Bulgarian Chemical Communications, Volume 50, Number 1, 2018
 
Contents:
   
 

Editorial
On the occasion of the 50th volume of our journal
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1

Kinetic and equilibrium modeling of the removal of Cr (VI) ions by chemically treated Zea mays (Corn) cob from aqueous solutionst
Original Research Article
Pages 7 – 15
A. R. Abbas, Misbah, M. Riaz, M. A. Hanif, M. Suleman, Y. Gull
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Abstract
In the present study, biosorption of Cr (VI) from aqueous solutions was conducted using chemically treated Zea mays (corn) cob. The effect of various parameters like biosorbent size and dose, pH, contact time and initial metal concentration necessary for establishment of equilibrium biosorption of Cr (VI) ion using chemically treated Zea mays (corn) cob was studied. Biosorbent was treated with different chemicals such as NaOH, acetone and HCl for surface modification. The biosorbent dose providing maximum percentage removal (23.7 %) was 0.3 g, while with 0.5 g maximum metal uptake (14.2 mg/g) was observed. The Zea mays (corn) cob biosorbent shows maximum adsorption capacity for different pretreated and untreated samples. For estimation of the removal of metal, Cr (VI) concentration was analysed before and after the biosorption process by atomic absorption spectrophotometry (AAS). SEM and EDX analysis provided information on the biosorption of Cr (VI) on the biosorbent surface. The data obtained were analyzed using Langmuir isotherm and Freundlich isotherm models, pseudo first- and pseudo second-order kinetic models. From the result it followed that Langmuir isotherm and pseudo second-order kinetic model best fitted the experimental data having higher R2 value. Finally, the results were analyzed statistically.

   
2

Preparation of carbon paste electrode containing polyaniline-activated carbon composite for amperometric detection of phenol
Original Research Article
Pages 16 – 20
H. Arslan, D. Şenarslan, B.S. Çevrimli, H. Zengin, D. Uzun, F. Arslan
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Abstract
In this study, a novel carbon paste electrode was prepared using the salt form of polyaniline (pani)-activated carbon composite sensitive to phenol. Polyphenol oxidase enzyme was immobilized to the modified carbon paste electrode by cross-linking with glutaraldehyde. The amperometric determination is based on the electrochemical reduction of o-quinone generated in the enzymatic reaction of phenol at -0.15 V vs. Ag/AgCl. The effects of pH and temperature were investigated and optimum values were found to be 8.0 and 45 °C, respectively. The linear working range of the electrode was 1.0×10-6 - 5.0×10-5 M, R2 =0.9819. The storage stability and operation stability of the enzyme electrode
were also studied.

   
3

Employing reverse osmosis for the removal of ortho-toluidine from wastewater
Original Research Article
Pages 21 – 26
Aref Shokri
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Abstract
Ortho-Toluidine (OT) is a dangerous and persistent organic pollutant in the industrial wastewater and needs treatment before disposal. In this project, the performance of reverse osmosis membrane system (RO 90) for the removal of OT from aqueous solutions is investigated. The influence of different operational variables such as pressure, concentration, pH and the volumetric flow rate of feed was considered in the removal performance of the OT. The influence of feed flow rate on the rejection percentage and the permeate flux was not the same. The results showed that at the optimum conditions obtained for rejection, (feed concentration at 80 mg/l, the pressure of feed at 50×105��/��2, pH at 7, and feed flow rate at 8×10−5��3/��), the rejection percentage and the permeate flux were 97.8%, and 38.5×104 ��3/��2.��, respectively.

   
4

Using UV/ZnO process for degradation of Acid red 283 in synthetic wastewater
Original Research Article
Pages 27 –32
A. Shokri, K. Mahanpoor
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Abstract
In this research, the photocatalytic degradation of Acid red 283 (AR283) was investigated by the UV/ZnO process in a batch photoreactor. The experiments revealed that the ZnO nanocatalyst and UV light had a slight influence when they were used separately. The impact of various factors such as initial pH, initial dosage of dye and catalyst on the degradation efficiency was investigated. The degradation and mineralization of AR 283 were estimated by HPLC and COD tests, respectively. At optimum conditions (0.3 g/L of catalyst, pH 8 and initial concentration of AR283 25 mg/l), the removal of AR283 and COD were 99.5 and 58.5% at 60 and 120 min of reaction, respectively. The pseudo-first-order kinetics of the removal of AR283 can be explained in terms of the Langmuir–Hinshelwood model. The apparent rate constant (Kapp =27.2× 10−3min−1) was obtained.

   
5

Crystal structure of 4-amino-N-pyrimidin-2-ylbenzenesulfonamide
Original Research Article
Pages 33 – 36
V. Gomathi, R. Selvameena
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Abstract
4-Amino-N-pyrimidin-2-ylbenzenesulfonamide (sulfadiazine) was recrystallised from a mixture of ethanol and N,N-dimethylformamide. The structure of sulfadiazine was confirmed by single crystal X-ray diffraction study to be monoclinic, space group P21/c, a=13.6210(9)Å, b=5.9250(3)Å, c=14.9910(9)Å, α= γ =90°, β=114.574(2)°, T=293(2)K, Z=4, F(000)= 520, Dx=1.511 mg/m3, absorption coefficient = 0.290mm-1.

   
6

Synthesis, characterization and biological activities of a novel Mannich base 2-[(3, 4-dimethoxyphenyl)(pyrrolidin-1-yl)methyl]cyclopentanone and its complexes with Cu(II), Co(II), Ni(II) and Fe(II) ions
Original Research Article
Pages 37 – 43
M. Liaqat, T. Mahmud, M. Imran, M. Ashraf, A. U. Haq, M. Muddassar, T. Ahmad
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Abstract
One-pot, three-component Mannich reaction was carried out by condensation of 3,4-dimethoxybenzaldehyde, pyrrolidine and cyclopentanone in the presence of calcium chloride using ethanol as a solvent to afford a novel Mannich base (L). The resulting Mannich base (L) was isolated and complexed with Cu(II), Co(II), Ni(II) and Fe(II) ions. The structures of the synthesized scaffolds were confirmed by IR, 1H NMR, 13C NMR, mass spectroscopy, TGA and elemental analyses. The metal contents were determined by ICP-OES. All compounds showed poor antibacterial activities. The anti-enzymatic activities of the Mannich base (L) and its metal complexes were checked against jack bean urease. The Mannich base ligand (L), its nickel and iron complexes showed potent antiurease activity with IC50 values of 9.25±0.002, 1.42±0.003, 5.41±0.005 μM, respectively, and were superior inhibitors than the standard, thiourea (IC50 21.25±0.15 μM). The probable binding mode of the most active Ni(II) complex was determined using molecular docking simulations.

   
7

QSAR study on the physico-chemical parameters of barbiturates by using topological indices and MLR method
Original Research Article
Pages 44 – 49
E.Esmaeili, F.Shafiei
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Abstract
In this study the relationship of the Randic' (1X), Balaban (J), Szeged (Sz), Harary (H), Wiener (W), Hyper-Wiener (WW) and Wiener polarity (Wp) with the polarizability (POL), molar refractivity (MR) and octanol/water partition coefficient (logP) of barbiturates is studied. The chemical structures of the molecules were optimized using ab initio 6-31G basis sets method and Polak-Ribiere algorithm with conjugated gradient within Hyper Chem 8.0 environment. The multiple linear regressions (MLR) and backward methods (with significance at the 0.05 level) were employed to give the QSAR models. After MLR analysis, we studied the validation of linearity between the molecular descriptors in the best models for the used properties. The predictive powers of the models were discussed by using the method of cross-validation. The results have shown that the combination of two descriptors (Wp, W) is excellent for predicting the polarizability, and the descriptor (WW) is useful for modeling and for predicting the molar refractivity and octanol/water partition of the corresponding barbiturates.

   
8

Stability of gold complex based on mercaptotriazole in acid and neutral media
Original Research Article
Pages 50 – 57
S. Dimitrijević, M. Rajčić Vujasinović, St. Dimitrijević, B. Trumić, A. Ivanović
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Abstract
Stability of the gold complex based on mercaptotriazole in two acid electrolytes with different pH values and in a neutral medium was investigated in this work. Investigation was performed by visual monitoring and electrochemical characterization of the electrolytes in a period of one year or until first visible signs of complex decomposition. Electrochemical characterization of the gold complex based on mercaptotriazole was performed by open circuit potential measurement, cycling voltammetry method and by recording the polarization curves. The pH values of the electrolytes were measured before and after each electrochemical experiment. These tests were performed at different starting pH values: 2, 4 and 7 at optimal concentration of gold in the electrolyte of 2.5 g/dm3. For electrolytes with pH values of four and seven, the first visible signs of the complex decomposition appeared tree months after synthesis. Electrolyte with pH value of two was visually stable for a period of one year.

   
9

Nanosized Zn2SnO4 powders synthesized by coprecipitation and consecutive hydrothermal treatment in two different alkaline media
Original Research Article
Pages 58 – 62
V. Blaskov, I Stambolova, L. Dimitrov, M. Shipochka, D. Stoyanova, A. Eliyas
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Abstract
A two-step method has been applied to the synthesis of zinc orthostannate, Zn2SnO4. As a first step X-ray amorphous hydroxide precursor had been obtained by coprecipitation of Zn(NO3)2 and SnCl2 solutions using Na2CO3. In the second step the precursor was subjected to hydrothermal treatment (HT) in the presence of sodium hydroxide or ammonium hydroxide. The samples have been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and UV-Vis spectroscopy. The precursor powder showed absorption edge at about 423 nm, while the absorption band of the HT samples, obtained in NH4OH and NaOH, is shifted to 441 nm and 471 nm, respectively. The treatment of the amorphous precipitate in the presence of sodium hydroxide leads to a higher degree of crystallization, smaller sizes of the crystallites and higher photocatalytic activity for discoloration of the textile dye Methylene Blue (MB).

   
10

Effect of controlled volume variation on the osmotic rate in aqueous solutions
Original Research Article
Pages 63 – 68
I. L. Minkov, E. D. Manev, S. V. Sazdanova, K. H. Kolikov
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Abstract
The evolution of the osmotic pressure in aqueous solutions was studied experimentally as a function of time in two different regimes: of constant and variable solution volume. Quantitative dependence of the solvent osmotic rate on the relative solution volume variation was established as well. Glucose, a biologically active substance, was chosen as a reference solute for the complex tests. A custom made osmotic cell was used. A novel operative experimental approach, employing controlled limited variation of the solution volume was developed and applied for the purpose. First of all, the obtained kinetic dependencies reveal strong divergence in the rates of the process at the two experimental regimes. The rise of pressure is much faster at constant solution volume, while the solvent influx is many times greater in the regime of variable volume. Moreover, the rate of the osmotic process is being modified by varying the solution volume. We consider the effects established here by means of an artificial semipermeable membrane to be of relevance for the processes taking place in the real living cells and tissues.

   
11

Quercetin content and ratios to total flavonols and total flavonoids in Bulgarian fruits and vegetables
Original Research Article
Pages 69 – 73
S. Tsanova-Savova, F. Ribarova, V. Petkov
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Abstract
Flavonoids as bioactive compounds in vegetable foods have been the subject of numerous research projects. Quercetin, with its powerful antioxidant activity, has also been and is currently in the focus of studies on plant species identification, and on its role in healthy nutrition. The current literature sources provide diverse information on its content in particular plant species but there are almost no data on its ratios to other flavonoids representatives. The aim of this survey was to provide information about quercetin analysis and content as a major flavonols representative and quercetin ratios to total flavonols, expressed as a sum of myricetin, quercetin and kaempferol and to total flavonoids in Bulgarian fruits and vegetables. The survey covered 17 fruit and 13 vegetable samples, complying with the current sampling requirements, with a view to food composition assessment. Quercetin and other flavonols analysis by High Performance Liquid Chromatography (HPLC) method; Total flavonoid content was determined by the aluminum chloride colorimetric assay. Evidence is presented on quercetin content in fruits and vegetables and on its ratio to total flavonols and total flavonoids content. The results demonstrate that quercetin is most frequently the major flavonol representative in the majority of the analyzed samples. There is, though, an interesting exception, presented by the representatives of the Cruciferae family - broccoli and Brussels sprouts - where the quercetin ratio to total flavonoids is very high, reaching up to almost 50%. In fruits, quercetin in strawberries is only 44.0% of the total flavonols, thus demonstrating once again the need for a complex approach in the analysis of the data for flavonoids content. The supplementation of the flavonoids composition and content data with evidence about their ratios will enable more correct identification of the biodiversity and will allow to compensate, though to only a certain extent, the effect of the biological variation on the accuracy of the analysis, and will enrich the information needed to build up a data base for flavonoids in foods.

   
12

Coffee grounds as low-cost adsorbent for the removal of copper (II) and lead (II) from aqueous solutions
Original Research Article
Pages 74 – 81
J. Seniūnaitė, R. Vaiškūnaitė, D. Paliulis
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Abstract
This work aims to study the removal of Cu (II) and Pb (II) from aqueous solutions with commercial coffee wastes (coffee grounds). Materials with no further treatment such as coffee residues from café may act as adsorbents for the removal of Cu (II) and Pb (II). Coffee ground fraction <200 μm was used in the experimental research. The effect of pH (2.0, 3.0, 4.0 and 5.0), contact time (15, 30, 60, 90, 120, 150, 180, 300, 480 and 720 min) and initial concentration of Cu(II) and Pb(II) (10 mg/L, 20 mg/L, 30 mg/L, 40 mg/L, 50 mg/L) on the adsorption was studied. The optimum values of the process variables were: contact time, 120-720 minutes; pH, 5.0; initial Cu(II) and Pb(II) concentration 20 mg/L. Equilibrium data fitted well to Langmuir and Freundlich models for Pb (II) and Cu (II) with high R2 values. Studies have shown that coffee grounds are a suitable adsorbent for heavy metals removal from water.

   
13

The selective catalytic reactions for improvement of characteristics of gasolines
Original Research Article
Pages 82 – 88
L. R. Sassykova, Zh. T. Basheva, M. K. Kalykberdyev, M. Nurakhmetova, A. T. Massenova, K. S. Rakhmetova
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Abstract
The aim of the research is the development of selective catalysts for the processes improving service performance of gasolines: catalytic hydrogenation of gasoline fractions and production of octane-increasing component of fuel additives – diisopropyl ether (DIPE). The data on the content of organic compounds in the gasoline fractions after the reaction of catalytic hydrogenation show that benzene was absent, the content of aromatic compounds was reduced from 55.12% (wt.) to 32.5% (wt.). The olefins content was reduced from 0.23% (wt) to 0.11% (wt), and the paraffins content - from 12.41% (wt.) to 11.99% (wt), whereas the iso-paraffins content increased from 30.08% (wt) to 34.09% (wt). The content of naphthenes increased from 2.12% (wt.) to 10.14% (wt.). The developed catalytic method of DIPE synthesis from iso-propanol and propane under mild conditions allowed production at a yield of 30.5-68.5%. The most active and stable catalysts for synthesis of DIPE from iso-propanol are molybdenum- and nickel-containing catalysts. The maximum DIPE yield in the optimal temperature range (250-300 оС) was 62.0-68.5%.

   
14

Laboratory system for artificial fog generation with controlled number and size distribution of droplets
Original Research Article
Pages 89 – 93
O. D. Ivanov, Y. I. Ralev, P. V. Todorov, I. P. Popov, K. N. Angelov, J. L. Pérez-Díaz, M. K.Kuneva
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Abstract
In this article a system for generation of fogs is presented, which can be used in testing equipment and experiments that require control of the amount and size distribution of aerosol particles. The main goal of the system development is to eliminate the human error and to improve the results on producing artificial fog with predictable parameters.

   
15

System for generation of fogs with controlled impurities
Original Research Article
Pages 94 – 99
O.D. Ivanov, Y. I. Ralev, P. V. Todorov, I. P. Popov, J. L. Pérez-Díaz, M. K. Kuneva
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Abstract
In this article a system for generation of fogs is presented, which can be used for testing fog sensors under laboratory conditions. Our prototype is able to generate fogs with various chemical composition (up to 6 kinds of fluids), amount, diameters and size distribution of droplets with spraying driven by pulses of different duration (0.2 to 5.5 seconds). Thus, sensors for use in different areas can be tested, for example: control of attacks with CBRN (Chemical, Biological, Radiological, and Nuclear) agents, measurements of industrial pollutants, dust pollution, detection of poisonоus gases, etc. The main goal of the system development is to eliminate the human error and to improve the results of producing artificial fog with predictable parameters. An important advantage of this system is that it allows the amount of impurities in fog to be precisely controlled

   
16

HNO3 immobilized on nano SiO2: A novel efficient heterogeneous catalytic system for the synthesis of 2-substituted oxazolines, imidazolines, thiazolines, and 2-aryl-1H-benzimidazoles under solvent-free conditions
Original Research Article
Pages 100 – 110
K. Nikoofar, Sh. Moazzez Dizgarani
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Abstract
HNO3 immobilized on nano SiO2 (HNO3@nano SiO2) was examined for the synthesis of 2-substituted oxazolines, imidazolines, thiazolines and 2-aryl-1H-benzimidazole derivatives under solvent-free conditions. The results confirmed its excellent efficiency in the preparation of the mentioned heterocycles. The method proved to be simple, green, and convenient; the synthesized nanocatalyst was efficient in a vast domain of substrate transformations to the corresponding products in good yields. The recovery and reusability of the synthesized nanocatalyst was investigated in 4 runs without registering activity loss. The mechanism of the transformations is proposed.

   
17

Effect of LXR agonist T0901317 and miR-33inhibitor on SIRT1-AMPK and circulating HDL-C levels
Original Research Article
Pages 111 – 118
A. Mohammadi, H. Fallah, B. Shahouzehi, H. Najafipour
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Abstract
Cardiovascular diseases (CVD) are still the leading cause of mortality and morbidity worldwide. Liver X receptors (LXRs) and sterol regulatory element binding proteins (SREBPs) play an important role in lipid homeostasis. LXRs affect SREBPs and promote lipid synthesis and reverse cholesterol transport (RCT). MicroRNA-33 down regulates AMPK, ABCA1 and CPT1 mRNA. Sirt1 also affects LXR and SREBP activity through deacetylation. We assessed the effect of LXR agonist and miR-33 inhibitor on Srebp-2, Sirt1, AMPK expression, and lipid profile. Twenty four mice were divided into four groups (n=6) and the study duration was 7 days. Group I, the control group, did not receive any treatment, group II received 30 mg/kg/48 h LXR agonist (T0901317) through i.p. injection, group III received 1 mg/kg/48 h antagomiR-33 by i.p. injection and group IV received a combination of T0901317 and antagomiR-33. miR-33, AMPK, Sirt1, Srebf-2 and Srebf1c gene expression were quantified by real time PCR, and AMPK, Sirt1 and Srebp-2 protein expression by western blotting. T0901317 administration increased miR-33 and srebf-2 expression. Co-administration of T0901317 and antagomiR-33 reduced srebf-2 and miR-33 levels and increased HDL-c levels. AMPK was reduced in those groups which received T0901317. Sirt1 gene and protein expression remained unchanged. In spite of progress in drug discovery for atherosclerosis and metabolic diseases, these disorders are not fully controlled. It seems that there is a synergistic effect between T0901317 and antagomiR-33 which reduce intracellular sterol levels and increase cholesterol transport to hepatocytes, therefore this can be considered as a therapeutic alternative in atherosclerosis and cardiovascular diseases.

   
18

Protective effect of chard extract on glycoprotein compounds and enzyme activities in streptozotocin-induced hyperglycemic rat lungs
Original Research Article
Pages 119 – 123
O. Sacan, O. Ertik,Y. Ipci, L. Kabasakal, G. Sener, R. Yanardag
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Abstract
In the present study, the protective effect of chard on glycoproteins, hydroxyproline, advanced oxidation protein products and enzyme activities in the lung tissue of streptozotocin (STZ) – induced hyperglycemic rats were examined. Male, Sprague Dawley rats were grouped as control, hyperglycemic, chard, insulin, chard+insulin given hyperglycemic rats. Hyperglycemia was induced by as a single dose of STZ (60 mg/kg) administered intraperitoneally. Fourteen days after the rats were made hyperglycemic, chard extract was administered to rats 2 g/kg/day by gavage and/or insulin a dose of 6U/kg/day for 45 days. Glycoprotein components, prolidase activity and levels of hydroxyproline and advanced oxidation protein products were significantly increased in the lung tissues of hyperglycemic rats; on the other hand, paraoxonase and arylesterase activities were decreased. Treatment with chard and/or insulin reversed these effects. These results suggested that chard possesses a significant beneficial effect on abnormal glycoprotein metabolism and enzyme activities in STZ- induced hyperglycemic rats.

   
19

Evaluating the process efficiency of industrial wastewater treatment plants using data envelopment analysis approach case study: Khuzestan steel company treatment plant
Original Research Article
Pages 124– 132
K. Rahbari, A. H. Hassani, M. R. Mehrgan, A. H. Javid
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Abstract
Designing a mathematical model with the possibility of changing the experimental parameters and variables not only helps to evaluate the performance of the treatment plant but also predicts its behavior. In this paper, to assess the efficiency of Khuzestan steel company treatment plant, data envelopment analysis (DEA) model was used. Input and output parameters of the treatment plant (Oil, COD, TSS, pH) were determined (2009-2014). Malmquist Productivity Index was used to express the changes in total productivity and Window Analysis was employed for calculation of efficiency and performance trends over time. The results showed that the treatment plant efficiency in the removal of COD, Oil, TSS and pH from the input wastewater was 68%, 62%, 81% and 4%, respectively. Treatment plant efficiency in removing pollutants (COD, TSS, Oil) was approximately 70%, so the performance of the system is efficient and the produced wastewater matches environmental standards. On the other hand, the results showed the high power of DEA models in the calculation and classification of years in terms of efficiency.

   
20

Study on intrinsic sulfidation of iron oxides and oxidation behavior of sulfidation products
Original Research Article
Pages133 – 140
L. Shang, J. Li, Sh. Zhao, Y. Tian, Zh. Zhang, L. Zhang
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Abstract
The study simulated the sulfur corrosion process in an oil tank to evaluate intrinsic sulfidation of iron oxides and oxidation behavior of sulfidation products at room temperature. The methods of SEM and EDS were used to characterize the microstructure and surface state of the sulfidation products of Fe2O3, Fe3O4 and Fe(OH)3, which are the dominant components of rust. The surface chemical state of sulfidation and oxidation products was characterized by XPS measurement to analyze the oxidation degree and oxidation mechanism of the sulfidation products. The results showed that three kinds of iron oxides can produce the same kind of iron-sulfur compounds after sulfidation, but the microstructure and elemental distributions of these iron-sulfur compounds are different. The main components of the sulfur corrosion products of the three iron oxides are identical. The sulfur corrosion process of iron oxides converts iron oxides into FeS2 and FeSO4, which is accompanied by the formation and transformation of FeS and S8. At room temperature the sulfidation products of iron-sulfur compounds are finally oxidized to Fe2O3 and FeSO4..

   
21

A prediction model for equilibrium adsorption capacity of the saline soil in the estuary region of Yangtze River
Original Research Article
Pages 141 – 144
A.J. Shao, S.W. Wang, D.Y. Sun
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Abstract
In order to study the changes of water and salt in the estuary region of Yangtze River, the composition and the proportion of the salt in Yinyang and Daxing were determined by long-term monitoring. To understand the relationship between the salt in the soil and in external solutions in these areas, adsorption experiments of the soil samples in Yinyang and Daxing at different concentrations (0~10g/L) were carried out. The adsorption capacity of the soil in these areas is negative, which means that the soils in these areas are mainly desorbed in solutions with concentrations in the range of 0~10g/L. It is found that these soils are well described by using the Freundlich linear isothermal formula. The fitting formula provides a kind of guidance for future production practice.

   
22

Effect of boron and boron-nickel on low-temperature impact toughness of hot-rolled Nb-added HSLA H-beams
Original Research Article
Pages 145 – 150
G.T. Cui, Z.C. Wang, X.В. Wang, X. Wang, J.Q. Gao
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Abstract
Nb-treated HSLA steels alloyed with 11ppm of B and 11ppm of B + 0.5mass% of Ni were studied to find an effective method to improve the low-temperature impact properties of HSLA H-beams. The mechanical properties and microstructure of the experimental steels were investigated by uniaxial tensile test, Charpy impact test (V-notch), transmission electron microscopy (TEM) and X-ray diffraction (XRD), respectively. The results indicated that the absorbed energy at -50℃ can reach up to 44.4 J from 13 J with the addition of 11ppm of B, and to 121 J with the addition of 11 ppm of B + 0.5 mass% of Ni. The precipitate of Nb carbonitride and the grains can be significantly refined by B addition, and precipitates with diameter up to 30 nm were detected. The Fe23(C,B)6 precipitates were suppressed by the simultaneous addition of B and Nb. No Fe-Ni intermetallic was detected by using XRD method. It was assumed that the B in solid solution state and the homogeneously distributed Ni have beneficial effects on the low-temperature impact properties of Nb-treated HSLA steel.

   
23

Arsenate and arsenite removal by Fe-modified activated carbon supported nano-TiO2: influence factors and adsorption effect
Original Research Article
Pages 151 – 160
F. X. Qin, C. F. Wei, Z. K. Wang, G. Li, X. L. Li, Y. J. Li
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Abstract
In this paper, the preparation of Fe-modified activated carbon supported nano-TiO2 (Fe-TiO2/AC) particles and the test results of the properties of the synthesized material, including crystallinity structure, surface morphology, functional groups, and surface texture, obtained using X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy, are presented. The removal rates of arsenic were evaluated using batch tests under several simulated conditions, including pH, ionic strength, material dosage, and initial arsenic concentration. The results indicated that arsenic removal was effective in weak alkaline conditions, and the maximum adsorption for arsenic was observed at pH = 8. The arsenic removal rate was improved by increasing the ionic strength and the adsorbent dosage. The adsorption of As(III) and As(V) reached equilibrium within 3 h and 1.14 h, respectively. The pseudo-second-order model satisfactorily described the adsorption processes. Isotherm data were fitted using the Freundlich equation. The isotherm results showed that the maximum adsorption capacities of Fe-TiO2/AC were 28.66 mg·g−1 for As(III) and 35.22 mg·g−1 for As(V). In the adsorption process, nano-TiO2 and Fe2O3 played key roles in increasing the adsorption efficiency and converting As(III) to As(V). Moreover, the presence of Fe(III) accelerated the oxidation of arsenic.

   
24

Isotope signatures and hydrochemistry as tools in assessing nitrate source in shallow aquifer of Hebei, China
Original Research Article
Pages 161 – 170
H.C. Pang, J.J. Fang, Y.F. Liu, H.S. Cai, F.L. Liu, T.Z. Gao
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Abstract
Hebei Plain plays an important role in China, where municipal, agricultural and industrial water supplies are highly dependent on groundwater resources. It is crucial to investigate hydrochemical characteristics in shallow aquifer for sustainable utilization of groundwater resources. Major components of groundwater samples showed obvious zonation patterns from the piedmont area, the central area to the coastal area, the hydrochemical types changed from HCO3-SO4-Ca-Mg and HCO3-Cl-Ca-Mg types to HCO3-SO4-Na-Ca, SO4-Cl-Na-Ca and SO4-Cl-Na types. A study using stable deuterium and oxygen isotopes was performed to elucidate groundwater flow and occurrence. Groundwater is of meteoric origin, and a large proportion is subject to evaporation. In the area, the aquifer system is recharged from irrigation return flow and seawater intrusion, which significantly affects groundwater chemistry. But data show that excessive nitrate nitrogen seriously polluted the groundwater environment in Hebei plain. This paper determined and monitored the composition characteristics of stable nitrogen and oxygen isotopes to trace the source of nitrogen pollutionfrom 2009 to 2015. The results indicated that the average concentrations of nitrate nitrogen were 0.00 to 121.50 mg·L-1, the total average over the seven-year monitoring period was 17.64±1.55 mg·L-1. Each area displayed various concentrations of nitrate nitrogen. The largest value of nitrate nitrogen, 29.49 mg·L-1, was found in the coastal area, which exceeded the Standard for Drinking Water Quality of China(SDWQC) by a factor of 2.95; followed by the value in the piedmont area, 15.78 mg·L-1, exceeding the Standard by a factor of 1.58 and the lowest value was found in the central area, 3.88 mg·L-1, below the Standard. According to isotope signatures, the source of groundwater nitrate is dominated by manure and waste in the coastal area and the central area, whereas in the piedmont area it is dominated by agricultural fertilizers.

   
25

Experimental study on the feasibility of reducing coal dust by alkaline solution
Original Research Article
Pages 171 – 175
.H. Y. Guo, Zh. X. Gao, Ch. Y. Fu, Y. Luo, D. P. Xia
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Abstract
In order to investigate the feasibility of reducing coal dust by alkaline solution, three representative samples of bituminous D, bituminous C and bituminous B coal with different metamorphic degrees were collected and soaked in0.2 mol/L, 0.5 mol/L, 1.0 mol/L NaOH, respectively, for 5 days. The variation characteristics of coal wettability index were analyzed by the ways of contact angle, pulverized coal subsidence, reverse permeation and scanning electron microscopy (SEM). The results showed that the contact angle of coal samples after soaking in the alkaline solution decreased, the reverse permeation effect obviously increased, and the sedimentation effect of pulverized coal also increased. At the same time, the coal wettability index tended to increase with the decrease of metamorphic degree of the coal and the increase of NaOH concentration. After the samples were soaked in alkaline solution, the pores and fissures, and the roughness of the coal surface significantly increased, and the change trend was consistent with wettability, which indicated that the contact of alkaline solution with the coal structure was the main reason for the enhancement of coal wettability. The study provided experimental support for application of alkaline solution in coal mine dust removal, and had potential application foreground.

   
26 INSTRUCTIONS TO THE AUTHORS    
27 CONTENTS