Effects of organic acids on dissolution of Fe and Mn from weathering coal gangue

Understanding the effects of organic acids(OA) on the transformation of Fe and Mn to surface water from the weathering coal gangue is of great bene?t to risk assessment and remediation strategies for contaminated water and soil. Based on the investigation on surface water in the central coal districts of the Guizhou Province, 18 water samples were collected for heavy metal analysis. The results indicated that the p H value of surface water is low(3.11–4.92), and Fe concentration(1.31–5.55 mg L^(-1)) and Mn concentration(1.90–5.71 mg L^(-1)) were, on average,10.86 and 34.33 times the limit of Surface Water Quality Standards, respectively. In order to evaluate the effects of the OA on the dissolution of Fe and Mn from the weathering coal gangue, column elution and batch leaching experiments were conducted. The results show that the low molecular weight of organic acids(LMWOAs, i.e., oxalic,tartaric, malic and citric acids) and fulvic acids signi?-cantly accelerated the dissolution of Fe and Mn; in addition, when the concentration of OA reached 25 mmol L^(-1),the concentrations of Fe, and Mn were 1.14–67.08 and1.11–2.32 times as high as those in 0.5 mmol L^(-1)OA,respectively. Furthermore, the migration of Fe and Mn was signi?cantly in?uenced by the p H and Eh, especially for Fe; the ion Mn was dissolved from the gangue more easily than the ion Fe in the column leaching, which was contrary to the results of batch leaching.

Topology optimization in lightweight design of a 3D-printed flapping-wing micro aerial vehicle

Topology optimization is an effective method to obtain a lightweight structure that meets the requirements of structural strength.Whether the optimization results meet the actual needs mainly depends on the accuracy of the material properties and the boundary conditions,especially for a tiny Flapping-wing Micro Aerial Vehicle(FMAV)transmission system manufactured by 3D printing.In this paper,experimental and numerical computation efforts were undertaken to gain a reliable topology optimization method for the bottom of the transmission system.First,the constitutive behavior of the ultraviolet(UV)curable resin used in fabrication was evaluated.Second,a numerical computation model describing further verified via experiments.Topology optimization modeling considering nonlinear factors,e.g.contact,friction and collision,was presented,and the optimization results were verified by both dynamic simulation and experiments.Finally,detailed discussions on different load cases and constraints were presented to clarify their effect on the optimization.Our methods and results presented in this paper may shed light on the lightweight design of a FMAV.