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Tetracyclines (TCs) are widely used antibiotics in human and veterinary medicine and as growth promoters in the world. Sulfate radical-based advanced oxidation processes have been of great interest due to the high oxidizing potential of sulfate radical to degrade refractory organic pollutants in aqueous solution. In this study, the degradation of antibiotic TC in aqueous solution by silver-activated persulfate (Na2S2O8) in the presence of ultrasound irradiation under various conditions has been investigated. The effects of several parameters such as Ag2SO4, Na2S2O8 concentration, temperature, ultrasonic (US) power, initial TC concentration and initial pH on the degradation of TC were investigated. More than 83% of TC removal was achieved within 120 min under optimal conditions. The optimum operational conditions were found to be as follows: Ag2SO4 dosage 3.5 mmol/L, Na2S2O8 concentration 70 mmol/L, reaction temperature 25 °C, US power 120 W, initial TC concentration 50 mg/L, pH 3.0 and contact time 120 min. The degradation of TC in the persulfate/Ag(+)/US process followed the pseudo-first-order kinetics.

This study investigated the amount of Pb, Cd, Cr, Ni, Zn and Cu in samples of imported Indian rice (Oryza sativa) available in Iranian markets. Twenty brands of Indian rice which widely-consumed were collected from Iranian local markets. Five samples of each brand were collected and analyzed. After the rice grains were digested through acid digestion method, Pb, Cd, Cr, Ni, Zn, Cu values of each brand were determined by atomic absorption spectrometer. The results showed that cadmium content could not be detected in rice samples (Cd<0.015 mg kgG 1 ).The mean values of lead, chromium, nickel, Zinc and Cu were 0.33±0.25, 0.631±0.43, 0.128±0.047, 3.47±2.12 and 2.08±0.33 mg kgG 1 , respectively. The results revealed that the mean value of lead in the samples was a little higher than recommended value by FAO/WHO guidelines. Moreover, with determining the degree of Provisional Tolerable Weekly Intake (PTWI) of Pb, Cd, Cr, Ni, Zn and Cu for one person receives less of these metals compared with the standards set by FAO/WHO. Of course, it should be noted that with the increasing rate of food sources contaminated with heavy metals and due to their bioaccumulation in body tissues and the subsequent health risks, it is recommended to use utter products.