Abstract Research subject: Low biodegradation rate of plastics, especially different grades of the polyethylene leads to many environmental problems. To reduce these effects, pro-oxidant added to the polyethylene to increase the photo-degradation and subsequently the bio-degradation rate of the polymer matrix. Besides the pro-oxidant, it seems that the photocatalysts can affect on the photo-degradation of the polyethylene and the subject of this study is to examine this idea. Research approach: Photodegradable films of LDPE were prepared by melt blending of the polymer with cadmium selenide (CdSe) and trisilver phosphate (Ag3PO4) as photo-catalysts and manganese stearate as pro-oxidant. The samples were irradiated with visible and ultra-violet light. Scanning electron microscopy (SEM), dynamic mechanical thermal analysis (DMTA), differential scanning calorimetry (DSC) and viscometry measurements were used to investigate the microstructure of the films. Main results: FTIR spectra indicated to increment of the carbonyl index (CI) and vinyl index (VI) of the samples with photo-catalysts. In addition, SEM imaged confirmed higher and more homogeneous photo-degradation for these samples in comparison with other ones. Also, the dynamic-mechanical-thermal analysis showed that the polyethylene samples without the additives had higher modulus compared to other samples. However, the crystallinity of the samples with photo-catalysts increased due to nucleating agent effects of their particles. The viscosity of the samples containing the photo-catalysts and  pro-oxidants decreased significantly and the modeling results showed that this decrement  was due to the polymer chain degradation and reduction of their molecular weights. In general, the results showed that the combination of the photo-catalysts and the pro-oxidants had synergistic effect on the photo-degradation of the LDPE and accelerates its degradation process a lot more in comparison when only the pro-oxidant was used.

Background and Objective: Malachite green is an extensively used biocide in the aquaculture industry, and is highly effective against important protozoal and fungal infections. It is also used as a food coloring agent, food additive, and medical disinfectant as well as a dye in the silk, wool, jute, leather, cotton, paper, and acrylic industries. Therefore, the elimination of malachite green in wastewater of aquaculture and textile, paper and acrylic industries is essential in order to prevent its adverse effects on aquatic organisms. In this study, degradation of malachite green with titanium dioxide nanoparticles (TiO2 NPs) under UV light was investigated. Method: For this reason, the effects of parameters such as different concentrations of malachite green (3. 5, 7 and 14 mg L-1) and the Nano-catalyst concentrations (1. 30, 2. 60, and 5. 20 mg) in constant temperature (25° C) and constant UV intensity (12 W, 230 V, 50 Hz) during 180 minutes were studied. Findings: The best degradation rate of malachite green was found in the concentration of 3. 5 mg L-1 malachite green, pH: 9, and 2. 60 mg of TiO2 NPs. Although with an increase in titanium dioxide nanoparticles the efficiency and removal rate of malachite green increased, the increase in the photo catalyst had no effects on increasing the efficiency of photo degradation. An increase in pH (9) may improve the removal rate of malachite green through increasing free radicals. An increase in the initial concentration of malachite green decreased the efficiency and removal rate of malachite green. Discussion and Conclusion: Therefore, the photo degradation of malachite green in the presence of TiO2 NPs photo catalyst could be a function of pH, the initial concentration of malachite green and concentration of TiO2 NPs.

Phenol is considered as one of the major environmental concerns due to its characteristics including chronic toxicity, biological stability, and increasing the toxicological intermediates after biological degradation. Therefore, the aim of this study was to evaluate the photo-degradation of phenol using the titanium dioxide (TiO2) photo-catalyst on ordered mesoporous carbon (CMK-3) support under UV irradiation. In this study, the effects of some parameters including pH value (4, 5, 6, 7, 8, 9, 10), TiO2/CMK-3 concentration (0. 05, 0. 1, 0. 15, 0. 3, 0. 5 g/L), irradiation time (30, 60, 90, 120, 150 min), and phenol concentration (50, 100, 150 and 200 mg/L) were assessed. The properties of the CMK-3 and TiO2/CMK-3 were compared using the transmission electron microscopy (TEM), X-ray powder diffraction (XRD) and N2 adsorption-desorption isotherm. The results revealed that the process studied was remarkably affected by the parameters, and the optimum values of the parameters were as follows: pH=6, TiO2/CMK-3 concentration =0. 15 g/L, phenol concentration = 100 mg/L, and irradiation time=150 min. The phenol degradation efficiency and total organic carbon (TOC) removal efficiency for phenol were 96% and 74%, respectively. Moreover, the stability greater than 7 times for the studied photo-catalyst was indicative of its high potential to be used in photo-degradation processes for the elimination of pollutants.

Phenol is among toxic pollutants with a resilient degradability behavior the total removal of which via traditional techniques is impossible. In this research, Carbon-doped TiO2 nano-photocatalyst is produced via sol-gel technique. Various techniques are used to characterize TiO2 nano-photocatalyst such as XRD, FT-IR, EDX, and FE-SEM. Based on the results, the carbon introduced into titania structure has led to response towards visible light. The synthesized catalyst was implemented for photocatalytic removal of phenol in a fluidized bed reactor under UV and visible light. The effects of several significant parameters were investigated such as phenol concentration, pH, time, C/Ti molar ratio and catalyst content. The degradation of Phenol using this nanocomposite is 84 % under UV irradiation during a 180 min period and 70 % under visible irradiation during a 420 min period.