Hexagonal Ni(OH)2 nanosheets for stabilizing Pickering emulsion and Congo red adsorption

Abstract

In this paper, hexagonal Ni(OH)2 nanosheets were prepared by hydrothermal method with nickel chloride hexahydrate as matrix and ammonia as precipitant. The lateral size of Ni(OH)2 nanosheets was about 100–250 nm. The structure of the Ni(OH)2 sheets was characterized by XRD, SEM, IR, TGA etc. Pickering emulsion was prepared by using Ni(OH)2 nanosheets as stabilizer and dichloromethane (DCM) as oil phase. Furthermore, the stability factors of Pickering emulsion and the adsorption of Congo red (CR) on interface particle layer were studied. The adsorption equilibrium of CR was analyzed by Langmuir adsorption model and Freundlich adsorption model, and the adsorption process was researched by pseudo-first-order kinetics and pseudo-second-order kinetics. Compared with Ni(OH)2 in the water phase, the Ni(OH)2 in interface particle layer exhibited a much higher adsorption capacity and a faster deposition rate. The adsorption mechanism of CR can be mainly attributed to electrostatic interaction between the positively charged interface particle layer and the anionic CR molecules. It can be expected that as a promising adsorbent for CR removal in water treatment, the Ni(OH)2 sheets in Pickering interface layer can provide a new strategy for dye adsorption.