Search

The exploitation of visible light active photocatalysts for the removal of various pollutants has been given tremendous consideration in water and wastewater treatment. Herein, a novel In2S3/CeO2 n–n type heterojunction photocatalyst was successfully synthesized by a two-step method involving hydrothermal synthesis and subsequent ultrasonic treatment to couple In2S3 with CeO2 (5, 10 and 15 wt%). The as-synthesized samples were characterized extensively using analytical techniques such as XRD, UV-vis-DRS, SEM-EDX, TEM, BET, PL, EIS and XPS to examine the chemical composition, phase structure, morphology and photo-chemical characteristics of the materials. Subsequently, the In2S3/CeO2 nanostructures were employed in the degradation of oxytetracycline (OTC) (10 mg L−1) and reduction of Cr(VI) (50 mg L−1) in aqueous solutions, upon exposure to visible light. Under optimised experimental conditions, the nanocomposite constituting 10 wt% CeO2 (In2S3/10 wt% CeO2) showed the highest activity, reaching 87.9% OTC degradation and 97.5% Cr(VI) reduction after 60 min and 40 min of visible light irradiation, respectively. The nature and contribution of active species in the photocatalytic process were revealed through radical scavenging studies. Finally, a plausible band structure, charge separation and transfer mechanism were crafted to illustrate the synergy between In2S3 and CeO2 which led to improved degradation kinetics. This work demonstrated a simple route for improving the visible light-mediated activity of In2S3 by coupling with CeO2 and the potential versatility of the composite material for the removal of both organic and inorganic pollutants from water.

Utilization of environmentally friendly and effective synthesis methods to fabricate visible light responsive photocatalysts with impressive catalytic performance is desirable in photocatalytic water treatment. Herein, we employed the powerful and environmentally benign ultrasonic synthesis to hybridize hydrothermally prepared NiNb2O6 with varying amounts of RGO (5, 10 and 15 wt%) obtained via a modified Hummers’ method. The samples were characterized extensively using analytical techniques such as XRD, SEM-EDX, TEM, UV-Vis DRS, PL, XPS, M-S and EIS, and subsequently employed for the degradation of doxycycline (DOX) and tetracycline hydrochloride (TC) in water under visible light exposure. The binary nanocomposites displayed enhanced activity compared to NiNb2O6, with the highest activity attained over the 10 wt% RGO sample (NiNb2O6/10 wt% RGO) which achieved 89.2% and 94.1% DOX and TC removal in 80 min, respectively. This was ascribed to improved visible light response, and charge separation and transfer. Furthermore, the influence of pH, pollutant initial concentration and photocatalyst dose was investigated. The hydroxyl radicals and holes were identified as the predominant reactive species responsible for degradation of both DOX and TC. Finally, a feasible charge transfer pathway was proposed to explain the formation of the reactive species and GC-MS analysis was employed to track the degradation route of DOX. This work presents a simple and effective route for coupling RGO and NiNb2O6 nanoparticles for antibiotic pollution abatement which is currently a major environmental concern.

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.

This study presents the first reports for ZnO/CuxO sequentially sputtered leading to stable and uniform films effective accelerated degradation of the emerging pollutant Norfloxacin (NFX) under visible light. The most effective ZnO film was sputtered from a Zn -target for 4 min followed by Cu-sputtering for 30 s on non-thermal resistant polystyrene (PS). The NFX-degradation proceeded more readily on ZnO/CuxO compared to ZnO-films although the conduction band potential energy position of the two semiconductors were iso-energetic. By X-ray photoelectron spectroscopy (XPS), Cu2O was identified as the predominant Cu-oxidation state in the sputtered film. A mechanism for the NFX degradation is suggested in which the holes generated by Cu2O transfer to ZnO in the ZnO(n)/CuO(p) in the hetero-junction. This transfer is favored by the electrostatic interaction between both semiconductors. The catalyst optical properties and surface potential were monitored during NFX degradation. Stable repetitive NFX degradation kinetics was observed under visible light on the sputtered ZnO/CuxO films. The use of appropriate scavengers allowed the identification of the intermediate radical species (ROS). XPS analysis provided the proof for redox catalysis taking place within the time of NFX abatement. The application of ZnO/CuxO films in a photo-reactor for the degradation of emerging pollutants seems feasible due to the low cost of Zn and Cu and the fast kinetics found for NFX degradation.

The design and fabrication of environmentally benign, visible light-responsive heterojunction photocatalysts remain a viable route towards sustainable exploitation of photocatalysis for water treatment. In this contribution, binary nanostructures consisting of varying ratios of In2S3 and Yb2O3 (In2S3/Yb2O3) were obtained via a two-step method involving hydrothermal synthesis and ultrasonic treatment. The prepared materials were characterised extensively to reveal information about their morphology, optical properties, phase composition, chemical states and electrochemical properties. Subsequently, the nanocomposite photocatalysts were investigated for their dual role of photooxidation of the emerging pollutant; norfloxacin (NFX) and photoreduction of the toxic heavy metal; Cr(VI) in spiked water samples. The photocatalytic activity of the nanocomposites was found to be dependent on the photocatalyst composition (ratio of In2S3:Yb2O3) and dose, contact time and initial concentration of the pollutant. Under optimised conditions, Cr(VI) reduction efficiency reached 96.4% in just 45 min of visible light irradiation and the degradation rate is 28.84 times and 3.90 times higher than that of Yb2O3 and In2S3, respectively. Equally, over 95.0% NFX degradation was achieved in 50 min, under optimal conditions. The enhanced activity is credited to efficient visible light absorption, remarkable charge separation and transfer, leading to increased lifetime of the photogenerated charge carriers. Moreover, the possible degradation route for NFX was crafted based GC-MS analysis. Finally, the photostability and recyclability of the composite photocatalyst was probed and a plausible charge transfer mechanism was proposed. This work demonstrates the effectiveness of the ultrasonication method for preparing binary nanostructures and the versatility of the photocatalysts towards detoxification of both organic and inorganic pollutants in water.

Over the years, significant effort has been devoted to the applications of graphitic carbon nitride (g-C3N4) nanomaterials due to their outstanding properties. Which include thermal, mechanical, and electrical properties, non-toxicity, low-cost, metal-free nature, large surface area, optical, ease of preparation, environmental friendliness, biocompatibility and chemical inertness. In this article, the various applications and prospects of g-C3N4 materials in biomedicine, sensors, energy conversion and storage, hydrogen production, mixed matrix membranes for water treatment, and photocatalytic degradation of aqueous organic pollutants has been critically reviewed. Moreover, key aspects of photocatalytic CO2 reduction and the suitability of g-C3N4 as photocatalyst have been covered. The review also discusses theoretical aspects, attributes, current trends/challenges and future considerations associated with the energy and environmental application of g-C3N4 nanostructures. It is believed that this review will provide a current comprehensive knowledge of the applications of g-C3N4 to readers and researchers to identify research gaps and could inspire researchers to synthesize novel g-C3N4-based materials for use in potential diverse fields.

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.

Over the years, there has been an increase in the number of countries facing water stress and scarcity resulting from persistent high temperatures and prolonged dry conditions. These conditions result in an insufficient supply of clean water for human consumption and agricultural purposes. The situation is further compounded by water pollution by organic, inorganic, and microbial species that render some of the available water unusable. Therefore, there is a need to develop advanced water treatment technologies that can complement the current methods to ensure efficient water and wastewater treatment. Efficient treatment of wastewater is key in augmenting the fresh water supply and such water can also be used for crop irrigation, thereby reducing the demand for fresh water. This chapter presents a concise review of the application of various graphene quantum dot-derived nanostructures in water treatment. Such nanostructures have been explored in the catalytic removal of organic pollutants and inorganics as well as the abatement of microbial pollution. Furthermore, graphene quantum dot materials have been exploited as adsorbents as well as additives in membranes to improve water flux, rejection properties, and antifouling behavior. Graphene quantum dot-based nanostructures are promising materials toward water treatment to ensure adequate food supply and security.

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.

Engineering photocatalytic materials for renewable energy generation and environmental decontamination has always been a very exciting prospect to counter the global energy demands and pollution challenges. Graphitic carbon nitride (g-C 3 N 4 ), a polymeric, metal-free semiconductor with a mild band gap (2.7 eV) has become hot-spot in various scientific exploits such as environmental pollution mitigation, energy generation and storage, organic synthesis, sensors, etc. These applications exploit the interesting properties of g-C 3 N 4 such as good visible light absorption, graphene-like structure, good thermal and chemical stability and photocatalytic properties. In this review we begin with an overview of the fundamental aspects of photocatalysis as a pollution remediation strategy. This is followed by an introduction to graphitic carbon nitride as a photocatalyst, preparation strategies and its properties. Subsequently, a comprehensive and critical discussion of the various most recent developments towards enhancing the visible light photocatalytic properties of g-C 3 N 4 for pollution alleviation, selected results and important photocatalytic degradation mechanisms, is given. Summary remarks and future perspective conclude the review.

Gelatin grafted environment-friendly hydrogel composite was utilized to perform the effective adsorption of methyl violet (MV) dye. Due to non-toxic, high surface zone and biodegradability, gelatin has received considerable attention for sustainable applications. Gelatin grafted methyl methacrylate (GE-g-MMA) hydrogels were prepared through the microwave-assisted green method. The GE-g-MMA hydrogel showed the highest swelling of 1039.4 %. Graphite (Gph) was introduced in GE-g-MMA hydrogel matrix to construct gelatin grafted methyl methacrylate/graphite (GE-g-MMA/Gph) hydrogel composite for adsorptive removal of poisonous methyl violet (MV) dye from water. The GE-g-MMA hydrogel and GE-g-MMA/Gph hydrogel composite were described through FTIR, XPS, SEM, Raman, XRD, TGA and BET techniques. Various adsorption factors like adsorbent dose, % removal of dye, contact period and solution pH were examined to develop ideal adsorption conditions. The GE-g-MMA/Gph hydrogel composite exhibited high adsorption efficiency of 99.9 % in 40 min (pH 9, MV: 50 mg L−1, adsorbent dose: 20 mg, MV volume: 20 ml). Experimental analysis results revealed that the synthesized GE-g-MMA/Gph hydrogel composite has a high capacity to remove MV molecules from aqueous solution at 25 °C. The values of the regression coefficient (R2) in case of Frendluich (0.999), Langmuir (0.978), Dubinin-Radushkevitch (0.936) and Temkin (0.931) clearly showed that the Freundlich isotherm fitted best to the adsorption process and pseudo-first-order kinetics demonstrated the better fit of adsorption with highest R2 (0.935). The GE-g-MMA/Gph hydrogel composite is economical, after six regeneration cycles, the adsorption efficiency of 95.8 % has been maintained.

In this work, 2-hydroxyethyl methacrylate cross-linked gum tragacanth hydrogel (GumT-cl-HEMA) was systematically synthesized to attain maximum swelling (396.9 %) by simple microwave-assisted green polymerization technique. The prepared GumT-cl-HEMA hydrogel was further modified by using TiO2 nanoparticles to generate TiO2 loaded 2-hydroxyethyl methacrylate cross-linked gum tragacanth (GumT-cl-HEMA/TiO2) hydrogel composite. The GumT-cl-HEMA hydrogel and GumT-cl-HEMA/TiO2 hydrogel composite were characterized through XPS, BET, XRD, FTIR, TGA and SEM. The GumT-cl-HEMA hydrogel and GumT-cl-HEMA/TiO2 hydrogel composite were used to perform adsorption to separate the molecules of malachite green (MG) from water. Batch adsorption parameters were examined to analyze the pH effect, time effect and adsorbent dose for the adsorption of malachite green dye from aqueous solution. The inclusion of TiO2 particles inside the GumT-cl-HEMA hydrogel led to increased adsorption rates and stability. The adsorption was accurately followed the pseudo second order model and Langmuir isotherm model. The reported GumT-cl-HEMA/TiO2 hydrogel composite removal efficiency was 99.3 % adsorbent dose = 90 mg, MG = 50 ppm, pH = 7, volume = 50 mL and time = 80 min). The synthesized samples were regenerated and then reused for five repeated adsorption-desorption cycles. The construction of GumT-cl-HEMA hydrogel and GumT-cl-HEMA/TiO2 hydrogel composite gives a facile scheme for efficient adsorbents.

Recently, one-dimensional nanomaterials gained significant attention in environmental remediation for the degradation and removal of various toxic pollutants in water bodies. Herein in this report, we prepared good visible-light response ytterbium and yttrium vanadates (YbVO4, and YVO4) photocatalyst with unique morphologies has been synthesized using simple MOF precursor followed by calcination route. The YbVO4 exhibited bitter-gourd like structure and YVO4 presented nano-rice structure as an added advantage for photocatalytic application. The as-synthesized samples were systematically characterized by XRD studies and transmission electron microscope (TEM) analysis and UV–vis diffuse reflectance spectra (DRS) studies, respectively. These one dimensional YbVO4 and YVO4 exhibited different absorption co-efficient from the UV to visible range with bandgap energies of 2.17 eV, and. 3.15 eV, respectively. The photocatalytic activities of YbVO4 and YVO4 have been investigated towards the photodegradation of aqueous methyl orange (MO) under the visible-light irradiation. Due to higher visible light absorption capacity with a narrow bandgap value of 2.17 eV, the YbVO4 exhibited higher photocatalytic degradation ability towards the MO degradation. As a result, the YbVO4 and YVO4 showed the removal rate of about 81% and 65% removal towards the MO removal with 360 min irradiation time.

Heterogeneous photocatalysis process is emerging technology for the removal of toxic pollutants, but the photocatalytic responses of the widely studied materials like TiO2 and ZnO are still not good enough under the visible light and NIR region. Herein, we have prepared a highly proficient novel visible light active heterojunction photocatalyst using low bandgap semiconductor carbon nitride (g-C3N5) and cerium titanate (CeTi2O6). The CeTi2O6/g-C3N5 heterojunction with hefty surface area and fabulous visible-light response was achieved by a simple wet chemical synthesis route. The structural and morphological features of the CeTi2O6/g-C3N5 heterojunctions were premeditated by the X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), elemental analysis (EDS), and X-ray photoelectron spectroscopy (XPS) studies respectively. The CeTi2O6/g-C3N5 heterojunction exhibited outstanding photocatalytic response under the visible light towards the degradation of endocrine rupture material 2,4-dichlorophenol (2,4-DCP) than its single components. Radicals trapping experiments confirmed that the superoxide radicals, as well as hydroxide radicals, played the most prominent role in the removal of 2, 4 DCP. This study will offer new insight into the development of novel low bandgap g-C3N5 based stable photocatalyst materials with tunable bandgap for the degradation of hazardous pollutants.

Adequate, clean water and energy are the cornerstones of human existence and global development. However, water scarcity due to climate change and pollution and the depletion of fossil fuels together with their negative impact on the environment, pose a great global threat. Solar assisted-photocatalysis is a promising tool for environmental pollution mitigation and for generating alternative renewable energy. This review provides a one-stop, comprehensive read on the most recent developments in graphene based photocatalysts towards removal of organic (dyes, emerging pollutants), inorganic (heavy metals, oxides of nitrogen), microbial pollutants and fuel generation from carbon dioxide reduction and water splitting. We began by providing a brief overview of the positive attributes of photocatalysis and the use of graphene in photocatalytic nanostructures. This is followed by the investigation of the latest applications of graphene based photocatalyst in water treatment, air purification, disinfection and energy generation. Details on the specific roles of graphene materials during photocatalysis and the underlying mechanisms propelling the different photocatalytic reactions, are outlined. Finally, some remarks in terms of the current research on graphene materials in photocatalysis for environmental pollution abatement and fuel generation and future considerations, concludes the review.

Neodymium/gadolinium/europium, nitrogen and sulphur tridoped titania (Nd/Gd/Eu, N,S-TiO 2 ) was hybridised with pre-synthesised gadolinium oxide decorated multiwalled carbon nanotubes (MWCNT-Gd) using a sol–gel method. Subsequent to drying and calcination, composite photocatalysts: MWCNT-Gd/Nd,N,S-TiO 2 , MWCNT-Gd/Gd,N,S-TiO 2 and MWCNT-Gd/Eu,N,S-TiO 2 , were obtained and characterised using TEM, SEM-EDX, UV–vis, XPS, XRD and FT-IR. Acid blue 74 (AB74) was used as a model dye to investigate the photocatalytic degradation properties of the prepared materials under simulated solar light irradiation. Coupling the different tridoped titania with MWCNT-Gd enhanced their activity compared to MWCNT/TiO 2 , MWCNT-Gd/TiO 2 and MWCNT/Gd,N,S-TiO 2 . MWCNT-Gd/Gd,N,S-TiO 2 showed the highest activity towards AB74 degradation reaching 100% decolourisation after 150 min of irradiation. Total organic carbon analysis revealed that over 50% of the AB74 molecules were completely mineralised after 180 min of irradiation in the presence of MWCNT-Gd/Gd,N,S-TiO 2 .

Oxidised single walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs) were each incorporated into a neodymium, nitrogen and sulphur tridoped TiO2 (Nd,N,S–TiO2) to form composite photocatalysts: SWCNT/Nd,N,S–TiO2 and MWCNT/Nd,N,S–TiO2. The fabricated composite photocatalysts were exploited for the photocatalytic degradation of eriochrome black T (EBT) and eosin blue shade (EBS) from single and mixed dye solutions. Incorporation of the carbon nanotubes significantly improved visible light response and the photocatalytic activity of the composites compared to MWCNT/TiO2, SWCNT/TiO2 and tridoped TiO2. The SWCNTs incorporating photocatalyst displayed superior photocatalytic activity over its MWCNTs incorporating counterpart. From single dye solutions degradation studies, the SWCNT/Nd,N,S–TiO2 reached maximum degradation efficiencies of 96.9% and 89.2% for EBS and EBT, respectively. Similarly, maximum degradation efficiencies of 61.4% and 54.1% were recorded from mixed dye solutions using SWCNT/Nd,N,S–TiO2, for EBS and EBT, respectively. First order kinetics studies revealed that EBS is degraded faster than EBT both from single and mixed dye solutions. Total organic carbon (TOC) analyses suggest a relatively high degree of complete mineralisation of both EBS (73.6% TOC removal) and EBT (66.2% TOC removal). The SWCNT/Nd,N,S–TiO2 composite photocatalyst displayed sufficient stability (88.8% EBS removal) after being reused for five times.

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 phot...

Herein, MnWO4 nanorods coupled with g-C3N4 nanosheets were fabricated by a simple hydrothermal method, followed by an ultrasonication method. Morphological features, chemical composition, optical properties and crystallographic information of the prepared materials were obtained using SEM-EDX, TEM, XRD, XPS, FT-IR, UV–vis DRS, and PL techniques. The synthesized MnWO4@g-C3N4 nanocomposite displayed excellent photocatalytic activity towards ofloxacin (OFX) under visible light irradiation. Moreover, the influence of reaction parameters such as the catalyst dosage, pollutant concentration and presence of inorganic anions (Cl−, CO32− and SO42−), was investigated during the photocatalytic process. Notably, among the inorganic anions, SO42− and CO32− significantly hampered OFX degradation, while Cl− ions showed minimal effect on the degradation process. The apparent rate constant for MnWO4@g-C3N4 from first order kinetics was 3.5 and 4.8 times higher than that of pure g-C3N4 and MnWO4, respectively. Based on the obtained results, the possible charge transfer mechanism was proposed. The enhanced photocatalytic performance of the binary nanocomposite could be ascribed to the synergistic effect between MnWO4 nanorods and g-C3N4 nanosheets resulting in efficient visible light utilization and inhibition of the charge carrier recombination. This work demonstrates the potential application of MnWO4@g-C3N4 nanostructures in the photocatalytic removal of emerging pollutants in water.

Multiwalled carbon nanotubes were synthesised by the nebulised spray pyrolysis method and purified to remove amorphous carbon and fullerenes. The purified multiwalled carbon nanotubes were oxidised using a 3:1 H2SO4/HNO3 mixture to introduce carboxylic groups and to a smaller extent hydroxyl groups on the walls of the carbon nanotubes. Subsequently, the oxidised carbon nanotubes were chlorinated using oxalyl chloride to generate acyl chloride groups through which phosphorylation took place. 4-Aminophenyl methylphosphonate was attached to the multiwalled carbon nanotubes via an amidation reaction. FT-IR and XPS confirmed the presence of PO, PO and PCP functional groups in the phosphorylated carbon nanotubes. Polymerisation of the phosphorylated carbon nanotubes with cyclodextrins was achieved using hexamethylene diisocyanate as a bifunctional linker. Surface morphology of the polymer was investigated by SEM while FT-IR was used to confirm the polymerisation reaction. Moreover, the thermal stability of the polymer was probed using TGA while BET was employed to determine the surface area and pore volume of the polymer. Furthermore, the polymer was tested for the removal of cobalt and 4-chlorophenol from synthetic aqueous solutions of the pollutants. The polymer displayed potential as an adsorbent for both cobalt and 4-chlorophenol.

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.

A simple sol-gel method was employed to prepare gadolinium, nitrogen and sulphur tridoped titania decorated on oxidised multiwalled carbon nanotubes (MWCNT/Gd,N,S-TiO2), using titanium (IV) butoxide and thiourea as titanium and nitrogen and sulphur source, respectively. Samples of varying gadolinium loadings (0.2%, 0.6%, 1.0% and 3.0% Gd3+) relative to titania were prepared to investigate the effect of gadolinium loading and the amounts of carbon nanotubes, nitrogen and sulphur were kept constant for all the samples. Furthermore, the prepared nanocomposites were evaluated for the degradation of naphthol blue black (NBB) in water under simulated solar light irradiation. Higher degradation efficiency (95.7%) was recorded for the MWCNT/Gd,N,S-TiO2 (0.6% Gd) nanocomposites. The higher photocatalytic activity is attributed to the combined effect of improved visible light absorption and charge separation due to the synergistic effect of Gd, MWCNTs, N, S and TiO2. Total organic carbon (TOC) analysis revealed a higher degree of complete mineralisation of naphthol blue black (78.0% TOC removal) which minimises the possible formation of toxic degradation by-products such as the aromatic amines. The MWCNT/Gd,N,S-TiO2 (0.6% Gd) was fairly stable and could be re-used for five times, reaching a maximum degradation efficiency of 91.8% after the five cycles.

Gadolinium oxide nanoparticles of diameters