Single-step synthesis of NiS2 based on deep eutectic solvent: Mechanistic insights and adsorption performance for rhodamine B

NiS 2 is synthesized in a single step at atmospheric pressure using different nickel salts (NiSO 4 ·6H 2 O, NiCl 2 ·6H 2 O, and Ni (CH 3 COO) 2 ·4H 2 O) in choline chloride-ethylene glycol deep eutectic solvent (ChCl-EG DES). The effects of nickel salt types and reactant concentration ratios on the phase and morphology of the products are investigated. Results show that NiS 2 can be obtained when 0.1 M Ni (CH 3 COO) 2 ·4H 2 O and 0.2 M S 0 are used, while impurity S is also found in products when NiCl 2 ·6H 2 O is used. The synthesis mechanism of NiS 2 is proposed through the investigation of the SO 4 2− concentration, pH of the reaction system, and structure of the ChCl-EG DES. DES acts as a reaction solvent and structure-directing agent. The synthesized NiS 2 is used as an adsorbent to remove rhodamine B (RhB) from wastewater. The analysis indicates that the adsorption behavior aligns well with the pseudo-second-order kinetic model and the Freundlich isotherm model. The zeta potential and Fourier-transform infrared spectra of NiS 2 with adsorbed RhB show that the adsorption process is based on electrostatic interaction.