Iranian Journal of

Background and Objective: Excessive consumption of antibiotics and the entrance of the potentially hazardous substances to the environment has become one of the environmental concerns. Today, adsorption is one of the efficient and reliable methods for the removal of this class of compounds. The aim of this study was to synthesize chitosan-Fe₃O₄ and to compare the efficacy of removing erythromycin antibiotics from aqueous humorous media by this adsorbent and chitosan.
Materials and Methods: The structural properties of the synthesized adsorbent were analyzed by TEM, PSA, VSM techniques. Various parameters including pH (1-11), contact time (0-60 min), adsorbent concentration (1-5 g/L), and initial concentrations of erythromycin (5-50 mg/L) was evaluated for the removal efficiency. For data analysis, Excel software was used. The equilibrium constant and the kinetic constants were calculated from the first-order kinetic model using Freundlich and Langmuir isotherms.
Results: The results indicated that increased pH and initial concentration of erythromycin increased the dose of adsorbents and the contact time of removal efficiency. The highest absorption efficiency at pH of 3 for both adsorbents, the contact time 30 min for modified chitosan and 50 min for chitosan, the dose of adsorbent 2 g/L for modified chitosan, and 3 g/L for chitosan and the initial concentration of erythromycin for each of the two adsorbents was 10 mg/L and the erythromycin adsorption by both adsorbents follows the Langmuir isotherm and the pseudo second order kinetics.
Conclusion: According to these results, chitosan modified with Fe₃O₄ can be used as a more effective adsorbent than chitosan for removal of erythromycin by adsorption method.
 

Background and Objective: The application of ultraviolet photolysis in the removal of microbial contamination can develop the use of wastewater sources. In this research, the efficiency of UVC-LED for removing Escherichia coli was evaluated in pulsed radiation mode with continuous radiation.
Materials and Methods: In order to conduct this research, 4 UVC-LEDs with a short wavelength of 12 MW were used to produce ultraviolet rays. LEDs create waves with a wavelength of 260-280 nm. The distance between the LED and the plates was considered to be about 0.5 cm, 1 cm, and 2 cm. In order to investigate the effect of discontinuous radiation on UVC-LED performance, 2 Hz and 1 Hz frequency were used. In this case, the power source is connected 2 times and 1 time respectively in every second. The variables of radiation time (t) in seconds, radiation distance (d) in centimeters, and radiation frequency (f) in Hz were used for valuation.
Results: The results showed that in discontinuous irradiation, although the effectiveness increases with the increase of irradiation time, and practically at times higher than 280 seconds, bacteria do not remain in the samples, but the performance of discontinuous irradiation compared to continuous irradiation in removing bacteria at irradiation intervals of 1 cm, 0.5 cm and time 20 s has only achieved logarithm 4 or in other words 99.99% removal, which is considered the weakest performance of continuous radiation. Also, in the discontinuous radiation mode, after 280 s time and 2 cm distance, the radiation performance towards the complete removal of bacteria is equal to the logarithm of 6 or 99.999%, which is equal to the amount of bacteria removal in continuous radiation.
Conclusion: The efficiency of pulsed radiation was greater as compared to continuous radiation.