Statistical Evaluation of UV/TiO2/H2O2 and Fe2+/H2O2 Process for the Treatment of Coloured Wastewater; A Comparative Study

In this work, two types of advanced oxidation processes; photocatalytic oxidation, UV/TiO2/H2O2 and classic Fenton oxidation, Fe2+/H2O2, have been applied for the treatment of a model wastewater containing reactive azo dyes, C.I. Reactive Violet 2 (RV2) and C.I. Reactive Yellow 3 (RY3). In order to evaluate the effect of the initial concentration of catalysts, γ(TiO2) or [Fe2+], initial concentration of oxidant, [H2O2] or the initial oxidant/catalyst mole ratio [H2O2]/[Fe2+] and pH on apparent mineralization and decolourization rates, a response surface method (RSM) D-optimal design was used. Mineralization was described by pseudo-first-order kinetics with the highest observed rate constants; km,UV = 0.0065 min–1 in the case of UV/TiO2/H2O2 process and km,F = 0.0213 min–1 in the case of Fenton process. A kinetic model describing decolourization on wavelengths of maximum absorbance for studied dyes, λmaxRV2 550 nm, and λmaxRY3 385 nm, was composed of two first-order in-series reactions with corresponding decolourization rates. The effects of each factor on the efficiency of the applied processes were found to be significant

The Potential of Fe-exchanged Y Zeolite as a Heterogeneous Fenton-type Catalyst for Oxidative Degradation of Reactive Dye in Water

The study aimed to investigate the potential of Fe-exchanged zeolites of Y-type as a catalyst in heterogeneous Fenton-type processes for the degradation of model organic pollutant, reactive azo dye C.I. Reactive Blue 137, in water. The research work was directed to investigate the influence of process variables, such as FeY catalyst dosage, Fenton reagent ratio, and initial operating pH on the efficiency of the treatment process. The performance of the studied heterogeneous process was compared with corresponding homogeneous Fenton-type processes, while the influence of UV light on both heterogeneous and homogeneous processes was investigated as well. The results of FeY catalyst characterization indicate that the iron content is mainly built into the inner zeolite micropores providing the benefit to zeolite stability and activity of the catalyst. Based on the decolorization and the mineralization degree of RB137 model wastewater, the overall process efficiency was estimated. Homogeneous and heterogeneous Fenton processes yielded similar decolorization and mineralization, but the concentration of Fe ions in the bulk after treatment was significantly lower in the latter case. Moreover, the use of the heterogeneous catalyst allowed the UV-assisted process to be operated at milder pH conditions, pH 5, while the most suitable pH for the dark heterogeneous process showed to be pH 3

Reactive Dye Degradation by AOPs; Development of a Kinetic Model for UV/H2O2 Process

An application of UV/H2O2 process for the treatment of model wastewater containing organic reactive azo dye C.I. Reactive Blue 137 (RB137) was studied. The efficiency of applied process for decolorization and mineralization of RB137 model solution is discussed. The influence of operating process parameters, initial pH and initial concentration of H2O2, as well as initial dye mass concentration on process effectiveness was investigated. Both direct UV photolysis and OH radical attack were assumed as RB137 degradation mechanisms and a detailed kinetic model for dye degradation by UV/H2O2 process was proposed. The predicted system behavior was compared with experimentally obtained results of decolorization and mineralization of RB137 wastewater. A sensitivity analysis for the evaluation of importance of each reaction used in the model development was also included

Azo Dyes, Their Environmental Effects, and Defining a Strategy for Their Biodegradation and Detoxification

Intenzivan industrijski razvoj popraćen je sve većom kompleksnošću sastava otpadnih voda, što u smislu učinkovite zaštite okoliša i održivog razvoja nalaže potrebu pospješivanja kvalitete postojećih te uvođenjem novih postupaka obrade otpadnih voda, kao iznimno važnog čimbenika u interakciji čovjeka i okoliša. Posebnu znanstveno-tehnološku pozornost zahtijevaju novosintetizirani ksenobiotici, poput azo-boja, koji su u prirodi veoma teško razgradivi. Azo-boje podložne su bioakumulaciji, a zbog alergijskih, kancerogenih, mutagenih i teratogenih svojstava nerijetko su prijetnja zdravlju ljudi i očuvanju okoliša. Primjenu fi zikalnokemijskih metoda za uklanjanje azo-boja iz otpadnih voda često ograničavaju visoke cijene, potrebe za odlaganjem nastalog štetnog mulja ili nastanak toksičnih sastojaka razgradnje. Biotehnološki postupci su, zbog mogućnosti ekonomične provedbe i postizanja potpune biorazgradnje, a time i detoksifi kacije, sve zastupljeniji u obradi svih vrsta otpadnih voda, pa tako i onih koje sadržavaju azo-boje.Intense industrial development has been accompanied by the production of wastewaters of very complex content, which pose a serious hazard to the environment, put at risk sustainable development, and call for new treatment technologies that would more effectively address the issue. One particular challenge in terms of science and technology is how to biodegrade xenobiotics such as azo dyes, which practically do not degrade under natural environmental conditions. These compounds tend to bioaccumulate in the environment, and have allergenic, carcinogenic, mutagenic, and teratogenic properties for humans. Removal of azo dyes from effl uents is mostly based on physical-chemical methods. These methods are often very costly and limited, as they accumulate concentrated sludge, which also poses a significant secondary disposal problem, or produce toxic end-products. Biotechnological approach may offer alternative, lowcost biological treatment systems that can completely biodegrade and detoxify even the hard-to-biodegrade azo dyes

Б1.В.ОД.7 История и семантика орнамента 2017

The possibilities of treating industrial effluents and water purification by advanced oxidation processes have been extensively studied; photocatalysis has emerged as a feasible alternative solution. In order to apply the photocatalytic treatment on a larger scale, relevant modeling approaches are necessary. The scope of this work was to investigate the applicability of recently published kinetic models in different reactor systems (batch and CSTR) under UVA or UVC irradiation and in combination with two types of TiO2 catalyst, AEROXIDE® P25 and PC-500 for degradation of azo dyes (C.I. Reactive Violet 2, and C.I. Mordant Yellow 10), oxalic acid and their mixtures. The influences of reactor geometry and irradiation intensities on pollutant oxidation efficiency were examined. The effect of photon absorption by dyes in water matrix was thoroughly studied. Relevant kinetic models were introduced to the mass balance for particular reactor system. Resulting models were sufficient for description of pollutant degradation in batch reactors and CSTR. Experimental results showed 1.15 times higher mineralization extents achieved after 7 cycles in CSTR than in batch photoreactor of similar geometry within the equivalent time-span. The application of CSTR in-series could simplify the photocatalytic water treatment on a larger scale. This work is licensed under a Creative Commons Attribution 4.0 International License