction is terminated and colour developed by the addition of a weak alkaline solution. The assay procedure is simple to use, specific, accurate, robust and readily adapted to automation. This procedure should find widespread applications in biomass enzymology and in the specific assay of endo-1,4-β-glucanase in general.

Different types of inks having certain medicolegal importance: Deciphering the faded and physically erased handwriting

Disappearing ink is a type of ink which could be used to forge documents as it will fade away without any trace within 40–65h. Erasable ink is another type of ink easily removed by certain rubbers incorporated in each pen. Both types of inks were applied separately on different types of papers (checks, standard white foolscap, and plain white A4 paper). For vanishing ink, it was observed visually in the first 6h and then every 6h. It was found that the vanishing ink disappeared completely within 2h on checks, 36h on standard white foolscap paper, and 40h on plain white A4 paper. For erasable ink, the written strokes were manipulated manually using the incorporated eraser. Deciphering the faded writing failed by the conventional methods, but oblique light can reveal the indentation marks. The faded writing became visible when treated with weak alkaline (NaOH) solutions. Erasable ink was deciphered with the aid of infra-red radiation combined with VSC-6000 as clear white traces against red fluorescence. It was concluded that the use of a weak (NaOH) solution is an effective method for revealing the faded writing, and the infra-red illumination is also effective.

Formation of diazohydroxides ArN2OH in aqueous acid solution: polarographic determination of the equilibrium constant KR for the reaction of 4‐substituted arenediazonium ions with H2O

In aqueous acid (pH <4) solutions, in the dark, and in the absence of reductants, arenediazonium ions, ArN2+ decompose spontaneously through the rate‐limiting formation of the extremely unstable aryl cation that reacts with any nucleophile present in its solvation shell (DN + AN mechanism). However, in weak acidic and alkaline solutions, ArN2+ react with H2O and OH− at the terminal nitrogen to give azo adducts of the type ArN2OH that are in equilibrium with the parent ArN2+. The diazohydroxide, in this case an acid, is in equilibrium with its conjugate base, and diazoate ArN2O−. The equilibrium constant for reaction with OH− has been determined for a limited number of ArN2+ from kinetic measurements but not with H2O (KR). Here, we have exploited the electrochemical properties of ArN2+ to determine, for the first time, the equilibrium constants KR of formation of 4‐substituted X–ArN2OH (XH, Me, MeO, Br, and NO2), which can decompose in several ways including Z–E isomerization or further reaction with OH− to give diazoate ArN2O−. The technique applied was differential pulse polarography, which is very selective and sensitive. The determined pKR values are 5–6, and they are somewhat higher than those obtained for the reaction of ArN2+ with alcohols ROH (pKDE = 3–5) under similar acidic conditions. The KR values are not very sensitive to changes in the nature of the substituent in the aromatic ring and a linear Hammett plot with a slope of ρ = 0.58 was obtained. Copyright © 2013 John Wiley & Sons, Ltd.

Efficient One-Pot Synthesis of Mussel-Inspired Molecularly Imprinted Polymer Coated Graphene for Protein-Specific Recognition and Fast Separation

Molecular imprinting at nanomaterial surfaces has shown good prospects to extract templates easily and to achieve excellent performances such as large binding capacity and fast adsorption. In this work, we describe a one-step approach to synthesize a novel surface protein-imprinted nanomaterial employing graphene as the supporting substrate and dopamine as the polymerizing monomer. By simply immersing graphene oxide (GO) in a weak alkaline solution of dopamine (DA) containing bovine hemoglobin (BHb), GO nanosheet was readily converted to reduced GO (RGO) by dopamine with simultaneous capping by a thin polydopamine film imprinted with BHb leading to the BHb imprinted PDA@RGO nanomaterials. Fourier transform infrared (FT-IR), ultraviolet–visible (UV–vis), Raman spectra, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption experiments have been used to characterize the resulting imprinted PDA@RGO. The whole reaction process was conducted...