Enhanced adsorption performance of hierarchical S-doped Ni(OH)2 hollow nanocomposites for the removal of Congo red

In this work, nonmetallic S was doped into hierarchical Ni(OH)2 hollow microspheres by ethanol solvothermal method using thiourea as sulfur source. Although the morphology of precursor Ni(OH)2 is maintained, the surface states and pore properties had greatly changed after S doping. Using the as-prepared S-doped Ni(OH)2 as adsorbents for the removal of Congo red (CR), the S-doped Ni(OH)2 exhibited much better adsorption capacity compared with undoped Ni(OH)2. The adsorption behavior of both Ni(OH)2 and S-doped Ni(OH)2 followed the pseudo-second-order kinetic model and intraparticle diffusion model. The equilibrium data of Ni(OH)2 could be better fitted by Langmuir model, while Freundlich model could be better used to describe the S-doped Ni(OH)2 with a much larger adsorption capacity toward CR. The tuned microstructure and changed surface states of adsorbent after S doping may be responsible for the enhanced adsorption performance. Therefore, the doping of S species into hierarchical Ni(OH)2 paves a new way to tune the microstructure and surface states of Ni-based materials.