Rare earth doped Titania/Carbon nanomaterials composite photocatalysts for water treatment

PhD. (Chemistry)Pre-synthesised gadolinium oxide decorated multiwalled carbon nanotubes (MWCNT-Gd) were coupled with titania to form nanocomposite photocatalysts (MWCNT-Gd/TiO2) using a sol-gel method. Rare earth metal ions (Eu, Nd and Gd), nitrogen and sulphur tridoped titania were decorated on MWCNT-Gd to yield composite photocatalysts (MWCNT-Gd/Eu/Nd/Gd/N,S-TiO2) by a similar method, using thiourea as nitrogen and sulphur source. Different carbon nanomaterials were incorporated into tridoped titania to form various composite photocatalysts (MWCNT/Gd,N,S-TiO2, MWCNT/Nd,N,S-TiO2, SWCNT (single walled carbon nanotube)/Nd,N,S-TiO2 and rGO (reduced graphene oxide)/Nd,N,S-TiO2) via the sol-gel method. Likewise, gadolinium doped graphitic carbon nitride (g-C3N4-Gd3+) was obtained by heating a mixture of gadolinium nitrate hexahydrate and cyanoguanidine and subsequently hybridised with MWCNT/TiO2 using the sol-gel method to yield composite photocatalysts with varying g-C3N4-Gd3+ loadings. All the prepared photocatalysts were characterised by microscopic tools (FE/FIB-SEM-EDX, TEM), crystallographic technique (XRD), spectroscopic tools (UV-Vis, Raman and FT-IR) and nitrogen sorption technique (BET)

Magnetron Sputtering of Transition Metal Nitride Thin Films for Environmental Remediation

The current economic and ecological situation encourages the use of steel to push the technological limits and offer more cost-effective products. The enhancement of steel properties like wear, corrosion, and oxidation resistance is achieved by the addition of small amounts of chemical elements such as Cr, Ni, Si, N, etc. The steel surface can be protected by different treatments such as heating and coating, among others. For many decades, coatings have been an effective solution to protect materials using thin hard films. Several technologies for thin film deposition have been developed. However, some of them are restricted to certain fields because of their complex operating conditions. In addition, some deposition techniques cannot be applied to a large substrate surface type. The magnetron sputtering deposition process is a good option to overcome these challenges and can be used with different substrates of varying sizes with specific growth modes and for a wide range of applications. In this review article, we present the sputtering mechanism and film growth modes and focus on the mechanical and tribological behavior of nitride thin films deposited by the magnetron sputtering technique as a function of process conditions, particularly bias voltage and nitrogen percentage. The biomedical properties of transition metal nitride coatings are also presented

Graphite modified sodium alginate hydrogel composite for efficient removal of malachite green dye

Herein, porous sodium alginate/graphite based hybrid hydrogel was fabricated as an effective adsorbent for organic pollutant. Sodium alginate was modified through graft polymerization of acrylic acid and subsequently loaded with graphite powder to enhance its adsorption capability. The synthesized sodium alginate cross-linked acrylic acid/graphite (NaA-cl-AAc/GP) hydrogel composite was utilized in the removal of malachite green (MG) dye from aqueous solution using batch adsorption experiments. The NaA-cl-AAc/GP hydrogel composite was characterized by infrared spectroscopy, Raman spectroscopy, thermo-gravimetric analysis, scanning electron microscopy, x-ray photoelectron spectroscopy and x-ray diffraction. Under optimized experimental conditions, a maximum adsorption capacity of 628.93 mg g−1 was attained for malachite green dye. Moreover, the adsorption process could be well described by the Langmuir isotherm model and pseudo-second-order kinetic model. The hydrogel composite also showed 91% adsorption after three consecutive cycles of dye adsorption-desorption. Therefore, the NaA-cl-AAc/GP hydrogel composite is a potentially favourable material towards dye pollution remediation owing to its better swelling rate, environment friendliness, high adsorption potential and regeneration capability

Advances in Magnetically Separable Photocatalysts: Smart, Recyclable Materials for Water Pollution Mitigation

Organic and inorganic compounds utilised at different stages of various industrial processes are lost into effluent water and eventually find their way into fresh water sources where they cause devastating effects on the ecosystem due to their stability, toxicity, and non-biodegradable nature. Semiconductor photocatalysis has been highlighted as a promising technology for the treatment of water laden with organic, inorganic, and microbial pollutants. However, these semiconductor photocatalysts are applied in powdered form, which makes separation and recycling after treatment extremely difficult. This not only leads to loss of the photocatalyst but also to secondary pollution by the photocatalyst particles. The introduction of various magnetic nanoparticles such as magnetite, maghemite, ferrites, etc. into the photocatalyst matrix has recently become an area of intense research because it allows for the easy separation of the photocatalyst from the treated water using an external magnetic field. Herein, we discuss the recent developments in terms of synthesis and photocatalytic properties of magnetically separable nanocomposites towards water treatment. The influence of the magnetic nanoparticles in the optical properties, charge transfer mechanism, and overall photocatalytic activity is deliberated based on selected results. We conclude the review by providing summary remarks on the successes of magnetic photocatalysts and present some of the future challenges regarding the exploitation of these materials in water treatment

Investigating the Usability of Alkali Lignin as an Additive in Polysulfone Ultrafiltration Membranes

The effects of natural and synthetic polymer additives on the properties of ultrafiltration membranes were studied. The use of NaOH to remove the residual additive remaining in the membranes during coagulation was also investigated, as was the effect of NaOH post-treatment relative to membrane performance. To evaluate the residual additives present, ATR-FTIR was used. Contact-angle analysis and water-absorption experiments were used to examine the hydrophilic properties of the prepared membranes. Membranes modified with lignin (Lig) were found to absorb more water (94% water uptake) than other membranes. In general, the contact angles were found to be low for membranes treated with NaOH. Membrane permeability was greatest in lignin_polysulfone (Lig_PSf), followed by polyvinylpyrrolidone_polysulfone (PVP_PSf), and with polyethylene glycol_polysulfone (PEG_PSf) the least permeable, similar to the trend observed in water uptake. A ‘Robeson plot’ analogue showed that Lig_PSf membranes had high separation factors regardless of the size of the solute being rejected. This study indicates the feasibility of using cheap, readily available additives to increase the performance of membranes

Synchronic coupling of Cu2O(p)/CuO(n) semiconductors leading to Norfloxacin degradation under visible light: Kinetics, mechanism and film surface properties

The study presents the first evidence for Norfoxacin photodegradation by uniform, adhesive and robust CuOx-polystyrene (CuOx-PES) films under visible light. Repetitive Norfloxacin degradation was attained on CuOx-PES films activated by visible light. The smooth CuOx-PES surface properties were investigated by diffuse reflectance spectroscopy (DRS). The band-gap of the Cu2O and CuO making up CuOx films were estimated by Tauc's method. By atomic force microscopy (AFM) the CuOx micro-agglomerated size was determined as well as the relatively small roughness of 22.4 +/- 10% nm and the distance between the Norfloxacin anchoring points on the CuO peaks. Evidence is presented by transmission electron microscopy (TEM) for the uniform distribution of Cu-clusters on the PES. The degradation of Norfloxacin was monitored in the range 2-20 mg/L, a Norfloxacin concentration far above the concentrations found in treated wastewaters. Proof of redox processes occurring in the CuOx during Norfloxacin degradation were monitored by (XPS). Deconvolution of the Cu2p3/2 peaks revealed Cu2O and CuO in different percentages before and after Norfloxacin degradation. The CuOx-PES samples were made up by Cu2O(p) and CuO(n) with an approximate ratio of Cu2O: CuO = 3: 1 before Norfloxacin degradation. Highly oxidative radical species and photogenerated holes Cu(2)Ovb (h(+)) were identified during Norfloxacin degradation. A mechanism is suggested for the Norfloxacin degradation involving highly oxidative radicals detected by scavenging experiment and the limits for the validity of this method are discussed. (C) 2017 Elsevier Inc. All rights reserved

Nd,N,S-TiO₂ Decorated on Reduced Graphene Oxide for a Visible Light Active Photocatalyst for Dye Degradation: Comparison to Its MWCNT/Nd,N,S-TiO₂ Analogue

Neodymium, nitrogen, and sulfur tridoped titania (Nd,N,S-TiO₂) was decorated on reduced graphene oxide (rGO) and multiwalled carbon nanotubes (MWCNTs) via a simple sol–gel method. The prepared photocatalysts were characterized by FE-SEM-EDX, TEM, UV–vis, BET, FTIR, Raman, and XRD. Aqueous solutions of eriochrome black T (EBT) and eosin blue shade (EBS) were used to evaluate the photocatalytic activity of the composites under simulated solar light irradiation. Degradation of the dyes was performed in single and mixed dye solutions. The reduced graphene based photocatalyst (rGO/Nd,N,S-TiO₂) showed improved photocatalytic activity over the MWCNT/Nd,N,S-TiO₂ composite in both single and mixed dye solutions. In the single dye solutions, a maximum degradation of 99.3% and 94.6% was achieved for EBS and EBT, respectively. Moreover, a maximum degradation efficiency of 65.7% and 58.9% was attained by rGO/Nd,N,S-TiO₂ for EBS and EBT, respectively, from mixed dye solutions. These experimental results suggest the potential application of the composite photocatalysts for dye pollution remediation. Furthermore, radical scavenging experiments confirmed the superoxide and hydroxyl radicals as the active species during dye degradation. Total organic carbon analyses revealed a fairly high degree of complete mineralization of both dyes reducing the potential formation of toxic degradation byproducts