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In this study, highly photoactive BiOI nanoparticles (NPs) under sunlight irradiation were synthesized by a facile precipitation method using polyvinylpyrrolidone (PVP) at room temperature. The as-prepared catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transition electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR) and UV-vis diffuse reflectance spectra (UV-vis DRS). The results of XRD showed that PVP did not have any significant effect on tetragonal crystalline structure of BiOI. Also, using different amounts of PVP in the synthesis led to different morphologies and sizes of BiOI particles. It was found that using 0.2 g of PVP in the synthesis method changed morphology from 1-μm platelets to NPs with size under 10 nm. In addition, the photocatalytic performance of prepared photocatalysts was evaluated in the photodegradation of reactive blue 19 (RB19) dye under sunlight irradiation. The BiOI synthesized using 0.2 g PVP (BiOI0.2) showed higher degradation efficiency compared to BiOI prepared without any additive. Excellent visible light photocatalytic properties of nano-scaled BiOI0.2 samples compared to BiOI platelets could be attributed to higher surface-to-volume ratio and narrow band-gap energy of as-prepared BiOI0.2 NPs.

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A new method for breaking oil in water emulsion based on flocculation of droplets in high intensity ultrasonic standing wave field was developed in this study and the effect of initial droplets size, type of disperse phase as well as the time of sonication and the height of emulsion in the chamber on the extent of interdroplet interactions were investigated. The results showed that type of disperse phase affects the efficiency of separation process through controlling the initial size of droplets. For the two types of disperse phase in question the efficiency of separation was calculated to be 42.7% for canola oil/water emulsion and 37% for sunflower oil/ water emulsion. The time of sonication was found to have a positive contribution to the percent of flocculation and coalescence, so that the largest aggregates were formed after 30 minutes treatment. Also, the optimum height of emulsion in the treatment chamber was determined to be k/4 at which the strongest flocculation and highest percent of coalescence took place. Increasing the height of emulsion did not significantly influence the course of aggregation and separation.