Transition metal sulfide semiconductors have achieved significant attention in the field of photocatalysis and degradation of pollutants. MoS₂ with a two dimensional (2D) layered structure, a narrow bandgap and the ability of getting excited while being exposed to visible light, has demonstrated great potential in visible-light-driven photocatalysts. However, it possesses fast-paced recombination of charges. In this study, the coupled MoS₂ nanosheets were synthesized with ZnO nanorods to develop the heterojunctions photocatalyst in order to obtain superior photoactivity. The charge transfer in this composite is not adequate to achieve desirable activity. Therefore, heterojunction was modified by reduced graphene oxide (RGO) nanosheets and carbon nanotubes (CNTs) to develop the RGO/ZnO/MoS₂ and CNTs/ZnO/MoS₂ ternary nanocomposites. The structure, morphology, composition, optical and photocatalytic properties of the as-fabricated samples were characterized through X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM), Energy-Dispersive X-ray (EDX), elemental mapping, Photoluminescence (PL), Ultraviolet–Visible spectroscopy (UV-VIS), and Brunauer-Emmett-Teller (BET) techniques. The photo-catalytic performance of all samples was evaluated through photodegradation of aniline in aqueous solution. The combination of RGO or CNTs into the ZnO/MoS₂ greatly promoted the catalytic activity. However, the resulting RGO/ZnO/MoS₂ ternary nanocomposites showed appreciably increased catalytic performance, faster than that of CNTs/ZnO/MoS₂. Charge carrier transfer studies, the BET surface area analysis, and the optical studies confirmed this superiority. The role of operational variables namely, solution pH, catalyst dosage amount, and initial concentration of aniline was then investigated for obtaining maximum degradation. Complete degradation was observed, in the case of pH = 4, catalyst dosage of 0.7 g/L and aniline concentration of 80 ppm, and light intensity of 100 W. According to the results of trapping experiments, hydroxyl radical was found to be the main active species in the photocatalytic reaction. Meanwhile, a plausible mechanism was proposed for describing the degradation of aniline upon ternary composite. Moreover, the catalyst showed excellent reusability and stability after five consecutive cycles due to the synergistic effect between its components. Total-Organic-Carbon concentration (TOC) results suggested that complete mineralization of aniline occurred after 210 min of irradiation. Finally, a real petrochemical wastewater sample was evaluated for testing the catalytic ability of the as-fabricated composites in real case studies and it was observed that the process successfully quenched 100% and 93% of Chemical Oxygen Demand (COD) and TOC in the wastewater, respectively.

Various nanocomposites of TiO₂–ZnO, TiO₂–ZnO/CS, and TiO₂–ZnO/CS–Gr with different molar ratios were synthesized by sol–gel and ultrasound-assisted methods and utilized under UV irradiation to enhance the photocatalytic degradation of tetracycline. Characterization of prepared materials were carried out by XRD, FT-IR, FE-SEM, EDX and BET techniques. The TiO₂–ZnO with the 1:1 molar ratio supported with 1:2 weight ratio CS–Gr (T1‒Z1/CS1‒Gr2 sample) appeared as the most effective material at the optimized operational conditions including the tetracycline concentration of 20 mg/L, pH = 4, catalyst dosage of 0.5 g/L, and 3 h of irradiation time. As expected, the graphene had a significant effect in improving degradation results. The detailed performances of the T1‒Z1/CS1‒Gr2 were compared with ternary nanocomposites from EDX and BET results as well as from the degradation viewpoint. This novel photocatalyst can be effective in actual pharmaceutical wastewater treatment considering the applied operational parameters.

ZnO/TiO ₂ anchored on a reduced graphene oxide (rGO) ternary nanocomposite heterojunction was synthesized via the multi-step method including hydrothermal, solvothermal and sol–gel methods.

This work aimed at developing a natural compound-based hydrogel adsorbent to remove diclofenac as a model pharmaceutical from water. First, graphene oxide–chitosan (GO–CTS) and amine graphene oxide–chitosan (AGO–CTS) hydrogel adsorbents were synthesized via a facile mechanical mixing method. The synthesized materials were characterized through Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), scanning and transmission electron microscopy (SEM and TEM), Raman spectroscopy, and thermogravimetric analysis (TGA) techniques. In the second stage, adsorption experiments were conducted to determine the best GO to CTS ratio and find the optimized adsorption parameters, including the initial drug concentration, adsorbent dosage, pH, and temperature. The results showed that the optimal GO to CTS mass ratio is 2 : 5 and thus the same ratio was selected as the AGO to CTS mass ratio to understand the effect of amine-functionalization on removal efficiency. The optimal adsorption parameters were determined to be pH of 5, C_i of 100 ppm and dosage of 1.5 g L⁻¹, where 90.42% and 97.06% removal was achieved for optimal GO–CTS and AGO–CTS hydrogel adsorbents, respectively. Langmuir and Freundlich isotherms models were employed to investigate the adsorption behavior of diclofenac onto the synthesized hydrogels. The results revealed that the adsorption tends to be of the monolayer type and homogeneous, as the results were in better accordance with the Langmuir model than the Freundlich model. The thermodynamics of adsorption demonstrated that the adsorption is exothermic, exhibiting higher removal efficiency at lower temperatures. Furthermore, Gibb's free energy change of adsorption (ΔG) suggested that the adsorption is spontaneous, being more spontaneous for AGO–CTS than GO–CTS hydrogels. Finally, the regeneration ability of the hydrogel adsorbents was studied in five consecutive cycles. The adsorbent maintained its efficiency at a relatively high level for three cycles but a considerable decrease was observed between the third and the fourth cycle, indicating that the hydrogels were recoverable for three cycles.