Matei Macoveanu

DECOLORIZATION OF DISPERSE RED 354 AZO DYE IN WATER BY SEVERAL OXIDATION PROCESSES-A COMPARATIVE STUDY

The degradation of the Disperse Red 354 azo dye in water was investigated in laboratory-scale experiments, using four advanced oxidation processes (AOPs): ozonation, Fenton, UV/H2O2, and photo-Fenton. The photodegradation experiments were carried out in a stirred batch photoreactor equipped with an immersed low-pressure mercury lamp as UV source. Besides the conventional parameters, on acute toxicity test with a LUMIStox 300 instrument was conducted and the results were expressed as the percentage inhibition of the luminescence of the bacteria Vibrio fisheri. The results obtained showed that the decolorization rate was quite different for each oxidation process. After 30 min reaction time the relative order established was: UV/H2O2/Fe(II) > Dark/H2O2/Fe(II) > UV/H2O2=O3 > UV/H2O2/Lyocol. During the same reaction period the relative order for COD removal rate was slightly different: UV/H2O2/Fe(II) > Dark/H2O2/Fe(II) > UV/H2O2 > UV/H2O2/Lyocol > O3. A color removal of 85% and COD of more than 90% were already achieved after 10 min of reaction time for the photo-Fenton process. Therefore, the photo- Fenton process seems to be more appropriate as the pre-treatment method for decolorization and detoxification of effluents from textile dyeing and finishing processes. Sulphate, nitrate, chloride, formate and oxalate were identified as main oxidation products.

Catalytic wet peroxide oxidation of phenol over Fe-exchanged pillared beidellite

This study presents an evaluation of the catalytic performances of a Fe-exchanged Al-pillared synthetic beidellite for the wet hydrogen peroxide oxidation of phenolic aqueous wastes. The catalyst was prepared by a cation doping technique, its properties being determined by DRX, BET and chemical analysis techniques. All the tests were performed on a laboratory scale set-up. Important factors affecting catalyst activity and phenol removal efficiencies were studied, i.e. the effect of pH, temperature, catalyst concentration and the stability of the catalyst. The experimental results indicate that the use of this catalyst allows a total elimination of phenol and a significant removal of chemical oxygen demand, without significant leaching of Fe ions. Thus, considering the lowest Fe concentrations in solution after oxidation, at pH=5, 50 degrees C, and 180 min. COD removal efficiency of 87.9% was obtained. It was also observed that by using this catalyst, it is possible to extend the range of pH values for which Fenton-type oxidations can occur.

On the retention of uranyl and thorium ions from radioactive solution on peat moss

The efficiency of the radioactive uranyl and thorium ions on the peat moss from aqueous solutions has been investigated under different experimental conditions. The sorption and desorption of uranyl and thorium ions on three types (unmodified peat moss, peat moss treated with HNO(3) and peat moss treated with NaOH) of peat moss were studied by the static method. Peat moss was selected as it is available in nature, in any amount, as a cheap and accessible sorbent. Study on desorption of such ions led to the conclusion that the most favourable desorptive reagent for the uranyl ions is Na(2)CO(3) 1M while, for the thorium ions is HCl 1M. The results obtained show that the parameters here under investigation exercise a significant effect on the sorption process of the two ions. Also, the investigations performed recommend the peat moss treated with a base as a potential sorbent for the uranyl and thorium ions from a radioactive aqueous solution.

Adsorption potential of mercury(II) from aqueous solutions onto Romanian peat moss

This study was undertaken to evaluate the adsorption potential of Romanian peat moss for the removal of mercury(II) from aqueous solutions. The batch system experiments carried out showed that this natural material was effective in removing mercury(II). The analysis of FT-IR spectra indicated that the mechanism involved in the adsorption can be mainly attributed to the binding of mercury(II) with the carboxylic groups of Romanian peat moss. Adsorption equilibrium approached within 60 min. The adsorption data fitted well the Langmuir isotherm model. The maximum adsorption capacity (qmax) was 98.94 mg g−1. Pseudo–second-order kinetic model was applicable to the adsorption data. The thermodynamic parameters indicate that the adsorption process was spontaneous as the Gibbs free energy values were found to be negative (between −17.58 and −27.25 kJ mol−1) at the temperature range of 6–54°C.

Adsorptive Performances of Alkaline Treated Peat for Heavy Metal Removal

The adsorptive performances of alkaline treated peat have been investigated for the removal of Pb(II), Co(II), and Ni(II) ions from aqueous solutions. The influence of initial metal ions concentration and equilibrium contact time was studied in a series of batch experiments, in comparison with natural peat. An increasing of adsorption capacity of alkaline treated peat was obtained for all studied heavy metals (23.07% - Pb(II), 23.53% - Co(II), and 26.19% - Ni(II)). The Langmuir isotherm model was the best model for the mathematical description of studied heavy metals adsorption on alkaline treated peat. A significant decrease of equilibrium contact time in case of alkaline treated peat was also found. The kinetics of Pb(II), Co(II), and Ni(II) uptake by alkaline treated peat followed the pseudo-second order mechanism. The FT-IR spectrometry analysis showed that carboxylic (-COO-) and hydroxyl (-OH) groups play an important role in the heavy metals binding process. The heavy metal could by easily eluted from the loaded adsorbent with 0.1 mol/L HCl and the adsorbent may be reused in several adsorption/desorption cycles. The alkaline treated peat has better adsorption characteristics for the removal of heavy metals from aqueous solutions, and the cost of this treatment is very low.

Adsorption of Lead(II) Ions from Aqueous Solution onto Lignin

The adsorption of lead(II) ions from aqueous solution onto lignin was investigated in this study. Thus, the influence of the initial solution pH, the lignin dosage, the initial Pb(II) ion concentration and the contact time were investigated at room temperature (19 ± 0.5 °C) in a batch system. Adsorption equilibrium was approached within 30 min. The adsorption kinetic data could be well described by the pseudo-second-order kinetic model, while the equilibrium data were well fitted using the Langmuir isotherm model. A maximum adsorption capacity of 32.36 mg/g was observed. The results of this study indicate that lignin has the potential to become an effective and economical adsorbent for the removal of Pb(II) ions from industrial wastewaters.

Characteristics of sorption of uncomplexed and complexed Pb(II) from aqueous solutions onto peat

Batch experiments aimed at the sorption of Pb(II) onto peat were performed from an aqueous solution in both the absence and presence of common complexing agents (acetate or citrate). The influence of the initial pH of the solution, metal ion concentration and contact time on the sorption efficiency of Pb(II) was examined at ambient temperature (18 ± 0.5) °C for each experiment. The results showed that the presence of acetate improved the efficiency of the sorption process, while the presence of citrate in the aqueous solution decreased the efficiency of the Pb(II) sorption onto peat. The equilibrium data fitted well with the Langmuir isotherm model and confirmed the monolayer sorption of uncomplexed and complexed Pb(II) species onto peat. The values of maximum sorption capacities (qmax) were 135.13 mg g−1 for Pb(II) complexed with acetate, q > 79.36 mg g−1 for uncomplexed Pb, q > 38.46 mg g−1 for Pb(II) complexed with citrate. The kinetics of Pb(II) sorption onto peat, in both the absence and presence of complexing agents, indicated a pseudosecond order mechanism. Analysis of IR spectra showed that carboxylic and hydroxyl groups had an important role in the binding process of Pb(II) species onto peat.

Valorisation of romanian peat for the removal of some heavy metals from aqueous media

AbstractIn this study, the sorption of some potential toxic heavy metal ions (Pb(II), Hg(II) and Cd(II), respectively) onto Romanian peat was investigated as a function of initial solution pH, sorbent dose, initial metal ions concentration and contact time, at room temperature (20 ± 0.5°C), in batch system. The uptake capacity of tested heavy metals decreased by decreasing the initial solution pH, suggesting that competition exists between hydrogen ions, present in high concentration in strong acid media and metal ions. The experimental data were evaluated using Langmuir and Freundlich isotherm models. The isotherm data followed the Langmuir model, and the maximum sorption capacity increases in the order Cd(II) < Pb(II) < Hg(II). The kinetics of metal ions sorption was rather rapid, with at least 68% of sorption occurring in 30 min. The experimental data were satisfactory correlated with pseudo-second-order kinetic model, which means that in the sorption mechanism the chemical interaction between positive...

Application of Low-Cost Sorbent for Oil Spill Sorption Using Response Surface Methodological Approach

The paper deals with oil spill clean-up using peat as low-cost sorbent material. Light fuel oil of regional production has been used in all experiments as the representative petroleum product. The design of experiments and response surface methodological approach has been used for the investigation of sorption process. A regression equation (response surface model) has been proposed for the prediction of removal efficiency as a function of design variables (factors), i.e., sorbent dosage, drainage time and initial thickness of oil slick on water. A very good agreement between the experimental data and response surface model has been found. The linkage between the removal efficiency and factors has been illustrated via response surface plots and contour lines maps. Based on the regression equation the maximal removal efficiency has been found by optimization.

Modelling and simulation of dispersions of powder emissions from multiple sources with the mathematical model Pol 15sm

AbstractOver the last decades, air pollution has become one of the greatest challenges negatively affecting human health and the entire environment, including air, water, soil, vegetation, and urban areas. Lately, special attention has been given to mathematical modelling for diffusion of pollutants in the atmosphere as a particularly effective and efficient method that can be used to study, control and reduce air pollution. The diversity of models developed by different research groups imposed a rigorous understanding of model types in order to apply them correctly according to local or regional problems of air pollution phenomenon. Thus the authors have developed and improved two mathematical models for dispersion of air pollutants. This paper presents a case study of dispersion of powders in suspension originating from 14 point sources that correspond to 5 economic agents in the agroindustrial area of Vaslui city using a computer simulation based on the mathematical model Pol 15sm, for multiple point s...