Experimental and theoretical study on the corrosion inhibition of mild steel by nonanedioic acid derivative in hydrochloric acid solution

The corrosion performance of mild steel (MS) in 1M HCl solution was examined by weight loss (WL), potentiodynamic polarization (PDP), electrochemical impedance spectroscopy (EIS), electrochemical frequency modulation (EFM), and open circuit potential (OCP) measurements in the absence and presence of nonanedihydrazide. PDP measurements indicated that nonanedihydrazide acts as a mixed inhibitor due to its adsorption on the MS surface, exhibiting an inhibition efficiency of more than 97%. The surface morphology investigation of the protective layer on the MS surface confirmed that adsorption of nonanedihydrazide molecules occurred via chemical adsorption following Langmuir's isotherm model. The effect of temperature on the corrosion performance in the presence of nonanedihydrazide was investigated in the range of 303-333 K, showing that the inhibition efficiency increased with an increase in the inhibitor concentration and decreased with an increase in temperature. A new green corrosion inhibitor was synthesised and theoretical computations were conducted to completely understand the inhibition mechanism. Nonanedihydrazide molecules were investigated by DFT (density functional theory) using the B3LYP functional to evaluate the relationship of corrosion inhibition performance and the molecular structure. The computed theoretical parameters presented significant support for understanding the inhibitive mechanism revealed by the inhibitory molecules and are in good agreement with WL, PDP, EIS, (EFM), and OCP results.

Application of dyes extracted from Alternanthera dentata leaves and Musa acuminata bracts as natural sensitizers for dye-sensitized solar cells

The natural dyes anthocyanin and chlorophyll were extracted from Musa acuminata bracts and Alternanthera dentata leaves, respectively. The dyes were then applied as sensitizers in TiO₂-based dye-sensitized solar cells (DSSCs). The ethanol extracts of the dyes had maximum absorbance. High dye yields were obtained under extraction temperatures of 70 to 80°C, and the optimal extraction temperature was approximately 80°C. Moreover, dye concentration sharply decreased under extraction temperatures that exceeded 80°C. High dye concentrations were obtained using acidic extraction solutions, particularly those with a pH value of 4. The DSSC fabricated with anthocyanin from M. acuminata bracts had a conversion efficiency of 0.31%, short-circuit current (I_sc) of 0.9mA/cm², open-circuit voltage (V_oc) of 0.58V, and fill factor (FF) of 62.22%. The DSSC sensitized with chlorophyll from A. dentata leaves had a conversion efficiency of 0.13%, I_sc of 0.4mA/cm^-2_,V_oc of 0.54V, and FF of 67.5%. The DSSC sensitized with anthocyanin from M. acuminata bracts had a maximum incident photon-to-current conversion efficiency of 42%, which was higher than that of the DSSC sensitized with chlorophyll from A. dentata leaves (23%). Anthocyanin from M. acuminata bracts exhibited the best photosensitization effects.

Experimental and theoretical studies of Schiff bases as corrosion inhibitors

Background

Relatively inexpensive, stable Schiff bases, namely 3-((4-hydroxybenzylidene)amino)-2-methylquinazolin-4(3H)-one (BZ3) and 3-((4-(dimethylamino)benzylidene)amino)-2-methylquinazolin-4(3H)-one (BZ4), were employed as highly efficient inhibitors of mild steel corrosion by corrosive acid.

Findings

The inhibition efficiencies were estimated based on weight loss method. Moreover, scanning electron microscopy was used to investigate the inhibition mechanism. The synthesized Schiff bases were characterized by Fourier transform infrared spectroscopy, nuclear magnetic resonance spectroscopy and micro-elemental analysis. The inhibition efficiency depends on three factors: the amount of nitrogen in the inhibitor, the inhibitor concentration and the inhibitor molecular weight.

Conclusions

Inhibition efficiencies of 96 and 92% were achieved with BZ4 and BZ3, respectively, at the maximum tested concentration. Density functional theory calculations of BZ3 and BZ4 were performed to compare the effects of hydroxyl and N,N-dimethylamino substituents on the inhibition efficiency, providing insight for designing new molecular structures that exhibit enhanced inhibition efficiencies.

An overview on cellulose-based material in tailoring bio-hybrid nanostructured photocatalysts for water treatment and renewable energy applications

A combination between the nanostructured photocatalyst and cellulose-based materials promotes a new functionality of cellulose towards the development of new bio-hybrid materials for various applications especially in water treatment and renewable energy. The excellent compatibility and association between nanostructured photocatalyst and cellulose-based materials was induced by bio-combability and high hydrophilicity of the cellulose components. The electron rich hydroxyl group of celluloses helps to promote superior interaction with photocatalyst. The formation of bio-hybrid nanostructured are attaining huge interest nowadays due to the synergistic properties of individual cellulose-based material and photocatalyst nanoparticles. Therefore, in this review we introduce some cellulose-based material and discusses its compatibility with nanostructured photocatalyst in terms of physical and chemical properties. In addition, we gather information and evidence on the fabrication techniques of cellulose-based hybrid nanostructured photocatalyst and its recent application in the field of water treatment and renewable energy.

Extraction, preparation and application of pigments from Cordyline fruticosa and Hylocereus polyrhizus as sensitizers for dye-sensitized solar cells

Current study employs mixture of chlorophyll-anthocyanin dye extracted from leaves of Cordyline fruticosa as new sensitizers for dye-sensitized solar cell (DSSCs), as well as betalains dye obtained from fruit of Hylocereus polyrhizus. Among ten pigments solvents, the ethanol and methanol extracts revealed higher absorption spectra of pigments extracted from C. fruticosa and H. polyrhizus respectively. A major effect of temperature increase was studied to increase the extraction yield. The results indicated that extraction temperature between 70 and 80°C exhibited a high dye concentration of each plant than other temperatures. The optimal temperature was around 80°C and there was a sharp decrease of dye concentration at temperatures higher than this temperature. According to experimental results, the conversion efficiency of DSSC fabricated by mixture of chlorophyll and anthocyanin dyes from C. fruticosa leaves is 0.5% with short-circuit current (Isc) of 1.3mA/cm^-2_, open-circuit voltage (Voc) of 0.62V and fill factor (FF) of 60.16%. The higher photoelectric conversion efficiency of the DSSC prepared from the extract of H. polyrhizus was 0.16%, with Voc of 0.5V, Isc of 0.4mA/cm^-2 and FF of 79.16%. The DSSC based betalain dye extracted from fruit of H. polyrhizus shows higher maximum IPCE of 44% than that of the DSSCs sensitized with mixed chlorophyll-anthocyanin dye from C. fruticosa (42%).

Solar photocatalytic degradation of 2-chlorophenol with ZnO nanoparticles: optimisation with D-optimal design and study of intermediate mechanisms

In this study, the photocatalytic degradation of toxic pollutant (2-chlorophenol) in the presence of ZnO nanoparticles (ZnO NPs) was investigated under solar radiation. The three main factors, namely pH of solution, solar intensity and calcination temperature, were selected in order to examine their effects on the efficiency of the degradation process. The response surface methodology (RSM) technique based on D-optimal design was applied to optimise the process. ANOVA analysis showed that solar intensity and calcination temperature were the two significant factors for degradation efficiency. The optimum conditions in the model were solar intensity at 19.8 W/m², calcination temperature at 404 °C and pH of 6.0. The maximum degradation efficiency was predicted to be 90.5% which was in good agreement with the actual experimental value of 93.5%. The fit of the D-optimal design correlated very well with the experimental results with higher values of R ² and R ²_adj correlation coefficients of 0.9847 and 0.9676, respectively. The intermediate mechanism behaviour of the 2-chlorophenol degradation process was determined by gas chromatography-mass spectrometry (GC-MS). The results confirmed that 2-chlorophenol was converted to acetic acid, a non-toxic compound.

Physicochemical characterization of cellulose nanocrystal and nanoporous self-assembled CNC membrane derived from Ceiba pentandra

This research involves the rare utilisation of the kapok fibre (Ceiba pentandra) as a raw material for the fabrication of cellulose nanocrystal (CNC) and self-assembled CNC membranes. The isolation of CNC from Ceiba pentandra began with the extraction of cellulose via the chemical alkali extraction by using 5wt% NaOH, followed by the typical acidified bleaching method and, finally, the CNC production through acid hydrolysis with 60wt% H₂SO₄ at the optimum time of 60min. The prepared CNC was then employed for the preparation of self-assembled membrane through the water suspension casting evaporation technique. The obtained CNC membrane was characterised in terms of its composition, crystallinity, thermal stability, as well as, structural and morphological features with the use of several techniques including FTIR, XRD, AFM, TEM, FESEM, and TGA. The FESEM and AFM analyses had illustrated the achievement of a self-assembled CNC membrane with a smooth surface and a well-distributed nano-porous structure, with the porosity of 52.82±7.79%. In addition, the findings proved that the self-assembled CNC membrane displayed good adsorption capability indicated by the recorded efficiency of 79% and 85% for 10mg/L and 5mg/L of methylene blue in an aqueous solution, respectively.

Antioxidant Activities of 4-Methylumbelliferone Derivatives

The synthesis of derivatives of 4-Methylumbelliferone (4-MUs), which are structurally interesting antioxidants, was performed in this study. The modification of 4-Methylumbelliferone (4-MU) by different reaction steps was performed to yield the target compounds, the 4-MUs. The 4-MUs were characterized by different spectroscopic techniques (Fourier transform infrared; FT-IR and Nuclear magnetic resonance; NMR) and micro-elemental analysis (CHNS). The in vitro antioxidant activity of the 4-MUs was evaluated in terms of their free radical scavenging activities against 2,2-diphenyl-1-picrylhydrazyl (DPPH), Nitric oxide radical scavenging activity assay, chelating activity and their (FRAP) ferric-reducing antioxidant power, which were compared with a standard antioxidant. Our results reveal that the 4-MUs exhibit excellent radical scavenging activities. The antioxidant mechanisms of the 4-MUs were also studied. Density Function Theory (DFT)-based quantum chemical studies were performed with the basis set at 3-21G. Molecular models of the synthesized compounds were studied to understand the antioxidant activity. The electron levels, namely HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital), for these synthesized antioxidants were also studied.

Synthesis, inhibition effects and quantum chemical studies of a novel coumarin derivative on the corrosion of mild steel in a hydrochloric acid solution

BACKGROUND

The acid corrosion inhibition process of mild steel in 1 M HCl by 4-[(2-amino-1, 3, 4-thiadiazol-5-yl)methoxy]coumarin (ATC), has been investigated using weight loss technique and scanning electron microscopy (SEM). ATC was synthesized, and its chemical structure was elucidated and confirmed using spectroscopic techniques (infrared and nuclear magnetic resonance spectroscopy).

FINDINGS

The results indicated that inhibition efficiencies were enhanced with an increase in concentration of inhibitor and decreased with a rise in temperature. The adsorption equilibrium constant (K) and standard free energy of adsorption (ΔGads) were calculated. Quantum chemical parameters such as highest occupied molecular orbital energy, lowest unoccupied molecular orbital energy (EHOMO and ELUMO, respectively) and dipole moment (μ) were calculated and discussed. The results showed that the corrosion inhibition efficiency increased with an increase in both the EHOMO and μ values but with a decrease in the ELUMO value.

CONCLUSIONS

Our research show that the synthesized macromolecule represents an excellent inhibitor for materials in acidic solutions. The efficiency of this macromolecule had maximum inhibition efficiency up to 96 % at 0.5 mM and diminishes with a higher temperature degree, which is revealing of chemical adsorption. An inhibitor molecule were absorbed by metal surface and follow Langmuir isotherms low and establishes an efficient macromolecule inhibitor having excellent inhibitive properties due to entity of S (sulfur) atom, N (nitrogen) atom and O (oxygen) atom.

Coumarins as Potential Antioxidant Agents Complemented with Suggested Mechanisms and Approved by Molecular Modeling Studies

Syntheses of coumarins, which are a structurally interesting antioxidant activity, was done in this article. The modification of 7-hydroxycoumarin by different reaction steps was done to yield target compounds. Molecular structures were characterized by different spectroscopical techniques (Fourier transformation infrared and nuclear magnetic resonance). Antioxidant activities were performed by using various in vitro spectrophometric assays against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and hydrogen peroxide (H2O2). All compounds exhibited high efficiency as antioxidants compared to ascorbic acid. The highest efficiency scavenging activity was found for compound 3 (91.0 ± 5.0), followed by compounds 2 and 4 (88.0 ± 2.00; and 87.0 ± 3.00). Ascorbic acid C was used as a standard drug with a percentage inhibition of 91.00 ± 1.5. The mechanism of the synthesized compounds as antioxidants was also studied. Hartree-Fock-based quantum chemical studies have been carried out with the basis set to 3-21G, in order to obtain information about the three-dimensional (3D) geometries, electronic structure, molecular modeling, and electronic levels, namely HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital), to understand the antioxidant activity for the synthesized compounds.

Properties and Applications of Polyvinyl Alcohol, Halloysite Nanotubes and Their Nanocomposites

The aim of this review was to analyze/investigate the synthesis, properties, and applications of polyvinyl alcohol-halloysite nanotubes (PVA-HNT), and their nanocomposites. Different polymers with versatile properties are attractive because of their introduction and potential uses in many fields. Synthetic polymers, such as PVA, natural polymers like alginate, starch, chitosan, or any material with these components have prominent status as important and degradable materials with biocompatibility properties. These materials have been developed in the 1980s and are remarkable because of their recyclability and consideration of the natural continuation of their physical and chemical properties. The fabrication of PVA-HNT nanocomposites can be a potential way to address some of PVA's limitations. Such nanocomposites have excellent mechanical properties and thermal stability. PVA-HNT nanocomposites have been reported earlier, but without proper HNT individualization and PVA modifications. The properties of PVA-HNT for medicinal and biomedical use are attracting an increasing amount of attention for medical applications, such as wound dressings, drug delivery, targeted-tissue transportation systems, and soft biomaterial implants. The demand for alternative polymeric medical devices has also increased substantially around the world. This paper reviews individualized HNT addition along with crosslinking of PVA for various biomedical applications that have been previously reported in literature, thereby showing the attainability, modification of characteristics, and goals underlying the blending process with PVA.

Photostabilizing Efficiency of PVC in the Presence of Schiff Bases as Photostabilizers

The photostabilization of polyvinyl chloride (PVC) films by Schiff bases was investigated. Polyvinyl chloride films containing 0.5 wt % Schiff bases were produced using the same casting method as that used for additive-free PVC films from tetrahydrofuran (THF) solvent. The photostabilization activities of these compounds were determined by monitoring the carbonyl, polyene and hydroxyl indices with irradiation time. The changes in viscosity average molecular weight of PVC with irradiation time were also monitored using THF as a solvent. The quantum yield of chain scission (Φcs) for the studied complexes in PVC was estimated to range between 4.72 and 8.99 × 10(-8). According to the experimental results, several mechanisms were suggested, depending on the structure of the additive. Ultra violet (UV) absorption, peroxide decomposition and radical scavenging were suggested as the photostabilizing mechanisms.

Hydrogen Peroxide Scavenging Activity of Novel Coumarins Synthesized Using Different Approaches

New derivatives of 7-hydroxy-4-methylcoumarin were synthesized using a chemical method and a microwave-assisted method to compare the feasibility, reaction times, and yields of the product. The newly synthesized coumarins were characterized by different spectroscopic techniques (FT-IR and NMR) and micro-elemental analysis (CHNS). In vitro antioxidant activities of these compounds were evaluated against hydrogen peroxide and were compared with standard natural antioxidant, vitamin C. Our results reveal that these compounds exhibit excellent radical scavenging activities.

Novel macromolecules derived from coumarin: synthesis and antioxidant activity

The rational design of 4-hydroxycoumarins with tailor-made antioxidant activities is required nowadays due to the wide variety of pharmacologically significant, structurally interesting of coumarins and researcher orientation toward green chemistry and natural products. A simple and unique coumarins have been achieved by reaction of 4-hydroxycoumarin with aromatic aldehyde accompanied with the creation of a macromolecules have 2-aminothiazolidin-4-one. The molecular structures of the compounds were characterized by the Fourier transformation infrared and Nuclear magnetic resonance spectroscopies, in addition to CHN analysis. The scavenging abilities of new compounds against stable DPPH radical (DPPH•) and hydrogen peroxide were done and the results show that the compounds exhibited high antioxidant activates.

Effect of solvents on the extraction of natural pigments and adsorption onto TiO2 for dye-sensitized solar cell applications

Nine solvents, namely, n-hexane, ethanol, acetonitrile, chloroform, ethyl-ether, ethyl-acetate, petroleum ether, n-butyl alcohol, and methanol were used to extract natural dyes from Cordyline fruticosa, Pandannus amaryllifolius and Hylocereus polyrhizus. To improve the adsorption of dyes onto the TiO2 particles, betalain and chlorophyll dyes were mixed with methanol or ethanol and water at various ratios. The adsorption of the dyes mixed with titanium dioxide (TiO2) was also observed. The highest adsorption of the C.fruticosa dye mixed with TiO2 was achieved at ratio 3:1 of methanol: water. The highest adsorption of P.amaryllifolius dye mixed with TiO2 was observed at 2:1 of ethanol: water. H.polyrhizus dye extracted by water and mixed with TiO2 demonstrated the highest adsorption among the solvents. All extracted dye was adsorbed onto the surface of TiO2 based on Fourier Transform Infrared Spectroscopy (FTIR) analysis. The inhibition of crystallinity of TiO2 was likewise investigated by X-ray analysis. The morphological properties and composition of dyes were analyzed via SEM and EDX.

New coumarin derivative as an eco-friendly inhibitor of corrosion of mild steel in Acid medium

The anticorrosion ability of a synthesized coumarin, namely 2-(coumarin-4-yloxy)acetohydrazide (EFCI), for mild steel (MS) in 1 M hydrochloric acid solution has been studied using a weight loss method. The effect of temperature on the corrosion rate was investigated, and some thermodynamic parameters were calculated. The results indicated that inhibition efficiencies were enhanced with an increase in concentration of inhibitor and decreased with a rise in temperature. The IE value reaches 94.7% at the highest used concentration of the new eco-friendly inhibitor. The adsorption of inhibitor on MS surface was found to obey a Langmuir adsorption isotherm. Scanning electron microscopy (SEM) was performed on inhibited and uninhibited mild steel samples to characterize the surface. The Density Function theory (DFT) was employed for quantum-chemical calculations such as E_HOMO (highest occupied molecular orbital energy), E_LUMO (lowest unoccupied molecular orbital energy) and μ (dipole moment), and the obtained results were found to be consistent with the experimental findings. The synthesized inhibitor was characterized by Fourier transform infrared (FTIR) and nuclear magnetic resonance (NMR) spectroscopic studies.

Quantum chemical assessment of benzimidazole derivatives as corrosion inhibitors

Background

The majority of well-known inhibitors are organic compounds containing multiple bonds and heteroatoms, such as O, N or S, which allow adsorption onto the metal surface. These compounds can adsorb onto the metal surface and block active surface sites, reducing the rate of corrosion.

Results

A comparative theoretical study of three benzimidazole isomers, benzimidazole (BI), 2-methylbenzimidazole (2-CH₃-BI), and 2-mercaptobenzimidazole (2-SH-BI), as corrosion inhibitors was performed using density functional theory (DFT) with the B3LYP functional basis set.

Conclusions

Nitro and amino groups were selected for investigation as substituents of the three corrosion inhibitors. Nitration of the corrosion inhibitor molecules led to a decrease in inhibition efficiency, while reduction of the nitro group led to an increase in inhibition efficiency. These aminobenzimidazole isomers represent a significant improvement in the inhibition efficiency of corrosion inhibitor molecules.

Diagnosis and management of ruptured hepatoma: single center experience over 10 years

INTRODUCTION

Spontaneous rupture is a dramatic presentation of HCC and it carries high mortality rate. To study the outcomes of ruptured HCC patients managed at a tertiary referral centre in Malaysia.

METHODS

A retrospective review of all ruptured HCC patients managed as inpatient at the Department of Hepatobiliary Surgery, Hospital Selayang between January 2001 and December 2010. Data was retrieved from the hospital electronic medical records, Powerchart (Cerner Corporation Inc., USA) and supplemented with registry from Interventional Radiology record of chemoembolization and registry from hepatobiliary operative surgery records.

RESULTS

There were 22 patients admitted with confirmed diagnosis of ruptured HCC over 10 years period. The common clinical findings on presentation were abdominal pain and presence of shock (36.4%). The mortality rate was 81.8% with only four patients noted to be alive during the follow up. One year overall survival for ER and DR are 40.0% and 72.7% respectively and the median survival in patients treated with DR was 433.3 days whereas it was 212.5 days in ER group.

CONCLUSIONS

This study supports the clinical practice of TAE should be the first line treatment followed by staged surgery in suitable candidates with ruptured HCC.

Inhibition effects of a synthesized novel 4-aminoantipyrine derivative on the corrosion of mild steel in hydrochloric acid solution together with quantum chemical studies

1,5-Dimethyl-4-((2-methylbenzylidene)amino)-2-phenyl-1H-pyrazol-3(2H)-one (DMPO) was synthesized to be evaluated as a corrosion inhibitor. The corrosion inhibitory effects of DMPO on mild steel in 1.0 M HCl were investigated using electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, open circuit potential (OCP) and electrochemical frequency modulation (EFM). The results showed that DMPO inhibited mild steel corrosion in acid solution and indicated that the inhibition efficiency increased with increasing inhibitor concentration. Changes in the impedance parameters suggested an adsorption of DMPO onto the mild steel surface, leading to the formation of protective films. The novel synthesized corrosion inhibitor was characterized using UV-Vis, FT-IR and NMR spectral analyses. Electronic properties such as highest occupied molecular orbital energy, lowest unoccupied molecular orbital energy (EHOMO and ELUMO, respectively) and dipole moment (μ) were calculated and discussed. The results showed that the corrosion inhibition efficiency increased with an increase in the EHOMO values but with a decrease in the ELUMO value.

Visible light photocatalytic activity of Fe(3+)-doped ZnO nanoparticle prepared via sol-gel technique

The optical properties of a ZnO photocatalyst were enhanced with various dopant concentrations of Fe(3+). Doped ZnO nanoparticles were synthesized via a sol-gel method without the use of capping agents or surfactants and was then characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and ultraviolet-visible (UV-Vis) spectroscopy. The results showed that ZnO has a wurtzite, hexagonal structure and that the Fe(3+) ions were well incorporated into the ZnO crystal lattice. As the Fe(3+) concentration increased from 0.25 wt.% to 1 wt.%, the crystal size decreased in comparison with the undoped ZnO. The spectral absorption shifts of the visible light region (red shift) and the band gap decreases for each Fe-ZnO sample were investigated. The photocatalytic activities of the ZnO and Fe-ZnO samples were evaluated based on the degradation of 2-chlorophenol in aqueous solution under solar radiation. The samples with a small concentration of Fe(3+) ions showed enhanced photocatalytic activity with an optimal maximum performance at 0.5 wt.%. The results indicated that toxicity removal of 2-chlorophenol at same line of degradation efficiency. Small crystallite size and low band gap were attributed to high activities of Fe-ZnO samples under various concentrations of Fe(3+) ions compared to undoped ZnO.

Simultaneous removal of AOX and COD from real recycled paper wastewater using GAC-SBBR

A lab-scale granular activated carbon sequencing batch biofilm reactor (GAC-SBBR), a combined adsorption and biological process, was developed to treat real wastewater from a recycled paper mill. In this study, one-consortia of mixed culture (4000-5000 mg/L) originating from recycled paper mill activated sludge from Kajang, Malaysia was acclimatized. The GAC-SBBR was fed with real wastewater taken from the same recycled paper mill, which had a high concentration of chemical oxygen demand (COD) and adsorbable organic halides (AOX). The operational duration of the GAC-SBBR was adjusted from 48 h to 24, 12 and finally 8 h to evaluate the effect of the hydraulic retention time (HRT) on the simultaneous removal of COD and AOX. The COD and AOX removals were in the range of 53-92% and 26-99%, respectively. From this study, it was observed that the longest HRT (48 h) yielded a high removal of COD and AOX, at 92% and 99%, respectively.

Application of response surface methodology (RSM) for optimisation of COD, NH3-N and 2,4-DCP removal from recycled paper wastewater in a pilot-scale granular activated carbon sequencing batch biofilm reactor (GAC-SBBR)

In this study, the potential of a pilot-scale granular activated carbon sequencing batch biofilm reactor (GAC-SBBR) for removing chemical oxygen demand (COD), ammoniacal nitrogen (NH3-N) and 2,4-dichlorophenol (2,4-DCP) from recycled paper wastewater was assessed. For this purpose, the response surface methodology (RSM) was employed, using a central composite face-centred design (CCFD), to optimise three of the most important operating variables, i.e., hydraulic retention time (HRT), aeration rate (AR) and influent feed concentration (IFC), in the pilot-scale GAC-SBBR process for recycled paper wastewater treatment. Quadratic models were developed for the response variables, i.e., COD, NH3-N and 2,4-DCP removal, based on the high value (>0.9) of the coefficient of determination (R(2)) obtained from the analysis of variance (ANOVA). The optimal conditions were established at 750 mg COD/L IFC, 3.2 m(3)/min AR and 1 day HRT, corresponding to predicted COD, NH3-N and 2,4-DCP removal percentages of 94.8, 100 and 80.9%, respectively.

A Novel Hydrazinecarbothioamide as a Potential Corrosion Inhibitor for Mild Steel in HCl

2-(1-methyl-4-((E)-(2-methylbenzylidene)amino)-2-phenyl-1H-pyrazol-3(2H)-ylidene)-hydrazineecarbothioamide (HCB) was synthesized as a corrosion inhibitor from the reaction of 4-aminoantipyrine, thiosemicarbazide and 2-methylbenzaldehyde. The corrosion inhibitory effects of HCB on mild steel in 1.0 M HCl were investigated using potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). The results showed that HCB inhibited mild steel corrosion in acidic solution and inhibition efficiency increased with an increase in the concentration of the inhibitor. The inhibition efficiency was up to 96.5% at 5.0 mM. Changes in the impedance parameters suggested that HCB adsorbed on the surface of mild steel, leading to the formation of a protective film. The novel corrosion inhibitor synthesized in the present study was characterized using Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR) spectral data.

Green synthesis, antimicrobial and cytotoxic effects of silver nanoparticles using Eucalyptus chapmaniana leaves extract

OBJECTIVE

To synthesize silver nanopaticles from leaves extract of Eucalyptus chapmaniana (E. chapmaniana) and test the antimicrobial of the nanoparticles against different pathogenic bacteria, yeast and its toxicity against human acute promyelocytic leukemia (HL-60) cell line.

METHODS

Ten milliliter of leaves extract was mixed with 90 mL of 0.01 mmol/mL or 0.02 mmol/mL aqueous AgNO3 and exposed to sun light for 1 h. A change from yellowish to reddish brown color was observed. Characterization using UV-vis spectrophotometery and X-ray diffraction analysis were performed. Antimicrobial activity against six microorganisms was tested using well diffusion method and cytoxicity test using 3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide, a yellow tetrazole was obtained on the human leukemia cell line (HL-60).

RESULTS

UV-vis spectral analysis showed silver surface plasmon resonance band at 413 nm. X-ray diffraction showed that the particles were crystalline in nature with face centered cubic structure of the bulk silver with broad beaks at 38.50° and 44.76°. The synthesized silver nanoparticles efficiently inhibited various pathogenic organisms and reduced viability of the HL-60 cells in a dose-dependent manner.

CONCLUSIONS

It has been demonstrated that the extract of E. chapmaniana leaves are capable of producing silver nanoparticles extracellularly and the Ag nanoparticles are quite stable in solution. Further studies are needed to fully characterize the toxicity and the mechanisms involved with the antimicrobial and anticancer activity of these particles.

Novel pyranopyrazoles: synthesis and theoretical studies

A series of pyranopyrazoles, namely, 7-(2-aminoethyl)-3,4-dimethyl-1-phenyl-1H-pyrazolo[3,4-b]pyridin-6(7H)-one (2), (Z)-3,4-dimethyl-1-(4-((4-nitrobenzylidene)amino)phenyl)pyrano[2,3-c]pyrazol-6(1H)-one (5), 1-(4-(3,4-dimethyl-6-oxopyrano[2,3-c]pyrazol-1(6H)-yl)phenyl)-3-(naphthalen-1-yl)urea (6), (Z)-ethyl 4-((3,4-dimethyl-6-oxo-1,6-dihydropyrano[2,3-c]pyrazol-5-yl)diazenyl)benzoate (8) and 3,4-dimethyl-N-(naphthalen-1-yl)-6-oxopyrano[2,3-c]pyrazole-1(6H)-carboxamide (9) were synthesized and characterized by means of their UV-VIS, FT-IR, ¹H-NMR and ¹³C-NMR spectral data. Density Functional Theory calculations of the synthesized pyranopyrazoles were performed using molecular structures with optimized geometries. Molecular orbital calculations have provided detail description of the orbitals, including spatial characteristics, nodal patterns, and the contributions of individual atoms.

Antifungal activities of new coumarins

Newly synthesized coumarins 4-((5-mercapto-4-phenyl-4H-1,2,4-triazol-3-yl)-methoxy)-2H-chromen-2-one and 4-((5-(phenylamino)-1,3,4-thiadiazol-2-yl)-methoxy)-2H-chromen-2-one were tested against selected types of fungi and showed significant activities. DFT calculations of the synthesized coumarins were performed using molecular structures with optimized geometries. Molecular orbital calculations provide a detailed description of the orbitals, including spatial characteristics, nodal patterns, and the contributions of individual atoms.

Direct acetylation and determination of chlorophenols in aqueous samples by gas chromatography coupled with an electron-capture detector

A method was developed that offers a rapid, simple and accurate technique for the determination of chlorophenols at trace levels in aqueous samples with very limited volumes of organic solvents. These compounds were acetylated, then preliminarily extracted with n-hexane. The enriched chlorophenols were directly analyzed using gas chromatography with an electron-capture detector. The detection limits were in the range of 0.001-0.005 mg/L, except for 2-chlorophenol, which was always above 0.013 mg/L. Relative standard deviation for the spiked water samples ranged from 2.2 to 6.1%, while relative recoveries were in the range of 67.1 to 101.3%.

Performance evaluation of a granular activated carbon-sequencing batch biofilm reactor pilot plant system used in treating real wastewater from recycled paper industry

A pilot scale granular activated carbon-sequencing batch biofilm reactor with a capacity of 2.2 m3 was operated for over three months to evaluate its performance treating real recycled paper industry wastewater under different operational conditions. In this study, dissolved air floatation (DAF) and clarifier effluents were used as influent sources of the pilot plant. During the course of the study, the reactor was able to biodegrade the contaminants in the incoming recycled paper mill wastewater in terms of chemical oxygen demand (COD), adsorbable organic halides (AOX; specifically 2,4-dichlorophenol (2,4-DCP)) and ammoniacal nitrogen (NH3-N) removal efficiencies at varying hydraulic retention times (HRTs) of 1-3 days, aeration rates (ARs) of 2.1-3.4 m3/min and influent feed concentration of 40-950 mg COD/l. Percentages of COD, 2,4-DCP and NH3-N removals increased with increasing HRT, resulting in more than 90% COD, 2,4-DCP and NH3-N removals at HRT values above two days. Degradation of COD, 2,4-DCP and NH3-N were seriously affected by variation of ARs, which resulted in significant decrease of COD, 2,4-DCP and NH3-N removals by decreasing ARs from 3.4 m3/min to 2.1 m3/min, varying in the ranges of 24-80%, 6-96% and 5-42%, respectively. In comparison to the clarifier effluent, the treatment performance of DAF effluent, containing high COD concentration, resulted in a higher COD removal of 82%. The use of diluted DAF effluent did not improve significantly the COD removal. Higher NH3-N removal efficiency of almost 100% was observed during operation after maintenance shutdown compared to normal operation, even at the same HRT of one day due to the higher dissolved oxygen concentrations (1-7 mg/l), while no significant difference in COD removal efficiency was observed.

Antimicrobial and antioxidant activities of new metal complexes derived from 3-aminocoumarin

3-Aminocoumarin (L) has been synthesized and used as a ligand for the formation of Cr(III), Ni(II), and Cu(II) complexes. The chemical structures were characterized using different spectroscopic methods. The elemental analyses revealed that the complexes where M=Ni(II) and Cu(II) have the general formulae [ML(2)Cl(2)], while the Cr(III) complex has the formula [CrL(2)Cl(2)]Cl. The molar conductance data reveal that all the metal chelates, except the Cr(III) one, are non-electrolytes. From the magnetic and UV-Visible spectra, it is found that these complexes have octahedral structures. The stability for the prepared complexes was studied theoretically using Density Function Theory. The total energy for the complexes was calculated and it was shown that the copper complex is the most stable one. Complexes were tested against selected types of microbial organisms and showed significant activities. The free radical scavenging activity of metal complexes have been determined by measuring their interaction with the stable free radical DPPH and all the compounds have shown encouraging antioxidant activities.

The use of umbelliferone in the synthesis of new heterocyclic compounds

New coumarin derivatives, namely 7-[(5-amino-1,3,4-thiadiazol-2-yl)methoxy]-2H-chromen-2-one, 5-[(2-oxo-2H-chromen-7-yloxy)methyl]-1,3,4-thiadiazol-2(3H)-one, 2-[2-(2-oxo-2H-chromen-7-yloxy)acetyl]-N-phenylhydrazinecarbothioamide, 7-[(5-(phenylamino)-1,3,4-thiadiazol-2-yl)methoxy]-2H-chromen-2-one and 7-[(5-mercapto-4-phenyl-4H-1,2,4-triazol-3-yl)methoxy]-2H-chromen-2-one were prepared starting from the natural compound umbelliferone. The newly synthesized compounds were characterized by elemental analysis and spectral studies (IR, ¹H-NMR and ¹³C-NMR).

Chlorophenols in Tigris River and drinking water of Baghdad, Iraq

A study was conducted on a stretch of Tigris river crossing Baghdad city to determine the concentration of some chlorophenols pollutants. Aqueous samples were preliminary enriched about 500 times and the chlorophenols have determined using high performance liquid chromatography HPLC. Limits of detection LOD were (0.007-0.012 mg L(-1)), relative standard deviations RSD% were 2.4%-5.59% and relative recoveries were 51.06%-104.07%. The existence of chlorophenols in Tigris river was in the range 0.023-4.596 mg L(-1). The developed method suggested in this study can be applied for routine analysis and monitoring of chlorinated phenols in environmental aqueous samples.

MAFRAM- a new fate and risk assessment methodology for non-volatile organic chemicals

The main goal of this paper was to introduce an environmental fate and risk assessment methodology for comparing and establishing the general features of new and existing non-volatile organic chemicals (NVOCs) used in agricultural activities, based on simple and readily available properties. This methodology is a computer program called the multimedia agricultural fate and risk assessment model (MAFRAM). This model is a combination of the EQC-2V model, which describes the fate of NVOCs, with the ecological relative risk (EcoRR) approach, which assesses the ecotoxicological risk to agro-ecosystems. MAFRAM divides the agricultural environment into two main zones, which are the on- and off-farm zones. Each zone is subdivided into six compartments, including the air, water, soil, sediment, aboveground plants, and roots. The required input data are the chemical-physical properties of the pesticide, biota data, and environmental properties. The MAFRAM output includes the inter-compartmental transport and transfer rates, the primary loss mechanisms, chemical concentration, amount, residence time, and the rank of risk in each compartment. In addition, it can provide several secondary results. The MAFRAM application was illustrated using typical homogenous region properties and was run with an illustrative emission rate of 1 kg/h into air, using spinosad as a case study.