Treatment of arsenic (III) contaminated water by dynamically modified iron-coated sand (DMICS)

Abstract

In this paper, dynamically modified iron-coated sand (DMICS) was synthesized by dynamic soaking of iron onto the sand. The DMICS was tested for As(III) removal from the aqueous solution by adsorption studies. The effects of particle size, initial arsenic concentration and adsorbent dose on arsenic removal efficiencies were evaluated by batch kinetic studies. Two batch kinetic models i.e. chemical reaction rate and pseudo-second order have been applied to see the behaviour of As(III) adsorption over DMICS. Langmuir, Freundlich and Temkin isotherms were used to describe the equilibrium studies data. Langmuir isotherm was found better fit when compared with other isotherms based on coefficient of correlation (R2) values. The maximum adsorption capacity of DMICS was calculated as 0.29 mg/g as per Langmuir isotherm. The adsorption process was pH-dependent and maximum arsenic removal occurred in the pH range of 6–8. Scanning electron microscope was conducted on arsenic-loaded sand whereas, X-ray diffractogram (XRD) analysis was conducted on plain sand, DMICS and arsenic-loaded DMICS. XRD spectra supported the presence of arsenic on the surfaces of DMICS. The breakthrough and exhaustion times for 60 cm media column were 114 h and 200 h, respectively, based on column studies data. The DMICS has shown a good potential for arsenic remediation from aqueous medium.