Highly efficient scavenging of Ni(II) by porous hexagonal boron nitride: Kinetics, thermodynamics and mechanism aspects

Intending to remove Ni(II) from wastewater, porous p-BN was employed to recovery Ni(II) by batch and X-ray photoelectron spectroscopy technique. The performances and mechanism of p-BN for Ni(II) sorption had been studied by diverse characterization technologies. The kinetic data was calculated to conform a pseudo-second-order model, and isotherm data fitted to a Freundlich equation. We obtained a high removal rate and a high adsorption capacity. A possible mechanism can be expressed from XPS results. The surface of p-BN is B–OH/B–NH2 enriched and exhibits a weak alkalinity. When p-BN contact with Ni(II) solution, the hydroxide ions releases from the surface while there is a formation of B–O⋯Ni; the small group of B–O⋯Ni is acting with hydroxide ions, thereby forming B–O⋯Ni(OH)2 and continuously adsorbs Ni(II) to form B–O⋯Ni(OH)ONi(OH) like as precipitated nucleus. Then, due to the interaction of hydroxyl-O with electron-deficient B, the veil-like Ni(OH)2 generated from precipitated nucleus evenly attaches to p-BN. The bonding state of Ni(II) on p-BN by XPS spectra revealed that the process of adsorbing Ni(II) onto p-BN was chemisorption through the formation of Ni(OH)2 and the interaction between hydroxyl-O and electron-deficient B. The analyses implied that p-BN is a promising candidate for recovery of Ni(II) from wastewater.