Efficient system for encapsulation and removal of paraquat and diquat from aqueous solution: 4-sulfonatocalix[n]arenes and its magnetite modified nanomaterials

Abstract Efficient encapsulation of paraquat and diquat herbicides by 4-sulfonatocalix[n]arene (n = 4, 6, 8) in water have been examined by Benesi Hilderbrandt equation which explicit 1:1 complexation of 4-sulfonatocalix[n]arene with paraquat and diquat. The binding constants have been calculated and 4-sulfonatocalix[8]arene has been observed to show the utmost binding affinity for paraquat and diquat. The covalently linked 4-sulfonatocalix[n]arene modified magnetite nanomaterials have also been synthesized and used as nanoadsorbent for the efficient removal of paraquat and diquat from aqueous solution. Magnetite nanoparticles modified with 4-sulfonatocalix[8]arene exhibit high adsorption efficiency for both, paraquat and diquat. The effects of contact time, dosage amount and temperature have been investigated on adsorption process. The nanoadsorbent can be easily separated from the aqueous solution using external magnet and can be regenerated and reused. The adsorption isotherm and kinetic analysis have also been performed.