Adsorption of methylene blue cationic phenothiazine dye with mono and few layered tungsten disulphide nanosheets (WS2)

Textile manufacturing effluents exhibit high concentrations of Methylene blue (MB), with serious health impacts to both the population and the environment. In this study, MB was removed from water using the as-synthesized tungsten disulfide nanosheets produced at different residence times, yielding grey and black coloured products (i.e., WS ₂ , G and WS ₂ , B). The morphological and surface chemistry properties were determined using SEM, HRTEM, FTIR, Rama spectroscopy, and ZetaSizer. The FTIR results showed distinguished functional groups, which represent the tungsten and sulfur's basic vibrations inside the layered structure. SEM reveals that the as-synthesised materials both have a morphology consisting of nanosheets flake-like (nanosheets), The point of zero charge (pHpzc) is 1.90 for G-WS ₂ and 2.47 for B-WS ₂ ​. This means that both materials exhibit positively charged surfaces at pH levels below their pHpzc values and negatively charged surfaces at pH levels above their pHpzc values. The adsorption studies were carried out under the optimized conditions (pH of 7.15, MB concentration of 250 mg/L, the adsorbent dosage of 60 mg, and contact time of 60 min), the maximum removal efficiency of 95.8% and 98.9% was achieved for G-WS ₂ and B-WS ₂ , respectively. The the calculated qe value equals (140, 35 and 155, 80 mg g ^− 1 ) is more near to the experimental value. The thermodynamics shows that the reaction was endothermic in nature verified by positive ΔH ⁰ and ΔS ⁰ . The reusability tests at optimum conditions shows that WS ₂ , B is highly stable and can be rendered economically feasible catalyst.