Phosphate Removal from Secondary Effluents Using Coal Gangue Loaded with Zirconium Oxide

Phosphorus from secondary effluents and coal gangue from coal mining have caused serious environmental problems. The feasibility of phosphate removal from secondary effluents using calcinated coal gangue loaded with zirconium oxide (CCG-Zr) was explored. Major influencing factors like the calcinated temperature, CCG-Zr ratio, adsorbent dose, time and solution pH, etc. were investigated. Newly developed CCG-Zr accomplished a significantly higher phosphate removal for phosphate (93%) compared with CCG (35%) at a calcinated temperature of 600 °C and CCG-Zr mass ratio of 1:1. For CCG-Zr the maximum phosphate removal rate (93%) was noted at an initial phosphate concentration of 2 mg/L within 20 min. The CCG-Zr displayed a higher phosphate removal rate (85−98%) over a wide range of solution pH (2.5~8.5). The adsorption isotherms fitted better to the Freundlich (R2 = 0.975) than the Langmuir model (R2 = 0.967). The maximum phosphate adsorption capacity of the CCG-Zr was 8.55 mg/g. These results suggested that the CCG-Zr could potentially be applied for the phosphate removal from secondary effluents

Experimental investigation on physical and mechanical properties of excavated soil- and fine recycled concrete aggregate-based unfired clay bricks containing compound additives

The excavated soil waste and the demolished concrete can be used as the source of natural aggregates’ replacement in concrete. With this purpose, this paper presents two orthogonal experiments (i.e., compression and flexure) to examine the feasibility of jointly using excavated soil and fine recycled concrete aggregate (FRCA) to manufacture unfired clay bricks (UCBs). The water-to-cement ratio (w/c), the cement-to-excavated soil ratio (c/s), the FRCA-to-excavated soil ratio (a/s), and the compound additive content (AC) were selected as the variables in the mix proportion. The test results show that excavated soil & FRCA-based UCBs exhibit the favourable water absorption, bulk density, compressive strength and flexural strength. From the perspective of physical and mechanical properties, the optimal mix proportion is the case of w/c= 0.65, a/s = 0.5, c/s = 0.3, AC= 5%. A grey relational analysis was performed to evaluate the parametric sensitivity of physical properties to four factors. The result revealed that the water absorption is the most sensitive to a/s, and the bulk density is the most sensitive to c/s; in contrast, both of them have the least sensitivity to AC. The prediction models of compressive strength and flexural strength were developed to gain the confidence of recycling excavated soil and FRCA in UCBs. A Scanning Electron Microscope (SEM) was carried out to investigate the mechanism of strength increase of excavated soil & FRCA-based UCBs with different mix proportions, and the result demonstrated that the primary reason of the strength increase is owning to the formation of more hydration products and the tighter internal structure

Phonon blockade in a quadratically coupled optomechanical system with two-phonon driving

We propose a scheme to enhance phonon blockade effect in a quadratically coupled optomechanical system. By applying a degenerate parametric drive to the mechanical oscillator, we introduce a mechanical parametric amplifier (MPA) to the system. We show that the phonon blockade can be achieved in both the single-phonon resonant regime and multipath interference regime due to the optomechanical nonlinearity and MPA. By combining the two regimes together, we show that the phonon blockade effect is enhanced compared to the regime without MPA. What is more, the two-time second-order correlation function gradually tends to one without rapid oscillations in our scheme, which suggests that high time resolution is not necessary in the detection

Quantitative Assessment of Soil Physical Quality in Northern China Based on S-theory

ABSTRACT Quantitative assessment of soil physical quality is of great importance for eco-environmental pollution and soil quality studies. In this paper, based on the S-theory, data from 16 collection sites in the Haihe River Basin in northern China were used, and the effects of soil particle size distribution and bulk density on three important indices of theS-theory were investigated on a regional scale. The relationships between unsaturated hydraulic conductivityKi at the inflection point and S values (S/hi) were also studied using two different types of fitting equations. The results showed that the polynomial equation was better than the linear equation for describing the relationships between -log Ki and -logS, and -log Kiand -log (S/hi)2; and clay content was the most important factor affecting the soil physical quality index (S). The variation in the S index according to soil clay content was able to be fitted using a double-linear-line approach, with decrease in the S index being much faster for clay content less than 20 %. In contrast, the bulk density index was found to be less important than clay content. The average S index was 0.077, indicating that soil physical quality in the Haihe River Basin was good

Estimation of the Critical Value of the Second-Phase Particles in the Microstructure of AZ31 Mg Alloy by Phase-Field Methods

In this study, phase-field models were employed to simulate the effects of second-phase particles (SPPs) on grain growth of the AZ31 Mg alloy, under realistic spatial and temporal scales, at 350 °C, during annealing. The particle sizes ranged from 0 to 7 μm, and the particles with large volume fractions were used in the paper. The results reveal that the volume fractions and sizes of the SPP affect grain growth and that the volume fractions and sizes of the SPP on pinning exhibited critical values. When the SPP volume fraction is f = 5%, the SPP is at the maximum critical size, rμmmax; when the SPP size is r=1 μm, the SPP minimum critical volume fraction is fmin = 0.25% and the maximum critical volume fraction is fmax = 20%. The critical values increase with the increase of the sizes or volume fractions of the second-phase particles. Finally, the average grain size, particle size, and particle volume fraction obtained from the simulation were fitted according to the Zener relationship, and the obtained results showed that the fitting indices were in the range of 0.33–0.50. The results were compared with the experimental results. The simulation results obtained in this study will provide an important academic reference for understanding the mechanism and law of grain growth, an important reference for accurate control of grain size and properties of the material, a reference for the development of the annealing treatment process of Mg alloy, and a theoretical guide for the use of recrystallization process to control the microstructure of Mg alloy and improve the plastic-forming properties

Experimental study on dissolution effect and water purification mechanism of broken coal and rock mass in goaf

Research on the dissolution effect and the water purification mechanism of fractured coal and rock mass in the goaf area of underground reservoir is the key to realizing the safe and efficient operation of underground reservoir in mine.This paper takes the underground water reservoir formed by the mining of 31409 working face in Jinjie coal mine as example, and selects the broken coal rock mass in the mining area and deionized water for the experimental study of pollutant release law.We analyse the law of dissolution action of broken coal rock mass in the mining area, and explore the mechanism of the influence broken coal rock mass exerts on the characteristics of the water body.We discover the law of pollutant release of broken coal rock mass under different temperature and weathering degrees, and analyse precipitation and dissolution that occurs during the water purification process in underground water reservoir.The water-rock interaction of dissolution, the adsorption and precipitation of clay mineral surfaces and soluble organic matter in the rock body constitute the water purification characteristics of the groundwater reservoir, with dissolution, adsorption and precipitation each playing a dominant role in influencing mine water quality at different time scales

Estimation of the Critical Value of the Second-Phase Particles in the Microstructure of AZ31 Mg Alloy by Phase-Field Methods

In this study, phase-field models were employed to simulate the effects of second-phase particles (SPPs) on grain growth of the AZ31 Mg alloy, under realistic spatial and temporal scales, at 350 °C, during annealing. The particle sizes ranged from 0 to 7 μm, and the particles with large volume fractions were used in the paper. The results reveal that the volume fractions and sizes of the SPP affect grain growth and that the volume fractions and sizes of the SPP on pinning exhibited critical values. When the SPP volume fraction is f = 5%, the SPP is at the maximum critical size, rμmmax; when the SPP size is r=1 μm, the SPP minimum critical volume fraction is fmin = 0.25% and the maximum critical volume fraction is fmax = 20%. The critical values increase with the increase of the sizes or volume fractions of the second-phase particles. Finally, the average grain size, particle size, and particle volume fraction obtained from the simulation were fitted according to the Zener relationship, and the obtained results showed that the fitting indices were in the range of 0.33–0.50. The results were compared with the experimental results. The simulation results obtained in this study will provide an important academic reference for understanding the mechanism and law of grain growth, an important reference for accurate control of grain size and properties of the material, a reference for the development of the annealing treatment process of Mg alloy, and a theoretical guide for the use of recrystallization process to control the microstructure of Mg alloy and improve the plastic-forming properties

Effect of Biochar on Soil Temperature under High Soil Surface Temperature in Coal Mined Arid and Semiarid Regions

High soil surface temperature and loosened soil are major limiting factors of plant productivity in arid and semi-arid coal mining areas of China. Moreover, the extensive and illegitimate burning of crop residues is causing environmental pollution; whereas, these residues could be converted to biochar to benefit soil quality. In this study, the effect of wheat straw biochar (WSB) at rates of 0% (control, CK), 1% (low, LB), 2% (medium, MB) and 4% (high, HB) on soil temperature at different depths (5, 10, 15, and 20 cm) and moisture levels (10 and 20%) was investigated under high soil surface temperature of 50 °C and air humidity of 40%. Our data suggested that soil bulk density was inversely, and soil moisture was directly corelated with soil thermal parameters. Moreover, the increasing rate of WSB addition linearly decreased the soil thermal properties. The maximum decrease in soil bulk density at both moisture levels (10% and 20%) was measured in HB treatment compared to respective CKs. The highest decrease in soil thermal conductivity (59.8% and 24.7%) was found under HB treatment in comparison to respective controls (CK10% and CK20% moisture). The soil volumetric heat capacity was also strongly corelated with soil moisture content (r = 0.91). The WSB treatments displayed differential responses to soil temperature. Under 10% soil moisture, temperature of LB, MB and HB treatments was higher as compared to CK at 5–20 cm depth, and MB treated soil had the smallest increase in temperature. At the 15-cm depth, the MB treatment decreased the temperature by 0.93 °C as compared to the CK20%. Therefore, the effect of WSB on soil temperature was influenced by soil moisture content, soil depth and WSB application rates. It suggested that MB treatment could be a useful farming practice for mitigating soil temperature fluctuation