In this paper, spherical a-Fe 2 O 3 nanoparticles (NPs) were supported on the surface of 12-tungstosilicic acid (12-TSAÁ7H 2 O) using two different solid-state dispersion (SSD) and forced hydrolysis and reflux condensation (FHRC) methods. Photocatalytic activity of supported a-Fe 2 O 3 NPs (a-Fe 2 O 3 /12-TSAÁ7H 2 O) for tetracycline (TC) degradation in aqueous solution was investigated using UV/H 2 O 2 process and the results were compared with that of pure a-Fe 2 O 3 NPs. a-Fe 2 O 3 and 12-TSAÁ7H 2 O were synthesized according to previous reports and all products were characterized by using FTIR, SEM, EDX and XRD. Design of experiments (DoEs) was utilized and photocatalytic degradation process was optimized using full factorial design. The experiments were designed considering four variables including pH, the initial concentration of TC, catalyst concentration and H 2 O 2 concentration at three levels. TC concentration reduction in the medium was measured using UV/Vis spectroscopy at k max = 357 nm. The results of experiments indicated that supporting a-Fe 2 O 3 NPs on the surface of 12-TSAÁ7H 2 O through SSD and FHRC methods caused to improve the filtration, recovery and photocatalytic activity of NPs. Also, it was indicated that those NPs supported through SSD method, have better photocatalytic performance than those supported through FHRC method. The statistical analyses revealed that the maximum TC degradation (97.39%) is obtained under those conditions in which pH and catalyst concentration variables are at maximum levels and the initial concentration of TC and H 2 O 2 concentration variables are at minimum levels (pH 8, catalyst concentration = 150 ppm, initial concentration of TC = 30 ppm, H 2 O 2 concentration = 0.1 ppm). A first order reaction with k = 0.0098 min-1 was observed for the photocatalytic degradation reaction.

There are various methods for the synthesis of carbon nanoparticles. Each laboratory uses one of them depending on its abilities and available tools. Adding nanoparticles, especially Nano carbons, to some materials changes their behaviours. For example, adding carbon to iron matrix leads to an increase in its compressive strength and adding carbon to plastics results in a remarkable increase in their thermal resistance. Therefore, synthesis of such compounds from the wastes is a good achievement. The purpose of this study is the synthesis of carbon nanoparticles from the wastes (disposable containers made of polystyrene) using the designed reactor and heat system. In the used reactor, as high pressures and temperatures above 700 ºC are used along with appropriate catalysts for different periods, all of the materials lose their macro structures and fragment into Nano-size particles. Each of the mentioned conditions is optimized with each other and type of initial materials. The effects of different parameters such as time, catalyst quantities, and the ration of polystyrene to catalyst available on the obtained particle sizes have been investigated. Time and catalyst ratio are the fundamental parameters in this method. The carbon nanoparticles that we have extracted from disposable containers also helps the environment and reduces the recycling costs of polystyrene wastes.

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