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Iron-modified titanium dioxide nanostructured catalyst was synthesized by sol–gel method. Due to the important impacts of surface properties on the catalytic activity, the catalyst surface is investigated. To have a complete characterization of the catalyst, TEM, SEM, XPS, XRF, XRD, BET, and TGA–DTA techniques were used. XRF analysis reveals the iron loading of the synthesized catalyst as Fe2O3/TiO2= 0.21 %. XRD results imply that the catalyst is composed of anatase and rutile phases. The SEM image indicates the mesoporousity of the nanoparticles. Clusters are observable in the TEM images. The main objective of activity tests is focused upon the comparative evaluation of H2O2addition and the application of air bubbling. Experimental results specified that the optimum amount for H2O2dosage is 12.5 ml. Moreover, it has been observed that an increase in the aeration flow rate shows a positive effect on the degradation of phenol and the optimum aeration flow is 9 l/min. Furthermore, it has been shown that the addition of copper as additive ion to phenol solution boosts the degradation of phenol; the highest phenol degradation efficiency after 120 min (43.85 %) was attained under this condition.

In this work, TiO2and doped TiO2photocatalysts (Fe/TiO2and Cu/TiO2) were synthesized by the sol–gel method. The main objective of this study was to investigate the influence of dopants on the structure, morphology, and activity of the catalysts in powder and immobilized states. XRF, XRD, and SEM methods were used to characterize the catalysts. The structure and phase distribution of the nanocrystalline powders were identified by XRD. Nanoparticles crystallite size and the degree of crystallinity were affected by doping. The anatase contents of catalysts were achieved as follows: TiO2(5.89 %) < Fe/TiO2(42.17 %) < Cu/TiO2(70.28 %). It was indicated that the activity of the catalysts strongly depends on the anatase content. Under the same circumstances, copper-modified TiO2exhibited a twofold higher photocatalytic activity compared with TiO2. The nanostructured catalysts were immobilized on light expanded clay aggregate (LECA) granules in order to investigate the effect of a novel support on the activity of the catalysts. Morphological changes are recognizable in the SEM images. Activity tests indicated that the best catalytic performance was assigned to Cu/TiO2/LECA. After 120 min of irradiation, 61 % degradation of phenol in synthetic wastewater was achieved. The high photocatalytic activity of Cu/TiO2/LECA confirms that LECA is as an excellent support.

In this paper, an algorithm, called ACS-OPHS, is proposed to tackle the Orienteering Problem with Hotel Selection (OPHS). This algorithm is strongly based on the Ant Colony System (ACS); however, it differs from the ACS in the way the paths are constructed, in tuning a parameter of the transition rule and in the pheromone trails updating rules. The ACS-OPHS uses a bi-directional search strategy and employs a novel and fast approach to identify all feasible intermediate hotels in an offline manner. Moreover, in the ACS-OPHS, the relative importance of exploitation versus exploration is determined according to the progress of the algorithm in approaching to the global optima. The ACS-OPHS is a simple and well-performing approach to solve the OPHS. Concerning the standard benchmark instances, it outperforms the state-of-the-art algorithms in several instances and produces competitive solutions in reasonable time. This algorithm also improves the best known results of four instances with unknown optimal solutions.