Synthesis and Application of Fe-Doped TiO2 Nanoparticles for Photodegradation of 2,4-D from Aqueous Solution

Enhancement in photocatalytic selectivity of TiO2-based nano-catalyst through molecular imprinting technology

Improvement in the photocatalytic selectivity is imperative for the effective and efficient utilization of catalysts. In this study, a molecularly imprinted polymer-coated iron-doped titanium dioxide (Fe-TiO2@MIP) nanocomposite was successfully synthesized by precipitation polymerization while using RB-19 as a template. The synthesized nanocomposites (Fe-TiO2@MIP and Fe-TiO2@NIP) were characterized by Fourier transform infrared spectroscopy (FT-IR), atomic force microscopy (AFM), field emission scanning electron microscopy (FESEM) with energy dispersive X-ray (EDX), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer-EMMETT-Teller (BET), and UV-visible spectrophotometry. The optimized binding experiments revealed a high imprinting factor of 5.0 for RB-19. The catalytic degradation efficiency and selectivity of Fe-TiO2@MIP enhanced to almost complete degradation of RB-19 from 70% for the parent Fe-TiO2 and 76% for Fe-TiO2@NIP. An outstanding degradation selectivity of RB-19 was achieved compared to other competitive dyes. Finally, the analysis of the non-degraded and degraded RB-19 by ESI-MS revealed the presence of different intermediates that fits well with the proposed degradation mechanism. The study opens new possibilities of selective photo-degradation of targeted contaminants that may ultimately lead to efficient use of photocatalysts.

Synthesis and Application of Innovative and Environmentally Friendly Photocatalysts: A Review

Modern society faces two major challenges: removing pollutants from water and producing energy from renewable sources. To do this, science proposes innovative, low-cost, and environmentally friendly methods. The heterogeneous photocatalysis process fits perfectly in this scenario. In fact, with photocatalysis, it is possible both to mineralize contaminants that are not easily biodegradable and to produce hydrogen from the water splitting reaction or from the conversion of organic substances present in water. However, the main challenge in the field of heterogeneous photocatalysis is to produce low-cost and efficient photocatalysts active under visible light or sunlight. The objective of this review is to compare the new proposals for the synthesis of innovative photocatalysts that reflect the requirements of green chemistry, applied both in the removal of organic contaminants and in hydrogen production. From this comparison, we want to bring out the strengths and weaknesses of the proposals in the literature, but above all, new ideas to improve the efficiency of heterogeneous photocatalysis guaranteeing the principles of environmental and economic sustainability.

Efficient removal of 2,4-D from solution using a novel antibacterial adsorbent based on tiger nut residues: adsorption and antibacterial study

We engineered a tiger nut residue (TNR, a low-cost agricultural waste material) through a facile and simple process to take advantage of the introduced functional groups (cetylpyridinium chloride, CPC) in the removal of 2,4-dichlorophenoxyacetic acid (2,4-D) in batch mode and further investigated its impingement on bacterial growth in a yeast-dextrose broth. The surface characterizations of the adsorbent were achieved through Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller method (BET), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). The batch adsorption studies revealed that solution pH, adsorbent dose, temperature, and salt affected the adsorptive capacity of TNR-CPC. The equilibrium data were best fitted by Langmuir isotherm model with a maximum monolayer adsorption capacity of 90.2 mg g^-1 at 318 K and pH 3. Pseudo-second-order model best fitted the kinetics data for the adsorption process. Physisorption largely mediated the adsorption system with spontaneity and a shift in entropy of the aqueous solid-solute interface reflecting decreased randomness with an exothermic character. TNR-CPC demonstrated a good reusability potential making it highly economical and compares well with other adsorbents for decontamination of 2,4-D. The adsorption of 2,4-D proceeded through a probable trio-mechanism; electrostatic attraction between the carboxylate anion of 2,4-D and the pyridinium cation of TNR-CPC, hydrogen bonding between the hydroxyl (-OH) group inherent in the TNR and the carboxyl groups in 2,4-D and a triggered π-π stacking between the benzene structures in the adsorbate and the adsorbent. TNR-CPC reported about 99% inhibition rate against both gram-positive S. aureus and gram-negative E. coli. It would be appropriate to investigate the potential of TNR-CPC as a potential replacement to the metal oxides used in wastewater treatment for antibacterial capabilities, and its effects against airborne bacteria could also be of interest.

Photocatalytic Activity of Ti-SBA-15/C3N4 for Degradation of 2,4-Dichlorophenoxyacetic Acid in Water under Visible Light

In the present study, the photocatalytic activity of Ti-SBA-15/C₃N₄ catalysts was investigated to degrade 2,4-Dichlorophenoxyacetic acid (2,4-D) herbicides in water under visible light irradiation. The catalysts were synthesized via a simple hydrothermal method and characterized by various analytical techniques, including SAXS, N₂ adsorption-desorption isotherms, Zeta potential, PL, FT-IR, XRF, TGA, and UV-DRS. Our study indicated that the 2.5Ti-SBA-15/C₃N₄ had higher efficiency in the degradation of 2,4-D than Ti-SBA-15 and C₃N₄. The decomposition of 2,4-D reached 60% under 180 minutes of visible light irradiation at room temperature on 2.5Ti-SBA-15/C₃N₄. Moreover, the degradation of 2,4-D on Ti-SBA-15/C₃N₄ was pseudo-first-order kinetics with the highest rate constant (0.00484 min^-1), which was much higher than that obtained for other photocatalysts reported recently. Furthermore, the catalyst can be reused at least two times for photodegradation of 2,4-D solution under visible light irradiation within a slight decrease in catalytic activity.

One-Pot Synthesis of TiO2-rGO Photocatalysts for the Degradation of Groundwater Pollutants

A non-conventional approach to prepare titanium dioxide-reduced graphene oxide (TiO₂-rGO) nanocomposites based on solar photoreduction is here presented. The standard hydro-solvothermal synthesis of the TiO₂-rGO composites requires high temperatures and several steps, whereas the proposed one-pot preparation allows one to obtain the photocatalysts with a simple and green procedure, by exploiting the photocatalytic properties of titania activated by the solar irradiation. The TiO₂-rGO catalysts were tested in the solar photodegradation of a widely adopted toxic herbicide (2,4-Dichlorophenoxyacetic acid, 2,4-D), obtaining the 97% of degradation after 3 h of irradiation. The as-prepared TiO₂-rGO composites were more active compared to the same photocatalysts prepared through the conventional thermal route. The structural, optical, and textural properties of the composites, determined by Raman, Photoluminescence, Fourier Transform InfraRed (FTIR), UV-vis diffuse reflectance (DRS) spectroscopies, and N₂ absorption-desorption measurements, showed as the solar irradiation favors the reduction of graphene oxide with higher efficiency compared to the thermal-driven synthesis. Furthermore, the possible toxicity of the as-synthesized composites was measured exposing nauplii of microcrustacean Artemia sp. to solutions containing TiO₂-rGO. The good results in the 2,4-D degradation process and the easiness of the TiO₂-rGO synthesis allow to consider the proposed approach a promising strategy to obtain performing photocatalysts.