Development of hydrophilic GO-ZnO/PES membranes for treatment of pharmaceutical wastewater.

Membrane application in water reclamation is challenged by fouling which deteriorates membrane performance in terms of permeate flux and solute rejection. Several studies focusing on antifouling membranes incorporated with nanoparticles have been carried out, but these membranes are not yet a viable solution due to their high energy requirements and inability to completely remove or degrade trace organic compounds (TOrCs). Therefore, this study aims at fabricating polyethersulfone (PES) membranes for treatment of pharmaceutical wastewater by using a unique membrane synthesis approach. PES membranes were synthesised by casting two different solutions before coagulation. Therefore, the synthesis technique was called 'double-casting phase inversion'. The membranes were impregnated with nanohybrid graphene oxide-zinc oxide (GO-ZnO) to increase their hydrophilicity, rejection of pharmaceuticals (by decreasing membrane-solute hydrophobic interactions), resistance to organic fouling and photodegradation properties. The addition of GO-ZnO increased membrane hydrophilicity and pure water permeability. The rejection of TOrCs and anti-fouling properties were also improved due to a reduction in membrane-solute and membrane-foulant hydrophobic interactions, respectively. In addition to improved TOrC rejection properties and resistance to fouling, GO-ZnO/PES membranes degraded Brilliant Black.

Photoelectrochemical oxidation of p-nitrophenol on an expanded graphite-TiO2 electrode.

In the quest for more efficient photoanodes in the photoelectrochemical oxidation processes for organic pollutant degradation and mineralisation in water treatment, we present the synthesis, characterisation and photoelectrochemical application of expanded graphite-TiO2 composite (EG-TiO2) prepared using the sol-gel method with organically modified silicate. The Brunauer-Emmett-Teller surface area analyser, ultraviolet-visible diffuse reflectance, scanning electron microscopy, energy dispersive spectroscopy, X-ray diffractometry, Raman spectrometry and X-ray photoelectron spectroscopy were employed for the characterisation of the composites. The applicability of the EG-TiO2 as photoanode material was investigated by the photoelectrochemical degradation of p-nitrophenol as a target pollutant in a 0.1 M Na2SO4 (pH 7) solution at a current density of 5 mA cm(-2). After optimising the TiO2 loading, initial p-nitrophenol concentration, pH and current density, a removal efficiency of 62% with an apparent kinetic rate constant of 10.4 × 10(-3) min(-1) was obtained for the photoelectrochemical process as compared to electrochemical oxidation and photolysis, where removal efficiencies of 6% and 24% were obtained respectively after 90 min. Furthermore, the EG-TiO2 electrode was able to withstand high current density due to its high stability. The EG-TiO2 electrode was also used to degrade 0.3 × 10(-4) M methylene blue and 0.1 × 10(-4) M Eosin Yellowish, leading to 94% and 47% removal efficiency within 120 reaction time. This confirms the suitability of the EG-TiO2 electrode to degrade other organic pollutants.

Prediction of metal-adsorption behaviour in the remediation of water contamination using indigenous microorganisms.

In recent years, the adsorption of heavy metal cations onto bacterial surfaces has been studied extensively. This paper reports the findings of a study conducted on the heavy metal ions found in mine effluents from a mining plant where Co(2+) and Ni(2+) bearing minerals are processed. Heavy metal ions are reported to be occasionally present in these mine effluents, and the proposed microbial sorption technique offers an acceptable solution for the removal of these heavy metals. The sorption affinity of microorganisms for metal ions can be used to select a suitable microbial sorbent for any particular bioremediation process. Interactions of heavy metal ions (Co(2+) and Ni(2+)) and light metal ions (Mg(2+) and Ca(2+)) with indigenous microbial cells (Brevundimonas spp., Bacillaceae bacteria and Pseudomonas aeruginosa) were investigated using the Langmuir adsorption isotherm, pseudo second-order reaction kinetics model and a binary-metal system. Equilibrium constants and adsorption capacities derived from these models allowed delineation of the effect of binding affinity and metal concentration ratios on the overall adsorption behaviour of microbial sorbents, as well as prediction of performance in bioremediation systems. Although microbial sorbents used in this study preferentially bind to heavy metal ions, it was observed that higher concentrations (>90 mg/ℓ) of light metal ions in multi-metal solutions inhibit the adsorption of heavy metal ions to the bacterial cell wall. However, the microbial sorbents reduced Ni(2+) levels in the mine-water used (93-100% Ni(2+) removal) to below the maximum acceptable limit of 350 µg/ℓ, established by the South African Bureau of Standards. Competition among metal ions for binding sites on the biomaterial surface can occur during the bioremediation process, but microbial sorption affinity for heavy metal ions can enhance their remediation in dilute (<5 mg/ℓ heavy metal) wastewaters.

The occurrence and exposure risk assessment of psychoactive drug residues and metabolites in aquatic environment.

Increased use of psychoactive drugs and their continuous release into the aquatic environment threatens the aquatic life, human and animal's life. As such this study was aimed at investigating the occurrence and the associated exposure human health risks of psychoactive drugs residues. The psychoactive drugs investigated include amphetamine, methylphenidate, heroin, cocaine and metabolites included are mainly morphine, 6-acetylmorphine and benzoylecgonine. Method for analyzing these drugs was optimized and validated using ultra-high-performance liquid chromatography coupled to quadrupole-time of flight mass spectrometer (UHPLC-QTOF-MS) after solid phase extraction (SPE) sample pretreatment. Analytes of interest were separated through Acquity UHPLC BEH C18 column at 20 °C. The recovery percentages for the target analytes ranged from 82 % (amphetamine) to 121 % (heroin). The accuracy assessed through bias calculation ranged from 80 % (amphetamine) - 123 % (amphetamine) and the precision reported as a percentage of error in relation to the theoretical concentration values was between 0.03 % (6-acetylmorphine) and 1.93 % (morphine). The limit of detection (LOD) and limit of quantification (LOQ) varied from 0.03 µg/L (amphetamine) - 0.11 µg/L (morphine) and 0.09 µg/L (amphetamine) - 0.36 µg/L (morphine) respectively. Further to this, this study evaluated the associated potential toxicities of these compounds. The toxicological effects were evaluated using the margin of exposure (MOE) risk assessment approaches. The MOE of all psychoactive drugs in wastewater (influent and effluent) was above 1000, suggesting lesser adverse effects and toxicity on human. However, MOE of less than 1000 (755.86 and 994.04) were observed for heroin in Florida lake and Florida stream, suggesting that heroin possess a significant health risk to human through possible drinking of such contaminated water.

Removal of lead (II) from aqeouos waste using (CD-PCL-TiO2) bio-nanocomposites.

Lead (Pb) pollution is our water system is a major concern, as this metal is toxic even at low concentration. This study aim to fabricate a bio-nanocomposite (cyclodextrin-polycaprolactone titanium dioxide) that will be used as an adsorbent for the removal of lead in aqueous waste. In this study, titanium dioxide was synthesized via sol-gel technique then incorporated in a polymer blend (CD-PCL) via solution blending method. The resulting bio-nanocomposites were characterized using Scanning Electron Microscopy (SEM), transmission electron microscope (TEM) and Brunauer Emmett and Teller (BET). The effect of how factors such as pH, concentration and adsorbent dose affect the removal efficiency of the bio-nanocomposites were studies. Maximum adsorption of lead obtained was 98% at pH 9.7, 10 ppm with 0.005 g dosage. Kinetic studies and adsorption isotherms were also investigated. The adsorption data fit Langmuir isotherm. Pb (II) obeyed pseudo-second order kinetics.

Dendrimers, mesoporous silicas and chitosan-based nanosorbents for the removal of heavy-metal ions: A review.

The application of nanomaterials as nanosorbents in solving environmental problems such as the removal of heavy metals from wastewater has received a lot of attention due to their unique physical and chemical properties. These properties make them more superior and useful in various fields than traditional adsorbents. The present mini-review focuses on the use of nanomaterials such as dendrimers, mesoporous silicas and chitosan nanosorbents in the treatment of wastewater contaminated with toxic heavy-metal ions. Recent advances in the fabrication of these nanoscale materials and processes for the removal of heavy-metal ions from drinking water and wastewater are highlighted, and in some cases their advantages and limitations are given. These next-generation adsorbents have been found to perform very well in environmental remediation and control of heavy-metal ions in wastewater. The main objective of this review is to provide up-to-date information on the research and development in this particular field and to give an account of the applications, advantages and limitations of these particular nanosorbents in the treatment of aqueous solutions contaminated with heavy-metal ions.

Preparation and use of maize tassels' activated carbon for the adsorption of phenolic compounds in environmental waste water samples.

The determination and remediation of three phenolic compounds bisphenol A (BPA), ortho-nitrophenol (o-NTP), parachlorophenol (PCP) in wastewater is reported. The analysis of these molecules in wastewater was done using gas chromatography (GC) × GC time-of-flight mass spectrometry while activated carbon derived from maize tassel was used as an adsorbent. During the experimental procedures, the effect of various parameters such as initial concentration, pH of sample solution, eluent volume, and sample volume on the removal efficiency with respect to the three phenolic compounds was studied. The results showed that maize tassel produced activated carbon (MTAC) cartridge packed solid-phase extraction (SPE) system was able to remove the phenolic compounds effectively (90.84-98.49%, 80.75-97.11%, and 78.27-97.08% for BPA, o-NTP, and PCP, respectively). The MTAC cartridge packed SPE sorbent performance was compared to commercially produced C18 SPE cartridges and found to be comparable. All the parameters investigated were found to have a notable influence on the adsorption efficiency of the phenolic compounds from wastewaters at different magnitudes.

Fabrication of photocatalyst based on Eu3+-doped ZnS-SiO2 and sodium alginate core shell nanocomposite.

This research paper reports the photocatalytic properties of Zn-SiO2-Eu3+ and sodium alginate (Alg) based nanocomposites for the degradation of indigo carmine dye. Initially, Eu3+ doped ZnS-SiO2 nanophorphor was synthesized and after that it was incorporated within the grafted crosslinked polymer matrix of Alg with acrylamide-co-acrylic acid in different concentrations. Synthesized materials were characterized using XRD, Raman spectroscopy, FTIR, SEM/EDX, TEM and UV-vis diffuse reflectance spectroscopy. XRD and TEM analyses confirmed the formation of nanoparticles as well as the uniform distribution of the nanoparticles within the polymer matrix. The UV-vis and UV-vis DRS spectral analysis indicated that Eu3+ doping causes a red-shift in the absorption band, resulting in the reduction in band gaps. The synergic effect of ZnS and Eu3+ in the SiO2 evidenced the photocatalytic performance of the catalyst. Alg-cl-poly(AAM-co-MAA)/ZnS-SiO2-Eu3+ nanocomposites were found to be very effective for the degradation of indigo carmine under visible light. Highest photocatalytic performance (93.4%) was shown by the nanocomposite with the 20% concentration of the nanoparticle after 5h. The photocatalytic activity was mainly attributed to the intense light absorption in the visible region and narrow band gap energy.

Synthesis and characterisation of Pd-modified N-doped TiO2 for photocatalytic degradation of natural organic matter (NOM) fractions.

INTRODUCTION: The removal of natural organic matter (NOM) from water is becoming increasingly important in order to prevent the formation of carcinogenic disinfection by-products. The inadequate removal of NOM has a bearing on the capacity of the other treatment processes to remove organic micro-pollutants or inorganic species that may be present in the water. New methods are therefore currently being sought to effectively characterise NOM and also to ensure that it is sufficiently removed from drinking water sources. METHODOLOGY: Nitrogen- and palladium-co-doped TiO(2) was synthesised by a modified sol-gel method and evaluated for its photocatalytic degradation activity on NOM fractions under simulated solar radiation. The photocatalyst was characterised by FT-IR, Raman, XRD, DRUV-vis, SEM, TEM, EDS, XPS and TGA. FT-IR confirmed the presence of OH groups on thermally stable, nearly spherical anatase nanoparticles with an average diameter of 20 nm. PdO species appeared on the surface of the TiO(2) as small uniformly dispersed particles (2 to 3 nm). A red shift in the absorption edge compared to commercial anatase TiO(2) was confirmed by DRUV-vis. In order to gain a better insight into the response of NOM to photodegradation, the NOM was divided into three different fractions based on its chemical nature. RESULTS AND DISCUSSION: Photodegradation efficiencies of 96, 38 and 15 % were realised for the hydrophobic, hydrophilic and transphilic NOM fractions, respectively. A reasonable mechanism was proposed to explain the photocatalytic degradation of the NOM fractions. The high photocatalytic activity could be attributed to the larger surface area, smaller crystalline size and synergistic effects of the co-dopants N and Pd in the TiO(2) crystal.

Synthesis and DNA binding studies of Ni(II), Co(II), Cu(II) and Zn(II) metal complexes of N1,N5-bis[pyridine-2-methylene]-thiocarbohydrazone Schiff-base ligand.

The thiocarbohydrazone Schiff-base ligand with a nitrogen and sulphur donor was synthesized through condensation of pyridine-2-carbaldehyde and thiocarbohydrazide. Schiff-base ligands have the ability to conjugate with metal salts. A series of metal complexes with a general formula [MCl2(H2L)]·nH2O (MNi, Co, Cu and Zn) were synthesized by forming complexes of the N1,N5-bis[pyridine-2-methylene]-thiocarbohydrazone (H2L) Schiff-base ligand. These metal complexes and ligand were characterized by using ultraviolet-visible (UV-Vis), Fourier Transform Infrared (FT-IR), 1H and 13C NMR spectroscopy and mass spectroscopy, physicochemical characterization, CHNS and conductivity. The biological activity of the synthesized ligand was investigated by using Escherichia coli DNA as target. The DNA interaction of the synthesized ligand and complexes on E. coli plasmid DNA was investigated in the aqueous medium by UV-Vis spectroscopy and the binding constant (Kb) was calculated. The DNA binding studies showed that the metal complexes had an improved interaction due to trans-geometrical isomers of the complexes than ligand isomers in cis-positions.