Decontamination of hexavalent chromium and tri-ethyl phosphate stimulants through photacatalytic oxidation

In this paper, the photocatalytic decontamination of hexavalent chromium and tri-ethyl phosphate, two important wastewater contaminants, are studied by the ultraviolet / nano-titanium dioxide process. The pH value and synergic effect between the oxidation of tri-ethyl phosphate and the reduction of hexavalent chromium were investigated in different concentrations of tri-ethyl phosphate and hexavalent chromium. Furthermore, the effects of ultraviolet and nano-titanium dioxide were investigated in a solution which contained tri-ethyl phosphate and hexavalent chromium. Results of adsorptions showed that hexavalent chromium was adsorbed better in acidic pH while the better adsorption for tri-ethyl phosphate was occurred in alkalinity pH. The reduction rate of hexavalent chromium was higher in acidic solutions while it was obtained at natural pH for tri-ethyl phosphate. In co-adsorption of hexavalent chromium and triethyl phosphate pollutants, tri-ethyl phosphate slightly increased adsorption of hexavalent chromium, but hexavalent chromium had no influence on the adsorption of tri-ethyl phosphate on nano-titanium dioxide particles. In contrast, triethyl phosphate has an improving effect on the reduction reaction rate of hexavalent chromium which increases with the interaction of the concentration of tri-ethyl phosphate in mixture. The same is true for the oxidation rate of tri-ethyl phosphate

A computational study on the influence of the rheological behavior of polystyrene and its blends on their thermoforming ability

The present work aims at understanding the relationship between heating conditions, rheological behavior and thickness distribution that lead to the optimization of the latter in thermoforming. The materials used in this study were polystyrene, PS, high-impact polystyrene, HIPS, and a 50/50 w/w % blend of the two. The study was done by investigating computationally the influence of the material thermo-rheological properties on sheet temperature and final thickness distribution of a vacuum-produced part and relating the sheet heating conditions with the forming stage. When sheet temperature is uniform, the degree of strain hardening and the failure behavior in extension are the most important parameters in controlling the kinetics of the process and the thickness profile. In the case of nonuniform sheet temperature, the results show that an increased degree of strain-hardening is more relevant to the dynamics of the process than relatively small differences in sheet temperature. However, the solution of the inverse thermoforming problem (determining the heater temperature that induces a certain thickness distribution) showed that under practical processing conditions the effect of differences in thermal properties are predominant over the rheological ones