Adsorption of Rhodamine B pollutants from wastewater using MoS2: The critical role of crystal phase regulation

It is a key to disclose the structure-dependent adsorption capacity for design and optimization of adsorbent toward removal of dyestuff pollutants from wastewater. Due to this, the relationship between the crystal phase structure of MoS 2 and adsorption capacity for RhB (Rhodamine B) as a typical dyestuff contaminant was investigated. To compare with the commercial MoS 2 ( c MoS 2 ), the diffraction peak ascribed to (002) plane evidently moved toward low 2θ angle in 1T-MoS 2 , suggesting an enlarged interplanar spacing, which was confirmed by HRTEM characterization. 1T-phase displayed far higher adsorption capacity than 2H-phase, in which q t value of 1T-MoS 2 achieved 688.30 ± 10.1 mg/g at 500 mg/L RhB solution, and is 3.0 times larger than c MoS 2 containing 90 % 2H-MoS 2 . Besides, 1T-MoS 2 without sulfur vacancy also displays much higher adsorption capacity than the sulfur vacancy-rich ss MoS 2 , indicating that sulfur vacancy has no contribution to adsorption of RhB. On basis of R 2 criterion, the adsorptions for RhB over c MoS 2 , ss MoS 2 and 1T-MoS 2 well conformed to the pseudo-second order kinetics, indicating that chemical adsorption dominated during the adsorption process. Analysis of structure-dependent adsorption strongly demonstrated that 1T-MoS 2 had more excellent adsorption performance than c MoS 2 and ss MoS 2 due to the synergistic adsorptions of stronger coordination, electrostatic interaction and physisorption. To compare with other adsorbents, 1T-MoS 2 outperformed most of other adsorbents for adsorption of RhB. Cyclic adsorption experiments showed that 1T-MoS 2 possessed an excellent reusability. This work afforded an efficient strategy for crystal phase-mediated adsorption to achieve removal of RhB from wastewater.