Synthesis and characterization of bentonite based inorgano–organo-composites and their performances for removing arsenic from water

• Novel bentonite-based inorgano–organo-composite was optimally synthesized.
• The PDMDAAC–MnxOy-bentonite showed well adsorption towards arsenic.
• The hybrid materials were characterized by XRD, SEM and N2 adsorption-desorption.
• The better performance of PDMDAAC–MnxOy-bentonite was due to a synergistic effect.
• A synergy between modified lamella matrix and amorphous spherical particles

Four modifiers, amorphous iron (hydr)oxides (Fex(OH)y), manganese oxides (MnxOy) and cationic surfactants, cetyltrimethylammonium bromide (CTMAB), and poly(dimethyldiallylammonium chloride) (PDMDAAC), were used to synthesize single and complex modified bentonite. Arsenic removal by modified bentonite was investigated through effects of the type, combination and adding level of modifiers. X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and N2 adsorption-desorption were used to explore the characteristics of the original and modified bentonite. It was found that the type, combination and adding amount of modifiers would have a noticeable influence on the structure and adsorption behavior of resulting bentonite adsorbents. The complex modified bentonite, with manganese oxides and then PDMDAAC at proper addition level, showed the best adsorption properties for arsenic, which could be due to a synergistic effect between PDMDAAC and manganese oxides during modification process. PDMDAAC was found to be favorable for coating of manganese oxides onto bentonite. The adsorbing capacity of modified bentonite depended not only on specific surface area (SSA), but mainly on composite components and/or their specific surface properties.

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