الفهرس 
Nano adsorbents and water treatment
Synthesis of (Nano ZnO/MWCNTs) by the arc discharge method according to two systems (B) with varying the ACsOnly 14 pages are availabe for public view
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Abstract
Two different electrode systems (A and B) have been used by the arc discharge in order to prepare the nanocomposites (Nano ZnO/MWCNTs). For system (A), the dimensions of rectangular zinc cathode were (2 mm x 3 mm x 80 mm) while the graphite as a cylindrical electrode; its dimensions were (5 mm x 100 mm). For system (B), the dimensions of rectangular zinc electrode were (7 mm x 13 mm x 80 mm) while the graphite as a cylindrical electrode; its dimensions were (10 mm x 100 mm). The applied voltage was constant (70 V) and the used ACs were varied from (15 A) up to (70 A). The arc discharge carried out under deionized water as electrolyte medium. The impact of changing dimensions of the two electrodes on the properties of (Nano ZnO/MWCNTs) has been studied by using some techniques; TEM, XRD, EDX and FTIR. According to the two systems A and B at the discharge alternating current (Iac = 15 A); the average of outer diameters of produced MWCNTs were (7.30 nm) and (15.18 nm), respectively while the average of nano sizes of produced Nano ZnO were 12.24 nm and 15.36 nm, respectively. The results show the nano size of prepared (Nano ZnO/MWCNTs) was increasing by increasing the dimensions of the two electrodes. Zeta potential was (+13.0 mV) and (+13.8 mV) for the nano composites (Nano ZnO/MWCNTs) prepared according to systems A and B respectively. Zeta Potential of (Nano ZnO/MWCNTs) prepared according to system B was (21 mV, 13.8 mV, -29.5 mV and -32.2 mV) at pH values of (5, 7, 9 and 11), respectively and the pezo electric was clear at (pH =7.7). The impact of changing (Iac) on the nano size of (Nano ZnO/MWCNTs) has been studied. For system (A), the zinc electrode of small dimensions was broken with increasing the discharge current. According to system (B); R2 values of the linear correlations for the applied alternating electrical current (Iac) with the nano size of ZnO and the outer diameter of MWCNT in the prepared nanocomposites were (+ 99.55) and (+ 98.60), respectively. Heavy metal ions like; Fe+3, Co+2 and Cd+2 are leaked into Lakes and rivers due to the wastes of different industrial activities. These ions have harmful effects on human health. This work has discussed the effect of prepared (Nano ZnO/MWCNTs) on the dissolved ions (Fe+3, Co+2 and Cd+2) in water. According to the results obtained in this work for Fe+3 in an aqueous solution, the optimum dose of Nano ZnO/MWCNTs was (5 mg/100ml) with shacking at 200 rpm for a contact time of 60 minutes at 25 ºC and (pH = 12). For Co+2 aqueous solutions and Cd+2 aqueous solutions, the optimum dose of Nano ZnO/MWCNTs is (6 mg/100ml) with shacking at 200 rpm for a contact time of (60 minutes) at 25 ºC and (pH = 12) to remove these ions below the wellknown limits. The adsorption of Fe+3, Co+2 and Cd+2 ions from water by using Nano ZnO/MWCNTs obeys the pseudo-first order kinetic model and Freundlich adsorption isotherm model (multilayer and physical adsorption). The removal efficiencies for Fe+3, Co+2 and Cd+2 ions from aqueous solutions of low concentrations (0.5024 mg/l, 0.1504 mg/l and 0.0588 mg/l) were (95.36%, 97.01% and 96.43%), respectively. The removal efficiencies for Fe+3, Co+2 and Cd+2 ions from aqueous solutions of higher concentrations (1.0120 mg/l, 1.0091 mg/l and 0.3008 mg/l), respectively have reached (93.17%, 90.26% and 94.65%), respectively. In case of high concentrations of Fe+3 (4.0204 mg/l and 6.060 mg/l), the removal efficiencies were (90.01% and 88.86%), respectively. Different samples have been taken from El-Umoum Drain, Lake Mariout, Lake Manzala and the end of Al-Mahmoudia canal in the north of Egypt. El-Umoum drain lies in the west of Alexandria and it is one of basic sources of pollution for Lake Mariout. The (Nano ZnO/MWCNTs) has removed the dissolved ions of iron, cobalt and cadmium below the well-known limits in the collected samples. It is noticed that the residual traces of radioactive iodine isotopes are present in the urine of patients which receive radioactive therapy. Therefore, the waste water may be contaminated with radioactive isotopes. This work presents a new economic method for removing the stable iodine (127I-) and radioactive iodine (131I-) from aqueous solutions by using the nano adsorbent (Nano ZnO/MWCNTs). The adsorption process has been carried out by using the dose of nano adsorbent (5 mg/100ml) in an acidic medium of (pH = 5) at (25 ºC) with shacking at 200 rpm for a contact time (60 minutes). At low concentration of (0.1843 ppm) of stable (127I-) solution, the removal efficiency has reached (97.23%). At higher concentration of (0.5014 ppm), the removal efficiency has reached (89.75%). The adsorption process obeys the pseudofirst order kinetic model. The adsorption process is multilayer physical adsorption according to Freundlich isotherm model. The radioactive Iodine (131I) have been prepared by irradiating the natural Tellurium dioxide (130TeO2) targets with neutrons, the radioactive Tellurium (131Te) is produced and decays via β- emission to the radioactive Iodine (131I). The dose of nano adsorbent (10 mg) was added to (100ml) of radioactive iodine (131I-) solution of an activity (20 μCi) with shacking at 200 rpm for a contact time of (60 minutes) and was allowed to equilibrate for two days. After that, the solution (S) was filtered by a filter syringe with a pore size (450 nm) to separate the used nano adsorbent which had adsorbed (131I-). The filtrate from the first cycle was used to repeat the removal process and was considered as second cycle and so on until the fifth cycle. In each cycle, the both areas under peaks in the two spectrum of standard and filtrate of the same volume were measured by the 3x3 NaI (Tl) scintillation detector. Moreover, the spectral analysis was carried out using Gennie 2000 software. The removal efficiency for (131I-) was (34.16%) in the first cycle. This percentage reached (94.76%) after five cycles during ten days. The percentage of residual (131I-) reached (5.24%) and it was less than that (42.15%) due to the natural radioactive decay. In the case of stable iodine (127I-) solutions (0.1843 ppm, 0.5014 ppm, ..), the probability of collisions between the nano adsorbent particles and the ions of stable iodine (127I-) is great. On the other hand, for radioactive iodine (131I-) solution of an activity (20 μCi); the probability of collisions between the nano adsorbent particles and the dissolved traces ions of radioactive iodine (131I-) is small. Therefore nano adsorbent has low removal efficiency in the case of radioactive iodine (131I-) solutions, as compared to the removal efficiency in the case of stable iodine (127I-) solutions. The results have attributed to the nano adsorbent dose of (50 mg/100ml) is the optimum dose for adsorbing (131I-) in one cycle of treatment during two days only. This method may be applied to adsorb other radioactive iodine isotopes like; (124I, 125I and 131I) ions from acidic aqueous solutions because all iodine isotopes have the same chemical properties.