Distinguished Cd(II) Capture with Rapid and Superior Ability using Porous Hexagonal Boron Nitride: Kinetic and Thermodynamic Aspects

In present work, a systematical and comprehensive understanding for the adsorption of Cd(II) on porous hexagonal boron nitride (p-BN) was studied. The chemical compositions, morphology and surface functional groups of p-BN before and after adsorption were characterized by SEM, HRTEM, BET, XRD, and FT-IR. The effects of pH, adsorbent dosage, contact time and temperature on Cd(II) adsorption were investigated. The maximum adsorption capacity for Cd(II) achieves 184 mg.g(-1) at pH 7.0 and 313 K. The kinetic data fitted well with pseudo-second-order model and intra-particle diffusion model, indicating that the adsorption is mainly controlled by chemisorption, and the rate-limiting step is the molecular diffusion. The adsorption isotherms are in accordance with Freundlich and Langmuir model respectively, suggesting Cd(II) adsorbed on the heterogeneous surface through multilayer and monolayer adsorption. The thermodynamic parameters are calculated to confirm the spontaneous and endothermic process of Cd(II) sorption. Spectroscopic results from XPS imply that p-BN adsorbent had substantial functional groups and bonding sites, which is propitious to uptake Cd(II) from wastewater. These results revealed that p-BN is a promising candidate for Cd(II) scavenging.