Unprecedented adsorption densities of tetracycline on Fe-substituted defective MoOxS2-x with graphene oxides nanosheets: Effect of Fe3+ loading, hardness concentration and their stability for maxi-sorption.

The present study was to analyze the behaviour of defective nanocomposite material in the adsorption of tetracycline (TC) from waters. We aimed to synthesize O-rich defective MoS2 (MoOxS2-x) nanosheets by a simple hydrothermal method. The defective nanosheets were further modified by incorporation of Fe3+ ions with graphene oxide (GO), FeMoOxS2-x@GO, for the effective removal of TC from waters. The PXRD patterns confirms the formation of O-rich MoS2 and FeMoOxS2-x by representing their d-space values and further it was supported by XPS, TGA, FE-SEM and mapping analysis. The rod-like Fe particles on the flowery morphology on the sheets of GO confirms the formation of heterostructure of the composite. The maximum adsorption densities, calculated by Langmuir adsorption isotherm studies, of TC on FeMoOxS2-x@GO were 1.6018 mmol/g much higher compared to other studied materials of MoOxS2-x, FeMoOxS2-x and commercial MoS2. The developed defective FeMoOxS2-x@GO adsorbent is highly selective in the co-existing anions studies and highly stable at wide pH ranges without altering their adsorption ability. The spent material was washed with ethanol and the removal efficiency was maintained up to 6 cycles with minimum loss of efficiencies. The adsorption mechanism of TC on FeMoOxS2-x@GO was primarily governed by chemisorption, confirmed by kinetic and isothermal studies, and the main mechanism involved in this process includes π-π interactions, hydrogen bonding, and complexation. The role of Fe and hardness for the maxi-sorption and their stability after adsorption was analyzed. The results suggest that Fe and GO loaded MoOxS2-x have higher adsorption capacities and can pave a way for efficient removal of other antibiotics from water and wastewater.