BTCA/Ca2+-reinforced sodium alginate/chitosan/MWCNT aerogel for sustainable remediation of herbicide-contaminated water: Adsorption performance and molecular insights.

Abstract

The efficient removal of pesticide pollution from wastewater using adsorbents is highly desirable. A sodium alginate/chitosan/multi-walled carbon nanotube (SA-CS-MWCNTs) aerogel reinforced with 1,2,3,4-butanetetracarboxylic acid and Ca2+ was prepared for separate adsorption of sulfentrazone and diuron. The aerogel exhibited a hydrated compressive modulus of 45.60 kPa and 6.50% mass loss after 14 days of aqueous immersion, indicating improved mechanical and aqueous stability relative to the BTCA-treated control without CaCl2 treatment. Adsorption capacities reached 70.93 and 54.93 mg·g-1 for sulfentrazone and diuron, respectively. Nonlinear fitting favored pseudo-first-order kinetics for sulfentrazone and pseudo-second-order kinetics for diuron. The equilibrium adsorption data were described by the Langmuir model within the investigated concentration range. After five adsorption-desorption cycles, the aerogel retained adsorption capacities of 49.03 mg·g-1 for sulfentrazone and 33.77 mg·g-1 for diuron, demonstrating appreciable reusability. FTIR, XPS and density functional theory calculations revealed that adsorption was governed by multiple non-covalent interactions, including electrostatic attraction, hydrogen bonding, hydrophobic interactions and π-π stacking. These findings highlight the potential of BTCA/Ca2+-reinforced aerogels for herbicside adsorption.