Natalija Koprivanac

Removal of some reactive dyes from synthetic wastewater by combined Al(III) coagulation/carbon adsorption process

This study was designed to investigate the removal of reactive dyes, C.I. Reactive Red 45 and C.I. Reactive Green 8, from wastewater using a two-step, Al(III) coagulation/activated carbon adsorption method. The effect of pH and coagulant dosage as well as the effects of contact time and a powdered activated carbon dosage on dye removal have been studied. The process was optimized with reasonable consumption of coagulant and quantity of obtained sludge. Coagulation as a main treatment process followed by adsorption achieved almost the total elimination of both dyes from wastewater with significant reduction (90%) of chemical oxygen demand (COD), total organic carbon (TOC) and adsorbable organic halide (AOX). Besides high efficiency of dye removal, the combined treatment process offers many advantages for potential application such as coagulant savings, minimal amount of sludge formation and also a economic feasibility since it does not require high costs for chemicals and equipment.

Decolourization and mineralization of commercial reactive dyes by using homogeneous and heterogeneous Fenton and UV/Fenton processes

The oxidative decolourization and mineralization of three reactive dyes in separately prepared aqueous solutions C.I. Reactive Yellow 3 (RY3), C.I. Reactive Blue 2 (RB2) and C.I. Reactive Violet 2 (RV2) by using homogeneous and heterogeneous Fenton and UV/Fenton processes have been investigated. The effects of H(2)O(2), Fe(2+) and Fe(0) concentrations, Fe(2+)/H(2)O(2) and Fe(0)/H(2)O(2) molar ratios at pH 3 and T=23+/-1 degrees C have been studied. Optimal operational conditions for the efficient degradation of all three dye solutions (100 mg L(-1)) were found to be Fe(2+)/H(2)O(2)=0.5mM/20mM and Fe(0)/H(2)O(2)=2mM/1mM. The experimental results showed that the homogeneous Fenton process employing UV irradiation was the most effective. By using this process, the high levels of mineralization (78-84%) and decolourization (95-100%) were achieved. Pseudo-first-order degradation rate constants were obtained from the batch experimental data.

Prediction of rate constants for radical degradation of aromatic pollutants in water matrix: A QSAR study

We present the results of the QSAR/QSPR study on the degradation rate constants of 78 aromatic compounds by the hydroxyl radicals in water. A genetic algorithm and multiple regression analysis were applied to select the descriptors and to generate the correlation models. Additionally to DRAGON descriptors, the parameters from quantum-chemical calculations at semiempirical and at density functional theory level (B3LYP/6-31G(d,p)) were applied. The most predictive model is a four-variable model that had a good ratio of the number of variables and the predictive ability to avoid overfitting. As it was expected, the main contribution to the degradation rate was given by the E(HOMO) parameter. Additionally, a number of topological descriptors in selected models showed an importance of polarizability term regarding the degradation rate of compounds. Overall, the applied GA-MLRA approach with the use of quantum-chemical and DRAGON generated descriptors showed good results in this study. The obtained statistically robust structure-degradation rate model can be used for future studies of the presence of organic compounds in the environment, and especially their degradation by hydroxyl radicals as a part of a water/wastewater treatment.

Optimizing Polymer-Induced Flocculation Process to Remove Reactive Dyes from Wastewater

Since discharge limits are becoming stricter for industrial wastes, there is an intensive search for efficient and economical methods of pollution reduction. The polymer-induced flocculation process is described as the suitable treatment method for wastewater highly polluted by reactive dyes. According to preliminary tests, in which many flocculants were studied on two types of model reactive dyes wastewaters, a commercial cationic flocculant Levafloc R was shown to be most successful flocculating agent for dye removal. The optimum pH range and flocculant concentration was found. As the effect of mixing parameters on the process was significant, the optimum combination of the initial rapid mixing intensity, and duration of mixing in given flocculation tank geometry was also determined.

Minimization of organic content in simulated industrial wastewater by Fenton type processes: A case study

Pre-treatment of simulated industrial wastewaters (SIM1, SIM2 and SIM3) containing organic and inorganic compounds (1,2-dichloroethane, sodium formate, sodium hydrogen carbonate, sodium carbonate and sodium chloride) by oxidative degradation using homogeneous Fenton type processes (Fe2+/H2O2 and Fe3+/H2O2) has been evaluated. The effects of initial Fe2+ and Fe3+ concentrations, [Fe2+/3+], type of iron salt (ferrous sulfate vs. ferric chloride), initial hydrogen peroxide concentration, [H2O2], on mineralization extent, i.e., total organic content (TOC) removal, were studied. Response surface methodology (RSM), particularly Box-Behnken design (BBD) was used as modelling tool, and obtained predictive function was used to optimize the overall process by the means of desirability function approach (DFA). Up to 94% of initial TOC was removed after 120 min. Ferrous sulfate was found to be the most appropriate reagent, and the optimal doses of Fe2+ and H2O2 for reducing the pollutant content, in terms of final TOC and sludge production were assessed.

Photooxidation processes for an azo dye in aqueous media: modeling of degradation kinetic and ecological parameters evaluation.

Three photooxidation processes, UV/H(2)O(2), UV/S(2)O(8)(2-) and UV/O(3) were applied to the treatment of model wastewater containing non-biodegradable organic pollutant, azo dye Acid Orange 7 (AO7). Dye degradation was monitored using UV/VIS and total organic carbon (TOC) analysis, determining decolorization, the degradation/formation of naphthalene and benzene structured AO7 by-products, and the mineralization of model wastewater. The water quality during the treatment was evaluated on the bases of ecological parameters: chemical (COD) and biochemical (BOD(5)) oxygen demand and toxicity on Vibrio fischeri determining the EC(50) value. The main goals of the study were to develop an appropriate mathematic model (MM) predicting the behavior of the systems under investigation, and to evaluate the toxicity and biodegradability of the model wastewater during treatments. MM developed showed a high accuracy in predicting the degradation of AO7 when considering the following observed parameters: decolorization, formation/degradation of by-products and mineralization. Good agreement of the data predicted and the empirically obtained was confirmed by calculated standard deviations. The biodegradability of model wastewater was significantly improved by three processes after mineralizing a half of the initially present organic content. The toxicity AO7 model wastewater was decreased as well. The differences in monitored ecological parameters during the treatment indicated the formation of different by-products of dye degradation regarding the oxidant type applied.

Iron-Activated Persulfate Oxidation of an Azo Dye in Model Wastewater: Influence of Iron Activator Type on Process Optimization

The study explores the potential of iron-activated persulfate oxidation of an azo dye in model wastewater. The influence of the type of iron activator on process efficiency was investigated by using ferrous and zero valent iron. The Box-Behnken experimental design and response surface methodology were applied for the modeling of the Fe2+/S2O82- and Fe0/S2O82- processes. The combined effect of three important process parameters was investigated and presented by the means of the quadratic polynomial model. The statistical analysis of model performance was evaluated by ANOVA. The optimal process conditions giving the maximal mineralization for both processes were determined: pH 4.81, [Fe2+]=1.64  mM, and [S2O82-]=84.87  mM predicting 35.14% mineralization and pH 5.52; [Fe0]=4.27  mM and [S2O82-]=138.43mM predicting 54.38% mineralization by the Fe2+/S2O82- and Fe0/S2O82- processes, respectively. The predicted values of dye mineralization obtained by model equations were in good agreement with the experimental...

Metal complex dyes of nickel with schiff bases

Abstract Nickel complexes with Schiff bases 2-(2-pyridylmethyleneamino) phenol (PMAP) and 2-(2-quinolylmethyleneamino) phenol (QMAP) were prepared and the composition of the crystalline complexes was determined by elemental analysis, solubility, UV-Vis, IR and mass spectrometry. It was found that, for the Ni-PMAP complex, two ligands were bonded to one metal ion, giving a neutral complex with one molecule of water probably bonded in the inner sphere of the complex. With QMAP, nickel forms cationic complexes with a metal-to-ligand ratio of 2:2 and two molecules of acetate as anions. The solution properties of Ni-QMAP were investigated at different pH. The chromophoric properties of the complex were enhanced with increase in pH, while stability decreased with time. The application of QMAP as a spectrophotometric reagent for the determination of small amounts of nickel was investigated. Adherence to Beers law was observed from 0.00 to 5.00 μg/ml at pH 8, the most appropriate pH in respect to sensitivity and acceptable time stability of the complexes. Dyeing properties of both complexes were investigated on polyamide 66 and the influence of the addition of another phenyl ring to the ligand molecule on the dyeing properties of the complex is discussed.

Cleaner production processes in the synthesis of blue anthraquinone reactive dyes

Abstract One of the problems in reactive dye production is the soluble products which can pollute effluents, and which should not be discharged untreated into the open water. The production process of monochlorotriazine reactive dyes was studied using an anthraquinone reactive blue as a model. In order to decrease wastewater pollution, the production process was modified. The process stages were monitored using TLC. Different chromatographic systems were investigated; a selection of 12 chromatographic systems was made and it was established that the most favorable mobile phase for TLC of the investigated compounds was chloroform:isopropyl alcohol:ammonium hydroxide (2:4:1). Dye concentration in wastewater from the different synthesis procedures was determined spectrophotometrically. Process efficiency was estimated on the basis of production wastewater pollution. A coagulation/flocculation process was employed as a feasible method for the treatment of this type of wastewater. Optimal configuration of batch coagulation tank, applying rapid and slow mixing, was used. Inorganic coagulants (FeCl 3 6H 2 O and AlCl 3 6H 2 O) and a polymeric flocculant with 99.5% dye removal efficiency were used. On the basis of the experimental results, an economically more favorable and environmentally more friendly production procedure is postulated.

The comparison of photooxidation processes for the minimization of organic load of colored wastewater applying the response surface methodology

In this comparative study, the effectiveness of three photooxidation processes (UV/H(2)O(2), UV/S(2)O(8)(2-) and UV/O(3)) for degradation of an azo dye model pollutant was investigated using several process parameters. The process parameters such as initial pH, the concentrations of oxidant in the reactor inlet stream and the type of oxidant were considered. In order to investigate the influence of cross-factor effects of process parameters, the full factorial design was applied with three factors (two numeric and one categorical) at three levels combined with response surface modeling. The ANOVA results (R(2), F, p) showed high accuracy of developed quadratic model for the zero-order mineralization rate constants of AO7 model wastewater. Among process parameters studied, the type of oxidant and the concentration of oxidant were shown to be the most influential parameters of studied photooxidation processes. The highest rate of mineralization of AO7 model wastewater, k(obs)=7.507×10(-7) M s(-1), was obtained for UV/O(3) process at the initial pH 10 and oxidant reactor input rate of 0.6 mM min(-1). However, when comparing the operating costs for each process studied, it was evident that UV/H(2)O(2) process is 1.6 times less expensive than UV/O(3) process considering the mineralization of organic content of AO7 model wastewater.