We investigated the removal of metals from a circum-neutral mine discharge over a 0.5-km distance in a series of sequentially interconnected ponds from the exit of an 8-km tunnel that drains a gold mine. The geochemical and mineralogical processes controlling the evolution of metals in the drainage ponds were the focus of this research. We measured the pH and concentrations of dissolved inorganic carbon (DIC) and alkalinity in the aqueous phase and the concentrations of Ca, Mg, Na, Fe, K, Mn, Sr, and Zn in the aqueous phase and in sediments on the beds of the ponds. We calculated the saturated indices of metal oxides, metal carbonates, and the partition coefficients (D) for Mg, Sr, Mn, and Zn. The pH of the mine discharge increased while the concentrations of DIC and alkalinity decreased over the 0.5-km distance. The concentrations of Ca, Mg, Na, Fe, K, Mn, Sr, and Zn generally decreased while their concentrations in the sediment phase increased. Mineralogical and acid-base accounting and modeling results showed that all the metals in equilibrium with the aqueous phase were oversaturated, and the dominant mineral in the precipitated sediments was calcite. Forward geochemical modeling in combination with the Dₘg, DSᵣ, DMₙ, and DZₙ showed a low ionic strength solution indicating that these metals were removed from the mine discharge by adsorption and coprecipitation of calcites. Forward geochemical modeling results indicated that the groundwater exiting the tunnel had reached equilibrium with respect to ferrihydrite and goethite, suggesting that the precipitation of Fe-oxides were responsible for removing these metals from solution. Calcite precipitation removed about 16% of Ca²⁺, while 15% of Sr and 5% of Mg were scavenged from the mine water by coprecipitation with calcite and/or adsorption into calcite lattices. About 52% of total Fe from the mine water was scavenged through amorphous Fe(OH)₃ and goethite precipitation. About 23% of the Zn in the mine water was removed by sorption on Fe-oxides surfaces or coprecipitation with calcite, and 30% of the Mn in the mine water was removed by rhodochrosite precipitation and/or coprecipitation with calcite. Settling ponds, therefore, provide a framework where minerals precipitate, are adsorbed, or coprecipitated, such that mine water at acceptable contaminant level is released into the natural environment.

This study aims to assess interrelationships between serum lead (Pb), cadmium (Cd), arsenic (As), and mercury (Hg) concentrations in pregnant women in their third trimester and umbilical cord blood, while inter-metal correlations were also determined. This study is part of the PIPA project (Childhood and Environmental Pollutant Project), whose pilot study was carried out from October 2017 to August 2018 and will be presented here. Blood samples were obtained from 117 mother-umbilical cord pairs and analyzed concerning metal concentrations. A positive correlation was found between metal concentrations in mother and cord blood (R > 0.7, p < 0.001). The results indicate that mother metal concentrations are able to determine child metal concentrations (p < 0.001). The correlations between maternal blood metal concentrations were positive for all assessed metals except for As and Hg. The strongest correlations in this matrix were observed between Cd and Pb (R = 0.471 p = 0.000), Cd and Hg (R = 0.425 p = 0.000), and Pb and Hg (R = 0.427 p = 0.000). Umbilical cord correlations were lower compared to mother blood correlations. In general, the four analyzed metals displayed significant correlations to serum concentrations in both maternal and cord blood.

The optimisation tests of sodium percarbonate (biocide) with the formula 2Na₂CO₃·3H₂O₂, as a green oxidizing agent for biological deactivation of chicken manure, were carried out. The microbiological analysis of fresh manure which consisted of the enumeration of bacteria, fungi and eggs of intestinal parasites showed that the number of bacteria Enterobacteriaceae, i.e. 8.3 log₁₀CFU/g, and the bacteria E. coli, i.e. 6.96 log₁₀CFU/g, exceeded the required level in organic fertilizers. The Response Surface Methodology for three input parameters (biocide concentration, temperature and time) on the value of E. coli bacteria was applied. The obtained values of the coefficient of the multiple correlation R² and the adjusted coefficient Rₐdⱼ² were 0.90 and 0.75, respectively, which indicate a good fit of the data obtained with the model and the experimental data. It was concluded that a decrease in the count of the analysed microorganisms followed an increase in the sodium percarbonate concentration, an increase in the temperature and a longer time of contact of the manure sample with the biocide. The content of bioavailable macronutrients (P, N, Ca, Mg, K) in water extracts of fresh chicken manure before and after its biological deactivation was determined with the ICP-OES method. The concentration of phosphorous in fresh manure extract was 310 mg/l and decreased after addition of one of the following agents: 7.5 wt.% of sodium percarbonate to 66.9 mg/l or 3.0 wt.% of traditional hygienizing agent, i.e. calcium hydroxide to 5.7 mg/l.. The results of the concentration of N in chicken manure with sodium percarbonate was also higher than in sample with calcium hydroxide, i.e. 1040.0 mg/l and 860.0 mg/l, respectively. While the addition of 2Na₂CO₃·3H₂O₂ decreased the content of Ca, Mg and K in fresh chicken manure.

Surfactants are substances applicable in the removal of heavy metals from contaminated soil. This study aims to investigate the effects of surfactant mixtures, composed of nonionic, anionic, and cationic surfactants, on the removal efficiency of Cd and Zn by mixture design (MD). Central composite rotatable design (CCRD) was integrated to optimize the conditions of contaminated soil washing. However, as representatives of each type of surfactant, a single surfactant with the most effective Cd removal was selected for each type before MD and CCRD studies. Sodium dodecyl sulfate (SDS) and sodium laureth sulfate (SLES) were the most effective anionic surfactants, while dodecyl trimethyl ammonium bromide (DTAB) and polysorbate 80 (Tween 80) were chosen to represent cationic surfactants and nonionic surfactants, respectively. Two systems of SDS-DTAB-Tween 80 and SLES-DTAB-Tween 80 were studied to examine their roles in Cd and Zn removal by MD. The results indicate insignificant enhancement in mixed surfactant systems for Cd and Zn removal. DTAB was identified as an ineffective surfactant, but at present, the presence of Tween 80 in both systems compensated for the use of SDS and SLES. The system containing SLES was selected to study CCRD because of its low cost and biodegradation. Cd and Zn removal efficiencies were 45.2% and 47.7%, respectively, at 40 mmol/L of 5-mL SLES solution per gram of soil with a 200-rpm shaker speed for 8 h. The Cd concentration of treated soil met Thailand’s agricultural soil standard. However, the further increase in removal efficiency should be considered. Graphical Abstract

A series of Ho-modified Mn/Ti catalysts with various content of Ho were prepared by impregnation method, and the low-temperature catalytic performance was tested. Techniques of BET, SEM, XRD, H₂-TPR, and XPS were carried out to research the effects of Ho modification on the physicochemical properties of Mn/Ti catalysts. Results showed that appropriate Ho addition could reduce the starting temperature of Mn/TiO₂ catalyst to 100 °C. 0.2HoMn/Ti exhibiting a wider temperature range of 140~220 °C with nearing 100% NOₓ conversion. It was found that the 0.2HoMn/TiO₂ catalyst possessed a better dispersion of active component, enhanced redox capacity, a higher concentration of Mn⁴⁺ species, and a larger amount of Oᵦ content on the catalyst surface, which are all likely predominant factors related to the excellent SCR activity. Additionally, Ho improved the Lewis acid sites and enhanced the adsorption and activation ability of NH₃, as well as the NO to NO₂ oxidation ability. The selective catalytic reduction with ammonia (NH₃-SCR) deNOₓ mechanism over HoMn/Ti catalysts obeyed both the Eley–Rideal (E-R) and Langmuir–Hinshelwood (L-H) mechanisms under low-temperature reaction conditions.

Zeolitic imidazolate framework-8 (ZIF-8) has a sodalite topology. ZIF-8 is composed of zinc ion coordinated by four imidazolate rings. The pore aperture of ZIF-8 is 3.4 Å, which readily retains large gas molecules like N₂. In this work, mixed-matrix membranes (MMMs) have been fabricated by utilizing ZIF-8 and pristine cellulose acetate (CA) for O₂/N₂ separation. Membranes of pristine CA and MMMs of ZIF-8/CA at various ZIF-8 concentrations were prepared in tetrahydrofuran (THF). Permeation results of the fabricated membranes revealed increasing selectivity for O₂/N₂ with increasing pressure as well as ZIF-8/CA concentration up to 5% (w/w). The selectivity of O₂/N₂ increased 4 times for MMMs containing 5% (w/w) of ZIF-8/CA as compared with the pristine CA membrane. A thermodynamic model has also been developed to predict the permeability of gases through polymeric membranes. The results were compared with literature data as well as the pristine CA membrane produced in this work for model validation.

The drinking water treatment plant (DWTP) in L’Ampolla collects water from the River Ebro. The sludge generated during the water treatment processes applied accumulates some of the radionuclides present in the ingoing water. Gamma spectrometry measurements of the sludge were carried out monthly for a period of 17 years (2002–2018) to evaluate possible factors that might influence the radioactive content. These included the geology, river flow rate, suspended particulate matter, turbidity, water treatment processes, and industrial activities in the area of the river basin. The activity concentrations of ²¹⁴Pb, ²¹⁴Bi, ²²⁸Ac, ²²⁸Ra, and ²²⁶Ra from both the ²³⁸U and ²³²Th decay chains decreased significantly from 2012 onwards. This may be related to a change in the water treatment process in the L’Ampolla DWTP, and in particular, that potassium permanganate was no longer added to the raw water from 2011. Other isotopes such as ⁴⁰K, ⁷Be, and ²³⁴U/²³⁸U have not displayed the same behavior, which could support our hypothesis that the accumulation of radium isotopes in the sludge could be influenced by the use and nonuse of permanganate. A number of artificial radionuclides were also determined, which is consistent since L’Ampolla DWTP is located 70 km from a nuclear power plant, and the activities found for some of these radionuclides correlate with its annual liquid discharges into the river. The results therefore indicate that a relationship exists between the different factors in connection with the raw water and the radioactive content of the sludge generated by the plant under study.

Soil is the support medium for the development of several activities; however, improperly used soils can become a serious environmental issue. The aim of the current study is to determine the concentration of chemical elements in soil used as landfill in Southern Brazil. Samples were collected in different soil profiles and depths and analyzed based on the X-ray fluorescence technique. Results have indicated changes in cadmium and chromium concentrations, regardless of the collection depth. The presence of iron oxides/hydroxides and 1:1 low CEC kaolinite clay in the samples may have contributed to the translocation of these elements to the underground environment. Thus, the adopted technique was efficient and enabled identifying changes in the concentrations of the investigated elements, which can be associated with their translocation through soil profile (in depth), as well as in comparing such concentrations to the ones set by the current legislation.

Neurodegenerative disorders are commonly erratic influenced by various factors including lifestyle, environmental, and genetic factors. In recent observations, it has been hypothesized that exposure to various environmental factors enhances the risk of Alzheimer’s disease (AD). The exact etiology of Alzheimer’s disease is still unclear; however, the contribution of environmental factors in the pathology of AD is widely acknowledged. Based on the available literature, the review aims to culminate in the prospective correlation between the various environmental factors and AD. The prolonged exposure to the various well-known environmental factors including heavy metals, air pollutants (particulate matter), pesticides, nanoparticles containing metals, industrial chemicals results in accelerating the progression of AD. Common mechanisms have been documented in the field of environmental contaminants for enhancing amyloid-β (Aβ) peptide along with tau phosphorylation, resulting in the initiation of senile plaques and neurofibrillary tangles, which results in the death of neurons. This review offers a compilation of available data to support the long-suspected correlation between environmental risk factors and AD pathology. Graphical abstract .

Magnetic NiₓMgyZn₍₁₋ₓ₋y₎Fe₂O₄ nanoparticles were fabricated via the ethanol-assisted combustion process. The characterizations of the nanoparticles were illuminated by SEM, EDS, XRD, and VSM. The specific surface area and pore diameter distribution were measured by the Brunauer–Emmett–Teller (BET) measurement. Magnetic Ni₀.₄Mg₀.₃Zn₀.₃Fe₂O₄ nanoparticles calcined at 400 °C for 2 h with anhydrous ethanol of 20 mL were chosen to remove methyl blue (MB), and their adsorption performances for removal of MB from water environment were evaluated. Adsorption kinetics and adsorption isotherm experiments had been carried out; the adsorption mechanisms were well demonstrated by the pseudo-second-order kinetics model and Temkin isotherm model, respectively, which indicated that the removal of MB by Ni₀.₄Mg₀.₃Zn₀.₃Fe₂O₄ adsorbent was multimolecular layer chemisorption mechanism. The pH effect of the dye solutions was explored to reveal that the adsorption capacity remained a solidly high level when pH was above 5. After three times of recycling, the relative removal activity of MB onto the nanoparticles remained above 97.6% of its original removal activity. The adsorption process of MB removed by Ni₀.₄Mg₀.₃Zn₀.₃Fe₂O₄ adsorbent was further illuminated by cyclic voltammetry (CV) and electrochemical impedance spectra (EIS). Graphical Abstract Magnetic Ni₀.₄Mg₀.₃Zn₀.₃Fe₂O₄ nanoparticles were fabricated by the ethanol-assisted combustion method, and they were chosen to remove methyl blue. Adsorption experiments were performed, and the pseudo-second-order kinetics model and the Temkin isotherm model fitted well with the experimental data. When pH was above 5, the adsorption capacity remained at a solidly high level. After three times of recycling, the relative removal activity of the nanoparticles remained above 97.6% of its original removal activity. The adsorption process was further illuminated by CV and EIS.