Photocatalytic performance of Sn-doped TiO2 nanostructured mono and double layer thin films for Malachite Green dye degradation under UV and vis-lights

Removal of malachite green from water: Comparison of adsorption in a residue-derived AC versus photocatalytic oxidation with TiO2 and study of the adsorption-photocatalysis synergy

The literature rarely compiles studies devoted to the removal of pollutants in aqueous media comparing adsorption and photocatalytic degradation, and does not pay enough attention to the analysis of combined adsorption-photocatalytic oxidation processes. In the present manuscript, the removal of malachite green (MG) from aqueous solutions has been investigated in three different sustainable scenarios: i) adsorption on activated carbon (AC) derived from a residue, luffa cylindrica, ii) photocatalytic oxidation under simulated solar light using titanium dioxide (TP) and iii) combined adsorption-photocatalytic oxidation using TP-AC (70/30 wt./wt.) under simulated solar light. The study has revealed that in the three scenarios and studied conditions, the total removal of this endocrine-disrupting dye from the solution takes place in the assayed time, 2 h, in some cases just in a few minutes. MG adsorption in the AC is a very fast and efficient removal method. MG photocatalytic oxidation with TP also occurs efficiently, although the oxidized MG is not totally mineralized. MG removal using the TP-AC composite under simulated solar light occurs only slightly faster to the MG adsorption in the AC, being adsorption the dominating MG removal mechanism for TP-AC. Thus, more than 90% of the removed MG with TP-AC under simulated solar light is adsorbed in this carbon-containing composite. The obtained results highlight the interest in adsorption, being the selection of the most suitable removal method dependent on several factors (i.e., the cost of the AC regeneration, for adsorption, or the toxicity of the intermediate oxidation species, for photooxidation). Paying attention to MG photooxidation with TiO2, comparison of two working photodegradation schemes shows that the direct photodegradation of MG from solution, avoiding any initial dark equilibrium period, is more efficient from a time perspective. The use of scavengers has proved that MG photodegradation occurs via an oxidation mechanism dominated by superoxide anion radicals.

Molecular Docking and Green Synthesis of Bioinorganic TiO2 Nanoparticles against E.coli and S.aureus

This study used a simple solution evaporation approach to make a bioinorganic titanium dioxide (Bi-TiO2) photocatalyst for dye contaminant degradation. A variety of techniques, including X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDAX), and differential reflectance spectroscopy, had been employed to classify the structural and optical properties of the prepared bioinorganic photocatalyst (UV-DRS). Using simulated solar irradiation, the photocatalytic activity of the produced Bi-TiO2 nanoparticles was examined by detecting the degradation of a solution of methylene blue (MB) as a model dye molecule. The developed Bi-TiO2 photocatalyst demonstrates superior photocatalytic action than commercially available powder TiO2, according to photo-degradation experiments. E.coli and S.aureus bacterial strains were employed to assess the antibacterial activity of Bi-TiO2 nanoparticles. The most active molecules that gain antibacterial activity were examined in isolated or extracted components from the tulsi plant. The chosen compounds were docked with thymidylate kinase (TMPK), a potential therapeutic goal for the preparation of novel antibacterial drugs with the PDB ID of 4QGG. Five compounds, namely rosmarinic acid, vicenin-2, orientin, vitexin, and isoorientin, out of the 27 chosen compounds, showed a higher docking score and may aid in boosting antibacterial activity. The synthesized Bi-TiO2 nanoparticles produced antibacterial activity that was effective against Gram-positive bacteria. The nanomaterials that have been synthesized have a lot of potential in wastewater treatment and biomedical management technologies.

A review on TiO2/SnO2 heterostructures as a photocatalyst for the degradation of dyes and organic pollutants

Industrialization, civilization and human activities have all grown steadily in recent years. As a result, small and large industries discharge many organic pollutants into the environment and contribute to environmental pollution. These compounds are quite stable and challenging to break down over time, posing a long-term risk. The heterogeneous advanced oxidation processes technology has gained tremendous attention. It depends on the light-induced formation of e^-/h⁺ pairs, which combine with water and aqueous oxygen to generate highly reactive hydroxyl radicals that degrade the organic pollutants in a solution and convert them ultimately into non-toxic products. In this paper, the synergetic impact of TiO₂-SnO₂ coupling with other semiconductor materials and their photodegradation performance on toxic contaminants in an aqueous medium has been reviewed. In addition, multiple approaches for the synthesis of TiO₂-SnO₂ photocatalysts have been discussed. Among them, hydrothermal, sol-gel, electrospinning, precipitation and even their combination are extensively used to synthesize various forms of nanostructures. These techniques demonstrate better tunability for visible absorption, suppression of e^-/h⁺ pair recombination and enhanced e^-/h⁺ separation to improve photocatalytic performance. This paper also summarises the role of different operating factors such as catalyst loading, pH, pollutants variation concentration, various light sources and oxidizing agents on the photodegradation of organic pollutants.

Cetylpyridinium Trichlorostannate: Synthesis, Antimicrobial Properties, and Controlled-Release Properties via Electrical Resistance Tomography

Cetylpyridinium trichlorostannate (CPC-Sn), comprising cetylpyridinium chloride (CPC) and stannous chloride, was synthesized and characterized via single-crystal X-ray diffraction measurements indicating stoichiometry of C₂₁H₃₈NSnCl₃ where the molecules are arranged in a 1:1 ratio with a cetylpyridinium cation and a [SnCl₃]^- anion. CPC-Sn has shown potential for application as a broad-spectrum antimicrobial agent, to reduce bacteria-generated volatile sulfur compounds and to produce advanced functional materials. In order to investigate its controlled-release properties, electrical resistance tomography was implemented. The results demonstrate that CPC-Sn exhibits extended-release properties in an aqueous environment as opposed to the CPC counterpart.

Influence of Tin Doped TiO2 Nanorods on Dye Sensitized Solar Cells

The one-step hydrothermal method was used to synthesize Sn-doped TiO₂ (Sn-TiO₂) thin films, in which the variation in Sn content ranged from 0 to 7-wt % and, further, its influence on the performance of a dye-sensitized solar cell (DSSC) photoanode was studied. The deposited samples were analyzed by X-ray diffraction (XRD) and Raman spectroscopy, which confirmed the existence of the rutile phase of the synthesized samples with crystallite size ranges in between 20.1 to 22.3 nm. In addition, the bare and Sn-TiO₂ thin films showed nanorod morphology. A reduction in the optical band gap from 2.78 to 2.62 eV was observed with increasing Sn content. The X-ray photoelectron spectroscopy (XPS) analysis confirmed Sn⁴⁺ was successfully replaced at the Ti⁴⁺ site. The 3-wt % Sn-TiO₂ based DSSC showed the optimum efficiency of 4.01%, which was superior to 0.87% of bare and other doping concentrations of Sn-TiO₂ based DSSCs. The present work reflects Sn-TiO₂ as an advancing material with excellent capabilities, which can be used in photovoltaic energy conversion devices.

Synthesis, Antimicrobial Activity, and Photocatalytic Performance of Ce Doped SnO2 Nanoparticles

This work represented the synthesis of Ce doped SnO2 nanoparticles by a wet chemical method and was characterized by various characterization techniques. PXRD confirmed the presence of the rutile phase for Ce doped SnO2 nanoparticles. SEM image and elemental mapping showed agglomerated irregular shaped particles and uniform distribution of 5% Ce ions within the SnO2 lattice, respectively. Ce doped SnO2 nanoparticles showed antimicrobial activity against E. coli and prevented the growth of bacteria. The nanoparticles were found photocatalytic active and photocatalytic behavior was elucidated by the degradation of Malachite Green dye under UV light irradiation.

Adsorption removal of malachite green dye from aqueous solution

In this review, the state of the art on the removal of malachite green dye from aqueous solution using adsorption technique is presented. The objective is to critically analyze different adsorbents available for malachite green dye removal. Hence, the available recent literature in the area is categorized according to the cost, feasibility, and availability of adsorbents. An extensive survey of the adsorbents, derived from various sources such as low cost biological materials, waste material from industry, agricultural waste, polymers, clays, nanomaterials, and magnetic materials, has been carried out. The review studies on different adsorption factors, such as pH, concentration, adsorbent dose, and temperature. The fitting of the adsorption data to various models, isotherms, and kinetic regimes is also reported.

Principles and mechanisms of photocatalytic dye degradation on TiO2based photocatalysts: a comparative overview

Pictorial representation of all possible dye degradation reaction in UV light initiated indirect dye degradation mechanism. This mechanism is practically more important over visible light initiated direct mechanism.

Photocatalytic effect of TiO2and the effect of dopants on degradation of brilliant green

Photocatalysis speeds up the photoreaction in the presence of a catalyst. TiO2 has low toxicity, less resistance and less corrosion and has semiconductor properties. Its strong oxidative potential of the positive holes oxidizes water to create hydroxyl radicals. Moreover, TiO2 has been proven to be a tremendous photocatalyst compound by which many organic substrates have been shown to be oxidatively degraded under UV irradiation. In this research the photocatalytic effect of TiO2 on degradation of Brilliant Green (BG) was studied. In conjunction the effect of dopants such as Zn and Cu on photocatalysis of TiO2 were also studied. Structural and morphological properties of TiO2 were characterized by SEM and XRD. From this research the initial concentration of sample, pH of samples, chemical structure of dyes and catalyst loading were most valuable parameters for dye degradation. TiO2 showed excellent result on degradation of BG compared with doped TiO2. 99% degradation was obtained in presence of TiO2, followed by TiO2/Zn for 87% and TiO2/Cu for 46%. TiO2 doped with transition metals can increase or decrease photocatalytic degradation of dyes.

Enhancing the photocatalytic properties of TiO2 by coupling with carbon nanotubes and supporting gold

The photodegradation of methylene blue in aqueous solutions is studied using various photocatalysts, including neat TiO(2), CNT-TiO(2), Au-TiO(2), and Au-CNT-TiO(2) composites MB. Materials were synthesized and extensively characterized by XRD, TEM, DRFIT spectroscopy, N(2) adsorption-desorption isotherms, as well as diffuse reflectance UV-vis spectroscopy. By using CNT-TiO(2) composite as catalysts, it was found that CNT act as adsorbent and photosensitizer to improve the photoactivity of neat TiO(2). Among the CNT-TiO(2) composites with different CNT weight ratio (0.2-20%), the 2%CNT-TiO(2) shows the best photoactivity. When CNT content is larger than 2%, the surplus CNT may absorb and scatter light photons. Combined with the decrease of TiO(2) amount in composite, the photoactivity is reduced. To further improve the photoactivity of 2%CNT-TiO(2), different Au loads varying from 0.25% to 1% were introduced by the deposition-precipitation method. The 0.25%Au-2%CNT-TiO(2) composite had the highest photoactivity. The increase in activity was explained by the surface plasmon resonance of Au that makes the composite to absorb more photons than the 2%CNT-TiO(2), thus overcoming the disadvantages of surplus CNT addition. On the other hand, 0.25%Au-2%CNT-TiO(2) composite also presents higher activity than 0.25%Au-TiO(2) due to higher adsorption capacity provided by CNT introduction. The addition of CNT and Au simultaneously has a much stronger synergic role than when each of them is introduced individually.

Adsorption studies of hazardous malachite green onto treated ginger waste

Adsorption of malachite green (MG) from aqueous solution onto treated ginger waste (TGW) was investigated by batch and column methods. The effect of various factors such as initial dye concentration, contact time, pH and temperature were studied. The maximum adsorption of MG was observed at pH 9. Langmuir and Freundlich isotherms were employed to describe the MG adsorption equilibrium. The monolayer adsorption capacities were found to be 84.03, 163.9 and 188.6 mg/g at 30, 40 and 50 degrees C, respectively. The values of thermodynamic parameters like DeltaG degrees , DeltaH degrees and DeltaS degrees indicated that adsorption was spontaneous and endothermic in nature. The pseudo second order kinetic model fitted well in correlation to the experimental results. Rechienberg's equation was employed to determine the mechanism of adsorption. The results indicated that film diffusion was a major mode of adsorption. The breakthrough capacities were also investigated.

Spectroscopic studies on the oxidative decomposition of malachite green using ozone

Spectroscopic studies on the oxidative decomposition of Malachite Green (MG) using ozone were investigated. Parameters such as color removal, initial dye concentration, COD reduction, reaction temperature and pH were studied to determine optimum conditions for complete MG decomposition. Complete removal of MG color was achieved within 10 min of reaction with ozone. The ozone oxidation reaction time increased as concentration of MG increases, inferring, there would be increase in MG removal as concentration decreases. COD reduction was observed as reaction time increases and the rate of reaction monotonically increased as temperature increases. From the spectroscopic analysis of the intermediates and the by-products of MG reaction with ozone, a tentative mechanistic approach of MG decomposition was postulated. It was also observed that after five minutes of ozone oxidation, color removal rate in the wastewater containing Malachite Green obtained from a small scale local dyeing industry reached almost 90%.

Photocatalytic antibacterial performance of Sn(4+)-doped TiO(2) thin films on glass substrate

Pure anatase, nanosized and Sn(4+) ion doped titanium dioxide (TiO(2)) particulates (TiO(2)-Sn(4+)) were synthesized by hydrothermal process. TiO(2)-Sn(4+) was used to coat glass surfaces to investigate the photocatalytic antibacterial effect of Sn(4+) doping to TiO(2) against gram negative Escherichia coli (E. coli) and gram positive Staphylococcus aureus (S. aureus). Relationship between solid ratio of TiO(2)-Sn(4+) in coatings and antibacterial activity was reported. The particulates and the films were characterized using particle size analyzer, zeta potential analyzer, Brunauer-Emmett-Teller (BET), X-ray diffractometer (XRD), SEM, AAS and UV/VIS/NIR techniques. The results showed that TiO(2)-Sn(4+) is fully anatase crystalline form and easily dispersed in water. Increasing the solid ratio of TiO(2)-Sn(4+) from 10 to 50% in the coating solution increased antibacterial effect.

Batch removal of malachite green from aqueous solutions by adsorption on oil palm trunk fibre: equilibrium isotherms and kinetic studies

Oil palm trunk fibre (OPTF)--an agricultural solid waste--was used as low-cost adsorbent to remove malachite green (MG) from aqueous solutions. The operating variables studied were contact time, initial dye concentration, and solution pH. Equilibrium adsorption data were analyzed by three isotherms, namely the Freundlich isotherm, the Langmuir isotherm, and the multilayer adsorption isotherm. The best fit to the data was obtained with the multilayer adsorption. The monolayer adsorption capacity of OPTF was found to be 149.35 mg/g at 30 degrees C. Adsorption kinetic data were modeled using the Lagergren pseudo-first-order, Ho's pseudo-second-order and Elovich models. It was found that the Lagergren's model could be used for the prediction of the system's kinetics. The overall rate of dye uptake was found to be controlled by external mass transfer at the beginning of adsorption, then for initial MG concentrations of 25, 50, 100, 150, and 300 mg/L the rate-control changed to intraparticle diffusion at a later stage, but for initial MG concentrations 200 and 250 mg/L no evidence was found of intraparticle diffusion at any period of adsorption. It was found that with increasing the initial concentration of MG, the pore-diffusion coefficient increased while the film-diffusion coefficient decreased.

Kinetics and equilibrium studies of malachite green adsorption on rice straw-derived char

In this work, the potential feasibility of rice straw-derived char (RSC) for removal of C.I. Basic Green 4 (malachite green (MG)), a cationic dye from aqueous solution was investigated. The isotherm parameters were estimated by non-linear regression analysis. The equilibrium process was described well by the Langmuir isotherm model. The maximum RSC sorption capacity was found to be 148.74 mg/L at 30 degrees C. The kinetics of MG sorption on RSC followed the Lagergren's pseudo-first-order model and the overall rate of dye uptake was found to be controlled by external mass transfer at the beginning of adsorption, while intraparticle diffusion controlled the overall rate of adsorption at a later stage. The results indicated that RSC was an attractive adsorbent for removing basic dye from aqueous solutions.

Sonochemical and sonophotocatalytic degradation of malachite green: the effect of carbon tetrachloride on reaction rates

A comparative study between the sonolytic, photocatalytic and sonophotocatalytic oxidation processes of aqueous solutions of malachite green was carried out in the presence of carbon tetrachloride, under a low power ultrasonic field (<15 W) and using titanium dioxide as a photocatalyst. The effect of a number of parameters such as ultrasonic intensity, TiO2 crystalline structure and the presence of CCl4 were studied using an inexpensive reactor. Enhanced rates of sonolytic degradation of malachite green in the presence of CCl4 were demonstrated. On the other hand, the simultaneous use of sonolysis and photocatalysis in the presence of CCl4 does not improve the degradation rate of malachite green in comparison with the one obtained using only sonolysis, but it makes possible a faster oxidative degradation of some reaction intermediaries. Finally, in air saturated solutions both processes, the sonolytic and the photocatalytic one, follow a first-order rate law.