Mechanical activation as a means of accelerating the mineral dissolution may play an important role in chalcopyrite bioleaching. In the present work, the mechanical activation by ball-milling with 10 min, 30 min, 60 min, 90 min, 120 min and 180 min time periods of bioleaching of chalcopyrite was studied, and then evaluated by a Density Functional Theory (DFT) calculation. The results showed that the specific surface area increased sharply in the very beginning of mechanical activation and then increased slowly until the agglomeration of the particles occurred, while the chalcopyrite lattices increased with the mechanical activation. The reaction activity analyzed by cyclic voltammetry (CV) increased slowly in 30 min, increased quickly in the following 90 min, and then decreased, while the hydrophobicity analyzed by contact angles of the chalcopyrite after activation showed less of a change. The results showed that after 15 days of bioleaching, the Cu leaching by Sulfobacillus thermosulfidooxidans (S. thermosulfidooxidans) increased from 9.39% in the 0 min of mechanical activation to 87.41% in the 120 min of mechanical activation, and the copper leaching rate increased by about 78%. The DFT results provide solid proof that the activated chalcopyrite can be adsorbed more easily by cells with higher adsorption energies and stronger bonds.
The domoic acid (DA) produced by certain species of the marine pennate diatom genus Pseudo-nitzschia is highly neurotoxic and can induce nerve excitability and neurotoxicity by binding with ionotropic glutamate receptors, causing amnesic shellfish poisoning in humans who consume seafood contaminated with DA. In recent years, poisoning to humans caused by DA has occurred around the world, which has attracted increasing attention, and studies on DA production by Pseudo-nitzschia have become the hotpot. This article reviews the progress on the biosynthesis of DA by the typical diatom Pseudo-nitzschia, in which the metabolic pathway of the biosynthesis of DA and its precursors, i.e., geranyl pyrophosphate and L-glutamate, and the various environmental factors affecting DA production including temperature, light intensity, nutrients, trace metals, and alien bacteria are discussed. The detection methods of DA (including bioassays, enzyme linked immunosorbent assays, high performance liquid chromatography, capillary electrophoresis and biosensors), as well as the morphology and toxigenicity of Pseudo-nitzschia are also presented.
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