Issue 3 - [November]

The aim of this study was to optimize the removal of Naproxen (NPX) by the UV/ZnO photocatalytic process using response surface methodology based on Central Composite Design (CCD). The effect of parameters such as ZnO concentration, contact time, pH, temperature, and initial NPX concentration were studied. The ANOVA results indicated high coefficient values of adjusted R2 (0.9843) and predicted R2 (0.9695). The quadratic model with the highest R-squared designation was chosen to predict the NPX removal efficiency of the UV/ZnO process. Under optimal conditions that include an optimum initial NPX concentration of 21.59 mg/L, ZnO concentration of 371.15 mg/L, contact time of 73.92 min, pH of 6.87, and temperature of 24.35°C, a NPX removal efficiency value of 71.19% was obtained. The results show that the removal of NPX is most affected by the variables- initial NPX concentration, time, pH, and ZnO concentration, respectively, but temperature as a variable does not have a significant effect on the efficiency of the process. Moreover, the NPX photodegradation kinetics can be explained through the pseudo-first-order model. The UV/ZnO photocatalytic method has high potential for the removal of NPX, and that CCD is an appropriate method to optimize the operating conditions for NPX photodegradation.

Untreated wastewater can have important effects on the environment and human. The aim of the work was to evaluate the effectiveness of modified barley straw to remove malachite green from industrial wastewater. Studied variables were pH, contact time, initial malachite green concentration, and adsorbent dosage. Box–Behnken design method was used for modeling the process of adsorption. The results of analysis of variance showed that there are the significance relative among process parameters. The high value of R2 (0.9753) indicated that there was a high correlation between the predicted and experimental values. Removal efficiency of malachite green increased by increasing of modified barley straw dosage, pH and contact time, and decreasing of color concentration. Remove the color was better in alkaline conditions and the best pH was equal to 9.5. The optimum contact time to remove was 120 min. The findings of this study showed that Box-Behnken model can efficiently optimize the malachite green adsorption onto modified barley straw from aqueous solutions.

An optical sensor for colorimetric detection of Cr(VI) has been synthesized by immobilizing 1,5-diphenylcarbazide (DPC) into alginate/pectin films. The addition of cationic surfactant (CTAB) was used to increase the effectiveness of DPC immobilization by forming hydrophobic-ion pairs. At optimum condition, the films has good selectivity for Cr(VI) compare to other interference metals. The formation of violet color in the films showed its potential application for visual colorimetric detection of Cr(VI). The developed films in this study was found to be simple, rapid and sensitive sensor for direct determination of Cr(VI) with detection limit as low as 0.233 mg L–1 and time response was 8 minutes.

Zinc tungstate (ZnWO4) photocatalyst was synthesized by precipitation method and treated with different non-thermal plasma to study its morphology, structure and photocatalytic activity. The X-ray diffraction results revealed that the plasma-treated ZnWO4 exhibited only wolframite structure and its crystallinity was preserved. The SEM images of the samples demonstrated that the morphology of ZnWO4 was changed from non-uniform particle to flower and rod-like following plasma treatment. The enhanced photocatalytic activity of the treated ZnWO4 sample may be associated with the enhancement in the particle size reduction and increase of the surface area. Also, charge separation efficiency due to well-constructed space charge region along the longitudinal direction of the nano ZnWO4 may be affected the photocatalytic activity.