TiO₂-graphene (TiO₂-GR) composites were successfully prepared by a two-step solvothermal method using titanium dioxide and natural graphite powder. X-ray diffraction (XRD) patterns showed that graphene oxide (GO) was prepared from natural flake graphite by a modified hydrothermal pressurized oxidation method. The results of Fourier transform infrared spectroscopy (FTIR) proved that TiO₂-GR composites were synthesized during the process of hydrothermal reaction while GO was changed into graphene. X-ray photoelectron spectroscopy (XPS) demonstrated that TiO₂ particles contacted closely with graphene via Ti–O–C bonds. The results of Raman spectra confirmed the existence of graphene in the TiO₂-GR composite. Scanning electron microscopy (SEM) images showed that TiO₂ particles were oval and grafted on the graphene sheet which was smooth with ripples. UV-visible diffuse reflectance spectra demonstrated that there was a red shift in the absorption edge of TiO₂-GR composite. The experimental results indicated that the TiO₂-GR composite had significantly adsorption-photocatalytic activity for the degradation of methylene blue (MB) dyes. The adsorption capacity (q ₘₐₓ) of TiO₂-6%GR-4h for MB was 41.32 mg ⋅ g⁻ ¹ calculated based on the Langmuir adsorption model, which was about 3.3 times the adsorption capacity of TiO₂. Adsorption kinetics studies showed that the adsorption process fit well with the pseudo-second-order model. It proved that the TiO₂-GR composites were more efficient than the pure TiO₂ in the field of environmental protection.

As increased greenhouse gas concentrations (GHG: N₂O, CO₂, CH₄) in our atmosphere remain a major concern, better quantifying GHG fluxes from natural systems is essential. In this study, we investigate GHG concentrations in saturated riparian sediments (dry, wet, mucky), streambed hyporheic zone sediments (pools, riffles), and stream water in a New York mountain stream for summer baseflow conditions, and attempt to identify the primary drivers (e.g., DO, DOC, NO₃⁻, and NH₄⁺, temp) of GHG concentrations at these locations. Although DO, DOC, NO₃⁻, and NH₄⁺ concentration patterns certainly explained some of the observed trends, the overall differences in GHG abundance in riparian water vs. hyporheic pool water vs. hyporheic riffle water strongly suggest that water velocity/mixing with the atmosphere is a key control on GHG concentration across locations. When all floodplain locations are considered, in-stream pools are hot spots of CO₂ and CH₄ concentrations relative to other in-stream locations. On the other hand, riparian areas are hot spots of CH₄ and CO₂ concentrations relative to stream locations. No clear patterns are observed for N₂O.

Herbaspirillum chlorophenolicum strain FA1, a gram-negative bacterium isolated from activated sludge, was found to be able to use pyrene as sole carbon and energy sources. During biodegradation, the contribution of biosorption to the whole pyrene removal mattered in the early reaction stage, and biodegradation was the predominant process. Pyrene biodegradation was significantly enhanced with the presence of a typical carboxylated aromatic metabolite (phthalic acid) at concentrations of 30–50 mg l⁻¹, and the metabolite itself could also be efficiently biodegraded. For the purpose of practical application, immobilization of strain FA1 was carried out, and polyvinyl alcohol (PVA)-diatomite carrier by chemical method was proved to be the most efficient, with a PYR biodegradation of 92.8 % in 10 days. Investigation on the pyrene biodegradation kinetics by both free and immobilized cells showed that the experimental data fitted well to the first-order kinetic model. Besides, the PVA-diatomite carrier (chemical method) could be reused in at least eight consecutive biodegradation processes of PYR without any significant decrease in biodegradation efficiency. Further storage stability tests revealed that the ability to degrade pyrene using immobilized cells remained stable after storage at 4 °C for 45 days. Moreover, strain FA1 exhibited a relative broad substrate profile, including naphthalene, fluorene, phenanthrene, anthracene, fluoranthene, benzo[b]fluoranthene, benzene, toluene, and Tween 80. Taken together, results indicate that strain FA1 might be high potential in the development of treatment technologies for PAHs contamination.

Selenium (Se) has long been known as an effective antagonist for counteracting mercury (Hg) and arsenic (As) toxicity in many animal and plant species. This study is the first to assess a low-dose Se additive as an in situ remediation tool for As- and Hg-contaminated gold mine tailing material. Mine tailing material from an 1860s gold mine stamp mill site was treated with different concentrations of sodium selenite (0, 0.5, 1, 3, 8, and 15 mg Se/kg). Reclamation grass seeds planted in each treatment showed significantly decreased plant toxicity with increasing [Se], as measured by increases in biomass, % emergence, and root lengths. Leachate was collected from each pot after the grass was harvested. The lowest Hg and As concentrations measured in the leachate were associated with the 1 mg Se/kg treatment (94 and 71 % lower than concentrations in leachate from untreated tailing material) and increased with lower and higher Se treatments. Finally, earthworms (Eisenia andrei) were introduced to the experimental treatments. Earthworm [Hg] decreased with increasing [Se], but this effect was confounded by differing [Hg] in the tailing material. Earthworm [As] decreased with [Se] up to 3 mg Se/kg, then earthworm [As] increased with tailing [Se]. This experiment confirms that low-dose selenium additions (up to 3 mg Se/kg tailing material) can have beneficial effects by limiting toxicity and mobility of As and Hg from the tailing material for both grass and earthworms.

Within the last few years, the presence of bentazone herbicide has been observed in many water resources. For the first time, removal of bentazone using mesoporous silica was investigated revealing reversible adsorption. The adsorption isotherm was well described using the Freundlich model. The affinity towards bentazone is strongly affected by pH in the range of 2–7, decreasing with the increase of the pH, becoming negligible at the neutrality. Regeneration of the adsorbent was possible, and a recovery as high as 70 % was obtained using CH₃OH-NaOH solution. Furthermore, appreciable recovery (47 %) was also obtained using water. Applications on the purification of lake water and wastewaters, both characterized by a significant organic carbon load, spiked with 2 mg L⁻¹ bentazone were tested, observing removal yields in the range of 61–73 %. Taking advantage of the fast adsorption kinetics observed, an in-flow purification treatment was set-up, with quantitative removal of bentazone from polluted water.

The development of shirasu balloons (SB) modified with polydopamine (PDA) has been conducted. The aim of this research is to increase the performance of shirasu balloons in the adsorption of methylene blue (MB). The SB modified with PDA (SB/PDA) was prepared by immersing SB in the dopamine solution in the aerobic alkaline condition. The prepared material was characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS), specific surface area N₂ sorption, and zeta potential analysis. The adsorption behavior of SB and SB/PDA was investigated by studying the effect of the pH, adsorption kinetics, and effect of salt concentration. The adsorption kinetics of SB before and after modification was analyzed using two kinetics models, i.e., pseudo-first order and pseudo-second order. The adsorption isotherm was analyzed using Langmuir and Freundlich models. The adsorption study results showed that the adsorption isotherm fitted to Langmuir isotherm with a maximum capacity that could reach up to 26.17 mg g⁻¹ for SB and 36.23 mg g⁻¹ for SB/PDA. The adsorption kinetics showed that adsorption behavior followed the pseudo-second-order kinetic model and the equilibrium time for each material can be obtained at 5 min shaking time.

Textile wastewater was treated by adsorption in batch and column systems using electrochemically modified montmorillonite clay and activated carbon. Textile wastewater was obtained from a denim manufacturing process; according to the characterization of wastewater, non-biodegradable organic matter was found and it limits the application of biological treatments, and then an alternative method was evaluated. The adsorption process was performed with natural and modified materials; iron-modified montmorillonite was prepared at pH 7 using iron electrodes and activated carbon was treated with copper electrodes at pH 2, and 10–12 % of iron and copper respectively were found in the modified materials. Adsorption kinetics and isotherms of chemical oxygen demand (COD), color, and total organic carbon (TOC) were evaluated; the adsorption capacities for color were 50, 37, and 44 U PtCo/g for natural clay, activated carbon, and iron-modified clay, respectively. Adsorption kinetics of COD, color, and TOC data were best adjusted to Elovich model and isotherms data to Freundlich model, indicating chemisorption on heterogeneous materials. The regeneration of materials was performed in the presence and absence of hydrogen peroxide. Continuous systems were evaluated for color and TOC. Fe-modified clay was the best adsorbent, and data were best adjusted to Thomas and Yoon-Nelson models.

The aim of this study was to investigate the presence of metal contamination in water, sediments and three different fish species. All samples were taken from the Danube River in Belgrade Region, a location upstream from Grocka. Concentrations of Cd, Hg and Pb in water samples were not detected, while concentrations of Zn, Fe, Cu and As were in the range of 0.004–0.41 mg L⁻¹. Iron was the most deposited metal in sediment samples (17,530.00 mg kg⁻¹). For the purpose of heavy metal determination in fish tissue, silver carp, common carp and wels catfish were collected. Concentrations of Pb, Cd and As were determined in muscle, digestive tract and liver by inductively coupled plasma-optical emission spectrophotometry (IPC-OES). The highest concentration of Pb was in the digestive tract of all three fish species, while Cd was mostly deposited in the liver. The highest concentration of Hg was in the muscle tissue of wels catfish, and these values are above the maximum residual levels prescribed by the European Union and the maximum allowed concentrations (MACs) for Serbia. Concentration of As was mostly deposited in the liver, but under the MAC.

This study aims to evaluate a new biosorbent derived from co-composting eggshell with other organic materials (potato peels, grass clipping, and rice husk) for uptaking Pb(II) from an aqueous medium. This biosorbent contains a high amount of eggshell (30 % w/w; CES) and its performance was compared to mature compost without eggshell (CWES) and natural eggshell (ES). Sorption kinetics and equilibrium data were fitted to pseudo-second-order and Langmuir models, respectively. From a kinetic point of view, lead sorption into CES was fast, attaining equilibrium within less than 180 min. Batch experiments indicated that maximum sorption capacity of Pb into CES is 23 mg g⁻¹. The sorption capacity of CES was not significantly dependent on pH within the range of 2–5.5. In comparison to ES, organic matter of CES provided supplementary sites for lead sorption and an increase of 43 % in the sorption capacity was observed. Nevertheless, CWES was the biosorbent with higher sorption capacity. Still, this study points out the potential of new use of CES as an effective biosorbent to lead removal from aqueous matrices.

Metals are significant environmental pollutants, and their toxicity is a problem for all living organisms. Indeed, aquatic plants are particularly sensitive to the excess of metal ions. Several researches report that aquatic plants exposed to metal-induced toxicity showed similar responses (e.g. inhibition of growth and induction of oxidative stress). Meanwhile, many studies were involved to counter these toxicities. This paper provides a brief review of the role of the exogenous supply of some compounds in the alleviation or reduction of toxicity in aquatic plants generated by metals. Particular attention is given to the role of polyamine, proline, nitric oxide, glutathione and phytochelatin.