narges fallah

Organic dyes have attracted a lot of attention due to their long-term environmental toxicity and short-term damage to health. The process of photocatalysts with the use of semiconductors for efficient use of solar energy in the degradation of dye pollutants has received much attention for environmental improvement. Electron transfer is the most important and fundamental step in photocatalysts processes. The efficiency of electron transport is the function of the location energy level of valence layer and the conduction layer relative to the reduction potential of the adsorbed particles on the catalyst. One of the methods of preventing recombination of electrons/holes is direct conductivity of electron and holes to the other catalyst. This is possible using heterojunction photocatalysts with different valence and conduction band potentials. In other words, the coupling of two semiconductors, the valence and conduction bands, have different energy levels, causing more effective separation. The purpose of this study is to investigate different Load transmission mechanisms in pair and p-n junction photocatalysts.

Petrochemical industry effluents are one of the most hazardous effluents available, which contain toxic and biodegradable compounds, and their release into nature carries serious environmental risks. In this way, it is necessary to purify them. In this research, the Fenton method was used as one of the efficient advanced oxidation methods for Abadan petrochemical wastewater treatment. The effect of three parameters of ,  concentration and  ratio, and their interference on the dye removal efficiency of this effluent was performed using the design method of the Box-Bonken statistical test with the help of Design Expert software. In order to achieve the maximum amount of dye removal as an indicator of pollution, the optimal conditions were Selected by the software as , the amount of oxidizing , and the molar ratio . In these conditions, the highest rate of dye removal was predicted to be 79.5%, which in real conditions showed a yield of 72.5%, which is acceptable due to laboratory error (). The electro-Fenton method was also used to increase the removal efficiency. In the electro-Fenton method, under optimal conditions of Fenton process ( and ) and current density of , the maximum dye removal efficiency of 100% was obtained.

In this research, photocatalytic degradation method for COD(CHEMICAL OXYGEN DEMAND Value) removal has been introduced to treatment of petrochemical industries wastewater as an adaptable method and effective parameters in the process performance have been investigated. Therewith, by using commercial photocatalyst of titanium dioxide and empirical measurement of COD parameter, decrease percentage of this parameter of photocatalytic process during 90 minutes investigated via DOE&ANN method. To carry out experiments,A photocatalytic reactor with agitator used which UV-C lamps submerged within photocatalyst solution in the wastewater sample. Results of experiments at optimized conditions indicated that two models is in a good agreement with the consequences. These results demonstrated that photocatalyst concentration increase in the neutral pH state to optimized amount of 0.84 grams per liter under unlimited conditions and 2 grams per liter under limited conditions, causes removal increase of COD to 93 and 77 percent, respectively(from 180 to 90 and 294 respectively).

Platinum particles were grown directly by an electrodeposition process on electrochemically treated carbon paper (CP) for kinetic study of carbon monoxide (CO) desorption. The treatment on CP was performed by applying −2 V for cathodic oxidation over 5 min. Treated CP was characterized by FTIR to investigate the oxygen groups on its surface. CO surface coverage at each temperature was determined by monitoring changes in Had (adsorbed hydrogen) desorption charge during CO stripping at different desorption times (300 to 1800 s). CO coverage of the cathodic electrode is lower than non-treated one in all temperatures. Desorption rate constants were calculated for cathodic and non-treated electrodes. From 25 to 85 °C, rate constants for cathodic electrode are higher than the non-treated electrode at all temperatures. The activation energies for desorption, estimated from data obtained by the experiments, are 28480 and 18900 J.mol-1 for non-treated and cathodic electrode, respectively. This shows that CO desorption is easier on the surface of the cathodic electrode than non-treated electrode due to the presence of oxygen surface groups.

In this study, photocatalytic treatment was used to treat spent caustic wastewater of olefin petrochemical plants which is one of industrial wastewater with high total dissolved solids (TDS). For this purpose, by using the synthetic photocatalyst of ZNO and measuring the parameter of the chemical oxygen demand (COD), this parameter decrease percentage in the Photocatalyst process has been evaluated by means of Box- Behnken (BBD) design of experiment (DOE) and the artificial neural network (ANN) in a double-cylindricalshell photo-reactor. According to the implemented calculations, it can be resulted that the artificial neural network is more suitable method than the experimental design in modeling and forecasting the amount of COD removal. Modeling of this research showed that increasing the concentration of photocatalyst in a state of neutral pH, lead to enhance the COD removal till the optimal amount of 1.8 g/L without restrictions and 2 g/L with restrictions in the rate of 79% and 68%, respectively.

In this study, photocatalytic treatment was used to treat spent caustic wastewater of olefin petrochemical plants which is one of industrial wastewater with high total dissolved solids (TDS). For this purpose, by using the synthetic photocatalyst of the suspended TiO2 Doped Nitrogen(N-TiO2)and measuring the parameter of the chemical oxygen demand (COD), this parameter decrease percentage in the Photocatalyst process has been modeled and evaluated by means of Box-Behnken (BBD) design of experiment (DOE) in a double-cylindrical-shell photo-reactor. Modeling of this research showed that increasing the concentration of photocatalyst in a state of neutral pH, lead to enhance the COD removal till the optimal amount of 0.64 g/L without restrictions and 2 g/L with restrictions in the rate of 96% and 90%, respectively. In addition, the study of the parameters’ effects including oxidizer amount, aeration rate, pH and the amount of loaded catalyst indicate that all factors except pH have been had positive effect on the model and if the interactions are neglected, the COD removal efficiency will increase by increasing each of these factors (except pH).

Dye-containing wastewater generated from textile industries is a major source of environmental pollution. Azo dyes, which are the largest group of coloring agents, are widely used in industries.
This research investigated the photocatalytic decolorization and degradation of an azo dye Reactive Red 198 (RR198) in aqueous solution with TiO2-P25 (Degussa) as photocatalyst in slurry form using UV light. There is a significant difference in adsorption of dye on TiO2 surface with the change in the solution pH. The effect of various parameters such as catalyst loading, pH and initial concentration of the dye on decolorization and degradation have been determined. The optimum conditions of the reactor were acquired at dye concentration = 62 ppm, pH = 3.7, catalyst concentration = 2.25 g.L-1, in which dye removal efficiency was 98%. Catalyst loading (relevant coefficient = 19.25) and pH (relevant coefficient = −2.62) were resulted respectively as the most and less effective parameters on dye removal

In this study, the photocatalytic method was used for treating the spent caustic in the wastewater of Olefin units used in petrochemical industries which contain large amounts of total dissolved solids (TDS). By using the synthetic photocatalyst of suspended titanium dioxide and measuring the chemical oxygen demand (COD) which was reduced in the photocatalyst (lbc) process, the values of COD were modeled and evaluated by means of the Box-Behnken (BBD) and the artificial neural network (ANN) using experimental tests in a double-cylindrical-shell photo reactor. According to the applied calculations, it was found that the artificial neural network was a more suitable method than the experimental design in modeling and forecasting the amount of COD removal. The modeling employed in this research showed that increasing the concentration of the photocatalyst in a state of neutral pH enhanced the COD removal up to the optimal amount of 1.31 g/L without restrictions and 2 g/L with restrictions at the rate of 81% and 79%, respectively. In addition, the study of the parameter effects including oxidizer amount, aeration rate, pH, and the amount of loaded catalyst indicated that all factors except pH had a positive effect on the model; furthermore, if the interactions were neglected, the COD removal efficiency would increase by increasing each of these factors (except pH). In addition, there was no interaction between the aeration and the concentration of the photocatalyst, and the acidic pH was more suitable at low concentrations of the photocatalyst. Besides that, by increasing the pH, the efficiency of removal was reduced when the oxidant was at its low level. The results showed that photolysis and adsorption adoptions had a very small effect on the efficiency of the removal of COD compared to the photocatalyst adoptions, and it was insignificant. In addition, the photocatalytic method had an acceptable capacity for removing the phenol in the wastewater sample, whereas it was inefficient in reducing the sulfide solution in the wastewater.

Biodegradation of styrene by an aerobic microorganism (namely, Rhodococcus erythropolis PTCC 1767) as well as the effects of bacterial cultures non-adapated and adapted to 90 mg/l styrene were investigated. In both cases, an initial biomass concentration of 0.31 mg/l and styrene concentrations of 10, 20, 30, 50, 70, 90, and 150 mg/ l were used and the tests were carried out at 32 °C and at pH 7. The results showed that the unadapted bacterial cultures were capable of biodegrading 10 mg/l in 15 h; however, removal efficiency was observed to decrease with increasing initial styrene concentration such that at a concentration of 150 mg/l, only 17% of the biomass was degraded over 48 h. On the other hand, the adapted microorganisms were capable of completly degrading Styrene at various initial concentrations of 10 to 150 mg/l over 2.7‒45 h. The kinetics of styrene biodegradation by R. erythropolis PTCC 1767 was also studied. The styrene bioremoval data fitted to the Monod model and to five inhibition kinetic models (namely, Haldane, Webb, Yano, Aiba, and Teissier-type). Among these models, the Haldene one was found to fit satisfactorily the kinetic data (R2>0.99, SSE=0.008) with the following Haldane model parameters: qm=4.235 mg/g dry cell h; Ks= 7.594 mg/l; and Ki= 34.58 mg/l.

In this work, styrene removal from wastewater by using sugarcane waste (bagasse) as an adsorbent was studied. Equilibrium isotherms and kinetics were determined; the effects of bagasse particle size and concentration, solutions pH, and temperature on the biosorption of styrene were studied in batch experiments. Adsorption equilibrium data was successfully fitted to Langmuir isotherms (R2=0.986) and Freundlich isotherms (R2=0.96). Also, the kinetics of biosorption was fitted to pseudo-second order equations (K2=0.00146 g mg-1 min-1, qe=24.5 mg g-1 for particle size range of 88-105 μm). According to the obtained results, an empirical equation was presented that could be used to calculate the percentage of styrene adsorption. The results showed that an increase in temperature caused a decrease in styrene removal. Moreover, maximum uptake was observed with NaOH-treated bagasse. It was found that an increase in average particle size decreased the biosorption rate. According to the calculated heat of adsorption, this sorption can be classified as a chemical biosorption. The optimum uptake was determined to be 88% at a pH equal to 12.1, a temperature of 35 oC, a particle size of 420-500 μm, and a bagasse concentration of 1 g L-1.