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The use of modified clay minerals for adsorbing arsenic (As) in contaminated soils is an underexplored area of research. The adsorption behavior of As onto inorganically modified smectite and kaolinite both in aqueous and soil media was studied. X-ray diffraction, infra-red spectroscopy, scanning and transmission electron microscopy studies confirmed successful modification of smectite through Fe-exchange and Ti-pillaring, and kaolinite through phosphate binding. The modified smectites were more efficient than phosphate-bound kaolinite in adsorbing 2 As both in water and soil systems. Kinetic study revealed that the clay products reached adsorption equilibrium within h, and the data well fitted to the power function and simple Elovich equation (R 2 > 0.90). The Freundlich isotherm model best described the As adsorption data (R 2 > 0.86) of the modified clay products in both the systems. The Ti-pillared smectite exhibited the highest As adsorption capacity (156.54 µgg-1) in the aqueous medium, while the Fe-exchanged smectite was the best material in the soil system (115.63 µgg-1). The partition coefficient (Kd) and adsorption efficiency (%) data also maintained the similar trend. Precipitation of As and binuclear complex formation also took place in the soil system which made the metalloid non-labile as the time passed. The inorganically modified clay products reported here hold a great potential to adsorb As in contaminated groundwater, drinking water as well as soil.

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Rapid growth in population, industry, urbanization and intensive agriculture have led to soil and water pollution by various contaminants. Nanoremediation has become one of the most successful emerging technologies for cleaning up soil and water contaminants due to the high reactivity of nanomaterials (NMs). Numerous publications are available on the use of NMs for removing contaminants, and the efficiencies are often improved by modifications of NMs with polymers, clay minerals, zeolites, activated carbon, and biochar. This paper critically reviews the current state-of-the-art NMs used for sustainable soil and water remediation, focusing on their applications in novel remedial approaches, such as adsorption/filtration, catalysis, photodegradation, electro-nanoremediation, and nano-bioremediation. Insights into process performances, modes of deployment, potential environmental risks and their management, and the consequent societal and economic implications of using NMs for soil and water remediation indicate that widespread acceptance of nanoremediation technologies requires not only a substantial advancement of the underpinning science and engineering aspects themselves, but also practical demonstrations of the effectiveness of already recognized approaches at real world in-situ conditions. New research involving green nanotechnology, nano-bioremediation, electronanoremediation, risk assessment of NMs, and outreach activities are needed to achieve successful applications of nanoremediation at regional and global scales.