ABSTRACT
In this study, CaCO3 was used as a modifier for nano zero-valent iron (nZVI) surface to prevent rapid aggregation and effectively utilized for iron remediation from aqueous solution. Surface chemistry and morphology of CaCO3 encapsulated nZVI (CaCO3-nZVI) before and after treatment of contaminant iron solution were characterized by scanning electron microscopy-energy dispersive X-ray (SEM-EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The mechanisms of surface modification as well as iron remediation were well depicted with the help of these characterisation tools. Iron removal efficacy of 96.4% was achieved with 0.25 g/L adsorbent dose for an influent iron of 0.5 mg/L at pH 10 after a 3 h treatment process. When the influent concentration was increased to 10 mg/L, the removal capacity decreased to 92.1%. The study demonstrates that CaCO3 and nZVI in the encapsulated nanoparticle have a significant synergistic effect. The pseudo-second- order reaction kinetics and Freundlich isotherm model correctly portrayed the experimental data for iron removal by CaCO3-nZVI. The CaCO3-nZVI is a viable option for iron removal from various aqueous media due to its facile preparation, high iron removal capability, and reusability.
ABSTRACT
The toxic leachate generated from landfills is becoming a major nuisance to the environment and has vital role in groundwater contamination. This study evaluated the potential of zero valent aluminium (ZVAl) based advanced oxidation processes (AOPs) for stabilized landfill leachate treatment. Hydrogen peroxide (HP) and persulfate (PS) were used to generate additional radicals in aerated ZVAl acid process. ZVAl-acid system achieved 83% COD removal efficiency under optimized conditions such as acid washing time of 20 min, ZVAl dose of 10 g L-1 at initial pH 1.5. The highest exclusion efficiencies in terms of TOC, COD as well as color were 83.52%, 96% and 63.71% respectively in treatment systems showing the following order: ZVAl/H+/Air/HP/PS > ZVAl/H+/Air/PS > ZVAl/H+/Air/HP > ZVAl/H+/Air > ZVAl/H+. The involvement of other metals such as Fe and Cu in the process has been found. The reusability study revealed that ZVAl powder can be effectively used up to three cycles. The 28.48 mg/l of Al3+ residue was observed in this process which has to be removed before discharge of effluent. The study indicated that the ZVAl based AOPs is stable and active for the degradation of organic pollutants present in landfill leachate and a promising solution except for the aluminium discharge which has to be given special care.