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This paper reports the results of a study on the analysis and characterization of titanium dioxide (TiO2) nanoparticles (NPs) in samples that were collected from selected freshwater dams in South Africa. The study employed a combination of complementary techniques to ascertain the analytical procedures and the occurrence of TiO2 NPs in water. Characterization, identification and quantification of TiO2 NPs in surface water samples from five sampled dams was performed using several techniques including scanning electron microscopy-energy dispersive X-ray (SEM-EDX), fluorescence excitation–emission matrix (FEEM) and single particle inductively coupled plasma mass spectroscopy (SP-ICP-MS). The SP-ICP-MS technique was able to simultaneously determine the size and concentration of both the dissolved and particulate titanium (Ti) in water samples. The Ti-containing NPs were found at concentrations ranging from 8.3 × 104 parts/mL to 1.4 × 105 parts/mL in the presence of 14.9 μg/L to 243 μg/L dissolved Ti. The TiO2 nanoparticles were mostly composed of small agglomerates ranging from 102.9 nm to 158.9 nm in size.

This work reports on the fundamental factors influencing inter-foulant and foulant-membrane interactions during simulated dissolved organic matter removal using ceramic nanofiltration. Fouling tests were performed using sodium alginate (SAL), humic acid (HA) and bovine serum albumin (BSA) as model foulants. Fouling potentials of each foulant and their mixtures were investigated using feed solutions containing fixed concentrations of K+, Na+, Mg2+ and Ca2+ with a total ionic strength of 10 mM. The impact of modification by atomic layer deposition on fouling mitigation was also assessed. The flux decline in the first 100 min for single foulants was 4.16 × 10−2, 2.69 × 10−2 and 1.60 × 10−2 Lm−2 for SAL, HA and BSA, respectively. These results demonstrated that for the single foulants, deposition on the membrane surface in the early stages of filtration was primarily governed by membrane-foulant interactions. Interestingly, cake filtration was the least fouling mechanism in feed solutions composed of BSA and SAL (R2 = 0.519, 0.374 for BSA + SAL and BSA + SAL + HA, respectively) and the most favorable fouling mechanism of feed solution which included HA and SAL (R2 = 0.972). The water contact angle dropped from 58o to 35° after coating, thus improving its anti-fouling properties.

This study determined the physicochemical parameters, microbial properties and heavy metal speciation of groundwater in major towns of Ife North Local Government, Area of Osun State, Nigeria, with a view to evaluating the safety of groundwater. Water samples were collected during the dry season (December, 2015 to February, 2016) and wet season (May to July, 2016). A total of 72 samples were collected for the 6 months. Physicochemical parameters were determined in situ while total coliform count was done by membrane filtration techniques. The sequential extraction procedure was used to fractionate the metals (As, Pb, Cd, Cr, Cu, Mn, Ni and Zn) in the water samples. The concentrations of the metals were quantitatively determined using Atomic Absorption Spectrophotometer (AAS, PG 990 Series). The results of the physicochemical parameters of water showed that the pH (6.22–9.93), electrical conductivity (126.02–606.65 µs cm−1), total dissolved solids (78.37–705.31 mg L−1), oxidation reduction potential (303.44–330.17 mV) and temperature (25.83–28.93 °C) were within the limit stipulated for drinking and domestic water. The bacterial flora identified includes Escherichia coli, Yersinra spp, Entrerbacter spp, Citrobacter spp, Seirantia spp, Klebsella spp and Rhebrella spp. The metal speciation revealed free metal ions had the highest concentration with the order free metal ions > suspended particles > bound to organic substances. The study concluded that the groundwaters of the studied area were polluted with microorganisms and the investigated heavy metal, require treatment and monitoring to safeguard human health.

The information acquired by high resolution quadrupole-time of flight mass spectrometry (QTOF-MS) allows target analysis as well as retrospective screening for the presence of suspect or unknown emerging pollutants which were not included in the target analysis. Targeted quantification of eight azole antifungal drugs in wastewater effluent as well as new and relatively simple retrospective suspect and non-target screening strategy for emerging pollutants using UHPLC-QTOF-MS is described in this work. More than 300 (parent compounds and transformation products) and 150 accurate masses were included in the retrospective suspect and non-target screening, respectively. Tentative identification of suspects and unknowns was based on accurate masses, peak intensity, blank subtraction, isotopic pattern (mSigma value), compound annotation using data bases such as KEGG and CHEBI, and fragmentation pattern interpretation. In the targeted analysis, clotrimazole, fluconazole, itraconazole, ketoconazole and posaconazole were detected in the effluent wastewater sample, fluconazole being with highest average concentration (302.38 ng L−1). The retrospective screening resulted in the detection of 27 compounds that had not been included in the target analysis. The suspect compounds tentatively identified included atazanavir, citalopram, climbazole, bezafibrate estradiol, desmethylvenlafaxine, losartan carboxylic acid and cetirizine, of which citalopram, estradiol and cetirizine were confirmed using a standard. Carbamazepine, atrazine, efavirenz, lopinavir, fexofenadine and 5-methylbenzotriazole were among the compounds detected following the non-targeted screening approach, of which carbamazepine was confirmed using a standard. Given the detection of the target antifungals in the effluent, the findings are a call for a wide assessment of their occurrence in aquatic environments and their role in ecotoxicology as well as in selection of drug resistant fungi. The findings of this work further highlights the practical benefits obtained for the identification of a broader range of emerging pollutants in the environment when retrospective screening is applied to high resolution and high accuracy mass spectrometric data.

Three wastewater treatment plants (WWTPs) located in Gauteng province in South Africa were investigated to determine the diversity, co-occurrence and implications of their fungal communities using illumina sequencing platform and network analysis. Phylogenetic taxonomy revealed that members of the fungal communities were assigned to 6 phyla and 361 genera. Basidiomycota and Ascomycota were the most abundant phyla, dominated by the genera Naumovozyma, Pseudotomentella, Derxomyces, Ophiocordyceps, Pulchromyces and Paecilomyces. Phylogenetic analysis revealed the existence of fungal OTUs related to class lineages such as Agaricomycetes, Eurotiomycetes and Sordariomycetes indicating new fungal diversity in WWTPs. Dominant and rare fungal genera that can potentially be used in bioremediation such as Trichoderma, Acremonium, Talaromyces, Paecilomyces, cladophialophora and Saccharomyces were detected. Conversely, genera whose members are known to be pathogenic to human and plant such as Olpidium, Paecilomyces, Aspergillus, Rhodotorula, Penicillium, Candida, Synchytrium, Phyllosticta and Mucor were also detected in all WWTPs. Phylotype analysis confirmed that some fungal phylotypes were highly similar to the reported fungal pathogens of concern. Co-occurrence network analysis revealed that the fungal genera such as Minimedusa, Glomus, Circinella, Coltricia, Caloplaca, Phylosticta, Peziza, Candida, and Hydnobolites were the major networking hub in the WWTPs. The overall results in this study highlighted that WWTPs represent a potential source of beneficial fungi for bioremediation of pollutants in the ecosystem and the need to consider human and plant fungal pathogens during safety evaluation of treated wastewater for reuse.

This paper assesses the level of phenols and polycyclic aromatic hydrocarbons (PAHs) in the Nandoni dam situated in the Vhembe District, Limpopo Province, South Africa. About 55 villages are supplied with water sourced from the dam which is prone to contamination by different pollutants other than phenols and PAHs, due to its exposure to agricultural, human and animal activities around it. A quantitative determination of these pollutants was conducted using a gas chromatography-time-of-flight mass spectrometer (GC-TOF MS) after sample preparation that involved solid phase extraction (SPE). Water samples were collected on a seasonal basis in spring, summer, autumn, and winter. Several phenolic compounds (phenol, 2-chlorophenol, 2,6-dichlorophenol, 2,4,5-trichlorophenol, 2,4-dimethylphenol, 4-nitrophenol and p-cresol) were detected in the dam at concentration levels not suitable for drinking purposes. The recorded concentrations were generally higher than the SANS 241, US EPA and WHO acceptable limits in drinking water with up to 1.11 mg/L recorded for 2,4,5-trichlorophenol. The concentrations of PAHs (naphthalene, acenaphthene, pyrene, benz(a)anthracene and benzo(a)pyrene) fell within the threshold limits and were typically less than 0.1 μg/L. The water treatment plants sourcing water from the Nandoni dam use conventional treatment processes that focus more on removing contaminants such as microorganisms and heavy metals without considering the danger of long-term effects of organic contaminants, whose harmful health effects are observed after long periods of exposure. Therefore, this dam requires coordinated management of the water resources in order to maximize the economic and social welfare equitably without affecting human life and the ecosystem.

Carbon dot (CD) obtained from pine bark was loaded on three TiO2 polymorphs (anatase, rutile, and brookite abbreviated in this study as Ana, Rut, and Brk respectively) to evaluate their photocatalytic performance in rhodamine B (RhB) degradation under visible-LED light. The materials were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), x-ray powder diffraction (XRD), N2 sorption isotherm, and Fourier transform infrared (FT-IR), UV-diffused reflectance spectroscopy (UV-DRS), and x-ray photoelectron spectroscopy (XPS). The x-ray result shows that the different pure pristine polymorphs and their composites were successfully prepared with Rut and CD-Rut composite having the highest crystallite size of 23.06 and 21.64 nm respectively. The N2 sorption isotherm of the materials shows Ana, Brk and their composite exhibited type IV isotherm with H series hysteresis loop, which implies that they are mesoporous materials. The isotherm exhibited by Rut and CD-Rut suggests that they are non-porous. However, their pore size distribution (PSD) shows that the materials possess mesopores that may have resulted from interparticle voids due to particle aggregation. Results from the photocatalytic degradation experiments showed that the materials performed in the following order CD-Brk>Brk>CD-Ana>CD-Rut>Rut>Ana with a corresponding percentage RhB removal of 99.91, 76.78, 36.28, 27.50, 22.65, and 12% respectively. The excellent performance of CD-Brk and Brk over the others is attributed to their narrow bandgap energy of 2.00 eV making them more active under the visible-LED light. CD-Brk performed better than Brk because it possesses more surface-active sites resulting from its relatively higher surface area. In terms of degradation mechanism, CD-Brk which was stable after 4 cycles of degradation, showed that superoxide anion radical ( O 2 • − ) played major role in the degradation process.

Although Membrane Distillation (MD) is envisaged as a promising technology for achieving a cost-effective and sustainable recovery of water from saline solutions, membrane fouling and wetting remain the major challenges that compromise its separation efficiency. To mitigate the high fouling propensities of hydrophobic MD membranes while retaining their high salt rejection efficiencies, superhydrophobic poly-vinylidene fluoride (PVDF) nanofibre membranes embedded with silanized silica nanoparticles (f-SiO2NPs) were synthesised and coated with a hydrophilic active layer containing silver nanoparticles and carboxylated multi-walled carbon nanotubes (AgNPs/f-MWCNTs). While the f-SiO2NPs-modified PVDF nanofibres exclusively allow the transport of water vapour, the AgNPs/f-MWCNTs active provides hydrophilic and biocidal (i.e., biofouling control) properties. The morphology, hydrophobicity, thermal and mechanical properties of the PVDF membranes were rigorously characterized. The PVDF nanofibres were investigated for their resistance to flux decline using a solution containing Bovine Serum Albumin and a real complex effluent containing thermophilic bacteria. f-SiO2NPs-modified PVDF nanofibres showed the highest flux decline (82% after 60 h) associated with BSA adsorption induced by favourable hydrophobic-hydrophobic interactions. AgNPs/f-MWCNTs coated PVDF membranes showed a significant decrease in fouling (47% flux decline) and the highest salt rejections (99.8%). Remarkably, the coating layer showed high biocidal properties towards thermophilic bacteria when subjected to effluent. The current approach provides an important step towards a successful implementation of MD processes at a pilot-scale for water desalting.

The Z-scheme zinc molybdate/bismuth iron tungstate/reduced graphene oxide (ZnMoO4/BiFeWO6/rGO, ZM/BFW/rGO) ternary composite photocatalyst was prepared with rGO acting as an electron transmission mediator. The physicochemical properties of the materials were characterized by using a range of techniques such as SEM, TEM, EDS, FTIR, Raman, BET, TGA, and UV–vis DRS. The optical properties of the materials showed that ZM/BFW/rGO absorbed more visible light than the pristine ZnMoO4 (ZM) and BiFeWO6 (BFW). Thermal analysis showed enhanced stability of the ternary composite due to incorporation of thermally stable ZM. The composite material was used for photocatalytic degradation of 30 mg L–1 anthraquinonic acid blue 25 (AB 25) as the model pollutant under visible light irradiation. A degradation efficiency of 98% was achieved after 180 min degradation using ZM/BFW/rGO, while ZM and BFW showed only 24% and 36% dye removal efficiencies. About 70% total organic carbo (TOC) was attained with a ternary composite pho...

Sulfamethoxazole (SMX) is one of the antibiotics which is used to treat a variety of bacterial infections in both humans and animals. The inflow of this pharmaceutical drug from various sources into the aquatic environment necessitates the development of new and efficient technologies for its removal from water. As such, a stand-alone and robust photoanode made from a p-n heterojunction of BiOI and g-C3N4 anchored on exfoliated graphite was fabricated and used in the photoelectrocatalytic degradation of SMX pollutant. Herein, we report the synthesis, characterization and photoelectrochemical application of graphitic carbon nitride/bismuth oxyiodine/exfoliated graphite (g-C3N4/BiOI/EG) photoanode for removal of SMX as a target pollutant from the water. The g-C3N4/BiOI/EG nanocomposite was synthesized using ultrasonication method and characterized using X-RD, FTIR, Raman spectroscopy, TGA, FESEM coupled with EDS, TEM, UV–Vis DRS and XPS techniques. The results revealed that the BiOI microspheres and irregular g-C3N4 sheets were anchored on the structure of EG sheets. The electrochemical properties of the fabricated photoanodes were studied by CV and EIS using 5 mM [Fe(CN)6]3−/4- contained in 0.1 M KCl solution. The ternary g-C3N4/BiOI/EG photoanode was found to be displaying better electron-hole separation and optical properties due to the formation of p-n heterojunction in the ternary nanocomposite photoanode. The decrease in concentration of SMX was monitored using a UV–Vis spectrophotometer. The optimum current density and pH used were 5 mA cm−2 and 6.23 respectively. At the optimum conditions, the antibiotic removal efficiency was 88% with a rate constant of 7.65 × 10−3 min−1 and correlation coefficient (R2) of 0.997. The results showed that g-C3N4/BiOI/EG photoanodes can be applied in the photoelectrochemical degradation of pharmaceutical pollutants in water.

The presence of chlorophenols in various environmental media has become a human health concern. In this study, homogeneous cadmium sulfide (CdS) sub-microspheres were prepared through a solution phase and hydrothermal method, form cadmium acetate dihydrate and thiourea. CdS@TiO2 core-shell nanostructures were synthesized using the as prepared CdS (1:4), through two steps including the solution phase and hydrothermal methods. The prepared CdS sub-microspheres and CdS@TiO2 were characterized using a number of physico-chemical techniques such as X-ray diffraction (XRD), RAMAN spectroscopy, X-ray photoelectron spectroscopy (XPS), UV–vis Diffuse Reflectance Spectroscopy (UV–vis DRS), Scanning Electron Microscopy (SEM), Transmission Electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDX). The experimental results demonstrated that the morphology of the CdS sub-microspheres can be easily controlled by changing the ratio of cadmium acetate/thiourea. The SEM analysis revealed that the CdS sub-microspheres prepared by solution phase and hydrothermal methods possess an average size of around 149 and 470 nm respectively. The CdS sub-microspheres and CdS@TiO2 core-shell materials were evaluated for the visible light photocatalytic degradation of 2,4-dichlorophenol and 2,4,6-trichlorophenol. CdS@TiO2 showed up to 20% enhanced photocatalytic activity for the degradation of 2,4-DCP and 2,4,6-TCP compared to pure CdS. Up to 70% of 2,4-DCP and 2,4,6-TCP were removed in 6 h. The enhanced photoactivity can be attributed to the longer lifetime of photo-generated electron − hole pairs from the CdS@TiO2 compared to the pure CdS material.

A wide range of semiconductor-assisted photocatalytic nanomaterials (NMs) are currently being considered and investigated as potential photocatalysts in water treatment. The applications of nanocomposites composed of nano-structured titania (nano-TiO

The therapeutic efficiency of doxorubicin (DOX) is dependent on its sufficient accumulation within the nucleus of cancer cells. Taking advantage of the fascinating properties (e.g., multiple dense arrays of hyperbranches and high surface area) of bimetallic nanodendrites as well as the arginine-rich components of protamine sulfate (PS), we herein present a new type of PS-modified Au@PdNDs-based hydrophobic drug carrier in which DOX can effectively bind to the surface of the PS.Au@PdNDs nanocarrier via non-covalent attachment. Chemical characterization of the synthesized PS.Au@PdNDs.DOX showed the successful loading of DOX onto the surface of PS.Au@PdNDs. Darkfield and Hyperspectral imaging analysis of the PS.Au@PdNDs.DOX demonstrated the time-dependent uptake and prolonged accumulation capability for releasing its DOX cargo inside the nucleus. Specifically, data from the 3D-CytoViva fluorescence imaging did not only track the nanocarrier’s distribution but also confirmed its predominant accumulation in the nuclear compartment through clathrin-mediated endocytosis. Cytotoxicity assay showed that the PS.Au@PdNDs.DOX significantly inhibited cancer cell proliferation with maximum DOX release under acidic conditions (pH 4.5 and 5.5) than at normal physiological pH of 7.4. Moreover, the resultant PS.Au@PdNDs-based DOX nanocarrier efficiently improved the induction of apoptosis in MCF-7 cells compared to free DOX and passive targeted platform. In addition, loss of membrane integrity, mitochondria-apoptotic pathway, and internucleosomal DNA contents from cell cycle progression assay provided insights on the mechanism of cell death. Overall, the PS.Au@PdNDs.DOX nanocarrier may be employed for improved subcellular delivery of DOX as well as multimodal visualization in cancer therapy.

The adoption of green technology is very important to protect the environment and thus there is a need for improving the existing methods for the fabrication of carbon materials. As such, this work proposes to discuss, interrogate, and propose viable hydrothermal, solvothermal, and other advanced carbon materials synthesis methods. The synthesis approaches for advanced carbon materials to be interrogated will include the synthesis of carbon dots, carbon nanotubes, nitrogen/titania-doped carbons, graphene quantum dots, and their nanocomposites with solid/polymeric/metal oxide supports. This will be performed with a particular focus on microwave-assisted solvothermal and hydrothermal synthesis due to their favourable properties such as rapidity, low cost, and being green/environmentally friendly. These methods are regarded as important for the current and future synthesis and modification of advanced carbon materials for application in energy, gas separation, sensing, and water treatment. Simultaneously, the work will take cognisance of methods reducing the fabrication costs and environmental impact while enhancing the properties as a direct result of the synthesis methods. As a direct result, the expectation is to impart a significant contribution to the scientific body of work regarding the improvement of the said fabrication methods.

This review paper systematically evaluates current progress on the development and performance of photocatalytic nanofiber membranes often used in the removal of micropollutants from water systems. It is demonstrated that nanofiber membranes serve as excellent support materials for photocatalytic nanoparticles, leading to nanofiber membranes with enhanced optical properties, as well as improved recovery, recyclability, and reusability. The tremendous performance of photocatalytic membranes is attributed to the photogenerated reactive oxygen species such as hydroxyl radicals, singlet oxygen, and superoxide anion radicals introduced by catalytic nanoparticles such as TiO2 and ZnO upon light irradiation. Hydroxyl radicals are the most reactive species responsible for most of the photodegradation processes of these unwanted pollutants. The review also demonstrates that self-cleaning and antimicrobial nanofiber membranes are useful in the removal of microbial species in water. These unique materials are also applicable in other fields such as wound dressing since the membrane allows for oxygen flow in wounds to heal while antimicrobial agents protect wounds against infections. It is demonstrated that antimicrobial activities against bacteria and photocatalytic degradation of micropollutants significantly reduce membrane fouling. Therefore, the review demonstrates that electrospun photocatalytic nanofiber membranes with antimicrobial activity form efficient cost-effective multifunctional composite materials for the removal of unwanted species in water and for use in various other applications such as filtration, adsorption and electrocatalysis.

While water is a key resource required to sustain life, freshwater sources and aquifers are being depleted at an alarming rate. As a mitigation strategy, saline water desalination is commonly used to supplement the available water resources beyond direct water supply. This is achieved through effective advanced water purification processes enabled to handle complex matrix of saline wastewater. Membrane technology has been extensively evaluated for water desalination. This includes the use of reverse osmosis (RO) (the most mature membrane technology for desalination), pervaporation (PV), electrodialysis (ED), membrane distillation (MD), and membrane crystallization (MCr). Though nanofiltration (NF) is not mainly applied for desalination purposes, it is included in the reviewed processes because of its ability to reach 90% salt rejection efficiency for water softening. However, its comparison with other technologies is not provided since NF cannot be used for removal of NaCl during desalination. Remarkably, membrane processes remain critically affected by several challenges including membrane fouling. Moreover, capital expenditure (CAPEX) and operating expenditure (OPEX) are the key factors influencing the establishment of water desalination processes. Therefore, this paper provides a concise and yet comprehensive review of the membrane processes used to desalt saline water. Furthermore, the successes and failures of each process are critically reviewed. Finally, the CAPEX and OPEX of these water desalination processes are reviewed and compared. Based on the findings of this review, MD is relatively comparable to RO in terms of process performance achieving 99% salt rejections. Also, high salt rejections are reported on ED and PV. The operation and maintenance (O&M) costs remain lower in ED. Notably, the small-scale MD OPEX falls below that of RO. However, the large-scale O&M in MD is rarely reported due to its slow industrial growth, thus making RO the most preferred in the current water desalination markets.

Herein, a facile approach for preparing nickel oxide nanoparticles coupled with manganese oxide nanorods (NiONPs@MnO2NRs) was reported for the first time. The nickel oxide nanoparticles, manganese oxide nanorods, and nanocomposite material were prepared using simple and inexpensive co-precipitation, hydrothermal, and sonication methods. The structural integrity of the composite materials was interrogated using field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and ultraviolet–visible (UV–vis DRS) spectroscopy. FESEM and TEM results revealed an attachment of NiONPs onto the surface of MnO2NRs. Electrochemical techniques, which included cyclic voltammetry (CV), linear sweep voltammetry (LSV), and electrochemical impedance spectroscopy (EIS), were employed to interrogate the electrochemical signature of the nanocomposite. The results revealed that these materials are potential nanomediator for the immobilisation of electroactive species in electrocatalysis and electrochemistry. Upon applying the materials in the photocatalytic degradation of 10 mg L−1 bromophenol blue dye, NiONPs@MnO2NRs gave an efficiency of 81.5%, which was 2.8 and 4.3 folds higher than those obtained with NiONPs and MnO2NRs materials, respectively. The electrochemical characterisation results confirmed an increased separation of electron–hole pairs, which helped enhance the photocatalytic activity of the composite material. The results further indicate that the prepared composite material can be explored with other organic water pollutants such as pesticides and pharmaceuticals.

Herein, a dual Z-scheme heterojunction photocatalyst consisting of Co

There is great importance and need of improving existing carbon materials fabrication methods. As such, this work proposes to discuss, interrogate, and propose viable hydrothermal, solvothermal, and other advanced carbon materials synthetic methods. The advanced carbon materials to be interrogated will include the synthesis of carbon dots, carbon nanotubes, nitrogen/titania-doped carbons, graphene quantum dots, and their nanocomposites with solid/polymeric/metal oxide supports. This will be done with special mind to microwave-assisted solvothermal and hydrothermal synthesis due to their favourable properties such as rapidity, low cost, and green/environmentally-friendliness. Thus, these methods are important during the current and future synthesis and modification of advanced carbon materials for application in energy, gas separation, sensing, and water treatment. Simultaneously, the work will pay special cognizance to methods reducing the fabrication costs and environmental impact while enhancing the properties as a direct result of the synthesis methods. As a direct result, the expectation is to impart a significant contribution to the scientific body of work regarding the improvement of the said fabrication methods.

Water contamination with dyes is harmful to humans and the environment. This study investigated the photocatalytic activity of natural clay (GOL) mixed with carbon nanotubes (CNT) for removal of brilliant black (BB) in wastewater. The materials were characterized with FESEM-EDS, XRD, XRF, FTIR and UV-vis DRS. The natural clay contains 2.34 % TiO2 which is 75% more than most natural clays. SEM showed that CNT were well dispersed and mixed with clay. DRS spectra showed two absorption bands above 380 nm. CNT in GOL has decreased significantly the energy band gaps from 2.75 and 3.25 eV to 1.53 and 2.90 eV for GOL and 10% CNT–GOL, respectively. Photocatalytic activity was enhanced with degradation of BB increased from 66 to 95% with GOL and 10% CNT–GOL respectively after 45 min of visible light irradiation. The improvement can be attributed to the synergy of the interface heterojunction of clay and CNT. The presence of CNT reduces the e− and h+ (e− / h+) pairs recombination and facilitates the production of reactive oxygen species responsible for the decay of dye. The addition of H2O2 to the experiment (2 mmoL) confirmed the role of holes and hydroxyl radicals. Eighty-five percent of BB carbon content was removed with 10% CNT–GOL suggesting that mineralization occurred. After 45 min of visible light irradiation, the degradation kinetic studies followed a second-order reaction with a R2 = 0.997. Therefore, natural clay–CNT nanocomposites can be applied to treat dyes containing wastewaters.

This report narrates the successful application of a fabricated novel sensor for the trace detection of endosulfan (EDS). The sensor was made by modifying a glassy-carbon electrode (GCE) with polyaniline (PANI), chemically synthesized antimony oxide nanoparticles (AONPs), acid-functionalized, single-walled carbon nanotubes (fSWCNTs), and finally, the AONP-PANI-SWCNT nanocomposite. The electrochemical properties of the modified electrodes regarding endosulfan detection were investigated via cyclic voltammetry (CV) and square-wave voltammetry. The current response of the electrodes to EDS followed the trend GCE-AONP-PANI-SWCNT (−510 µA) &gt, GCE-PANI (−59 µA) &gt, GCE-AONPs (−11.4 µA) &gt, GCE (−5.52 µA) &gt, GCE-fSWCNTs (−0.168 µA). The obtained results indicated that the current response obtained at the AONP-PANI-SWCNT/GCE was higher with relatively low overpotential compared to those from the other electrodes investigated. This demonstrated the superiority of the AONP-PANI-SWCNT-modified GCE. The AONP-PANI-SWCNT/GCE demonstrated good electrocatalytic activities for the electrochemical reduction of EDS. The results obtained in this study are comparable with those in other reports. The sensitivity, limit of detection (LoD), and limit of quantification (LoQ) of AONP-PANI-SWCNT/GCE towards EDS was estimated to be 0.0623 µA/µM, 6.8 µM, and 20.6 µM, respectively. Selectivity, as well as the practical application of the fabricated sensor, were explored, and the results indicated that the EDS-reduction current was reduced by only 2.0% when interfering species were present, whilst average recoveries of EDS in real samples were above 97%.

Cake-enhanced concentration polarization (CECP) has been ascribed as the main cause of flux decline in dead-end filtration. An unfamiliar approach was used to investigate the role of CECP effects in the fouling of a nanofiltration membrane (NF-270) that poorly reject salts. Membrane&ndash, foulant affinity interaction energies were calculated from measured contact angles of foulants and membrane coupons based on the van der Waals/acid&ndash, base approach, and linked to resistance due to adsorption (Ra). In addition, other fouling mechanisms and resistance parameters were investigated using model organic and colloidal foulants. After selection, the foulants and membranes were characterized for various properties, and fouling experiments were conducted under controlled conditions. The fouled membranes were further characterized to gain more understanding of the fouling layer properties and flux decline mechanisms. Sodium alginate and latex greatly reduced membrane permeate flux as the flux declined by 86% and 59%, respectively, while there was minor flux decline when aluminum oxide was used as model foulant (&lt, 15% flux decline). More flux decline was noted when fouling was conducted with a combination of organic and colloidal foulants. Contrary to other studies, the addition of calcium did not seem to influence individual and combined fouling trends. Foulants adsorbed more on the membrane surface as the membrane&ndash, foulant affinity interactions became more attractive and pore blocking by the foulants was not important for these experiments. Hydraulic resistance due to cake formation (Rc) had a higher contributing effect on flux decline, while CECP effects were not substantial.

Two-dimensional (2D) carbon allotropes have unique physical, chemical, optical, mechanical and electrical properties. These materials have been designed and fabricated into novel materials for applications in catalytic, biomedical, optical and energy processes. In this book chapter, the unique properties, synthetic routes and applications of graphene-based photocatalysts are highlighted. The chapter summarises recent progress in the synthesis and fabrication of graphene-based semiconductor photocatalysts. The fundamental mechanisms behind catalytic enhancement in heterogeneous photocatalysis are discussed based on the formation of heterojunctions and other surface phenomena. These materials have recently attracted a lot of attention because of their environmental and energy applications. Environmental applications of the 2D-based photocatalytic materials, including photodegradation of pollutants, microbial inactivation, carbon dioxide reduction and water splitting, are also highlighted. Other applications such as nitrogen fixation and photoreduction of heavy metal were also discussed. Future directions and perspectives on this topic were summarised.

The work reports an investigation into the role played by the carbon residue from low-quality amorphous carbon nanotubes (aCNTs) and nitrogen doped aCNTs (aNCNTs) in the properties of solgel-synthesized TiO2 and NTiO2. The resutant modified nanohybrids are compared to nitrogen-doped TiO2 where the N is sourced from an ethylenediamine as an organic C and N precursor. The presence of carbon originating from ethylenediamine was confirmed by TGA and DTA while additional C doping originating from aCNT and aNCNT residues was confirmed by EDS and XRD spectroscopic techniques. XRD spectroscopy further demonstrated that the carbonaceous material residues resulted in the formation of TiC in TiO2–aCNT nanohybrids, and carbon nitride in NTiO2–aCNT nanohybrids. The TiC promoted photocatalytic performance of TiO2–aCNT nanohybrids while the carbon nitride residue increased charge recombination and thereby hampering the photocatalytic performance of NTiO2. A strong correlation exists between the optical properties and the photocatalytic performance in that NTiO2 has the lowest Eg (2.84 eV), second lowest charge recombination rate, and a high 2nd-order rate constant for the kinetics for CR dye removal. The TiO2–aCNT nanohybrids have the best overall performance in terms of dye adsorption, color removal through chemisorption, and UVA 254 TOC removal due to its low charge recombination. Therefore, the introduction of the carbonaceous materials into TiO2 significantly increases the adsorption capacity. Lastly, the presence of N in the carbonaceous materials further impedes the photocatalytic activity as observed by the low photocatalytic performance of NTiO2–aNCNT and TiO2–aNCNT nanohybrids.

Herein we present a two-stage phase inversion method for the preparation of nanocomposite membranes for application in ultra-low-pressure reverse osmosis (ULPRO). The membranes containing DA-stabilized xGnP (xGnP-DA-) were then prepared via dry phase inversion at room temperature, varying the drying time, followed by quenching in water. The membranes were characterized for chemical changes utilizing attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The results indicated the presence of new chemical species and thus, the inclusion of xGnP-DA in the polyethersulfone (PES) membrane matrix. Atomic force microscopy (AFM) showed increasing surface roughness (Ra) with increased drying time. Scanning electron microscopy (SEM) revealed the cross-sectional morphology of the membranes. Water uptake, porosity and pore size were observed to decrease due to this new synthetic approach. Salt rejection using simulated seawater (containing Na, K, Ca, and Mg salts) was found to be up to stable at &lt, 99.99% between 1&ndash, 8 bars operating pressure. After ten fouling and cleaning cycles, flux recoveries of &lt, 99.5% were recorded, while the salt rejection was &lt, 99.95%. As such, ULPRO membranes can be successfully prepared through altered phase inversion and used for successful desalination of seawater.

The synthesis of TiO2 nanohybrids fabricated using amorphous carbon nanotubes (aCNTs) and amorphous nitrogen doped carbon nanotubes (aNCNTs) via a microwave-assisted hydrothermal method is reported. The photocatalytic removal of Reactive Red 120 (RR 120) and organics from industrial textile wastewater using these nanohybrids is discussed. The synthesis process was shown to promote the removal of nano graphitic flakes from the outer walls of the aNCNTs and aCNTs and subsequent incorporation of these carbonaceous materials into TiO2 nanocrystals as such enabling a stronger interaction between the TiO2 and the carbonaceous material. This enabled the production of a surface plasmon resonance on the TiO2 and NTiO2 nanocrystals. The carbon residue was confirmed to be aCNTs and aNCNTs by TGA and DTA analyses. XPS analysis for the TiO2–aNCNT nanohybrids confirmed the C and N doping of TiO2 due to the amorphous residues from the aNCNTs. In addition, XPS and FTIR spectroscopic analysis confirmed the presence of surface oxygen-based groups. TEM micrograph analysis showed that aCNTs and aNCNTs promote the formation of monodispersed and small TiO2 particles; all below 7.4 nm. The NTiO2–aNCNT nanohybrids have the lowest energy band gap at 2.97 eV and the lowest PL intensity. The TiO2–aNCNT nanohybrids had superior adsorptive (98.2%) and photocatalytic (99%) removal for 20 ppm RR 120 dye solution at k1app 3.44 × 10−2 min−1. Lastly, all the nanohybrids demonstrate the formation of visible-light absorbing intermediates from VAT-dyed textile wastewater. The work demonstrates the possibility of the use of these nanohybrids to derive new products through photocatalytic nanohybrids.

Iron (Fe), zirconium (Zr) and titanium (Ti) oxides nanoparticles were each embedded onto a weak acid chelating resin for support using the precipitation method to generate three hybrid adsorbents of hydrated Fe oxide (HFO-P), hydrated Zr oxide (HZO-P) and hydrated Ti oxide (HTO-P). This paper reports on the characterization, performance and potential of these generated nanoadsorbents in the removal of toxic metal ions from acid mine drainage (AMD). The optimum contact time, adsorbent dose and pH for aluminium (Al) (III) adsorption were established using the batch equilibrium technique. The metal levels were measured using inductively coupled plasma-optical emission spectrometry. The scanning electron microscopy–energy dispersive X-ray spectroscopy results confirmed the presence of the metal oxides within the hybrid resin beads. HFO-P, HZO-P and HTO-P adsorbed Al(III) rapidly from synthetic water with maximum adsorption capacities of 54.04, 58.36 and 40.10 mg/g, respectively, at initial pH 1.80 ± 0.02. The adsorption of Al(III) is of the second-order in nature (R2 > 0.98). The nanosorbents removed ten selected metals from environmental AMD and the metal removal efficiency was in the order HTO-P > HZO-P > HFO-P. All three hybrid nanosorbents can be used to remove metals from AMD; the choice would be dependent on the pH of the water to be treated.

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This review looks into the efforts made towards commercializing nano-enable flat sheet membranes as well as the challenges that need to be overcome. There is a question mark on the argument that the nano-pores of the fillers play a significant role in the performance of the membrane. Non porous nanomaterials have been reported to cause in increase in water flux, yet there are still articles that credit the nano-pores of the nanomaterials for improved membrane performance. There are two points that are important to highlight: (1) the nanoparticles, e.g. zeolites, are smaller in diameter compared to the thickness, (2) the loading rate of the filler phase is significantly small in relation to continuous phase. Therefore, it cannot be correct to assume that the nanomaterials provide continuous flow channels in the selective layer. There is no dispute here that the addition of NP enhances the performance of a membrane, but it is the perception that the nano-pores are the reason that we disagree with.

As a potential remedy for addressing water shortage challenges, membrane distillation (MD) presents the possibility of alleviating the water demand in water scarce countries. It offers a promising approach to explore untraditional water resources. In the field of urine treatment, MD enables water recovery for potable use and the recovery of nutrients that can be used in boosting agricultural production. It is in this light that polyvinylidene fluoride/polytetrafluoroethylene (PVDF/PTFE) membranes modified with methyl functionalized silica nanoparticles (MfSNPs) were fabricated to produce microporous hydrophobic composite membranes for water recovery from urine. Contact angles of the membranes indicated an increase in the hydrophobicity brought about by the increase in PTFE loading. The increase in PTFE loading improved the membrane structure (as shown by SEM images) resulting in smaller evenly distributed pores and a porous spongy structure. The composite membrane attained the maximum water recovery of 80% from hydrolysed human urine samples at pH 10.5, against a water vapour gradient of 30 °C. The feed side temperature was kept at 50 °C and the permeate side at 20 °C. The highest permeate flux for the PVDF/PTFE nanocomposite membranes was 8 J/Jo,which is comparable to fluxes reported in the literature obtained in direct contact membrane distillation (DCMD) setups operated at the same temperature gradient. The permeate water quality was assessed and the results showed high rejection of ammonia (>95%), TOC (>98%), Na+ (>98%) and K+ (>89%) by the membranes. This suggests that the (combination/hybrid) convergence of membrane technology and nanotechnology in MD application is a viable alternative for urine treatment to provide sustainable and reliable clean water supply.

It is well known that natural organic matter (NOM) is the major precursor of disinfection by-products (DBPs) when inadequately removed NOM reacts with the disinfectant during chlorination and chloramination. Special interest in the DBP precursors is justified as it is essential to understand the reactivity and character of the precursors responsible for the formation of DBPs. This is vital in order to develop processes that will enhance precursor removal during drinking water treatment. The aim of this study was to investigate the impact of the characteristics of NOM within an oligotrophic water source on the formation of trihalomethanes (THMs) during drinking water treatment at Rand Water. Specific ultraviolet absorbance (SUVA) and molecular size distribution (MSD) were the main NOM characterisation techniques utilised during this study. The MSD was investigated by making use of high-performance size-exclusion chromatography (HPSEC). The MSD results showed a significant correlation between the high-molecular-weight (HMW) fraction of NOM and TTHM formation, specifically during the summer months. The positive correlation existing between SUVA and full scale NOM removal indicates that SUVA can be used to indicate NOM treatability during water treatment. A link between chloroform formation and the HMW fraction of NOM was also observed; however, the formation of bromodichloromethane (BDCM) was not due to the HWM fraction, as indicated by a weak regression coefficient. The results displayed are an indication that the aromatic fraction of NOM was the main precursor to TTHM formation, more prominently during summer.

Wastewater treatment plants (WWTPs) can be significant sources of antifungal resistant fungi, which can disseminate further in the environment by getting into rivers together with effluents discharged from WWTPs and pose a risk for human health. In this study, the presence of azole resistance was determined in fungal isolates from treated effluents of two WWTPs using the standard microdilution method from Clinical and Laboratory Standards Institute (CLSI). A total of 41 fungal isolates representing 23 fungal species and 16 fungal genera were obtained. Fungal genera related to the known human and/or plant pathogens such as Aspergillus, Fusarium, and Candida were detected. Among the observed species, the susceptibility of Aspergillus fumigatus and Fusarium oxysporum was tested against fluconazole (FCZ), ketoconazole (KTZ), itraconazole (ITZ), and voriconazole (VCZ). The isolate A. fumigatus was susceptible to KTZ, ITZ, and VCZ, while it showed resistance against FCZ. On the contrast, the isolate F. oxysporum showed resistance to KTZ, ITZ, and VCZ. Comparatively, VCZ showed highest activity against both A. fumigatus and F. oxysporum. Analysis of the gene Cyp51A for the A. fumigatus isolate showed no evidence of drug resistance that could be related to point mutations and/or tandem repeats in the gene. To the best of our knowledge, this is the first susceptibility test study on A. fumigatus and F. oxysporum isolates from the WWTPs of South Africa. In conclusion, this study indicated an urgent need for thorough investigation with larger group of fungal isolates from different regions of South Africa to broadly understand the role of WWTPs in the dissemination of azole antifungal drug resistance.

Antibacterial silver nanoparticles (AgNPs) were synthesised via an environmentally benign thermally-assisted one-pot and microwave-assisted experimental set-up using apple extract as a reducing agent. The formation of these AgNPs was confirmed by UV-Vis, XRD and EDS while their size distribution was determined by TEM micrographs. The AgNPs were uniformly distributed with diameters of 28.24 ± 1.15 nm and 22.05 ± 1.05 nm for the thermally-assisted one-pot and microwave-assisted reduction methods respectively. The rate of reduction was faster in a microwave-assisted reduction method compared to that of a thermally-assisted one-pot synthesis method. The antibacterial AgNPs were embedded in polyvinylidene fluoride (PVDF) nanofibre membranes and their antibacterial activity against Gram-positive Geobacillus stearothermophilus and Staphylococcus aureus and Gram-negative Pseudomonas aeruginosa and Klebsiella pneumoniae was studied. The antibacterial nanofibres successfully inhibited the growth of these mesophilic and thermophilic bacteria. Therefore, AgNP-embedded PVDF nanofibre membranes showed a high potential for use in water purification systems that are subject to contamination by mesophilic or thermophilic bacteria without compromising the rate of water recovery.

This paper, reports on the novel and green synthesis procedure for sulfonamides that involved the immobilization of Trametes Versicolor laccase onto the Fe3O4&ndash, graphene nanocomposite via glutaraldehyde (GA) crosslinking (Lac/Fe3O4/GO). Various parameters, mainly, activation time, GA, and laccase concentration were investigated and optimized. The results showed that the optimal contact time was 4 h, GA concentration was 5% while laccase concentration was 5 mg&middot, mL&minus, 1, at which a high enzyme activity recovery was achieved (86%). In terms of the stability of immobilized laccase to temperature and storage conditions, the performance of the nanobiocatalyst was found to significantly exceed that of free laccase. The results have indicated that nearly 70% of relative activity for immobilized laccase remained after the incubation period of 2 h at 55 &deg, C, but only 48% of free laccase remained within the same time period. Moreover, the immobilized laccase retained 88% of its initial activity after storage for 20 days. In case of the free laccase, the activity retained within the same time period was 32%. In addition, the nanobiocatalyst possessed better recycling performance as evidenced from the observation that after eight cycles of repeated use, it retained 85% of its original activity.

The extraction of valuable target ions through monovalent cation exchange membranes (MCEMs) has been increasingly attracting in modern energy and environmental fields. However, the separation performance of MCEMs in terms of the permselectivity and cation fluxes, is typically restricted by membrane architecture and applied materials. Recently, mussel-inspired surface modification methods have been deployed in new membrane fabrications with special surface characteristics and functions. Herein, a facile layer-by-layer assembly method was designed to construct a series of de novo positively-charged tannic acid/polyethyleneimine (TA/PEI) membranes containing a negatively-charged support membrane and a TA/PEI selective layer. Notably, the peculiar support membrane with a much dense structure and abundant cation exchange groups can enable our TA/PEI membranes to possess high total cation fluxes. The selective layer with vast positive charges ensures mussel-inspired TA/PEI assembled positively-charged membranes to have a high permselectivity. Most importantly, compared with the separation performance of the state-of-the-art MCEMs, the superior separation performance of our developed new MCEMs at 5 mA·cm