Classical chemical sciences
Corrosion resistance of two metals namely mild steel (MS), Nickel Titanium super elastic alloy has been evaluated in artificial urine in the absence and presence of sodium chloride. Potentiodynamic polarization study has been used to investigate the corrosion behaviour of these metals. The order of corrosion resistance of metals in artificial urine, in the absence and also in the presence of sodium chloride was Ni-Ti super elastic alloy > mild steel.
Keywords: Mild steel, nickel –Ti super elastic alloy, Artificial Urine, sodium chloride, implants, biomaterials
The objectives of the review are the collection, concise description and evaluation of the various chromatographic techniques used for the separation and quantitative determination of macro- and microcomponents present in beers.
Keywords: gas chromatography, high performance liquid chromatography, dark and pale beers, beer specialities
One of the primary requisites of any metal or alloy that is to be used in the mouth is that it must not produce corrosion products that could be harmful to the body. Some metallic elements that are completely safe in the elemental state can form hazardous or even toxic ions or compounds. Besides, the degradation of the alloy should be limited in order to guarantee its service life. Several metals and alloy have been in dentistry as bracket, band, orthodontic wires it is essential to know the corrosion resistance of this materials in the presence of saliva. The corrosion resistances of these materials have been evaluated by electrochemical studies such as polarization study and AC impedance spectra. The film formed on the metal surface has been analysed by surface analysis techniques such as SEM, EDX, X-ray, and AFM.
Keywords: corrosion resistance, metals, alloys, artificial saliva, bio-materials
Various biomaterials are implanted in the human body. Sometimes artificial organs are also implanted in the body. For this purpose various metals and alloys such as Ni-Al-Fe intermetallic alloys, titanium alloy, NiTi alloy, CoCrMo alloys, magnesium alloy, Cr- Ni stainless steel, Cr-Ni-Mo stainless steel, 316L stainless steel have been employed. The corrosion resistance of these biomaterials in various synthetic body fluids such as Ringer’s solution, Hank’s solution, simulated body fluids, artificial urine, blood, and serum have been investigated. Usually the corrosion resistance of these materials is investigated by electrochemical studies such as polarization, AC impedance and cyclic voltammetry study. The nature of the film formed on the metal surface has been analysed by surface analysis techniques such as SEM, AFM, etc. Study of this review paper will be very useful and time saving to researchers who would like to investigate the corrosion resistance of biomaterials in synthetic body fluids. The research findings will be very useful to the medical field.
Keywords: Ringer solution, Hank solution, simulated body fluids, artificial urine, blood and serum
An efficient and facile reaction has been shown between 2-hydroxychalcone with hydrazine hydrate in ethanol in presence of catalytic amount of glacial acetic acid under irradiation of solar thermal energy to afford 2-pyrazoline. Cyclised product established on the basis of IR, NMR, MS, 13C NMR and elemental analysis.
Keywords: 2’-Hydroxychalcone, 2-pyrazoline, solar energy, photocyclisation
New and efficient methods have been developed for the synthesis of ß-enaminones and ß-enamino esters in the presence of a catalytic amount of tris(hydrogensulfato)boron or trichloroacetic acid as highly efficient catalysts at 120 C under solvent-free conditions. Both methods are simple, and provide desired products in good yields and short reaction times.
Keywords: ß-enaminones, ß-enamino esters, tris(hydrogensulfato) boron, trichloroacetic acid.
Materials and environmental chemistry
The spectrum and levels of synthetic pyrethroids in the Weija Lake waters and sediments have been investigated as a case study. Sampling was done at eight sampling locations along the Lake. Liquid-liquid extraction using 3:1 acetone/hexane mixture and soxhlet extraction were used for extraction of the pyrethroid from the water and sediment samples respectively. Analysis of the pyrethroids extracts was done with gas chromatography equipped with electron capture detector. In all, seven synthetic pyrethroids namely, fenpropathrin, cyfluthrin, cypermethrin, fenvalerate, deltamethrin, allethrin, and permethrin were detected in the Lake waters. In addition to the above pyrethroids, bifenthrin and lambda cyhalothrin were detected in the sediments. Cyfluthrin was the most ubiquitous pyrethroid in the Weija water with 100 percent occurrence, while, cyfluthrin, fenvalerate were the most ubiquitous pyrethroids. Both were detected with 87.5 percent occurrence. The concentrations of the detected pyrethroids ranged from 0.10 – 3.50 ng L-1 and 0.15 – 6.60 ng g-1 for the water and sediment samples respectively. The concentrations of detected pyrethroids in the Weija waters were far below maximum residue limits set by European Union (EU) and the Japanese Government. The results therefore suggest that pyrethroids residue concentration in the Weija waters may not pose health hazard in terms of synthetic pyrethroid pollution.
Keywords: synthetic pyrethroid residues; Weija lake, sediment, lake water
This study characterised the polycyclic aromatic hydrocarbons (PAHs) in five road paving asphalt samples randomly collected from two hot mix asphalt (HMA) plants in Port Harcourt, Nigeria. The Σ16PAHs of the samples ranged from 103.79 mg kg-1 - 190.93 mg kg-1. Naphthalene, acenaphthylene, fluorene and benzo[g,h,i]perylene were not detected in any of the samples. The characteristic isomer ratios of the asphalt samples were also calculated to serve as a reference for road runoffs and leachates studies.
Keywords: asphalt, polycyclic aromatic hydrocarbons (PAHs), diagnostic isomer ratios
The inhibitive effect of aqueous extract of Saffron leaves toward the corrosion of aluminium in 2 M HCl solution has been investigated by weight loss and electrochemical polarization study. The extract functions as a good inhibitor. The inhibition efficiency increased with extract concentrations. The plant extract behaves as cathodic–type inhibitor. Surface morphology has been analysed using SEM.The adsorption of the extract components on the aluminium surface follows Temkin adsorption isotherm.
Keywords: saffron; HCl corrosion inhibitor; aluminium; Tafel; LP and SEM
This research deals with the application of polyaniline coated onto wood sawdust (PAni/SD) for the removal of anionic or acidic dyes from aqueous solutions. Acid Green 25 (AG25) was selected as test probe throughout of the current investigation as a typical anionic dye. Adsorption experiments were carried out using batch system in order to do equilibrium adsorption isotherm, kinetics and thermodynamic studies. The results indicated that unmodified wood sawdust is a very poor adsorbent for anionic dyes, but when coated by polyaniline (PAni/SD), it is changed into a very efficient adsorbent material for adsorption of AG25 from aqueous solutions. It was found that chemical modification of agricultural wastes such as sawdust with polyaniline is leaded to a great enhancement in anionic dye removal efficiency. The findings seem to be important for application of the introduced biocomposite of polyaniline as an efficient new nonconventional adsorbent in dye removal technology.
Keywords: Acid green 25, Removal, sawdust, polyaniline, isotherm, kinetics, thermodynamic
Well-ordered self assembling monolayer’s (SAMs) using glycine were formed on the carbon steel surface by immersion method. This leads to ordered, robust monolayers bound to the surface in a bi dentate manner. Monolayer formation takes place when carbon steel is immersed in an aqueous solution containing 60ppm of Cl– and 50 ppm of glycine for 5 minutes, and rinsing the physisorbed molecules in distilled water and heating in a hot air oven. The glycine monolayers on iron oxide steel carbon can withstand rinsing with water, concentrated acid and base exposure. Additionally, these monolayers are stable over the course of one week. The formations of monolayers were confirmed by AFM study and FTIR spectra. The results of this study show that glycine monolayers adsorbed on metal surface can reduce electrochemical activity on the surface, often the first step in corrosion.
Keywords: Self–assembled monolayers, carbon steel surface, AFM, FTIR, corrosion, deposition method; Glycine
Three prominent hydrocarbon groups found in crude oil- Polycyclic Aromatic Hydrocarbon (PAH); Benzene, Toluene, Ethylbenzene and Xylene (BTEX) and Total Petroleum hydrocarbon (TPH) were used to study the ability of three chemical oxidants-Fenton’s reagent, potassium permanganate, and potassium persulfate to degrade hydrocarbons in crude oil inundated soils. This was done by spiking soil samples with Bonny light crude oil and subsequently treating the mixture with the different chemical oxidants at acidic, neutral and basic pH media for each of the oxidants. Oil extracts from the treated and untreated soil samples were later analyzed for the three hydrocarbon groups using a gas chromatograph (GC). Treatment with Fenton’s reagent proved very efficient in the removal of the hydrocarbons especially at the acidic pH with some components of TPH experiencing complete disappearance. Also the four ringed-PAHs were depleted more than the three ringed- ones at the indicated pHs. For the treatment with potassium persulfate, while the oxidant was good in the removal of BTEX at the different pHs, it was found to be very inefficient for the removal of PAHs. Generally, Four and five ringed–PAHs were degraded more than the three and two ringed-PAHs, an indication that degradation of PAHs by oxidants may be a function of hydrocarbon structure. Treatment with potassium permanganate was found to be pH dependent with most of the depletions occurring at acidic pH. Even though potassium permanganate was not as good as the other oxidants in the removal of aliphatic hydrocarbons(TPH), it was found to be effective in the removal of aromatic hydrocarbon (BTEX and PAH). Also the four ringed-PAHs such as pyrene, benzoanthracene, and chrysene were seriously attacked at all pHs. BTEX was also attacked more at acidic pH with above 90% removal at the acidic pH.
Keywords: Permanganates; Persulfates; Fenton’s reagent; Bonnylight crude oil; Soil remediation; Chemical oxidants
Industrial and engineering chemistry
The present article gives an overview on performance and aging kinetics of matrix and crumb rubber modified asphalts. Three types of asphalts such as crumb rubber modified asphalt, AH-70 and AH-90 have been introduced. Equations related to aging kinetics have also been used in crumb rubber modified asphalt system. The experimental results show that the aging process of two types of asphalts (crumb rubber modified asphalt and AH-70) are of first order kinetics, and the anti-aging performance of crumb rubber modified asphalt is found to be better than that of AH-70.
Keywords: performance; aging kinetics; crumb rubber modified asphalt
Some industrial synthetic methods for an analogous series of C1-5 alkyl cinnamates using different catalysts such as sulfonic acids (ptoluene- sulfonic acid), inorganic salts (NH4Fe(SO4)2·12H2O) and solid superacids (SO4 2-/La2O3-ZrO2-HZSM-5) are reviewed. Yields of an analogous series of C1-5 alkyl cinnamates are improved by the addition of the above mentioned catalysts. The main advantages of these methods are the simple process operation and low investment costs.
Keywords: overview; synthetic methods; catalysts; alkyl cinnamates
Corrosion is a natural process. It can be defined as the destructive attack of a metal through interaction with its environment. A corrosion inhibitor is a chemical compound that, when added to a liquid or gas in small amount decreases the corrosion rate of a metal or an alloy. Corrosion inhibitors are added to coolants, fuels, hydraulic fluids, boiler water, engine oil and many other fluids used in industry. The rate of various types of corrosion inhibitors which are used in different environment to reduce the corrosion of various metals and alloys are discussed in this paper.
Keywords: corrosion, inhibitors, additives, methods, metals