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Novel polyamidoamine (PAMAM) dendrimer-functionalized palygorskite (Pal) adsorbents, up to generation 4.0, with high adsorption capacity, were designed and efficiently synthesized by grafting PAMAM onto 3-aminopropyltriethoxysilane-modified palygorskite (NH 2 -Pal) surfaces. This was carried out using a divergent method including the Michael addition of methyl acrylate (MA) and amidation of the resultant ester moieties with ethylenediamine (EDA). The optimal conditions for Michael addition were achieved using 88.8 mmol MA (relative to 4.0 g NH 2 -Pal) at 323 K for 24 h. The optimal conditions for amidation of the resultant esters were achieved using 179.3 mmol EDA (relative to 2.1 g Pal-PAMAM G0.5) at 323 K for 48 h. All of the amino-terminated Pal-PAMAM G( n ) ( n = 0, 1, 2, 3 and 4) adsorbents exhibited very high density amino-terminated groups and adsorption capacities for both Pb 2 + and Reactive Red 3BS, which increased with increasing generation number. The maximum adsorption capacity for Pb 2 + at 293 K was 68.5 ± 3.3, 151.1 ± 5.7, 196.5 ± 6.1, 389.1 ± 9.6 and 694.4 ± 12.9 mg/g for Pal-PAMAM G( n ) ( n = 0, 1, 2, 3 and 4), respectively. The maximum adsorption capacity for Reactive Red 3BS at 293 K was 34.2 ± 2.7, 69.9 ± 4.3, 122.0 ± 6.4, 242.7 ± 7.1 and 322.6 ± 6.9 mg/g for Pal-PAMAM G( n ) ( n = 0, 1, 2, 3 and 4), respectively. [ABSTRACT FROM AUTHOR]

Abstract: A novel and efficient visible-light-responsive attapulgite composite photocatalyst was fabricated by introducing BiOBr–TiO2 hybrid oxides onto its surface using in-situ depositing technique (marked as ATT–BiOBr–TiO2). ATT–BiOBr–TiO2 nanocomposites with different molar ratios of r (r = n Ti /(n Ti + n Bi) were studied in order to achieve the best photocatalyst. The obtained samples were characterized by XRD, TEM, SEM and BET measurements. It was shown that BiOBr–TiO2 nanocomposite particles with average size of 10nm were introduced onto attapulgite fibers' surface without obvious aggregation. Compared with ATT, ATT–TiO2, ATT–BiOBr and BiOBr–TiO2, ATT–BiOBr–TiO2 exhibits exceptional visible-light photocatalytic activity in degradation of 20mg·L−1 methyl orange. The photodecomposition % of methyl orange increased along with the increasing content of TiO2 in the case of r ≤0.83 and decreased as r >0.83. 96.80% of methyl orange was removed by using ATT–BiOBr–TiO2 (r =0.83) within 120min. Possible mechanism was put forward. [Copyright &y& Elsevier]