A new cotton-based hydrogel nanocomposite was successfully prepared by free radical graft copolymerization of acrylamide (AAm) and acrylonitrile (AN) onto fabric followed by insertion of Ag nanoparticles. Ammonium persulfate (APS) was used as an initiator in the presence of a cross-linker, methylene bisacrylamide (MBA). Fourier transform infrared, thermogravimetric analysis, scanning electron microscopy, X-ray diffraction, and transmission electron microscopy were employed to confirm the structure of the hydrogel nanocomposite. Initially, the affecting variables onto graft polymerization (i.e. AAm, AN, MBA, APS, and silver concentrations) were systematically optimized to achieve a hydrogel with swelling capacity as high as possible. The resulted nanocomposite exhibits superhydrophilic and superhydrophobic properties. Therefore, the grafted fabric selectively separated water from oil/water mixtures with high separation efficiency. The influences of filter type, percentage of coated hydrogel on cotton, presence of silver nanoparticles, pH of solution, extracted oil type, as well as hydrogel nanocomposite on the separation efficiency of filters were also studied in detail. Moreover, pH of zero point charge (pHzₚc) of the hydrogel nanocomposite was determined by alkaline titration method, and a value of 6.5 was obtained.

The outstanding biological performance and non-food utilization of bioenergy grass possibly make it to be the best candidate for phytoremediation of heavy metal-contaminated soil, but evidence is limited. In this study, we conducted pot experiments to quantify the performance of two promising energy grasses, Arundo donax and Miscanthus sacchariflorus, in the phytoremediation of Zn- and Cr-contaminated soil. The results showed that (1) the biomass and root length of the two grasses were firstly increased and then kept stable or slightly decreased with increasing soil Zn/Cr concentration, implying that the two grasses had strong tolerance to Zn/Cr contamination; (2) the Zn/Cr concentration in the grass roots was two to seven times of that in the shoots, while both of them were positively correlated with the Zn/Cr concentration in soil; (3) the total accumulation of Zn/Cr in the grass (shoots + roots) was firstly determined by their concentration in the shoots and secondly determined by the shoots’ biomass, indicating that most of the Zn/Cr could be removed from contaminated soil by harvesting the aboveground parts; (4) the accumulating amount of the two grasses for Zn were 17.5 and 12.1 mg plant⁻¹, respectively; while the accumulating amount for Cr were 3.9 and 2.9 mg plant⁻¹, respectively. Taken together, the two energy grasses had strong tolerance and high accumulating ability for Zn/Cr, and therefore, they are promising candidates for the phytoremediation of Zn-/Cr-contaminated soil.

Poultry feed is often supplemented with low dosages of antibiotic to promote growth, making farms and animal processing facilities potential point sources of antibiotic-resistant fecal bacteria to aquatic ecosystems. In 2010 and 2011, we detected high concentrations of fecal indicator bacteria (FIB) in effluent released from a poultry processing plant into a headwater stream in Greenville, South Carolina. The FIB pollution became undetectable in 2012 with the plant under new management. To determine the plant’s impacts on the stream, we compared the genetic variations of Escherichia coli populations from upstream and downstream of the plant and from reference streams in the same watershed by classifying each isolate into an E. coli reference collection (ECOR) phylogenetic group. For tetracycline-resistant E. coli isolates, we analyzed the resistance genes, minimum inhibitory concentrations (MICs), gene transferability, and plasmid incompatibility groups (Inc). Distributions of ECOR groups upstream and downstream of the plant differed significantly in 2011 but not in 2012. The resistance genes tet(A) and tet(B) were prevalent, with tet(A) more likely to be found on the promiscuous IncP plasmid. A higher percentage of isolates having both tet(A) and tet(B) was found downstream in 2011 than in 2012. Dual-gene isolates did not have higher MICs than single-gene isolates but were more likely to transfer tet(A) on IncP. We propose that the processing plant acted not only as a point source of FIB but also as a factor influencing gene transferability. Additionally, given the results from 2012, the FIB impacts of the processing plant appeared to be reversible.

Sulfur hexafluoride (SF₆) has been evaluated by the Intergovernmental Panel on Climate Change (IPCC) as the substance with the highest global warming index. Because of its superior insulating and arc clearing capacities, it is commonly used as an insulator in electrical machines. SF₆waste products form in the process of storing, maintaining, and repairing the machines. SF₆emitted into the atmosphere remains for 3,200 years, causing global warming. Release into the mesosphere leads to photolysis and creation of highly toxic and corrosive by-products. A review of the literature related to the retrieval and separation of SF₆using a separating membrane indicates that research on the permeability of the separating membrane material is lacking. Additionally, research on the concentrations of the SF₆waste products and the separation/retrieval with operating conditions with optimal energy efficiency is only in the initial stages. Therefore, this research assessed the permeability of commercialized separation membranes polysulfone (PSf), polycarbonate (PC), and polyimide (PI) using the gases SF₆and N₂. Using an SF₆/N₂mixture with the same concentration as the SF₆waste products, we studied the separation and retrieval capacities of PSf, PC, and PI separation membranes under varying operating conditions. The permeability tests showed that the selective permeability of N₂/SF₆is highest for the PI membrane and lowest for the PC membrane. When the concentrations of SF₆retrieved from the mixture separation process were compared, the PC membrane was found to be the highest, with 95.6 % at 0.5 MPa. The retrieval percentage of SF₆was highest for PSf, with 97.8 % at an operating pressure of 0.3 MPa and a waste production of 150 cm³/min. The retrieval rates and retrieval failure rates have an inverse relationship. In total, 99 % of the supply of SF₆was identified via the retrieval rates and retrieval failure rates, so it could be confirmed that the separation of the SF₆/N₂mixture using a macromolecular hollow fiber separation membrane works properly.

The sulfate input and the occurrence of dryout and rewetting may promote the production of toxic methylmercury (MeHg) in a constructed wetland, Stormwater Treatment Area 2 (STA-2) in South Florida. Therefore, the aim of this study was to investigate the influences of inflow water quality, especially inflow sulfate, and the dryout and rewetting cycle on the mercury (Hg) methylation in three independent cells of STA-2 from 2000 to 2007. Because the majority of the total Hg (THg) bioaccumulated in fish is in MeHg form, THg concentration in mosquitofish was used to present the MeHg production in STA-2. Mosquitofish THg in Cells 1 and 2 (with median values of 0.101 and 0.02 mg/kg, respectively) were significantly higher than in Cell 3 and inflow (both with a median value of 0.01 mg/kg). The difference in mosquitofish THg among the three cells was likely a result of the drying and rewetting cycles occurred in Cells 1 and 2, which promoted the Hg methylation. Inflow sulfate, inorganic Hg, and chloride exhibited a significant correlation with mosquitofish THg in cells, suggesting that these inflow variables played important roles on the Hg methylation. The results indicate that inflow sulfate may likely stimulate sulfate-reducing bacteria and subsequently lead to produce MeHg in the three cells. Our findings in this study indicate that preventing the occurrence of dryout in wetland will help to decline the Hg methylation, and sulfate input is a key factor to influence the Hg methylation in wetland.

Aquatic weed Myriophyllum spicatum L. is one of the most invasive water plants known. In many countries, it is usually harvested and landfilled, where aerobic and anaerobic decomposition takes place. In this research, the kinetic, equilibrium, and desorption studies of biosorption of Pb(II), Cu(II), Cd(II), Ni(II), and Zn(II) ions onto compost of M. spicatum were investigated in batch experiments. Biosorbent was characterized by scaning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). SEM analysis showed that ion exchange between divalent cations Ca(II) and selected metals takes place. The results of FTIR exposed that carbonyl, carboxyl, hydroxyl, and phenyl groups are main binding sites for those heavy metal ions. The rate of adsorption of the five heavy metals was fast, which achieved equilibrium in 40 min, and followed the pseudo-second-order model well. Langmuir, Freundlich, and Sips equilibrium adsorption models were studied, and Sips isotherm gave the best fit for experimental data. Desorption by 0.1 M HNO₃did not fully recover the metals sorbed onto the compost, indicating that reusing this material as biosorbent is not possible. Furthermore, the use of spent biosorbent as a soil fertilizer is proposed.

Adsorption and degradation processes of triclosan (TCS) were studied in the laboratory using field-collected sediments of different physicochemical properties. Batch equilibrium experiment indicated that adsorption isotherms were fitted well to both linear and Freundlich model with linear sorption coefficients (K d) varied from 147 to 1,425 mL μg⁻¹. The sediment with a higher organic carbon content and a lower pH value had the greatest adsorption capability. Degradation experiment showed that triclosan was relatively stable in water with calculated half-life values ranged from 89 to 161 days. No degradation in sterilized water suggested that the loss of triclosan was due to biological processes. Degradation was more rapid in water-sediment system than in water, and the calculated half-life value in water-sediment systems ranged from 32 to 62 days. Methylation of triclosan was observed in all studied sediments, but the amount of methyl-triclosan (M-TCS) accounted for less than 5 % of the degradated TCS.

The coffee agro-industry generates a large volume of wastewater that is notable for its high organic strength as well as its color content. Due to the seasonal nature of the harvest (3–4 months per year), this particular industrial waste needs a treatment method that is both reliable and fast (in terms of start-up time). As part of investigating a system capable of treating a coffee wastewater, this research evaluated four electrochemical advanced oxidation processes (EAOPs) using boron-doped diamond (BDD) electrodes. The processes were anodic oxidation (AO), anodic oxidation with electrogenerated H₂O₂(AO-H₂O₂), electro-Fenton (EF), and photoelectro-Fenton (PEF). Experimental conditions were as follows: 40 mA cm⁻²current density (all EAOPs), 0.3 mmol Fe²⁺L⁻¹(Fenton systems), 300 mL air min⁻¹(AO-H₂O₂, EF, PEF), and 500 μW cm⁻²UV irradiation (photo-Fenton systems). The performance of the four EAOP treatment methods (in terms of color and organic carbon removal) was compared against two conventional chemical oxidation methods, namely, Fenton and photo-Fenton. The research indicated that the four EAOPs were better at removing color (89–93 %) and total organic carbon (TOC) (73–84 %) than the respective chemical Fenton (58 and 4.8 %) and photo-Fenton (61 and 7 %) methods. The trend in performance was as follows: AO-H₂O₂ > AO > PEF ≈ EF. It appeared that the ferrous iron reagent formed a dark-colored complex with some coffee components, diminishing the effect of Fenton reactions. In addition, the dark color of the wastewater limited the effect of light in the UV-Fenton processes. Analysis showed that acceptable levels of Fe²⁺(0.3 mmol L⁻¹) and energy (0.082–0.098 kWh g⁻¹TOC) were required by the EAOPs after 4-h treatment time. In conclusion, the use of electrochemical methods (equipped with BDD electrodes) seems a promising method for the effective treatment of coffee wastewaters.

Principal component analysis (PCA) was performed on chemical data of two sediment cores from an urban freshwater lake in Copenhagen, Denmark. X-ray fluorescence (XRF) core scanning provided the underlying datasets on 13 variables (Si, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Rb, Cd, and Pb). Principal component analysis helped to trace geochemical patterns and temporal trends in lake sedimentation. The PCA models explained more than 80 % of the original variation in the datasets using only two or three principal components. The first principal component (PC1) was mostly associated with geogenic elements (Si, K, Fe, Rb) and characterized the content of minerogenic material in the sediment. In the case of both cores, PC2 was a good descriptor emphasized as the contamination component. It showed strong linkages with heavy metals (Cu, Zn, Pb), disclosing changing heavy-metal contamination trends across different depths. The sediments featured a temporal association with contaminant dominance. Lead contamination was superseded by zinc within the compound pattern which was linked to changing contamination sources over time. Principal component analysis was useful to visualize and interpret geochemical XRF data while being a straightforward method to extract contamination patterns in the data associated with temporal elemental trends in lake sediments.

Textile industry is responsible for a large amount of polluted water released daily, mainly due to the dyes used. This article has aimed to study and improve methodologies for degrading textile effluents containing the dyes Acid Red 151 and Acid Blue 40 using an electrolytic reactor. Different solutions were prepared for the experiments in the electrolytic reactor with a 70 % TiO₂/30 % RuO₂anode. The textile effluents underwent 0 (control), 3, and 30 min treatment intervals. A suspension of Saccharomyces cerevisiae cells was used for toxicity tests and performed at the same day that samples were collected. The same test was applied to the samples after 15 days resting in order to verify changes in toxicity. The electrolytic treatment successfully removed the color in all effluents. However, the process efficiency varies according to the dye used and the experimental conditions, such as current and NaCl concentration. Also, it was observed that treatments longer than 30 min are very toxic to S. cerevisiae cells because of the high concentration of Cl₂.