Functionalization of Halloysite Nanotubes with Poly(amidoamine) Dendrimers and Their Application to Adsorptive Removal of Hexavalent Chromium

抄録

Halloysite nanotubes (HNTs) were modified with (3-aminopropyl)triethoxysilane to introduce amino groups on the HNT surfaces. Subsequently, poly(amidoamine) (PAMAM) dendrimers were synthesized on the HNT surfaces through the alkylation with methyl acrylate and amidation with ethylenediamine. The buildup of generation was confirmed by FT-IR and XPS analysis. In addition, the back titration with NaOH showed that the amount of amino groups increased with the increase in the generation of PAMAM dendrimers. The adsorption capacity of Cr(VI) ions had the maximum value at pH 3.0 and 30°C. The results of the temperature dependence suggest that the aminosilane layer is subject to degradation at higher temperatures. Under the above optimum conditions, the adsorption capacity increased to 0.95 mmol/g, or 49.3 mg/g, for the HNT sample with 7th generation. This value is higher than or comparable to those of other adsorbents prepared from HNT. These results emphasize that HNT samples with PAMAM dendrimers exhibit a significant potential as an adsorbent for removal of Cr(VI) ions from aqueous medium and wastewaters.