Photocatalysis over N-Doped TiO2 Driven by Visible Light for Pb(II) Removal from Aqueous Media

Integrating machine learning with experimental investigation for optimizing photocatalytic degradation of Rhodamine B using neodymium-doped titanium dioxide: a comprehensive approach with toxicity assessment

In this study, neodymium-doped titanium dioxide (Nd-TiO2) nanoparticles were synthesized via a hydrothermal method for the photocatalytic degradation of Rhodamine B (RhB) under UV and sunlight conditions. The properties of these NPs were comprehensively characterized. And optimization of RhB degradation was conducted using control-variable experiment and artificial neural networks (ANN) under various operational conditions and in the presence of competing compounds. The acute toxicity of both NPs, RhB, and the environmental impact of the photocatalytic treatment effluent on Danio rerio were evaluated. The Nd modification increased the catalyst's specific surface area and thermal stability. X-ray diffraction confirmed the tetragonal anatase phase in undoped TiO2, while Nd-doped TiO2 exhibited shifts in peaks and the presence of brookite and rutile phases. Nd (1 mol%) doped TiO2 demonstrated superior RhB photocatalytic degradation efficiency, achieving 95% degradation and 82% total organic carbon (TOC) removal within 60 min under UV irradiation. Optimization under sunlight conditions yielded 95.14% RhB removal with 0.28 g/L photocatalyst and 1% doping. Under UV light, 98.12% RhB removal was optimized with 0.97% doping, along with the presence of humic acid and CaCl2. ANN modeling achieved high precision (R2 of 0.99) in modeling environmental photocatalysis. Toxicity assessments indicated that the 96-h LC50 values were 681.59 mg L-1 for both NPs, and 23.02 mg L-1 for RhB. The treated dye solution exhibited a significant decline in toxicity, emphasizing the potential of 1% Nd-TiO2 in wastewater treatment.

Degradation of conjugated estrogen in visible light-driven intimately coupled photocatalysis and biodegradation system

Visible light-driven intimately coupled photocatalysis and biodegradation (VDICPB) is an efficient technology for removing recalcitrant contaminants, but the degradation pathway on 17β-estradiol 3-Sulfate (E2-3S) is still not clear. In this study, VDICPB based on N-doped TiO2 as a photocatalyst was established to investigate the removal and transformation of E2-3S in synthetic wastewater. VDICPB showed a satisfactory removal efficiency of 97.8 ± 0.4 %, which was much higher than that of independent photocatalysis (84.0 ± 2.2 %) or biodegradation system (71.4 ± 1.8 %). Steroid C/D-rings of E2-3S was broken in VDICPB since the transformation process reached terminal central pathway. Primary metabolites did not accumulate in VDICPB, resulting in a low expression of functional genes. E2-3S was mainly removed by cooperative interaction of photocatalysis and co-metabolism of biofilm. Photocatalysis led to deconjugation and microbes acted to mineralization. This study provides technical reference and theoretical support for the removal of new pollutants.

Reusable isotype heterojunction g-C3N4/alginate hydrogel spheres for photocatalytic wastewater treatment

Various visible-light-driven photocatalysts have been studied for practical applications in photocatalytic wastewater treatment via solar irradiation. Among them, g-C3N4 has attractive features, including its metal-free and environmentally friendly nature; however, it is prone to charge recombination and has low photocatalytic activity. To solve these problems, isotype heterojunction g-C3N4 was recently developed; however, the methods employed for synthesis suffered from limited reproducibility and efficiency. In this study, isotype heterojunction g-C3N4 was synthesized from various combinations of precursor materials using a planetary ball mill. The isotype heterojunction g-C3N4 synthesized from urea and thiourea showed the highest photocatalytic activity and completely decolorized Rhodamine B (RhB; 10 ppm) in 15 min under visible-light irradiation. Furthermore, to improve recyclability, isotype heterojunction g-C3N4 was immobilized in alginate hydrogel spheres. The isotype heterojunction g-C3N4/alginate hydrogel beads were used in 10 repeated RhB degradation experiments and were able to maintain their initial photocatalytic activity and mechanical strength. These achievements represent an advance towards practical, sustainable photocatalytic wastewater treatment.

Characterization of novel solar based nitrogen doped titanium dioxide photocatalytic membrane for wastewater treatment

The increasing presence of microbial and emerging organic contaminants pose detrimental effects on the environment and ecosystem such as diseases, pandemics and toxicity. Most of these synthetic pollutants are biorecalcitrant and therefore persist in the environment. Conventional water treatment methods are not effective thereby necessitating the development of advanced techniques such as photocatalysis and membrane processes. In this study, visible light-driven photocatalytic membrane was synthesized through the immobilization of nitrogen-doped nanoparticles onto the polyvinylidene fluoride (PVDF) membrane and performance evaluated with E.coli microbial contaminant removal. Characterization was done using Fourier transform infrared spectra, X-ray diffraction (XRD), water contact angle, Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX). The Nitrogen-doping of titanium dioxide red-shifted the light absorption to a visible range of 440 nm from 400 nm. Nitrogen dopant was detected at 1420 cm-1and 1170 cm-1 for nitrogen doped nanoparticles and 1346-1417 cm-1 for nitrogen doped titanium dioxide PVDF membrane. SEM-EDX confirmed presences of nitrogen in nitrogen doped titanium dioxide nanoparticles on membrane surface with nitrogen elemental composition of 0.01 % wt. The water contact angle reduced by 81.39o from 120.14o to 38.75o because of PVA immobilization of nitrogen-doped titanium dioxide and glutaraldehyde crosslinking. Nitrogen doping resulted in visible light active photocatalytic membranes with better hydrophilicity and fouling resistance. 8.42 E.coli log removal and a relative flux of 0.35 was obtained within 75 min. The developed photocatalytic membrane enables the use of sunlight hence a less costly method for decontamination of wastewater.

Rice husk valorization into sustainable Ni@TiO2/biochar nanocomposite for highly selective Pb (II) ions removal from an aqueous media

Herein, we successfully prepared sustainable nanocomposites from agriculture waste (rice husk)-derived biochar precursor, and followed by nickel-doped, base-treated titanium dioxide nanomaterials loading for efficient lead (Pb²⁺) removal from aqueous media. By varying the loading contents of active materials, the optimized sample (Ni_0.01@Na-TiO₂/BC) possessed an efficient Pb²⁺ adsorption capability of 122.3 mg g^-1 under the under optimum adsorption parameters, which is attributable to its specific surface area (138.09 m² g^-1) and excess functional sites. Kinetic and Isothermal examination illustrated that Pb²⁺ adsorption phenomena was well followed through pseudo 2nd order and Langmuir models. In addition, superior Pb²⁺ ions adsorption selectivity was recorded by optimized sample in a multi-metallic system over other existing ion (such as Cd²⁺, Mg²⁺, Ca²⁺, Cu²⁺, and Zn²⁺). Desorption experiments has been performed by using desorbing agent that demonstrates the good regeneration ability of sample. Hence, these findings provide new insight for the biowaste management by converting them into innovative adsorbents for commercial scale environmental remediation.

Removal of the Hazardous Congo Red Dye through Degradation under Visible Light Photocatalyzed by C,N Co-Doped TiO2 Prepared from Chicken Egg White

The C,N co-doped TiO2 photocatalyst was prepared by interacting the chicken egg white having various weights (1, 2, and 4 g) with 1 g of TiO2 in an autoclave through the hydrothermal process at 150°C. The C,N co-doped TiO2 photocatalysts were characterized using Fourier transform infrared (FTIR), X-ray diffraction (XRD), specular reflectance UV/visible (SRUV/Vis), and transmission electron microscope (TEM) instruments. The photocatalytic activity of the co-doped TiO2 was evaluated by monitoring the photo-decolorization of Congo red dye under visible light through a batch experiment. The characterization results assigned that the C and N atoms from the chicken egg white have been successfully co-doped into TiO2 through interstitial and substitutional combination, which could notably narrow their band gap energy entering into the visible region. In line with the gap narrowing, the co-doping C,N into TiO2 could remarkably improve the photocatalytic activity under visible light in the dye photo-decolorization. The enhancement of the photocatalyst activity of TiO2-C,N was controlled by the weight of the egg white introduced, and 2 g of the egg white resulted in the highest activity. Further, the best dye photo-decolorization, which was about 98%, of 10 mg/L Congo red dye in 100 mL of the solution under visible irradiation could be reached by applying TiO2-C,N prepared from 2 g of the egg white, within 45 min, at pH 7, and 50 mg of the photocatalyst mass.

Metallic or Metallic Oxide (Photo)catalysts for Environmental Applications

During the last century, industrialization intensified in a growing number of countries around the world, and in various industries, particularly in the chemical, pharmaceutical, cosmetics, horticulture, food, and petroleum sectors [...]

A critical review on N-modified TiO2 limits to treat chemical and biological contaminants in water. Evidence that enhanced visible light absorption does not lead to higher degradation rates under whole solar light

Intensive research has been focused on the synthesis of N-modified TiO₂ materials having visible light absorption in order to get higher solar photocatalytic degradation rates of pollutants in water. However, an exhaustive revision of the topic underlines several controversial issues related to N-modified TiO₂ materials; these issues concern (a) the methodology used for preparation, (b) the assessment of the structural characteristics, (c) the mechanistic action modes and (d) the raisons argued to explain the limited performances of the prepared materials for organic and biological targets photodegradation in water. Taking advantage of last year's progress in analytical chemistry and in material characterization methods, the authors show, for example, that some works in the literature controversially attribute the term nitrogen doping without enough analytical evidence. Additionally, some papers describe N-modified TiO₂ photocatalysts as being able to generate holes with enough oxidative potential to form hydroxyl radicals under visible light. This last assertion often derives from a no pertinent use of illumination sources, light filters, or targets or a limited understanding of the thermodynamic aspects of the studied systems. None of N-containing materials prepared by herein presented methods leads, under solar light, to a significant enhancement in pollutants degradation and microorganism's inactivation kinetics.

Synthesis and Characterization of Carbon and Carbon-Nitrogen Doped Black TiO2 Nanomaterials and Their Application in Sonophotocatalytic Remediation of Treated Agro-Industrial Wastewater

The conventional open ponding system employed for palm oil mill agro-effluent (POME) treatment fails to lower the levels of organic pollutants to the mandatory standard discharge limits. In this work, carbon doped black TiO₂ (CB-TiO₂) and carbon-nitrogen co-doped black TiO₂ (CNB-TiO₂) were synthesized via glycerol assisted sol-gel techniques and employed for the remediation of treated palm oil mill effluent (TPOME). Both the samples were anatase phase, with a crystallite size of 11.09–22.18 nm, lower bandgap of 2.06–2.63 eV, superior visible light absorption ability, and a high surface area of 239.99–347.26 m²/g. The performance of CNB-TiO₂ was higher (51.48%) compared to only (45.72%) CB-TiO₂. Thus, the CNB-TiO₂ is employed in sonophotocatalytic reactions. Sonophotocatalytic process based on CNB-TiO₂, assisted by hydrogen peroxide (H₂O₂), and operated at an ultrasonication (US) frequency of 30 kHz and 40 W power under visible light irradiation proved to be the most efficient for chemical oxygen demand (COD) removal. More than 90% of COD was removed within 60 min of sonophotocatalytic reaction, producing the effluent with the COD concentration well below the stipulated permissible limit of 50 mg/L. The electrical energy required per order of magnitude was estimated to be only 177.59 kWh/m³, indicating extreme viability of the proposed process for the remediation of TPOME.