Ana Lončarić Božić

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.

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.

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.

Decolorization and Mineralization of Reactive Dye by UV/Fenton Process

The photochemical degradation of C. I. Reactive Blue 2 (RB2) in aqueous solution has been studied using a homogeneous UV/Fenton process. The effects of applied H2O2, Fe2+ salt and RB2 concentrations at constant UV irradiation characteristics, the pH, and temperature were determined. By the application of 0.5 mM Fe2+ and 2.5 mM of H2O2 the complete color removal and mineralization extent of 73.8% were achieved. According to the color and TOC removal, it could be suggested that the studied UV/Fenton type process appeared as a viable technique for the treatment of wastewater containing such types of reactive dyes.