Comparison of Bioleaching of Heavy Metals from Sewage Sludge of Different Solid Concentrations Using Two Inocula

Two 10%(v/v) different inocula, iron-oxidizing bacteria and sulfur-oxidizing bacteria, were used to investigate the bioleaching of heavy metals from sewage sludge with 10-40 g/L sludge concentration in the batch experiment. The results demonstrated that most of bioleaching rates of Zn and Cu achieved above 80% and 60%, respectively, after 12 d in the sludge with different concentrations and inocula. The lower the solid concentration, the higher the removal rate of heavy metals and the quicker the removal speed in sludge. The system with iron-oxidizing bacteria had faster startup speed and was influenced by solid concentration lightly, while in the system with sulfur-oxidizing bacteria, the removal efficiency was affected by concentration seriously.

Static Yield Stress of Cement-based Grouting Material under Different Rheological Modes

To quantitatively estimate the workability of cement-based grouting material,from the perspective of rheology,the result of the static yield stress evaluated using the rate-controlled and stress-controlled modes,respectively,was compared using the Rheowin rheometer.Also,the correlation of workability and solid concentration of slurry with static yield stress was studied.Results show that the static yield stress of cement-based grouting slurry relates to the established slurry structure,and is the shear stress corresponding to the transformation of elastics to plastics;In rate-controlled mode,the static yield stress of the slurry is related to the shear rate.The higher the shear rate,the greater the yield stress of the slurry.For the stress-controlled mode,the result is more accurate and suitable for testing static yield stress under different water-cement ratios.Since the water-cement ratio has a good correspondence with the static yield stress and the static yield stress has a good correspondence with the slump flow of the slurry,the static yield stress is the minimum stress to be overcome when the slurry begins to flow and it reflects the yield behavior and structural stability of the cement.

Molecular Dynamics Simulations of Displacement Cascade in Ni-Based Concentrated Solid Solution Alloys

Single-phase concentrated solid solution alloys(SP-CSAs),including high-entropy alloys,have received extensive attention due to their excellent irradiation resistance.In this work,displacement cascade simulations are conducted using the molecular dynamics method to study the evolution of defects in Ni-based SP-CSAs.Compared with pure Ni,the NiCr,NiCo,and NiCu alloys exhibit a larger number of Frankel pairs(FPs)in the thermal peak stage,but a smaller number of surviving FPs.However,the NiFe alloy displays the opposite phenomenon.To explain these different observations for NiFe and other alloys,the formation energy and migration energy of interstitials/vacancies are calculated.In the NiFe alloy,both the formation energy and migration energy barrier are higher.On the other hand,in NiCr and other alloys,the formation energy of interstitials/vacancies is lower,as is the migration energy barrier of interstitials.The energy analysis agrees well with previous observations.The present work provides new insights into the mechanism behind the irradiation resistance of binary Ni-based SP-CSAs.

Estimation of solid concentration in solid-liquid two-phase flow in horizontal pipeline using inverse-problem approach

In this study,an inverse-problem method was applied to estimate the solid concentration in a solid-liquid two-phase flow.An algebraic slip mixture model was introduced to solve the forward problem of solid-liquid convective heat transfer.The time-average conservation equations of mass,momentum,energy,as well as the volume fraction equation were computed in a computational fluid dynamics(CFD)simulation.The solid concentration in the CFD model was controlled using an external program that included the inversion iteration,and an optimal estimation was performed via experimental measurements.Experiments using a fly-ash-water mixture and sand-water mixture with different solid concentrations in a horizontal pipeline were conducted to verify the accuracy of the inverse-problem method.The estimated results were rectified using a method based on the relationship between the estimated results and estimation error;consequently,the accuracy of the corrected inversion results improved significantly.After a verification through experiments,the inverse-problem method was concluded to be feasible for predicting the solid concentration,as the estimation error of the corrected results was within 7%for all experimental samples for a solid concentration of less than 50%.The inverse-problem method is expected to provide accurate predictions of the solid concentration in solid-liquid two-phase flow systems.

Transportation characteristics of gas-solid two-phase flow in a long-distance pipeline

In this study, experiments on fly ash conveying were carried out with a home-made long-distance positive-pressure pneumatic conveying system equipped with a high performance electrical capacitance tomography system to observe the transient characteristics of gas-solid two-phase flow. The experimen- tal results indicated that solids throughput increased with increasing solids-gas ratio when the conveying pipeline was not plugged. Moreover, the optimum operating state was determined for the 1000 m long conveying pipeline with a throttle plate of 26 orifices. At this state the solids throughput was about 12.97 t/h. Additionally, the transportation pattern of fly ash gradually changed from sparse-dense flow to partial and plug flows with increasing conveying distance because of the conveying pressure loss, These experimental results provide important reference data for the development of pneumatic conveying technology.