Periodic Mesoporous Organosilicas as adsorbents for the organic pollutants removal in aqueous phase

• Bulky phenylthiourea pesticide is chemisorbed on acid sites and exhibits a Freundlich isotherm.
• Ph-PMO-SO3H exhibits better adsorption behavior than SBA-15-SO3H or HFAU zeolite.
• The phenyl rings in the mesopores enhance significantly adsorption decreasing the water affinity.
• Pesticide abatement rate are up to 90% in water even at low concentrations when Ph-PMO-SO3H is used.

Heavy organic pollutants such as pesticides and pharmaceuticals are found in wastewater and are difficult to remove by microporous adsorbents because of their large size. Mesoporous organosilicas as potential adsorbents for removal of heavy organic pollutants from aqueous phase are investigated. Propylsulfonic acid-functionalized mesoporous silica (SBA-15-SO3H) and propylsulfonic acid-functionalized periodic mesoporous benzene-silica (Ph-PMO-SO3H) are prepared by co-condensation method. Textural and structural characterizations are conducted by X-ray diffraction, N2 physisorption, solid state NMR spectroscopy, elemental analysis and confirmed the structural integrity of the materials. Material adsorption behaviors are studied in pesticide, mesosulfuron methyl (MM), removal from aqueous phase. For all the materials, adsorption kinetics are well described by a pseudo-second order model indicating the chemisorption of the MM molecules via acid–basic interaction of the neutral form. Sorption isotherms are S-shape isotherms and can be well fitted by the Freundlich model. Ph-PMO-SO3H exhibits higher sorption rate (8.95 mg g−1 h−1) and better sorption capacity (9.70 mg g−1) than the mesoporous silica SBA-15-SO3H (4.16 mg g−1 h−1, 9.4 mg g−1). Furthermore, Ph-PMO-SO3H has also the best MM abatement rates in aqueous phase up to 95% for initial concentrations ranging from 4 to 10 ppm than microporous acidic zeolite (HFAU) (∼70%) and mesoporous silica SBA-15-SO3H (∼70%). The phenyl groups in sulfonic PMO material seem to enhance organic pollutant adsorption capacity either by reducing wall hydrophilicity or by favoring the interaction with MM phenyl rings.

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