Deep Eutectic Solvent/Surfactant-Engineered GO@TiO2 Advanced Material for Sustained and Ultrafast Adsorption of Hazardous Dye from Contaminated Aqueous Environment

Hybrid carbon-based materials are in demand to achieve the desired activities in various fields. However, such materials lack aqueous dispersibility or mechanical strength, which can be addressed by certain modifiers such as surfactants, polymers, metal oxides, and deep eutectic solvents (DESs), among others. Dodecyl trimethylammonium bromide (DTAB) and a typical DES (reline; choline chloride/urea, 1:2) have been employed in conjunction with graphene oxide–titanium oxide nanocomposites (GO@TiO2 NCs) to get advanced adsorbents (which are characterized by various physicochemical techniques). A model hazardous dye, methylene blue (MB), was used to study the adsorption potential of the above-developed material. The process was optimized in terms of the adsorbent dose, initial MB concentration, pH, and contact time. Various kinetic and adsorption isotherm models were used to analyze the data. Pseudo-second-order kinetics (R2 = 0.999) has been followed by the Langmuir adsorption isotherm (R2 = 0.998). Kinetics revealed that 100% MB adsorption was achieved with DES-based NC (DES-GO@TiO2), which is better than that with both DTAB-based (DT-GO@TiO2) and pure pristine material (GO@TiO2). It is proposed that DES (reline) couples TiO2 on the GO surface with an alternative route to drive MB from an aqueous background. Adsorption data were compared with other similar reported adsorbents, and it was found that the developed DES-based advanced material shows ultrafast MB adsorption (the rate of adsorption has been found to be 222 μg MB per gram of DES-GO@TiO2 in 1 s). The sustainability and economy of the adsorbent were revealed by repeating numerous adsorption cycles (up to seven times) without losing the adsorption efficiency. The study can be applied in various chemical industries where color or coloring material is involved in the effluent. Further, other similar greener DESs should be used in order to develop sustainable structure–performance relationship for a safer environment.