Iron pelletization with various seeding materials

Abstract

Recently, zero valent metals process was widely used for chemical treatments such as nitrate removal because this process is higher efficiency at low cost and leads to non-toxic waste. Nevertheless, the large amounts of iron were produced from zero valent metal process. This research approached this problem by coating iron oxide onto the surface of quartz sand in fluidized bed reactor which could reduce sludge volume significantly due to denser property of the pellet compared to puffy sludge. This study attempts to utilize several seeding materials as the media in the fluidized bed process for ferrous removal. Additionally, aeration and fenton pretreated were varied for changing ferrous to ferric ion was concentrated for process comparison. The result from fenton pretreated iron coated sand (F-ICS) showed that higher amount of iron tends to attach on the sand surface at pH 6.5. The recirculation rate was also found to affect iron precipitation in fluidize bed and the optimum flow rate was 2,100 mL/min (0.5 bed expand). Sand of 400g/L was found to be sufficient to remove 98% of 185 mg/L of total iron within 2 hr which provide specific coating capacity 0.456 mg/g. Iron coating ability of F-ICS seems to be diminished when reused repeatedly with the iron accumulation of 3.56 mg/g sand at the 11th cycle. While, three phase fluidized bed process was achieved at 20 mL/min which produce coating capacity 0.431 and 0.417 mg/g for quartz sand (T-ICS) and aluminum oxide 9T-ICAO) respectively. The results indicated the iron pellets obtained from three phase fluidized bed process have more stable at wider pH range. The adsorbed ability of iron pellets for the removal of copper were explained by Langmuir adsorption isotherm which provide a maximum adsorption capacities 0.249, 0.300 and 0.222 mg Cu/g for F-ICS, T-ICS and T-ICADO respectively. SEM and EDX spectrum reported that percent of iron occurred following iron pelletization process and copper became one of the principle elements on the surface of iron pellets after adsorption process.