Acid mine drainage (AMD) has long been a significant environmental problem that impairs water resources in historic or current mining industries throughout the world. One of the methods using passive treatment system at low cost to remove metals from solution involves the use of clays. The ability of three different adsorbents (montmorillonite K-10, bentonite (NT-25), and hydrotalcite (HT)) to remove Fe and Mn from aqueous solutions and acid mine drainage samples has been studied at different optimized conditions such as pH, amount of adsorbent and contact time. Flame atomic absorption spectrometer (FAAS) was used for measuring Fe and Mn concentrations. Langmuir and Freundlich isotherms were applied and isotherm coefficients were computed. A kinectic study was also developed for HT using the first order, second order and intraparticle diffusion models. A great amount of clay (more than 100 mg) and also contact times higher than 60 min had also no influence in the adsorption capacity for all adsorbents. HT was found to be the best among the studied clays removing more than 90 % of Fe and Mn for all AMD samples investigated. Moreover, the maximum adsorption capacity was 63.7 mg Mn g⁻¹ HT and 666.7 mg Fe g⁻¹ HT.

This study aimed to chemically and radiologically characterize the water resources influenced by a phosphogypsum stack in Imbituba, SC, Brazil and to identify the annual intake by ingestion. Surface water was collected at six points downstream of the phosphogypsum stack. Subsurface water samples were collected from a piezometer in the stack area. These samples were analyzed using a radiochemical method to determine the natural radionuclide content and an inductively coupled plasma optical emission spectrometry to determine the concentration of selected metals. The concentrations of radionuclides were also compared with current standards. The radionuclide concentrations in the surface waters samples were lower or similar to those found in other studies. The effective dose resulting from water ingestion is below the recommended reference levels for drinking water. Samples collected exhibited no increase in radioactivity, under the influence of phosphogypsum stacks.

Twenty-one plant leaf materials were screened for benzene adsorption efficiency in the static system, and the leaf material from Dieffenbachia picta, Acrostichum aureum, Ficus religiosa, Lagerstroemia macrocarpa, Alstonia scholaris, and Dracaena sanderiana were found to have high potential for benzene removal. The relation between quantity and composition of wax to benzene removal efficiency was studied. Although high quantities of wax occurred in some leaf materials, low benzene removal was clearly found if compared with other plant materials with the same wax quantity. Alpha-linoleic acid and dodecyl cyclohexane were found to be the main composition in plant leaf materials with high benzene adsorption, and it might be a key factor for benzene removal.

Measurements of solute dispersion in porous media is generally much more time consuming than gas dispersion measurements performed under equivalent conditions. Significant time savings may therefore, be achieved if solute dispersion coefficients can be estimated based on measured gas dispersion data. This paper evaluates the possibility for estimating solute dispersion based on gas dispersion measurements. Breakthrough measurements were carried out at different fluid velocities (covering the same range in Reynolds number), using O₂ and NaCl as gas and solute tracers, respectively. Three different, granular porous materials were used: (1) crushed granite (very angular particles), (2) gravel (particles of intermediate roundness) and (3) Leca® (almost spherical particles). For each material, 21 different particle size fractions were used. Gas and solute dispersion coefficients were determined by fitting the advection–dispersion equation to the measured breakthrough curves and in turn used to calculate gas and solute dispersivities as a function of mean particle size (D ₘ) and particle size range (R) for the 63 particle size fractions considered. The results show that solute and gas dispersivities are related and that their ratio depends on both R and D ₘ. Based on these observations a simple model for predicting the dispersivity ratio from D ₘ and R, was proposed.

In Asturias (north of Spain), mercury mining has been identified as a potential source of trace elements such as As, Sb, Pb, and Hg. In particular, at Los Rueldos mine site, some of these contaminants are dissolved in acidic mine drainage (AMD). Here we treated this leachate by means of nanofiltration to remove some of its pollutants. In order to improve our understanding of the geochemical factors involved in nanofiltration, we analyzed sediment geochemistry and the origin of acidic waters. In coherence with the observation of similar behaviors of As, Fe, and Al in the nanofiltration tests, a clear geochemical association between As, Sb, S, and Fe both in sediments and in the occurrence of AMD was detected. The FILMTEC™ NF-2540 membrane used in this study proved to be highly suitable for the treatment and concentration of the metallic and semimetallic contaminants in the acidic water, even at low pH and moderate pressures.

The comparative and competitive adsorption of Cr(VI) and Ni(II) in single and binary systems using coconut shell activated carbon (CSAC) was investigated. The CSAC was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM). The effects of pH, initial metal concentration, and temperature on the adsorption of metal ions were studied. Cr(VI) removal was found to be maximum (94.5 %) at pH = 2.0. While, Ni(II) removal was found to be maximum at pH = 9.0 (58.92 %). The adsorption capacity of Cr(VI) was greater than that of Ni(II) in single component system. Parameters of adsorption isotherm model, kinetics, and thermodynamics were calculated. The single ion equilibrium adsorption data were fitted to the Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models. The Langmuir and Freundlich models represented the equilibrium data better than the D-R model. The result of the fitting of D-R isotherm model indicated a physical adsorption process. The adsorption kinetic data of Cr(VI) and Ni(II) were found fitting well in pseudo second-order equation both in single and binary system (r 2 > 0.99) and intraparticle diffusion was the rate controlling step. The negative ΔG and the positive ΔH indicated the spontaneous and endothermic nature of the adsorption process. The extended Langmuir isotherm model fitted well with the competitive adsorption data of Cr(VI) and Ni(II). For the desorption experiments, EDTA showed the maximum desorption efficiency of 69 % for Cr(VI) and 81 % for Ni(II). © 2013 Springer Science+Business Media Dordrecht.

Ammonia emission from broiler houses is a major concern because of its impacts on the environment. To reduce ammonia emissions, it is necessary to understand the fate of ammonia/um in the broiler waste. In broiler waste, uric acid and urea hydrolyze to ammonia (NH₃) and a fraction of NH₃ converts to ammonium (NH₄ ⁺) depending on pH and temperature. Further, NH₄ ⁺ undergoes solid–liquid partitioning and the ammonia fraction is partitioned among the solid, liquid, and gas phases in the waste. Ammonium partitioning between solid and liquid phases in broiler cake and litter were measured at pH of 4, 6, and 7. Ammonium adsorption increased with pH in both broiler litter and cake. Adsorption capacity of the litter was much lower than broiler cake. Six NH₄ ⁺ adsorption/desorption isotherms (linear, Langmuir, Freundlich, Temkin, Redlich–Peterson, and Toth) were evaluated. The isotherm that provided the best fit for partitioning NH₄ ⁺ in litter or cake for each pH value was selected by comparing up to six sets of parameters modeled using linear and nonlinear (with five error functions) regressions. Despite high R ² values obtained using linear regression, linearizing the models introduced an offset into the model reducing their accuracy. The sum of normalized error was used to select the most suitable parameter set for each isotherm. While the nonlinear error functions were the more suitable for developing parameter sets in broiler litter, for cake, linear regression generally provided the most optimum parameter sets. Whereas the Freundlich, linear, and Temkin isotherms were the most suitable for broiler litter for pH of 4, 6, and 7, respectively, for the cake, the linear isotherm was the most suitable for the entire range of pH evaluated. Overall, due to its simplicity, the linear isotherm seems suitable for partitioning NH₄ ⁺ in the adsorbed and dissolved phases for simulating nitrogen fate and dynamics in broiler waste more accurately.

The processes of wind erosion of fertile soil, dune movement in sand deserts, dust storms in arid and semi-arid regions, as well as the emission and dispersion of agricultural or industrial dusts create a lot of problems and dangers for human life, environment, and infrastructure. Conventional ways to suppress dust emission to the atmosphere are agricultural fixation in the case of fertile soil surface and application of chemical agents to immobilize dust particulates onto the surface of soil, desert sand, country roads, or mining areas. However, these methods are often too expensive to be applied for large-scale suppression of sand dust. Chemical methods of dust suppression are often environmentally unfriendly due to the release of toxic reagents in water, air, and soil. This paper examines, for the first time, the microbially mediated aggregation of fine sand particles to suppress the emission of sand dust and its chemical and bacteriological pollutants. The bioaggregation reagent was a solution of calcium chloride and urea sprayed over the sand surface, which was preliminarily treated with the suspension of urease-producing bacteria. Quantity of calcium used for sand dust suppression was 15.6 g of Ca/m2. After the biotreatment of fine sand, the release of sand dust and its artificial pollutants to the atmosphere decreased in comparison with control by 99.8 % for dust, 92.7 % for phenantherene, 94.4 % for led nitrate, and 99.8 % for bacterial cells of Bacillus megaterium. This immobilization of dust and dust pollutants was due to the bioaggregation of fine sand particles. The sizes of 90 % of the sand dust particles increased from 29 μm in control to 181 μm after bioaggregation. Bioaggregation treatment of the soil surface could be a useful method to prevent the dispersion of dust and dust-associated chemical and bacteriological pollutants in water, air, and soil. © 2013 Springer Science+Business Media Dordrecht.

Although Cd concentrations in uncontaminated soils are usually low, pollution of soils by Cd from different sources of contamination pose problems. The application of soil amendments to increase plant production has been used as a viable alternative for recovery of soils contaminated with Cd. However, emphasis needs to be placed on the nature of Cd sorption processes in order that the amendments can be managed appropriately. A range of materials including vermicompost, sugarcane filter cake, palm kernel pie, lime, phosphate rock, and zeolite were used for the sorption studies. Total and nonspecific Cd sorption was estimated by batch experiments, and specific sorption was obtained by the difference between the former and the latter. Best adsorbents for specific Cd sorption from soil amendments were lime and zeolite. Langmuir adsorption isotherms fitted reasonably well in the experimental data, and their constants were evaluated, with R ² values from 0.80 to 0.99. The maximum adsorption capacity of Cd(II) was higher for mineral amendments than for organic amendments and ranged from 0.89 to 10.86 g kg⁻¹. The small value (0.08 L mg⁻¹) of the constant related to the energy of adsorption indicated that Cd was bound weakly to the palm kernel pie. Thermodynamic parameter, the Gibbs free energy, was calculated for each system, and the negative values obtained confirm that the adsorption processes were spontaneous. The values of separation factor, R L, which has been used to predict affinity between adsorbate and adsorbent were between 0 and 1, indicating that sorption was very favorable for Cd(II).