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The performance of reclamation cover systems could be affected by the colonization of plant roots, which may modify the hydrogeological properties of the construction materials. A four-year field investigation was conducted using six experimental cells with various soil layering designs over AMD-generating tailings reclaimed with an oxygen-barrier cover combined with an elevated water table. Both herbaceous and woody vegetation were installed on top of the cells to compare the influence on the properties of the cover material. Consecutive and undisturbed cores were collected from the cover's functional layer in 2020 and 2021, respectively. Root parameters, such as root length density, and hydrogeological properties were measured on the core samples to assess the possible relationships between the two categories of variables. Root observation trenches were also cut in each cell to better analyze the root density and occurrence profiles. Results showed that, within the four-year monitoring period of the study, both herbaceous and woody vegetation roots mostly colonized the top overburden layer of the cell (>86% visible roots) and barely occupied the functional layer of the reclamation cover (<10% visible roots). The observed maximum desorption rates for the functional layer were lower than the predicted values, which could be a short-term effect of the fine roots. No significant impact of roots on the main hydrogeological variables controlling the oxygen barrier efficiency were noted. At the end of the four-year study period, the hydrogeological behavior of the functional layer in all cells with/without vegetation/additional soil layers was found to be similar. [ABSTRACT FROM AUTHOR]

Clay-based masonry materials such as brick and tile constitute a significant part among construction and demolition debris. These bulky materials, if not reused or recycled, are mostly landfilled for disposal. In this study, three types of these waste materials including hand-made bricks (H-bricks), machine-made bricks (M-bricks), and ceramic tiles were employed and their capability for adsorption of Zn2+ was investigated through batch experiments. The characterization of the adsorbents was performed by using X-ray diffraction, X-ray fluorescence, optical microscopy, scanning electron microscopy imaging, and Brunauer-Emmett-Teller analysis. The effect of initial zinc concentration, contact time, solution pH, and adsorbent particle size on Zn2+ adsorption onto the adsorbents was studied. The results indicated that the removal efficiency is reduced by increasing initial zinc concentration. Furthermore, M-brick and tile showed better adsorption capacity for finer sizes, whereas uptake capacity of H-brick decreased by size reduction. Both linear and nonlinear regression were then applied to the data and revealed that adsorption onto M-brick followed Redlich-Peterson isotherm, whereas the data of H-brick and tile were best modeled by Koble-Corrigan isotherm. The maximum Zn2+adsorption capacities for M-brick, H-brick, and tile were obtained as 3.9, 2.45, and 1.76 mg g−1, respectively. Moreover, the kinetic data were modeled by using four well-known models. The adsorption kinetics of Zn2+ onto M-brick and tile was best represented by Elovich, and kinetic behavior of H-brick was found to obey the pseudo-second-order model. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 777-789, 2014 [ABSTRACT FROM AUTHOR]

Arsenic contamination in industrial and mining effluents has always been a serious concern. Recently, nano-sized iron particles have been proven effective in sorptive removal of arsenic, because of their unique surface characteristics. In this study, green synthesis of iron nanoparticles was performed using a mixed extract of two plant species, namely Prangos ferulacea and Teucrium polium, for the specific purpose of arsenic (III) removal from the aqueous environment. Results of UV-visible spectrometry, X-ray powder diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR) analyses confirmed the formation of iron nanoparticles from Prangos ferulacea (Pf) and Teucrium polium (Tp) extracts. The synthesized Fe nanoparticles morphology was studied via microscopy imaging. The particle size was 42 nm, as assessed by dynamic light scattering (DLS) analysis. Adsorption experiments were also designed and performed, which indicated 93.8% arsenic removal from the aqueous solution at 200 rpm agitation rate, 20 min agitation time, pH 6, initial concentration of 0.1 g/L, and adsorbent dosage of 2 g/L. Adsorption isotherm models were investigated, and the maximum uptake capacity was determined to be about 61.7 mg/g. The kinetic data were best represented by the pseudo-second kinetic model (R2 = 0.99). The negative value of Gibbs free energy, the enthalpy (−7.20 kJ/mol), and the entropy (−57 J/mol·K) revealed the spontaneous and exothermic nature of the adsorption process. Moreover, the small quantity of the activation energy confirmed the physical mechanism of arsenic adsorption onto iron nanoparticles and that the process is not temperature sensitive. [ABSTRACT FROM AUTHOR]

In this study, surface soils of the Bama Pb-Zn mine-impacted area were sampled for an area surrounding the mineral processing plant. After collecting 65 samples and analyzing them for initial Cu, Pb, Zn, and Cd metal contents, the area was zonated based on the concentration distribution using ordinary kriging in R. A single homogenous sample was prepared by mixing equal weights of each sample as being representative of the whole impacted area (S T ). Next, a synthetic model soil (S M ) was prepared according to the mean S T texture (S M ), divided into two portions, where one portion was amended with a biochar composite (10% w/w) (S MA ), both portions were artificially contaminated with Cu, Pb, Zn, and Cd (S MAC and S MC ). The mixed soil S T , and the model soils S MC and S MAC , were subjected to soil sequential extraction procedure to determine the variations in fractionation of heavy metals. Results showed that the fractionation in the unamended model soil (S MC ) was very close to the original real soil (S T ). Moreover, in both amended and unamended soils, Cd and Pb had the highest and the lowest mobility, respectively. Zn and Cu showed intermediate mobilities. The performance of the amendment was evaluated using a 150-day column leaching test taking leachate samples at designated time intervals, and Cu, Pb, Zn, and Cd concentrations were analyzed. Results of column leaching were in good agreement with the soil fractionation as Cd and Pb showed the highest and the lowest mobilities, respectively. Leaching through the soil column was also simulated by HP1 model. Results of simulation found in acceptable proximity to the experimental data despite remarkable differences due to limitations in defining soil to the simulation system.