Increasing use of metal and metal oxide nanoparticles [Me(O)NPs] in products means many will inevitably find their way into marine systems. Their likely fate here is sedimentation following hetero-aggregation with natural organic matter and/or free anions, putting benthic, sediment-dwelling and filter feeding organisms most at risk. In marine systems, Me(O)NPs can absorb to micro-organisms with potential for trophic transfer following consumption. Filter feeders, especially bivalves, accumulate Me(O)NPs through trapping them in mucus prior to ingestion. Benthic in-fauna may directly ingest sedimented Me(O)NPs. In fish, uptake is principally via the gut following drinking, whilst Me(O)NPs caught in gill mucus may affect respiratory processes and ion transport. Currently, environmentally-realistic Me(O)NP concentrations are unlikely to cause significant adverse acute health problems, however sub-lethal effects e.g. oxidative stresses have been noted in many organisms, often deriving from dissolution of Ag, Cu or Zn ions, and this could result in chronic health impacts.

A total of 50 rainwater samples were analyzed in order to investigate trace elements in wet precipitation of Juiz de Fora City, during February, 2010 and February, 2011. Samples were analyzed for major cations (H3O+, Na+, NH4+, K+, Mg2+ and Ca2+) and anions (NO3−, SO42−, Cl− and HCO3−), hydrogen peroxide (H2O2), some trace metals (Cu2+, Zn2+, Cd2+ and Pb2+), as well as some other physicochemical aspects like pH, conductivity and redox potential. Rainwater pH mean was of 5.77 (±0.52). Cations and anions mean values ranged from 7.12μEq L−1 (K+) to 39.6μEq L−1 (Ca2+). Principal Component Analysis (PCA) with Varimax normalized rotation was performed, grouping the major analyzed cations and anions into different factors. Mg2+, K+, Ca2+ and HCO3− were assigned to soil contribution, Na+ and Cl− to sea–salt contribution and NO3−, SO42− and NH4+ to anthropogenic sources. Hydrogen peroxide average concentration was of 19.2±17.5μmol L−1 with higher values in summer and lower in spring and autumn, reverse case was observed for H3O+ levels. Zn2+ (7.31±2.74)μg L−1 and Cu2+ (4.07±0.74)μg L−1 were within the range of other studied areas, while Cd2+ and Pb2+ were below the detection limit.

Activated natural siderite (ANS) was used to investigate its characteristics and mechanisms of As(V) adsorption from aqueous solution. Batch tests were carried out to determine effects of contact time, initial As(V) concentration, temperature, pH, background electrolyte, and coexisting anions on As(V) adsorption. Arsenic(V) adsorption on ANS well-fitted pseudo-second-order kinetics. ANS showed a high-adsorption capacity of 2.19 mg/g estimated from Langmuir isotherm at 25 °C. Thermodynamic studies indicated that As(V) adsorption on ANS was spontaneous, favorable, and endothermic. ANS adsorbed As(V) efficiently in a relatively wide pH range between 2.0 and 10.0, although the removal efficiency was slightly higher in acidic conditions than that in basic conditions. Effects of background electrolyte and coexisting anions were not significant within the concentration ranges observed in high As groundwater. Results of XRD and Fe K-edge XANES analysis suggested ANS acted as an Fe(II)/(III) hybrid system, which was quite effective in adsorbing As from aqueous solution. There was no As redox transformation during adsorption, although Fe(II) oxidation occurred in the system. Two infrared bands at 787 and 872 cm⁻¹after As(V) adsorption suggested that As(V) should be predominantly adsorbed on ANS via inner-sphere bidendate binuclear surface complexes.

TiO₂-mediated photodegradation is widely reported to degrade recalcitrant pollutants such as nitrophenolics. This paper investigated the TiO₂-mediated photodegradation of trinitrophenol (TNP) in aqueous solution irradiated by an artificial light source. About 28.4 % TNP degradation was attained over 450 min from an initial TNP concentration of 1,000 mg L⁻¹. Ionic chromatographic analysis further revealed the evolution of nitrite and nitrate anions and an unknown intermediate X during the photodegradation process. The trends of nitrite and nitrate anions indicate that the photodegradation process produced nitrite at first, which subsequently turned to nitrate in the presence of oxygen. The removal rate of COD was far slower than that of TNP, inferring the photodegradation reaction gradually mineralized the parent pollutants. The photodegradation of TNP could not proceed under anaerobic condition, presumably a result of oxygen deficiency that disabled the denitration process. Because of the volumetric loss of the test solution, follow-up irradiations were performed after addition of supplementary water. This follow-up irradiation period revealed that direct photolysis, i.e., irradiation in the absence of TiO₂photocatalysts, could not photodegrade TNP but gradually diminish the component X.

Ion exchange processes are effective for the removal of arsenic (As) from drinking water. However, the As uptake capacity of ion exchange resins is affected by the presence of other anions such as sulphates and nitrates. As these ions are typically found in groundwater, the design of ion exchange process aimed at removing As from groundwater may be affected by their presence. Therefore, to properly design an ion exchange process for As removal, it is important to characterise the ion exchange equilibria of As in solution in the presence of competing anions. This paper was aimed at obtaining a deeper understanding of the binary equilibria of As(V)Cl⁻ and SO₄ ²⁻/Cl⁻ and of the ternary equilibria of As(V)/SO₄ ²⁻/Cl⁻. To this purpose, a series of batch tests were carried out at different values of the total solution normality. These data were combined with those obtained through continuous flow column tests performed to collect equilibrium data over the entire ionic fraction domain. The equilibrium data were then described using two different models based on the assumption of ideal behaviour of both the liquid and the adsorbed phases: in the first model the resin was considered to have only one type of binding-sites, where two types of binding sites were assumed by the second model, named double-selectivity model. Among these two models, the latter provided the best fitting of binary equilibrium data for both As chlorides and sulphate chlorides systems. However, the same model was unable to fit the experimental data of As in the ternary system As(V)/SO₄ ²⁻/Cl⁻ with a satisfactory agreement probably due to the presence of non-ideality which the model did not account for.

Phosphorus (P) release and flux at sediment-water interface was hypothesized to vary with studied catchment branches due to differences in water chemistry of recharging groundwater. Stream water, seepage water, groundwater, and resurgence groundwater were collected, and their dissolved reactive P (DRP) concentrations and related water chemistry variables (pH, dissolved oxygen, cations, and anions) were measured to identify P sources in seepage water and resurgence groundwater and to look into their impacts on stream water DRP. Results showed that the groundwater-carried P concentrations were negligible, and, thus, not a direct source of DRP to stream water. However, the upwelling groundwater could contribute to stream water DRP by dissolving calcite-bound P in top sediments of branch 15. The seepage experiment indicated that in branch14, sediment release of reducible P was minimal. Furthermore, the presence of impermeable clay layer over the streambed of branch 14 prevented the transport of water and nutrients from beneath sediments to stream water, further reducing the P flux across the sediment-water interface. This study revealed that in branch 14, the recharge of anoxic groundwater did not significantly influence stream water P, due directly to its low P concentration, or indirectly to the lack of reducible P and the poor hydrological connectivity in bottom sediments. These results showed that differences between P soluble concentrations in small catchment streams can be explained by physicochemical processes at the sediment-water interface. More investigation is needed to assess whole catchment P dynamics.

Pseudomorphs of barite (BaSO₄) and Cd-rich ZnS after whewellite (CaC₂O₄·H₂O) occur within remnants of Scots pine bark tissues in the peat layer of a poor fen located near a zinc smelter in south Poland. A two-step formation of the pseudomorphs is postulated based on SEM observations: (1) complete dissolution of whewellite, possibly caused by oxalotrophic bacteria, and (2) subsequent bacterially induced precipitation of barite and spheroidal aggregates of ZnS together with galena (PbS) in voids left by the dissolved whewellite crystals. Local increase in pH due to microbial degradation of whewellite, elevated concentrations of Zn(II) and Ba(II) in pore water due to the decomposition of atmospheric particles of sphalerite and barite in the acidic (pH 3.5–3.8) environment, oxidation of S species during drying and rewetting of the peat layer, and subsequent partial reduction of sulfate anions by sulfur-reducing bacteria were all factors likely involved in the crystallization of ZnS and barite in the microenvironment of the post-whewellite voids.

Peroxicoagulation treatment of aqueous solution containing hazardous dye, Rhodamine B, with commercially available graphite as cathode and iron as anode has been studied. The effect of various operational parameters such as solution pH, applied voltage, electrode area, other ions, etc. on the dye removal was investigated. The experimental result showed that pH-regulated peroxicoagulation system is an efficient process for the dye removal. Ninety-five percent of the dye was removed after 180 min of electrolysis. Anions such as carbonate, bicarbonate, chloride and sulphate negatively affected the efficiency of peroxicoagulation system. From the present study, it can be concluded that peroxicoagulation process is an efficient tool for dye removal from aqueous solution.

The objective of this work was to evaluate the efficiency of a solar TiO₂-assisted photocatalytic process on amoxicillin (AMX) degradation, an antibiotic widely used in human and veterinary medicine. Firstly, solar photolysis of AMX was compared with solar photocatalysis in a compound parabolic collectors pilot scale photoreactor to assess the amount of accumulated UV energy in the system (QUV) necessary to remove 20 mg L⁻¹AMX from aqueous solution and mineralize the intermediary by-products. Another experiment was also carried out to accurately follow the antibacterial activity against Escherichia coli DSM 1103 and Staphylococcus aureus DSM 1104 and mineralization of AMX by tracing the contents of dissolved organic carbon (DOC), low molecular weight carboxylate anions, and inorganic anions. Finally, the influence of individual inorganic ions on AMX photocatalytic degradation efficiency and the involvement of some reactive oxygen species were also assessed. Photolysis was shown to be completely ineffective, while only 3.1 kJUV L⁻¹was sufficient to fully degrade 20 mg L⁻¹AMX and remove 61 % of initial DOC content in the presence of the photocatalyst and sunlight. In the experiment with an initial AMX concentration of 40 mg L⁻¹, antibacterial activity of the solution was considerably reduced after elimination of AMX to levels below the respective detection limit. After 11.7 kJUV L⁻¹, DOC decreased by 71 %; 30 % of the AMX nitrogen was converted into ammonium and all sulfur compounds were converted into sulfate. A large percentage of the remaining DOC was in the form of low molecular weight carboxylic acids. Presence of phosphate ions promoted the removal of AMX from solution, while no sizeable effects on the kinetics were found for other inorganic ions. Although the AMX degradation was mainly attributed to hydroxyl radicals, singlet oxygen also plays an important role in AMX self-photosensitization under UV/visible solar light.

Biodegradation tests with bacteria from activated sludge revealed the probable persistence of cyano-based ionic liquid anions when these leave waste water treatment plants. A possible biological treatment using bacteria capable of biodegrading similar compounds, namely cyanide and cyano-complexes, was therefore examined. With these bacteria from the genera Cupriavidus, the ionic liquid anions B(CN)₄⁻, C(CN)₃⁻, N(CN)₂⁻combined with alkaline cations were tested in different growth media using ion chromatography for the examination of their primary biodegradability. However, no enhanced biodegradability of the tested cyano-based ionic liquids was observed. Therefore, an in vitro enzymatic hydrolysis test was additionally run showing that all tested ionic liquid (IL) anions can be hydrolysed to their corresponding amides by nitrile hydratase, but not by nitrilase under the experimental conditions. The biological stability of the cyano-based anions is an advantage in technological application, but the occurrence of enzymes that are able to hydrolyse the parent compound gives a new perspective on future cyano-based IL anion treatment.