Introduction: Dye compounds are discharged into environment through wastewater produced during various industrial operations and procedures of production and consumption. Given their carcinogenic characteristics, dyes are threats to the environment. Oxidation by hydrogen peroxide and ultraviolet radiation (UV/H2O2) has been reported in various studies for degradation of dyes. In this study, we aimed to optimize direct blue 71 (DB71) removal by UV/H2O2 process, using response surface methodology.Methods: Based on an experimental study, performed by D-optimal method, effects of independent variables including pH, hydrogen peroxide concentration, and exposure time on dye removal efficiency were studied (a total of 25 treatments). Optimization of conditions and the analysis of the proposed model were performed using response surface methodology and ANOVA test, respectively.Results: The proposed model for dye removal was statistically significant at a confidence level of 95%. Poor model fit was insignificant at a confidence level of 95%. Dye removal efficiency was dependent on H2O2 concentration and radiation time. The process was not pH dependent and removal efficiency of DB71 at optimal conditions (220 mg/L hydrogen peroxide and irradiation time of 16 min) was 99.2%.Conclusion: Photochemical oxidation with hydrogen peroxide is an effective method for the from aqueous solutions. Experimental design with D-optimal method can removal of DB71 be used to optimize the process, reduce the number of experimental tests, and provide the best conditions for dye removal.

Background and Objective: Most of the dyes used in the textile industries can be toxic and carcinogenic. One of the suitable technologies to remove them is advanced oxidation processes. The main purpose of this study was to investigate the positive effect of adding oxidant Na2S2O8 to the photocatalytic process using TiO2 nano-particles immobilized on concrete and UV radiation for removal of Direct Blue71 dye.Materials and Methods: Concrete was covered by 40 g/m2 of TiO2 nanoparticles using SSP method. After selecting suitable oxidant concentration and optimum pH, initial dye concentration, UV irradiation intensity, and time, the efficiency and rate of dye removal and breaking amounts of benzene rings and COD variation were investigated in two systems of UV/TiO2 and UV/TiO2/ Na2S2O8.Results: In UV/TiO2 system, 50.48 percent dye removal was observed at initial dye concentration of 100 ppm, pH 9, and 90 Watt UV lamp after 55 minutes and for UV/TiO2/Na2S2O8 system, initial dye concentration of 200 ppm, pH 6.9, and 0.24 g/L oxidant under the same abovementioned conditions resulted in 88.65 percent dye removal.Conclusion: Oxidant addition increased the dye removal efficiency and decreased total time for complete decolorization indicating the positive effect of oxidant on photocatalytic process in dye removal.

Background and Aim: One of the important sources of environmental pollution existing in different industrial wastewater, including loom wastewater are dyes which are harmful for human health and environment. The purpose of this study was to investigate the efficiency of photochemical and sonochemical processes combined with hydrogen peroxide in removal of DB71 from aqueous solution.Material and Methods: This study was an experimental - laboratory study. At first, a reactor was designed and made. Then, optimum pH was determined which was 7 for photochemical and 3 for sonochemical process in constant condition. The effects of initial concentration of hydrogen peroxide, DB71 and contact time were studied at the constant optimum pH. Then data were interpreted and analyzed by use of Excel software and regression coefficient.Result: The results of this study showed that with increased initial concentration of DB71, its removal decreased. But removal efficiency of DB71 increased by increasing contact time and initial concentration of hydrogen peroxide. In addition, kinetic parameters were obtained by application of first–order (Langmuir-Hinshelwood) equations.Conclusion: The results showed that UV/ H2O2 and US/H2O2 processes can be effective in the removal of DB71 from aqueous solutions. Considering dye removal efficiency and availability, photochemical process combined with hydrogen peroxide can be recommended as a fast effective method for removal of dyes from aqueous solutions.

The present study used the adsorption process of activated carbon produced from agricultural wastes and the photocatalytic process of nano-ZnO to break down complex compounds available in removing Direct Blue 71 (henceforth, DB71). The two processes were done under three varied circumstancesadsorption/ photocatalytic, photocatalytic/ adsorption, and simultaneous use of the processes. First, DB71 was exposed to activated carbon produced from walnut and almond shells and the efficiency achieved at equilibrium time (45 and 60 minutes) was 55 and 60 percent, respectively. Then, DB71 was exposed to different dosages of nano-ZnO to remove the dye completely. The result showed that amount of AC/ZnO in an optimum condition for two walnut and almond shell absorbents were 0. 75/0. 096 and1/0. 096 g/L. Second, (photocatalytic/ adsorption) the complex compound of DB71 with a dosage of 0. 024 g/L was broken down as a result of UV radiation. The experiment proceeded with different dosages of walnut and almond shells after achieving the efficiency of 50% in removing DB71 in the second process. The amounts of AC/ZnO were 0. 75/0. 024 and 1/0. 024 for walnut and almond shells respectively under the optimum condition for the second process. In the third process advantages of the simultaneous use of photocatalytic and adsorption processes were taken in which different dosages of AC/ ZnO were used. Given the smaller dosages of nano-ZnO and less dye removal time, amounts of 0. 75/ 0. 288 g/L and 0. 75/0. 288 g/L were measured for walnut and almond shells. The findings show that photocatalytic/adsorption process was the more optimal process because of the less dosages of nano-ZnO, efficiency of removing DB71 and shorter dye removing time. Furthermore, the effect of the intensity of UV radiant on the efficiency and time of removing DB71 was also examined. The experiment revealed that removing COD in the optimum conditions were 47. 22 and 49. 6 and 62. 23 and 63. 15 percent using walnut and almond shell respectively both in the first experiment and the simulations use of adsorption and photocatalytic processes after 30 hours. While, in the second experiment (photocatalytic/ adsorption) 42. 21 and 39. 18 percent of COD were removed using walnut and almond shell respectively after 30 hours. The LC-mass test of photocatalytic/adsorption process also showed the degradation of DB 71 complex compounds.

In the present work, we have investigated the sorption efficiency of the treated activated carbon from walnut shell (ACW) towards Direct Red 81 (DR81) and Direct Blue 71 (DB71) for the removal from aqueous solution. The sorption study of ACW at the solid-liquid interface was investigated using kinetic, sorption isotherms, pH effect and amount of adsorbent. Experimental data were analyzed by Langmuir, Freundlich, Temkin and Dubinin-Radushkevich (D-R) isotherms. Langmuir isotherm model (R2=0.9664 and R2=0.9484) fitted the equilibrium data the best other isotherms for DR81 and DB71. According to the results maximum adsorption occurred in acidic pH.The results showed that the sorption processes of DR81 and DB71 on ACW are in good agreement with pseudosecond order kinetic. Maximum amount of adsorbent for adsorption of mentioned dyes was 1 gr.

Background: Nowadays, the development of new materials is emergent that can be used in the adsorption process to remove dyes from the aquatic environment. Therefore, in this study, the performance of raw Kaolin as a low cost adsorbent was evaluated in removing Direct Blue 71 (DB71) dye from aqueous solutions. Methods: For investigating the adsorption, various parameters were optimized and data were adjusted to four isotherm models: Freundlich, Dubinin– Radushkevich, Langmuir and Temkin, in order to determine the one presenting the best adjustment to the experimental data. Moreover, the kinetics study for adsorption was evaluated using diffusion, pseudofirst-order kinetic and pseudo-second-order kinetic models. Results: The results revealed that at the DB71 concentration of 10 mg/L, adsorbent dose of 2. 5 g/L, and contact time of 75 min, the DB71 removal reached 98. 5%. Adsorption data fitted best into the Langmuir and D-R adsorption isotherms. The maximum monolayer adsorption capacity was 36. 41 mg/g. The pseudo second order kinetics best described the kinetics of the adsorption system. Conclusion: It was revealed that Kaolin could be applied for DB71 dye removal from solution samples with the adsorption capacity of 36. 41 mg/g and thus could be used as a low-cost and effective adsorbent.

In the present paper, ZnO and manganese doped ZnO (Mn-ZnO) nanoparticles were synthesized via sol-gel method. The prepared samples were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). XRD results exhibited that Mn was successfully doped in the ZnO structure. SEM images confirmed that the particle size of ZnO and Mn-ZnO samples were in the nanometer ranges. Photocatalytic activity of ZnO and Mn-ZnO nanoparticles on the degradation of direct blue 71 (DB71) under UV light irradiation was investigated. DB71 degradation reached to 82% and 97% after 90 min irradiation using ZnO and Mn-ZnO photocatalysts, respectively. A mechanism for the behavior of the Mn-ZnO nanoparticles and the role of Mn in the enhancement of ZnO photocatalytic activity was proposed. The kinetic studies revealed that the photocatalytic degradation kinetics of DB71 would follow a pseudo first order reaction. Mn-ZnO nanophotocatalyst exhibited appropriate stability for several reuses.

The separation of nanocatalysts from the liquid phase often limits their use in industrial-scale processes due to their small size. To solve this problem, nanocatalyst is often embedded on the substrates. In this study, at the first stage, cerium doped TiO2 nanoparticles were prepared by the sol-gel method. Then, LECA granules are used as a support phase for immobilizing nanoparticles. Nanoparticles are characterized by Fourier-transform InfraRed (FT-IR) spectroscopy, X-Ray Diffraction (XRD), Field-Emission Scanning Electron Microscopy (FE-SEM), and nitrogen adsorption-desorption isotherms (BET). The FE-SEM studies showed a uniform coating of TiO2-Ce nanoparticles on the surface of LECA granules. A catalytic bed was constructed with a regular arrangement of the LECA granules and immersed in a photoreactor with the cyclic flow. The degradation of direct blue 71 (DB71) was investigated in the fixed bed photoreactor. The results showed that the fixed bed configuration (5. 3gr) could remove about 96% of the dye (DB71, 20ppm) during 1h irradiation under a UV light source. Furthermore, the ability of coated LECA granules in the degradation of dye was studied in the floating condition under sunlight. The results showed that with daily irradiation for 4 h, the catalyst can remove 94% of the color over three days.