Removal of Copper,Nickel and Zinc Ions from Aqueous Solution by Chitosan‐8‐Hydroxyquinoline Beads

In this work, 8‐hydroxyquinoline is used as the active sites in cross‐linked chitosan beads with epichlorohydrin (CT‐8HQ). The CT‐8HQ material was shaped in bead form and used for heavy metal removal from aqueous solution. The study was carried out at pH 5.0 with both batch and column methods and the maximum adsorption capacity of metal ions by the CT‐8HQ was attained in 4 h in the batch experiment. The adsorption capacity order was: Cu²⁺ > Ni²⁺ > Zn²⁺ for both mono‐ and multi‐component systems with batch conditions. From breakthrough curves with column conditions, the adsorption capacity followed the order Cu²⁺ > Zn²⁺ > Ni²⁺ for both mono‐ and multi‐component systems. The CT‐8HQ beads maintained good metal adsorption capacity for all five cycles with absorbent restoration achieved with the use of 1.0 mol L^–1 HCl solution, with 90% regeneration.     

Geochemical evolution of laterites from two areas of the semiarid region in Bahia State, Brazil

Lateritic covers developed during the Pleistocene in two distinct areas (Gentio do Ouro District and Sento Sé) of the State of Bahia, Brazil, have been investigated geochemically. Samples of the bedrock (gabbros, from the Gentio do Ouro District, and silicate facies iron formation and associated iron-rich banded carbonates, from the Sento Sé Area) and the lateritic products (latosols, cuirasses and pisolites) were analyzed for major and selected trace elements (Co, Cu, Cr, Ni, V, Pb, Ba, Au and ree). The purpose of the research was to study the geochemical evolution of the laterites and the relationship of weathering processes to secondary gold mineralization.Four types of element mobilities are recognized, defined by progressive depletion (type A) or enrichment (type C) in the sequence latosol-cuirasse-pisolite or by extreme enrichment (type B) or depletion (type D) in the cuirasse. Cr and V have similar behavior (type C), whatever the type of parent rock: however, when the original rocks are gabbros, Co, Cu and Ni demonstrate behavior A, B and A, respectively. Also Ti has the same type of mobility (type A), whatever the type of parent rock.The concentrations of some residual elements, e.g., Ti, V, Mn, Fe and Au, are inherited from the original rocks, that is, they exhibit higher values in the lateritic materials on parent rocks in which their contents are high.The enrichment of ree in the lateritic materials on iron-rich carbonates is attributed to relatively basic and reducing conditions at depth. This environment allowed the ions of these elements (Ce, Sm, Eu and Yb in the reduced ionic form) to stay in solution along with Fe²⁺. At shallow depht, under oxidizing conditions, the iron oxyhydroxides adsorbed the ree ions. This adsorption was more effective for La, Ce and Yb ions.The ree contents in the lateritic products from gabbros indicate a depletion of hree plus Eu, Nd and Sm are also depleted in cuirasses and Ce is depleted in pisolites. The loss of these ree and the slight concentration of lree in the red latosol of the Gentio do Ouro District are attributed to partial leaching of ree by a relatively acidic solution. The adsorption of ree by iron oxyhydroxides was less intense here than in the weathering of the iron-rich carbonates at Sento Sé Area. It was also more effective for La and Ce (ions). This type of weathering solution may be generated from oxidation of the accessory pyrite present in the gabbros of the Gentio do Ouro District. It may dissolve primary gold which then precipitates on encountering basic conditions at depth.     

Distribution and feeding ecology of three juvenile mojarras in a hypersaline tropical estuary in Northeastern Brazil

Although mojarra species usually demonstrate a wide distribution in tropical and subtropical estuaries, relatively little is known about the process influencing the spatial resource partitioning to nearshore habitats. Therefore, the aim of this study was check the existence of habitat and food partitioning among confamiliar species in a hypersaline estuary. The dietary compositions of three co‐occurring species of mojarras were determined, using samples collected with a beach seine from an inverse tropical estuary in Northeastern Brazil, during the rainy and the dry seasons of 2012. Eucinostomus argenteus and Ulaema lefroyi were abundant throughout the year, while Eugerres brasilianus was most abundant during the rainy season. Although these mojarras were found together in all areas of the estuary, there was evidence of habitat partitioning: E. argenteus and E. brasilianus were dominant in areas with submerged vegetation, while U. lefroyi was most abundant in areas with little habitat complexity and minimal shelter. All mojarras consumed, to different degrees, zooplankton, Bivalvia and Polychaeta. However, E. brasilanus also consumed a considerable amount of algae. Although the niches of the mojarra species appeared to significantly overlap, some resource partitioning patterns were apparent. While E. brasilanus was clearly different along the trophic niche, segregation of the other species was more important with respect to the spatial dimension. The different feeding strategies appear to minimize inter‐specific overlap and allow the co‐occurrence of these species in this hypersaline tropical estuary.     

Anatexis and fluid regime of the deep continental crust: New clues from melt and fluid inclusions in metapelitic migmatites from Ivrea Zone (NW Italy)

We investigate the inclusions hosted in peritectic garnet from metapelitic migmatites of the Kinzigite Formation (Ivrea Zone, NW Italy) to evaluate the starting composition of the anatectic melt and fluid regime during anatexis throughout the upper amphibolite facies, transition, and granulite facies zones. Inclusions have negative crystal shapes, sizes from 2 to 10 μm and are regularly distributed in the core of the garnet. Microstructural and micro‐Raman investigations indicate the presence of two types of inclusions: crystallized silicate melt inclusions (i.e., nanogranitoids, NI), and fluid inclusions (FI). Microstructural evidence suggests that FI and NI coexist in the same cluster and are primary (i.e., were trapped simultaneously during garnet growth). FI have similar compositions in the three zones and comprise variable proportions of CO₂, CH₄, and N₂, commonly with siderite, pyrophyllite, and kaolinite, suggesting a COHN composition of the trapped fluid. The mineral assemblage in the NI contains K‐feldspar, plagioclase, quartz, biotite, muscovite, chlorite, graphite and, rarely, calcite. Polymorphs such as kumdykolite, cristobalite, tridymite, and less commonly kokchetavite, were also found. Rehomogenized NI from the different zones show that all the melts are leucogranitic but have slightly different compositions. In samples from the upper amphibolite facies, melts are less mafic (FeO + MgO = 2.0–3.4 wt%), contain 860–1700 ppm CO₂ and reach the highest H₂O contents (6.5–10 wt%). In the transition zone melts have intermediate H₂O (4.8–8.5 wt%), CO₂ (457–1534 ppm) and maficity (FeO + MgO = 2.3–3.9 wt%). In contrast, melts at granulite facies reach highest CaO, FeO + MgO (3.2–4.7 wt%), and CO₂ (up to 2,400 ppm), with H₂O contents comparable (5.4–8.3 wt%) to the other two zones. Our results represent the first clear evidence for carbonic fluid‐present melting in the Ivrea Zone. Anatexis of metapelites occurred through muscovite and biotite breakdown melting in the presence of a COH fluid, in a situation of fluid–melt immiscibility. The fluid is assumed to have been internally derived, produced initially by devolatilization of hydrous silicates in the graphitic protolith, then as a result of oxidation of carbon by consumption of Fe³⁺‐bearing biotite during melting. Variations in the compositions of the melts are interpreted to result from higher T of melting. The H₂O contents of the melts throughout the three zones are higher than usually assumed for initial H₂O contents of anatectic melts. The CO₂ contents are highest at granulite facies, and show that carbon‐contents of crustal magmas are not negligible at high T. The activity of H₂O of the fluid dissolved in granitic melts decreases with increasing metamorphic grade. Carbonic fluid‐present melting of the deep continental crust represents, together with hydrate‐breakdown melting reactions, an important process in the origin of crustal anatectic granitoids.     

Transverse and longitudinal fluid flow modelling in fractured porous media with non‐matching meshes

A new discrete fracture model is introduced to simulate the steady‐state fluid flow in discontinuous porous media. The formulation uses a multi‐layered approach to capture the effect of both longitudinal and transverse permeability of the discontinuities in the pressure distribution. The formulation allows the independent discretisation of mesh and discontinuities, which do not need to conform. Given that the formulation is developed at the element level, no additional degrees of freedom or special integration procedures are required for coupling the non‐conforming meshes. The proposed model is shown to be reliable regardless of the permeability of the discontinuity being higher or lower than the surrounding domain. Four numerical examples of increasing complexity are solved to demonstrate the efficiency and accuracy of the new technique when compared with results available in the literature. Results show that the proposed method can simulate the fluid pressure distribution in fractured porous media. Furthermore, a sensitivity analysis demonstrated the stability regarding the condition number for wide range values of the coupling parameter.     

Identifying oceanographic conditions conducive to coastal impacts on temperate open coastal beaches

Natural Hazards - Warnings issued by meteorological or oceanographic agencies are a common means of allowing people to prepare for likely impactful events. Quantifying the relationships between...     

Core Jamming in Unconsolidated Formations

Geotechnical and Geological Engineering - In coring operations, core jamming is a permanent concern, taking place when the rock core sample becomes stuck within the inner core barrel, thus...