An Experimental Study of the Influence of the Preflush Salinity on Enhanced Oil Recovery Using Silica-Based Nanofluids

The underlying effect of preflush salinity and silica nanofluid (Si-NF) on oil production is examined. The influence of salinity on the stability of Si-NFs is studied. A series of sand-pack floodings evaluating oil production was conducted at different concentrations of preflush salinity (0 to 4 wt.%), followed by the injection of a Si-NF (0.5 wt.%) at the trail of which postflush water was injected. The effluent water and solids were collected and analyzed using X-ray fluorescence (XRF). Interfacial tension (IFT) and contact angle measurements were conducted on the Si-NF in the presence of salinity to confirm the effect. The Si-NF became unstable and formed precipitate in the presence of salinity. The sand-pack flooding showed that when the preflush salinity was increased, the displacement efficiency (ED) using the Si-NF and postflush injection was increased (ED = 44%). The XRF of the precipitated effluent revealed that the preflush salinity and Si-NF caused mineral leaching, which triggered pore clogging. The IFT value reduced from 13.3 to 8.2 mN/m, and the wettability was altered to be more strongly water-wet when the salinity increased. The primary mechanisms of oil recovery using the Si-NF after preflush salinity is attributed mainly to the clogging mechanism. This clogging helps block the high-perm area, shift the fluid flow to the oil-trapped zone, and free the oil out. Other contribution mechanisms are IFT reduction and wettability alteration.

Trace Mineral Leaching from Equine Compost

Mineral leaching from compost can be environmentally disruptive. Little information is available regarding trace mineral leaching from equine-sourced compost. The objective of this study was to quantify the mineral content and leaching potential of compost produced from feces of horses fed different amounts and forms (organic or inorganic) of trace minerals. Nine horses were fed three treatments in a 3 × 3 replicated Latin Square design. The dietary treatments were provided as a daily pellet: CON (pellet without added trace minerals), ING (added inorganic trace minerals), and ORG (added organic trace minerals). The added trace minerals were Co, Cu, Mn, and Zn. Feces were collected from each horse after a 16-day feeding period, combined with straw, composted, and then subjected to simulated rainfall to measure mineral mobility. Concentrations of Co, Cu, Mn, and Zn were greater in ING and ORG compared to CON compost (p < 0.05); additionally, ING had greater Zn than ORG compost (p < 0.05). More Cu leached from ING and ORG compared to CON (p < 0.05). The most Zn leached from ING, followed by ORG, and the least amount leached from CON compost (p < 0.05). Dietary trace mineral intake affected the trace mineral concentration in the compost and amount available to leach during rainfall events.

Dietary Trace Mineral Level and Source Affect Fecal Bacterial Mineral Incorporation and Mineral Leaching Potential of Equine Feces

Minerals excreted in feces have the potential to leach or runoff to water-ways, negatively impacting water quality. This study examined the effect of dietary trace mineral levels, and their source, on the leaching potential of minerals from equine feces. Nine horses were used in a replicated 3 × 3 Latin Square, with three dietary treatments provided as pellets: no added trace minerals (CON), added inorganic trace minerals (ING), and added organic trace minerals (ORG). Supplemental trace minerals included Co, Cu, Mn, and Zn. Horses were allowed ad libitum access to forage and fed their treatment pellets for 16 days prior to fecal sample collection. Estimated dietary mineral intake exceeded requirements for supplemented minerals. Regardless of the source, adding dietary trace minerals increased the fecal leaching potential of Cu, Zn, and P (p < 0.05). More Co leached from ORG compared to ING, while Zn leached in greater amounts from ING compared to ORG (p < 0.05). Fecal bacterial Zn content was greater (p < 0.05) for ORG compared to ING. Negative correlations were observed between bacterial mineral content and leaching for several minerals. Supplementing trace minerals in forms that increase microbial incorporation may provide a strategy to control fecal mineral leaching.

Mineral-leaching chemical transport with runoff and sediment from severely eroded rare-earth tailings in southern China

Rare-earth mining has led to severe soil erosion in southern China. Furthermore, the presence of the mineral-leaching chemical ammonium sulfate in runoff and sediment poses a serious environmental threat to downstream water bodies. In this paper, the characteristics of mineral-leaching chemicals in surface soil samples collected in the field were studied. In addition, NH4+ and SO42− transport via soil erosion was monitored using runoff and sediment samples collected during natural rainfall processes. The results demonstrated that the NH4+ contents in the surface sediment deposits increased from the top of the heap (6.56 mg kg−1) to the gully (8.23 mg kg−1) and outside the tailing heap (13.03 mg kg−1). The contents of SO42− in the different locations of the tailing heaps ranged from 27.71 to 40.33 mg kg−1. During typical rainfall events, the absorbed NH4+ concentrations (2.05, 1.26 mg L−1) in runoff were significantly higher than the dissolved concentrations (0.93, 1.04 mg L−1), while the absorbed SO42− concentrations (2.87, 1.92 mg L−1) were significantly lower than the dissolved concentrations (6.55, 7.51 mg L−1). The dissolved NH4+ and SO42− concentrations in runoff displayed an exponentially decreasing tendency with increasing transport distance (Y = 1. 02 ⋅ exp( − 0. 00312X); Y = 3. 34 ⋅ exp( − 0. 0185X)). No clear trend with increasing distance was observed for the absorbed NH4+ and SO42− contents in transported sediment. The NH4+ and SO42− contents had positive correlations with the silt and clay ratio in transported sediment but negative correlations with the sand ratio. These results provide a better understanding of the transport processes and can be used to develop equations to predict the transport of mineral-leaching chemicals in rare-earth tailings, which can provide a scientific foundation for erosion control and soil management in rare-earth tailing regions in southern China.

Mineral leaching chemicals transport with runoff and sediment from severely eroded rare earth tailings in southern China

Rare earth mining has led to severe soil erosion in southern China. Furthermore, the presence of the mineral leaching chemical ammonium sulfate in runoff and sediment poses a serious environmental threat to downstream water bodies. To study the transport characteristics of mineral leaching chemicals, soil on rare earth tailings was sampled in different positions, and runoff and sediment samples were collected along flow routes during three typical rainfall events. The results demonstrated that the NH4+ contents in the surface sediment deposits increased from the top of the heap (6.56 mg/kg) to the gully (8.23 mg/kg) and outside the tailing heap (13.03 mg/kg). The contents of SO42− in the different locations of the tailing heaps ranged from 27.71 to 40.33 mg/kg. During typical rainfall events, the absorbed NH4+ concentrations (2.05, 1.26 mg/L) in runoff were higher than the dissolved concentrations (0.93, 1.04 mg/L), while the absorbed SO42− concentrations (2.87, 1.92 mg/L) were lower than the dissolved concentrations (6.55, 7.51 mg/L). The dissolved NH4+ and SO42− concentrations in runoff displayed an exponentially decreasing tendency with increasing transport distance (Y=1.02*exp(-0.00312X), Y=3.34*exp(-0.0185X)). No clear trend with increasing distance was observed for the absorbed NH4+ and SO42− contents in transported sediment. The NH4+ and SO42− contents had positive correlations with the silt and clay ratio in transported sediment but negative correlations with the sand ratio. These results provide a better understanding of the transport processes and can be used to develop equations to predict the transport of mineral leaching chemicals in rare earth tailings.