Abstract
A new zerovalent iron chitosan-humic acid nanocomposite was prepared and tested for nitrate ion reduction in water. Humic acid was used for intramolecular cross-linking of the chitosan linear chains to increase the active sites on the chitosan biopolymer and then further used as a stabilizer to synthesize zerovalent iron nanoparticles by the reduction of iron (II) chloride with sodium borohydride. Characterization of the products was carried out using infrared spectroscopy, scanning electron microscope, energy dispersive X-ray, and X-ray diffractometer. Batch experiments were conducted for the reduction of nitrate in water using different concentrations of the products in different concentrations of nitrate ion and at different contact time. The adsorption equilibrium data for the nitrate solution gave a favorable adsorption according to the Langmuir equation. Varying the nanocomposite-to-nitrate ion ratio generally led to faster nitrate reduction, with the pseudofirst-order rate constant for the adsorption increasing with increase in nanocomposite-to-nitrate ion ratio. Nitrate removal efficiency of zerovalent iron chitosan-humic acid nanocomposite was further confirmed using real water samples obtained from drainage waste and river with an initial nitrate concentration of 18.00±0.01 and 12.00±0.12 ppm, respectively. The reduction of nitrate in water using the nanocomposite was concluded to be highly effective.
Highlights
There has been an increase in the discharge of toxic substances such as nitrate into the environment especially water bodies as a result of urbanization
This work hitherto describes the synthesis of zerovalent iron crosslinked chitosan-humic acid nanocomposite and its effective nitrate ion reduction in waste water
The synthesized ZvFe-CTS-Humic acid (HMA) was stable when exposed to open atmosphere for long period of hours
Summary
There has been an increase in the discharge of toxic substances such as nitrate into the environment especially water bodies as a result of urbanization. The application of zerovalent metal nanoparticles (Nps) for environmental remediation represents one of the innovative technologies especially in the chemical reduction of some oxoanions from drinking water and destruction of some organic pollutants [3,4,5]. Kumar and Chakraborty [7] have proposed that the reduction of nitrate by some zerovalent nanoparticles gives rise to ammonia or nitrogen, water, or hydroxyl ion. This could occur in the presence of protons. This work hitherto describes the synthesis of zerovalent iron crosslinked chitosan-humic acid nanocomposite and its effective nitrate ion reduction in waste water
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