Removal of anionic azo dyes from aqueous solutions by quaternary ammonium salt-functionalized fibers with adjustable surface microenvironments

摘要

Adsorption is one of the most effective methods to remove organic pollutants from water. A series of functionalized fiber adsorbents with cationic adsorption sites and different hydrophobic alkyl chains have been prepared by immobilizing quaternary ammonium salts (QASs) on polyacrylonitrile fiber (PANF). The hydro-phobicities of these QAS-functionalized fibers were evaluated by water uptake and contact angle analysis. These fibers were employed to remove anionic azo dyes (methyl orange, alizarin yellow R and methyl red from water. The fiber with a twelve-carbon alkyl chain (designated PAN(QAS-12)F) had the highest adsorption capacity for MO and the maximum adsorption capacity (Q(e)) is 1.82 mmol g(-1). The PAN(QAS-12)F dye adsorption process follows second-order kinetics and correlates with a Langmuir model. A possible adsorption mechanism that proposes electrostatic interactions as the primary interactive force and hydrophobic and weak hydrogen bonding interactions as secondary forces is presented. The QAS-functionalized fiber can be reused ten times while still maintaining a removal rate of 99% or higher. The QAS-functionalized fiber is also very suitable for continuous flow processes giving a MO removal rate of more than 90% for the treatment up to 1020 mL of MO-containing water. These QAS-functionalized fibers have very promising application potential.