Abstract:
This study aimed to understand adsorption mechanisms of single of heavy metals such as Mn, As and Fe and a combined heavy metal in simulated groundwater using iron oxide particles (IOP) and iron oxide coated sands (IOCS). The experiment was conducted in batch test. In order to understand mechanism of heavy metals adsorption, pseudo first-order and pseudo second-order of kinetic, and Langmuir and Freundlich isotherm models were applied by varying adsorbent dosages from 4 to 24 mg/L ,and 10 to 60 min of times. Optimal dosages for single heavy metals and a combined heavy metal removal were 12, 12, 20 and 16 mg/L of IOP, and 8, 12, 8 and 12 mg/L of IOCS, respectively. Moreover, heavy metals removal fitted well to the pseudo second-order kinetic model suggesting chemisorption process. For adsorption isotherm, Mn adsorbed using IOP and IOCS in single and combined heavy metal fitted better with Freundlich model which explained that Mn adsorbed on multilayer of IOP and IOCS surface. In contrast, Langmuir model was fitted with As and Fe in both single and combined heavy metals. Therefore, As and Fe adsorbed on monolayer surface for IOP and IOCS. Moreover, the presence of sulfate in water significantly reduced on single heavy metals adsorption except for Fe; however, sulfate had a negligible effect on combined heavy metals adsorption for As and Fe due to its weaker binding affinity for IOP and IOCS. Last but not least, after leaching test, IOP and IOCS were identified as non-hazardous waste except for Fe-adsorbed IOP. In conclusion, IOP and IOCS were effective adsorbents since they can remove heavy metals in simulated groundwater to an acceptable level according to CDWQS and WHO Standard.
