Current Physical Chemistry - Volume 7, Issue 4, 2017

Aims: In this study, copper extraction was investigated from chalcopyrite concentrate with hydrogen peroxide and acetic acid mix solution by using response surface methodology. Method: Experiments were planned using Box-Behnken in which various parameters such as leaching time, leaching temperature, H2O2 concentration, liquid-solid ratio, and stirring speed were defined as independent variables. Result: Under optimum experimental conditions, more than 80% of the copper was extracted with R2 value of 0.94 which indicates good fitness of the model. Conclusion: Moreover, other parameters except stirring speed were determined to be linearly effective on the result.

Aims: Zinc plant leach residues as well as other industrial wastes have remarkable economic value due to the contents of the high amount of valuable metals and also having a risk of polluting to the environment. Observations: It is generally accepted that these leach residues must be evaluated to eliminate the negative effects on human life. In this study, therefore, zinc and lead recoveries were investigated from environmentally hazardous zinc plant leach residue by means of a novel leaching agent namely choline chloride/urea mixture differently from conventional solvents. For this reason, the choline chloride/urea mixture which is ecocredential in 2:1 molar ratio was used in different concentration in the 25-95°C temperature range. Result: According to the results, zinc and lead recovery increased with increasing the reaction temperature but also undesirable increases in iron dissolution. The maximum zinc recovery which could be achieved was 56% for leach residue by pure choline chloride/urea mixture.

Aims: Ni-Mo alloy coatings could represent a key material for several leading applications of engineering. Indeed these coatings present excellent physico-chemical characteristics such as magnetism, wear-resistance, heat-conductivity, and electrocatalytic properties. Observations: Ni-Mo alloys have been electrowon, with a pH 5.8 sulphate catholyte containing 40 g/l Ni and Mo in the range 1-4 g/l, sodium citrate and acetic acid, at temperature in the range 25-50°C and current density in the range 10-100 mA/cm2. Methods: A cell having cathodic and anodic compartment separated by a polypropylene membrane has been used. Result: The effect of molybdenum ion concentration in the electrolyte, temperature and current density on coating morphology and the Ni-Mo deposit adherence on steel substrate as well as Mo content of the produced binary alloys have been investigated.

Aim: In this study, copper recovery from aqueous solutions by precipitation with sugar beet molasses, an industrial by-product, in the high temperature-pressure reactor was investigated. Method: Copper recovery experiments from hypothetical copper sulphate solutions (150 ml of 10 g Cu2+/L) were designed by RSM (Response Surface Methodology) using CCD route (Central Composite Design) to observe the effect of the parameters such as temperature (62.5-212.5°C), reaction time (30-90 min), stirring speed (75-325 rpm) and molasses amount (0.5-2.5 g). Observation: The response parameter for these experiments was selected as an amount of copper precipitated (%). Result: The results of the experiments showed that the maximum copper recovery are obtained as 93.50 % under the conditions of 212.5°C of temperature, reaction time of 60 min, stirring speed of 300 rpm and molasses amount of 1.5 g. Conclusion: Also, model equation derived from the experimental results showed that the copper recovery amount depending on the parameters can be described by a linear model equation.

Aim: In this study, the hydrodynamic behavior and mass transfer characteristics of a cocurrent down flow contacting reactor (CDCR) were investigated for air-tap water and airfermentation broth systems. Observation: As gas and liquid flow rates increased, the values of kLa and gas hold ups increased. The values of kLa measured in the air-fermentation broth system were all lower than those in the air-tap water system, but the values of gas hold up were higher. Result: Bacillus amyloliquefaciens bacterial was grown in a medium of 10 g L-1 glucose and the specific growth rate, maximum dry cell concentration, and yield of biomass on glucose were determined to be 0.310 h-1, 5.0 g dry cell L-1, 0.500 g dry cell g-1 glucose, respectively. Conclusion: The values of kLa and qO2, increased at active growth phase and then decreased with decreasing active cells.

Background: Amorphous silica is widely used in cement and ceramic industry and also for the synthesis of many advanced materials. Method: Generally, it is produced using sol-gel and precipitation method. In the present study, amorphous SiO2 was extracted from acidic pumice collected from Van Basin in Turkey by alkaline treatment method. Result: The identification and chemical compositions of the acidic pumice and the amorphous SiO2 were determined by XRD, FTIR, XRF and BET. Conclusion: The results showed that highly pure amorphous silica powder having a remarkable surface area (358 m2/g) with meso-pore structure was successfully extracted from the acidic pumice samples.

Aims: A low-cost medium for α-amylase is critical for the growing demands of industries. Method: In this study, α-amylase production was investigated using different agro-industrial products (wheat bran, cheese whey, soy bean cake, hazelnut oil cake) and supplemental nutrients (peptone, ammonium sulfate) using semi-solid substrate fermentation (SSSF). Observation: The experiments were planned in two stages. The first aim was to screen important nutrients for enzyme production using the Placket-Burman design. Result: Three components (wheat bran, cheese whey, and peptone) were determined to have an important effect on α-amylase production. The possibility of further optimization was examined by using the Central Composite Design. Conclusion: The maximum α-amylase activity was obtained (11,196 U/ml) using 4.9 g/l of wheat bran, 28.7 v/v% cheese whey, and 3.7 g/l of peptone.

Aim: The analysis of the gaseous and condensed thermodynamic function of all atoms of Mendeleev’s Periodic table was carried out and seventy nine equations of such type as Δg,f,sΨo = i ± f N, in which Δg,f,sΨo is thermodynamic function, N is the number of atom electrons and i and f are stoichiometric coefficients, have been formulated. Method: The obtained equations can be used for the next calculation of bond strength in heteroatomic compounds. Observations: The strength of C-H and C-C bonds (enthalpy) in alkanes, of C-C, C-H, C-O, C=O and O-H bonds in carbohydrates for condensed phases were calculated first time by using Widows-Excel-function «Search of the decision by a gradient descent method». Conclusion: The reduced magnitudes of the force of all bonds in condensed phase, compared to gas state, designated as the strength of the bond (Sb) of carbohydrates are necessary to explain the presence of significant hydrogen bonds, dipole-dipole- and dispersive interactions in biochemical molecules.

Aim: In this paper, we report that sodium benzoate is a good inhibitor for SO2 oxidation in the pH range 4.02-5.25 in the presence of Ag (I). Based on the observed results the following rate law is given and a free radical mechanism has been proposed. -d[S(lV)]/dt = (k1+ k2[Ag(I)]) [S(lV)]/1 + B [Sodium Benzoate] Methods: Experiments were carried out at 30≤T°C≤40, 4.02≤pH≤5.25, 1×10−3 mol/cm3≤ [S(lV)≤10×10−3 mol/cm3, 5×10−6 mol/cm3≤[Ag(I)]≤2.5×10−5 mol/cm3, 8×10−8 mol/cm3≤ [Sodium Benzoate]≤2×10-4 mol/cm3. Observation: Rate constants and the order of reaction were calculated and the reaction was found to be pseudo- first order in all cases. Result: The effect of pH and temperature are also discussed. The value of apparent activation (Ea) energy was determined to be 24.11 kJ mol-1. The activation of energy was calculated by Arrhenius equation (k = A e-Ea/RT).