Removing of organic toxicants from water by Al13–pluronic modified clay

Organometallic complexes made of Al13 polycations associated with triblock copolymers polyethylene oxide–polypropylene oxide–polyethylene oxide (PEO–PPO–PEO) were intercalated into montmorillonite to synthesise novel modified clay adsorbents. Three copolymers PEO–PPO–PEO (pluronics; BASF) with increasing PPO wt.% (20, 50, and 90%) were used at increasing ratios pluronic/Al13 in the pillaring solution. The resulting samples were characterised by X-ray diffraction (XRD), chemical analyses, combined TGA–DTA, IR spectrometry, and zeta potential measurements. In all cases, the organic and inorganic moieties are co-intercalated. Modified clays involving the most lipophilic pluronic are readily distinguished from the two other ones. For the two most hydrophilic polymers, the organic carbon content of the final clay composites reaches a maximum value whereas it increases regularly with the amount of polymer in the synthesis solution for the samples involving the most lipophilic pluronic. This is shown to be due to the physisorption of lipophilic pluronic molecules onto the external surface of clay layers. The adsorption capacity of the resulting materials towards 4-monochlorophenol (4-MCP) and 2,5-dichlorophenol (2,5-DCP) was then tested. Batch adsorption isotherms reveal that the hydrophobicity of the polymer is the main factor controlling the adsorption of organic pollutants.