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Monitoring of organophosphorus pesticides and remediation technologies of the frequently detected compound (chlorpyrifos) in drinking water

.P., Singh, S. & Jonnalagadda, B. (2008). Visible light induced heterogeneous advanced oxidation process to degrade pararosanilin dye in aqueous suspension of ZnO . Indian J. Chem. 4, 830-835. 42. Kwan, W.P. & Voelker, B.M. (2003). Rates of hydroxyl radical generation and organic compound oxidation in mineral- catalyzed Fenton-like systems. Environ. Sci. Technol. 37, 1150-1158. DOI: 10.1021/es020874g. 43. Wang, H., Xie, C., Zhang, W., Cai, Z., Cai, S., Yang, Z. & Gui, Y. (2007). Comparison of dye degradation efficiency using ZnO powders

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Equilibrium and rate of iron(III) extraction from chloride solutions by individual hydrophobic extractants and their mixtures

Equilibrium and rate of iron(III) extraction from chloride solutions by individual hydrophobic extractants and their mixtures

The main goal of this work was to study and compare the rate of iron(III) extraction from chloride solutions by commercial extractants: Alamine 336, TOPO and LIX 54 and their mixtures. Using the interfacial tension data, obtained for mixed systems, the values of surface mole fraction and molecular interaction parameter of extractants were estimated. Determination of the extraction rates was performed by using the Lewis-type stirred transfer cell. It was found that the extraction efficiency of extractants are changed in the following order: Alamine 336>TOPO>β-diketone. The addition of a chelating extractant to the system decreases the extraction efficiency, for example the addition of β-diketone to TOPO decreases the extraction efficiency by about 50%.

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Utilization of used contact masses from the oxidation state of sulfur(IV) oxide to sulfur(VI) oxide

Utilization of used contact masses from the oxidation state of sulfur(IV) oxide to sulfur(VI) oxide

The research was conducted to determine the influence of the urea concentration in the leaching solutions on the efficiency of recovery of vanadium and iron compounds from the used vanadium catalyst from the node of oxidation of sulfur dioxide to sulfur trioxide.

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Flue Gas Desulfurization by Mechanically and Thermally Activated Sodium Bicarbonate

Abstract

This paper presents the results of study on structural parameters (particle size, surface area, pore volume) and the sorption ability of mechanically and thermally activated sodium bicarbonate. The sorption ability of the modified sorbent was evaluated by: partial and overall SO2 removal efficiency, conversion rate, normalized stoichiometric ratio (NSR). Sodium bicarbonate was mechanically activated by various grinding techniques, using three types of mills: fluid bed opposed jet mill, fine impact mill and electromagnetic mill, differing in grinding technology. Grounded sorbent was thermally activated, what caused a significant development of surface area. During the studies of SO2 sorption, a model gas with a temperature of 300°C, of composition: sulfur dioxide at a concentration of 6292 mg/mn 3, oxygen, carbon dioxide and nitrogen as a carrier gas, was used. The best development of surface area and the highest SO2 removal efficiency was obtained for the sorbent treated by electromagnetic grinding, with simultaneous high conversion rate.

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Characterization and optimization of spectrophotometric colour removal from dye containing wastewater by Coagulation-Flocculation

Abstract

The performance of Vigna unguiculata coagulant (VUC) for colour removal from acid dye was investigated in this study. The proximate, structure and morphology of the coagulant were investigated using standard official methods, Fourier-Transform Infrared (FTIR) spectrometer and scanning electron microscopy (SEM), respectively. Response surface methodology (RSM) using face-centred central composite design (FCCD) optimized four process variables including pH, coagulant dosage, dye concentration and time. The colour removal efficiency obtained from the optimization analysis was 99.26% at process conditions of pH 2, coagulant dosage 256.09 mg/l, dye concentration 16.7 mg/l and time 540 min. The verification experiments agreed with the predicted values having a standard error value of 1.96%. Overlay contour plot established optimum areas where the predicted response variable is in an acceptable range (≥ 70%) with respect to optimum conditions. The FCCD approach was appropriate for optimizing the process giving higher removal efficiency when compared to the main effect plots.

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The optimization of low-magnesium zinc concentrate production process

The optimization of low-magnesium zinc concentrate production process

In this paper the result of the study on chemical leaching of zinc concentrate with H2SO4 solution was presented. The object of this work was to assess the effect of some parameters such as acid concentration, the leaching agent amount /stoichiometry amount or excess of acid were applied/, reaction time and temperature on the process. The investigation was performed as a active experiment according to Hartley's plan. The process optimisation procedure was based on the fuzzy logic system. Mainly, the parameters such as magnesium leaching efficiency and zinc losses were taken into account. It was stated that the highest magnesium leaching efficiency of 77.8% with low Zn-losses was reached when H2SO4 solution concentration was 2.5% for 20%-excess of acid, at temperature 25°C and process time of 1 hour.

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Thermally activated persulfate treatment and mineralization of a recalcitrant high TDS petrochemical wastewater

Abstract

Thermally activated persulfate efficiency for the treatment of a recalcitrant high TDS wastewater was investigated. The specific character of studied wastewater was high TDS content of around 23820 mg/L and BOD5/COD ratio of 0.07. Effective operational parameters including initial pH values of 3–9, reaction temperature of 40–80°C and persulfate concentrations of 0.5–5 g/L for COD removal were investigated in batch mode experiments. Removal efficiency was pH and temperature dependent. The COD and TOC removal of 94.3% and 82.8% were obtained at persulfate concentration of 4 g/L, initial pH value of 5 and temperature of 70°C after 180 min for initial COD concentration of 1410 mg/L. The pseudo first-order kinetic model was best fitted with COD removal (R2 = 0.94).

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Single-walled carbon nanotubes fractionation via electrophoresis

Single-walled carbon nanotubes fractionation via electrophoresis

This work presents the influence of the sonication time on the efficiency of the metallic/semiconducting (M/S) fractionation of diazonium salt functionalized single-walled carbon nanotubes (SWCNTs) via free solution electrophoresis (FSE) method. The SWCNTs synthesized via laser ablation were purified from amorphous carbon and catalyst particles through high vacuum annealing and subsequent refluxing processes in aqua regia solutions, respectively. The purified material was divided into two batches. The SWCNTs samples were dispersed in 1% SDS solution in ultrasound bath for 2 and 12 hours. Both dispersed SWCNTs samples were functionalized with p-aminobenzoic acid diazonium salt and fractionated via free solution electrophoresis method. Afterwards, the fractionated samples were recovered, purified from surfactant/functionalities by annealing and investigated via UV-Vis-NIR optical absorption spectroscopy (OAS). The efficiency of the fractionation process was estimated through the comparison of the van Hove singularities (vHS) presented in the obtained fractions to the starting SWCNTs.

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Optimization of electrocoagulation of instant coffee production wastewater using the response surface methodology

Abstract

The COD removal efficiency from an instant coffee processing wastewater using electrocoagulation was investigated. For this purpose, the response surface methodology was employed, using central composing design to optimize three of the most important operating variables, i.e., electrolysis time, current density and initial pH. The results based upon statistical analysis showed that the quadratic models for COD removal were significant at very low probability value (<0.0001) and high coefficient of determination (R2 = 0.9621) value. The statistical results also indicated that all the three variables and the interaction between initial pH and electrolysis time were significant on COD abatement. The maximum predicted COD removal using the response function reached 93.3% with electrolysis time of 10 min, current density of 108.3 A/m2 and initial pH of 7.0, respectively. The removal efficiency value was agreed well with the experimental value of COD removal (90.4%) under the optimum conditions.

Open access
The influence of leaching solution pH and addition of peroxide hydrogen on the recovery of some components from the used vanadium catalyst with urea solutions

The influence of leaching solution pH and addition of peroxide hydrogen on the recovery of some components from the used vanadium catalyst with urea solutions

The research was conducted to determine the influence of the pH of the leaching solutions and hydrogen peroxide addition on the efficiency of the recovery of vanadium, potassium and iron compounds from the used vanadium catalyst from the node of oxidation of sulfur dioxide to sulfur trioxide.

Open access