The main goal of this study was to explore the suitability and performance of bicomponent polymer membranes based on acrylonitrile copolymers-polyvinyl alcohol (PVA) mixtures and small quantities of anion (Purolite A100) or cation exchange resin (Purolite C150), prepared by phase inversion. Membranes were used for copper removal from synthetic wastewater solutions. A three detachable cylindrical compartment electrodialysis cell without recirculation of the electrolytes and synthetic solutions of various concentrations, similar to a copper electrowinning electrolyte, were used. The electrodialysis unit operates under galvanostatic control. The effect of pH on electrodialysis separation of Cu²⁺and on the solution conductivity has been also investigated. The laboratory electrodialysis cell performance was evaluated in terms of percent of extraction (pe) and current efficiency (ce). Experimental results showed that the ionic transfer in electrodialysis cell was especially affected by concentration. The highest values for the pe (>81 %) and the ce (>25 %) of copper ions were obtained at maximum concentration in copper ions (3 g/L), indicating a better performance of the ion extraction. The transport of copper ions was also correlated with flux data. The ion exchange membranes were characterized using FT-IR spectroscopy, ESEM, and electrochemical impedance spectroscopy.

The objective of this study was to compare the relative impact of humic and non-humic natural organic matter (NOM) on the aggregation behaviors of engineered TiO₂nanoparticles (nano-TiO₂). After exposure of nano-TiO₂to varying concentrations of Suwannee River fulvic acid (SRFA) and Bacillus subtilis exudate in high and low ionic strength (IS) solutions at pH 3 to pH 7.5, aggregation behaviors were evaluated via dynamic light scattering (DLS) measurements and sedimentation studies. Although pH, IS, and NOM concentration exerted strong controls on nano-TiO₂aggregation behaviors, suspensions exposed to either SRFA or bacterial exudate at normalized dissolved organic carbon (DOC) concentrations exhibited remarkably similar behaviors. In high IS systems, nano-TiO₂exposed to either SRFA or bacterial exudate sedimented rapidly, except in the presence of high NOM concentrations at pH 6 and 7.5. Low IS treatments exhibited a larger range of effects. In fact, relative to NOM-free controls, nano-TiO₂aggregates in SRFA and bacterial exudate exposures sedimented up to 14 times faster at pH 3 and up to 13 times slower at pH 7.5. Adsorption of organic molecules onto nano-TiO₂can enhance aggregation via colloidal bridging and/or charge neutralization, or with more complete surface coverage, can diminish aggregation via electrostatic repulsion and/or steric hindrance. Collectively, these data suggest that solution pH, IS, and NOM concentration, and to a lesser extent NOM origin, can control the fate and mobility of nano-TiO₂in geologic systems.

A method for simultaneous analysis of bisphenol A (BPA) and 17α-ethinylestradiol (EE2) in water supply was developed using solid-phase extraction and high-performance liquid chromatography with fluorescence detection. The linearity was evaluated between 2.5 and 200 μg L⁻¹(r> for the analytes. The limits of quantification were 1.5 and 2.1 ng L⁻¹for BPA and EE2, respectively. The extraction was made with C18 cartridges, and recoveries obtained varied between 70 and 102 % for the strengthening of 5 μg L⁻¹. After the validation, the method was applied in the determination of pollutants in surface water and water supply of Sao Luis, Brazil, where BPA was found in two of the eight samples analyzed, with concentrations of 1.11 and 3.61 μg L⁻¹.

Citrus peels were utilized for dynamic biosorption of Pb, Cd, and Zn from mono- and bi-component solutions in fixed-bed columns at feed concentrations of 0.1 meq/L. Uptake at breakthrough and saturation followed the order Zn < Cd < Pb in single-metal biosorption. An overshoot of the Zn or Cd effluent concentration was observed in Pb-Zn and Pb-Cd bimetal systems, where Pb displaced initially bound Zn and Cd. The desorption efficiency of the saturated column using 0.1 N nitric acid was 74 to 100 %, achieving a concentration factor (CF) of 34 to 129, based on the average desorbed metal concentration. The common practice of defining the concentration factor based on the peak concentration overestimates the CF value. Increasing Ca concentrations in Pb-Ca and Cd-Ca systems reduced target metal uptake, especially for Cd which had a lower affinity than Pb. Actual mining effluent was treated successfully. A sigmoid function was applied to describe experimental breakthrough data. A novel simple two-parameter model was introduced to simulate overshoot and desorption curves.

We analyzed, for the first time, the different fractions of metals present in the spent catalyst and changes they undergone during bioleaching and chemical leaching. Before bioleaching, Al (83.9 %) was found mainly in the residual fraction of the pretreated spent catalyst. Ni (61.3 %) was mainly present in the exchangeable fraction exhibiting its high environmental mobility. V (58.5) and Mo (49.3 %) mainly existed in the oxidizable fraction suggesting that highly oxidizing conditions would liberate these metals from the spent catalyst. During bioleaching with Acidithiobacillus thiooxidans, almost complete solubilization of the exchangeable as well as of reducible fraction was observed. Due to strong acidic conditions, part of oxidizable fraction of these metals was also solubilized. Bioleaching also affected the fractionation of metals remaining in the treated spent catalyst. At the end of the process, most of the metals remaining in the spent catalyst were found in the more stable fractions ensuring the safe disposal of spent catalyst. The leaching yields and fractionation behavior of metals during chemical leaching was found to be identical. The results of the present study strongly suggest that bioleaching is an effective method for removing metals from the spent catalyst.

Cadmium is a toxic element for living organisms. This metal causes different damages to the cell, generating oxidative stress. In order to elucidate cadmium tolerance mechanism and increase tomato plant tolerance by inoculating a Cd-tolerant Burkholderia strain, we analyzed malondialdehyde, hydrogen peroxide content, and the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), and glutathione S-transferase of two strains, one isolated from a soil contaminated with Cd (strain SCMS54) and the other from a soil without Cd (strain SNMS32). Strains SNMS32 and SCMS54 exhibited different SOD, CAT, and GR isoenzyme profiles in non-denaturing polyacrylamide gel electrophoresis analysis, with strain SCMS54 exhibiting an extra isoenzyme for all enzymes (Mn-SOD, CAT I, and GR IV, respectively). Despite accumulating more Cd, strain SCMS54 did not increase peroxide hydrogen and presented a fast antioxidant response (increasing SOD and CAT after 5 h of Cd exposure). In this way, strain SCMS54 exhibited a higher metabolic diversity and plasticity when compared to strain SNMS32, so it was selected for Cd–Burkholderia–tomato interaction studies. Inoculated tomato plants in the presence of Cd grew more than non-inoculated plants with Cd indicating that the SCMS54 increased tomato Cd tolerance. It appears that the strain isolated from Cd-contaminated soil (SCMS54) triggers a global stress response in tomato increasing plant tolerance, which may enable plants to be cultivated in Cd-contaminated soils.

The thiol-ene-based P(Penta3MP4/PEGDA/AAc) hydrogels were prepared by UV curing technique, then characterized and used as adsorbents for the investigation of the effect of process parameters such as pH of solution, contact time, and initial concentration of solution, on the removal of Ag(I) from aqueous solution. The results indicate that the adsorption of Ag(I) ions from aqueous solutions is strongly dependent on pH under experimental conditions. Both Langmuir and Freundlich isotherm models were applied to experimental data, and the results show that the adsorption process is well fitted to the Langmuir isotherm model. Selectivity, reusability, and applicability of hydrogels to radiographic film waste were investigated.

The samples of natural and iron-modified clinoptilolite (GC, Na-GC, Fe1-GC, and Fe2-GC) were assessed as adsorbent for arsenate removal by batch and column studies. The influences of retention time, pH, adsorbent dosage, and initial arsenate concentration on the arsenate adsorption efficiency were investigated. The experiments demonstrated that Fe1-GC has the highest arsenate removal efficiency with the adsorption capacity of 8.4 μg g⁻¹at equilibrium time of 60 min. Both the Fe1-GC and Fe2-GC removed arsenate effectively over the initial pH range 4–10. Adsorption capacity of Fe1-GC was adequately described by Freundlich isotherm. According to the results of the desorption performance experiments, the Fe1-GC was used six times until arsenic removal efficiency was reduced to 19 %. The adsorption percentage of arsenic increased with the diminish of initial concentration of arsenic and increase of adsorbent dose for all types of clinoptilolite. The column study demonstrated that Fe1-GC was achieved to reduce final arsenate of about 10 μg L⁻¹or below for up to 300 bed volumes in a continuous flow mode. The results of this study show that Fe1-GC can be used as an alternative adsorbent for arsenate removal.

A pilot-scale constructed wetland treatment system (CWTS) was designed and built to produce biogeochemical conditions promoting processes targeted for removal of arsenic from simulated Bangladesh groundwater. Two CWTS series were designed to promote coprecipitation and sorption of arsenic with iron oxyhydroxides under oxidizing conditions, and two series were designed to promote precipitation of arsenic sulfide and coprecipitation of arsenic with iron sulfide under reducing conditions. Arsenic removal performance was greater in series with oxidizing conditions than in series with reducing conditions (mean outflow concentrations of 64 and 108 μg L⁻¹, respectively). Additions of zero-valent iron (ZVI) to oxidizing series and to reducing series enhanced arsenic removal (mean removal efficiencies of 72 and 42 %, respectively) compared to unamended series (27 and 20 %, respectively). Arsenic removal performance was significantly greater (α = 0.05) in the oxidizing series amended with ZVI than in the other series, with removal extents, efficiencies, and rate coefficients ranging from 6 to 79 μg L⁻¹, 40 to 95 %, and 0.13 to 0.77 day⁻¹, respectively. Results from this pilot-scale study demonstrate that a CWTS can decrease concentrations of arsenic in arsenic-contaminated water to below the World Health Organization (WHO) drinking water quality guideline of 10 μg L⁻¹.

In this study, Scenedesmus quadricauda ABU12 was immobilized with sodium alginate to determine its potential for decolorizing indigo blue dye under different incubation conditions. The microalga was incubated at different pH (6.5–9.5), biomass concentrations (0.1–1.0 g l⁻¹), dye concentrations (12–75 mg l⁻¹) and temperatures (25–40°C). The concentration of biomass used significantly determined the rate of dye decolorization, as the lowest biomass concentration (0.10 g) was able to completely decolorize the dye by day 3, while the highest biomass concentration (1.00 g l⁻¹) attained 100 % decolorization on day 4. Neutral pHs supported the highest dye decolorization rates compared alkaline pHs. The rate of dye decolorization had a linear relationship with the concentration of the dye in solution as increasing dye concentration in the medium significantly reduced the rate of decolorization (p < 0.05). At 25°C, the rate of dye decolorization was consistently higher from day 2 to the end of the experiment. Infra-red analyses of the algal biomass and the dye solution was done in Kbr by pressing between flat aperture plates of sodium chloride and scanning from 4,000 to 625 cm⁻¹. This revealed the presence of functional groups associated with the biomass and dye that provided possible explanations for the decolorization of the dye under the different incubation conditions. These results showed that immobilized S. quadricauda is capable of decolorizing indigo blue dye at low biomass when immobilized with sodium alginate. However, this was dependent on the incubation temperature and dye concentration.