Re-election of Spodumene from Lithium Processing Tailings in Keeryin, Sichuan

This is an essay in the field of mineral processing engineering. In order to comprehensively evaluate the feasibility of spodumene beneficiation of certain lithium tailings in Sichuan, the mineralogy study of the lithium tailings beneficiation process and the test study of the whole beneficiation process were carried out. Through MLA/AMICS automatic mineral analysis, LA-ICP-MS laser ablation in-situ analysis and other technical means, the mineral composition of the tailings sample and the occurrence state of lithium in the sample were found; On the basis of a series of exploratory tests, the lithium separation process of "grinding-desliming-floating" was determined. For the lithium tailings with a Li2O grade of 0.51%, the high-efficient spodumene collector EM-PN10 is used to obtain a flotation spodumene concentrate with a Li2O grade of 4.32% and a Li2O recovery of 60.23% through a closed flotation process of one roughing, one sweeping and four finishing. After the flotation lithium concentrate is subjected to high-intensity magnetic separation, a spodumene concentrate with a Li2O grade of 5.07% and a recovery of 59.21% (relative to the raw ore) is finally obtained. The recovery and utilization index of spodumene determined by the test can provide certain technical support for the utilization of this kind of spodumene tailings

Spatial variation of human influences on grassland biomass on the Qinghai-Tibetan plateau

An improved understanding of increased human influence on ecosystems is needed for predicting ecosystem processes and sustainable ecosystem management. We studied spatial variation of human influence on grassland ecosystems at two scales across the Qinghai-Tibetan Plateau (QTP), where increased human activities may have led to ecosystem degradation. At the 10 km scale, we mapped human-influenced spatial patterns based on a hypothesis that spatial patterns of biomass that could not be attributed to environmental variables were likely correlated to human activities. In part this hypothesis could be supported via a positive correlation between biomass unexplained by environmental variables and livestock density. At the 500 m scale, using distance to settlements within a radius of 8 km as a proxy of human-influence intensity, we found both negatively human-influenced areas where biomass decreased closer to settlements (regions with higher livestock density) and positively human-influenced areas where biomass increased closer to settlements (regions with lower livestock density). These results suggest complex relationships between livestock grazing and biomass, varying between spatial scales and regions. Grazing may boost biomass production across the whole QTP at the 10 km scale. However, overgrazing may reduce it near settlements at the 500 m scale. Our approach of mapping and understanding human influence on ecosystems at different scales could guide pasture management to protect grassland in vulnerable regions on the QTP and beyond

Changes in grassland cover and in its spatial heterogeneity indicate degradation on the Qinghai-Tibetan Plateau

Arid grassland ecosystems undergo degradation because of increasing environmental and human pressures. Degraded grasslands show vegetation cover reduction and soil-patch development, leading to grassland fragmentation and changes in spatial heterogeneity. Understanding grassland degradation that involves soil-patch development remains a challenge over large areas with limited accessibility such as the Qinghai-Tibetan Plateau. We hypothesized that vegetation cover, its spatial heterogeneity and changes thereof over time retrieved from satellite data can indicate grassland development and degradation levels. To test the hypothesis, we studied these indicators from 2000 to 2016 and related them to previously described degradation levels on the eastern Qinghai-Tibetan Plateau (QTP) in 2004. We further use these indicators to map the new grassland development and degradation levels in 2016. We found that lower vegetation cover does not always indicate a more severe degradation; instead, higher spatial heterogeneity is a better correlate of degradation. Combined temporal changes in grassland cover and its spatial heterogeneity are related to the literature-defined degradation levels. We found that grassland areas on the eastern QTP have moved into new degradation stages from 2000 to 2016 using changes in grassland cover and its spatial heterogeneity as indicators. The normalized difference vegetation index (NDVI) as a proxy for grassland cover declined over time in the literature-defined degraded areas but increased in the desert areas from 2000 to 2016. Spatial heterogeneity generally increased across different degradation levels from 2000 to 2016; however, this increase was less pronounced in severely degraded and slightly deserted areas. Our newly defined degradation levels in 2016 included degradation, desertification, and improving levels. Across our study area, 63% of all areas were classified as degraded and 2% were at risk of desertification. The remaining areas (35%) classified as improving and re-growing occurred in higher-elevation or previously severely degraded grassland. Our study demonstrates that a combination of changes in grassland cover and in its spatial heterogeneity can indicate grassland degradation levels and serve as an early-warning signal for desertification threats

Occurrence of Scandium in a Ilmenite Ore in Northwest China

This is an essay in the field of process mineralogy. In order to find out the properties of low-grade titanium ore with scandium, chemical analysis, electron microscope, X-ray diffraction, automatic mineral analyzer and optical microscope are used to analyze the material composition and mineral embedding characteristics of the ore. From the perspective of process mineralogy, the occurrence state of titanium, iron, and scandium has been studied in detail. The results show that the scandium in the ore mainly occurs in calcium-magnesium silicate, with a distribution rate of 94.93%. An excellent scandium recovery index can be obtained by beneficiating and smelting this silicate mineral. The research results have important guiding significance for the selection and smelting of scandium associated with titanium ore and the next development and utilization of the deposit. It also has important implications for the study of the occurrence of scandium in similar scandium-bearing titanium deposits

Optimizing the Use of Cultivated Land in China’s Main Grain-Producing Areas from the Dual Perspective of Ecological Security and Leading-Function Zoning

In order to achieve the coordinated development of ecological protection and cultivated land use, ecological security and cultivated land use functions (CLUFs) in the study area were evaluated by constructing a comprehensive evaluation index system. The leading CLUFs were measured, and it was determined to use the normalized revealed comparative advantage (NRCA) index. The spatial superposition analysis of the ecological security level and the leading CLUFs was carried out to obtain the zoning of the coordinated development of ecological security and cultivated land use, and differentiated utilization strategies were proposed for different zones. The results of this study showed the following: (1) The ecological security level of cultivated land in Yuanyang County can be divided into high, medium, and low security levels, accounting for 30.68%, 43.42%, and 25.9% of the total cultivated land area, respectively. The overall ecological security level is high. (2) The current cultivated land use mainly has a production function, accounting for 38.39% of the total cultivated land area, the leading CLUFs that are 34.16% of the cultivated land are the ecological function, and 27.45% of the cultivated land is the living function. (3) The spatial superposition analysis of the ecological security level and leading CLUFs yielded four zones of cultivated land use enhancement, including a production core zone, and different control strategies were proposed for the different zones. These strategies may help to fully realize the multifunctionality of the cultivated land without compromising ecological protection. Implementing differentiated protection for cultivated land in different use zones can achieve the coordinated development of ecological protection and cultivated land use, thus promoting the sustainable use of cultivated land resources

A Perturbation Approach for Lateral Excited Vibrations of a Beam-like Viscoelastic Microstructure Using the Nonlocal Theory

In this paper, we investigate the lateral vibration of fully clamped beam-like microstructures subjected to an external transverse harmonic excitation. Eringen’s nonlocal theory is applied, and the viscoelasticity of materials is considered. Hence, the small-scale effect and viscoelastic properties are adopted in the higher-order mathematical model. The classical stress and classical bending moments in mechanics of materials are unavailable when modeling a microstructure, and, accordingly, they are substituted for the corresponding effective nonlocal quantities proposed in the nonlocal stress theory. Owing to an axial elongation, the nonlinear partial differential equation that governs the lateral motion of beam-like viscoelastic microstructures is derived using a geometric, kinematical, and dynamic analysis. In the next step, the ordinary differential equations are obtained, and the time-dependent lateral displacement is determined via a perturbation method. The effects of external excitation amplitude on excited vibration are presented, and the relations between the nonlocal parameter, viscoelastic damping, detuning parameter, and the forced amplitude are discussed. Some dynamic phenomena in the excited vibration are revealed, and these have reference significance to the dynamic design and optimization of beam-like viscoelastic microstructures

Extremal Analysis of Flooding Risk and Its Catastrophe Bond Pricing

Catastrophic losses induced by natural disasters are receiving growing attention because of the severe increases in their magnitude and frequency. We first investigated the extreme tail behavior of flood-caused economic losses and maximum point precipitation based on the peaks-over-threshold method and point process (PP) model and its extreme tail dependence. We found that both maximum point precipitation and direct economic losses are well-modeled by the PP approach with certain tail dependence. These findings were further utilized to design a layered compensation insurance scheme using estimated value-at-risk (VaR) and conditional VaR (CVaR) among all stakeholders. To diversify the higher level of losses due to extreme precipitation, we designed a coupon paying catastrophe bond triggered by hierarchical maximum point precipitation level, based on the mild assumption on the independence between flood-caused risk and financial risk. The pricing sensitivity was quantitatively analyzed in terms of the tail risk of the flood disaster and the distortion magnitude and the market risk in Wang’s transform. Our trigger process was carefully designed using a compound Poisson process, modeling both the frequency and the layered intensity of flood disasters. Lastly, regulations and practical suggestions are provided regarding the flood risk prevention and warning

Effects of Nanoscale Carbon Black Modified by HNO3 on Immobilization and Phytoavailability of Ni in Contaminated Soil

A surface-modified nanoscale carbon black (MCB) as Ni adsorbent in contaminated soil was prepared by oxidizing the carbon black with 65% HNO3. The surface properties of the adsorbent were characterized by zeta potential analysis, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIRs). Batch experiments were conducted to evaluate the improvement of Ni2+ adsorption by MCB. Greenhouse cultivation experiments were conducted to examine the effect of MCB on the DTPA-extractable Ni2+ in soil, Ni2+ uptake of ryegrass shoot, and growth of ryegrass. Results indicated that MCB had much lower negative zeta potential, more functional groups for exchange and complexation of cation, and more heterogeneous pores and cavities for the adsorption of cation than the unmodified parent one (CB). MCB showed enhanced sorption capacity for Ni (qmax, 49.02 mg·g−1) compared with CB (qmax, 39.22 mg·g−1). Greenhouse cultivation experiment results showed that the biomass of ryegrass shoot and the Ni uptake of the ryegrass shoot were significantly increased and the concentrations of DTPA-extractable Ni in soil were significantly decreased with the increasing of MCB amount. It is clear from this work that the MCB had good adsorption properties for the Ni and could be applied in the in situ immobilization and remediation of heavy metal contaminated saline-alkali soils

Flotation of a Pegmatite Type Spodumene Ore in Xinjiang

This is an essay in the field of mineral processing engineering. Li2O grade of a spodumene ore in Xinjiang is 1.04%. The lithium-containing minerals are mainly spodumene, Lithium-Muscovite and montebrasite. The gangue minerals are mainly quartz, albite and potassium feldspar. Under the condition of grinding finness -0.074 mm content 79.4%, using self-developed collector EM-PN51, the concentrate productswith Li2O grade 5.36%, Nb2O5 content 0.071%, Ta2O5 content 0.044% and Li2O recovery rate 87.38%, Nb2O5 recovery rate 87.33%, Ta2O5 recovery rate 88.26% can be obtained bythe closed flotation circuit of one-roughing, one-scavenging, three-cleaning. The comprehensive recovery of several valuable components in spodumene ore is realized