Abstract
Groundwater has long been identified as potential alternative of clean water supply due to its reliable quantity. However, pollution of groundwater due to anthropogenic factor still remains a challenging issue. To date, nanoscale zero valent iron (nZVI) has received great attention for its capability to treat various contaminants including chlorinated organics and metals. This study investigate Zinc (Zn) removal in aqueous solution by nanoscale zerovalent iron (nZVI). The characteristics study of the synthesized nZVI particles were investigated by its particle size and surface morphology using Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM). SEM and TEM analyses verified that the particles size of synthesized nZVI were 71nm (< 100 nm). Structure of nZVI congragate to each other and a thin layer of oxide layer formed on the outer part of the nZVI particle. In the batch study, removal kinetic of Zn increased from 0.14 to 0.18 mins-1 as the concentration of Zn increased from 0.1 to 0.5 ppm. However, the removal kinetic decreased from 0.162 to 0.148 mins-1 as the amount of nZVI was increased from 0.25 mg/L to 2.50 mg/L. At pH 7, removal kinetic reached 0.157 mins-1. However as the pH suspension decreases to pH 6.5, the removal kinetics decreased significantly to 0.144 mins-1. The same behaviour was observed at pH 9 where the removal kinetics was decreased to 0.117 mins-1. Removal kinetic of Zn significantly decreased at basic condition due to the formation of passivation layer which decreased the density of reactive surface area (e.g., Fe0 and Fe2+) on the surface of nZVI. Experimental results from this study can provide basic knowledge of effectiveness of Zn removal mechanisms by nZVI at different environment conditions and provide potential remediation technology for the treatment of toxic heavy metals in groundwater.
Highlights
IntroductionIndustrial, agricultural, mining and waste disposal are the anthropogenic activities have the potential to leach heavy metals (e.g., cadmium, lead and zinc) into groundwater [1]
Industrial, agricultural, mining and waste disposal are the anthropogenic activities have the potential to leach heavy metals into groundwater [1]
Chemical utilized for this study include, sodium borohydride (NaBH4) (99%, Aldrich), iron chloride (FeCL3) (98%, Aldrich), acetone (99%, Merck) for nano-scale zero valent iron (nZVI) synthesis, MOPs, pKa = 7.2 for pH 6.5 to 7.9 and hydrochloric acid (HCL) (0.1 M, Merck) for preparing buffer solution
Summary
Industrial, agricultural, mining and waste disposal are the anthropogenic activities have the potential to leach heavy metals (e.g., cadmium, lead and zinc) into groundwater [1]. There is an increased concern in Malaysia regarding the environmental impacts of groundwater contamination by the bioavailability and leaching of toxic heavy metals in soil and groundwater. The government takes serious efforts to remediate the contaminated groundwater to achieve cleaner soil and potable groundwater. The concentration of Zn in uncontaminated water is in a range of 10-10 to 10-6 M [2]. Human activities such as mining or steel production activities cause serious Zn contamination to surface and groundwater. Efforts on elucidating Zn contamination and its remediation initiatives in groundwater should be given serious attention
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