Toxic ion

Cells make use of many different types of membranes. All cells have a cytoplasmic membrane, or plasma membrane, that functions (in part) to separate the cytoplasm from the surroundings. In the early days of biochemistry, the plasma membrane was not accorded many functions other than this one of partition. We now know that the plasma membrane is also responsible for (1) the exclusion of certain toxic ions and molecules from the cell, (2) the accumulation of cell nutrients, and (3) energy transduction. It functions in (4) cell locomotion, (5) reproduction, (6) signal transduction processes, and (7) interactions with molecules or other cells in the vicinity. 

A further way in which metabolic control may be exercised is the artificial deprivation of required ions and cofactors, for example aconitase must have ferrous ions for activity. Conversely, addition of toxic ions is possible, for example aconitase is inhibited by cupric ions. Finally the use of metabolic analogues is possible. If monofluoroacetate is added to cells then monofluorocitrate is produced by titrate synthase and this compound inhibits the activity of aconitase. Great care has to be taken when using metabolic analogues, however, they are often less than 100% specific and may have unexpected and unwanted serious side effects. 

Redox reactions may cause mobile toxic ions to become either immobile or less toxic. Hexavalent chromium is mobile and highly toxic. It can be reduced to be rendered less toxic in the form of trivalent chromium sulfide by the addition of ferrous sulfate. Similarly, pentavalent (V) or trivalent (III) arsenic, arsenate or arsenite are more toxic and soluble forms. Arsenite (III) can be oxidized to As(IV). Arsenate (V) can be transformed to highly insoluble FeAs04 by the addition of ferrous sulfate. 

CORPEX Technologies, Inc., offers CORPEX technology for the decontamination of undesirable and toxic ions or radionuclides from contaminated surfaces and coatings. The vendor states that the process can operate as either a batch or semicontinuous process. The commercially available CORPEX technology uses patented, innovative chelation chemicals to control and recover radioactive and other types of hazardous metal ions from soils, concrete, steel, and other materials. 

The chemical treatment of wastes can result in the material being converted to products that are nontoxic and environmentally acceptable. The methods fall into several categories that include acid/base neutralization, oxidation or reduction, and precipitation of toxic ions as insoluble solids. Many of the disposal procedures suggested in this book fall into these categories. 

Those that form very toxic ions... 

Bravo, C. A., Non Toxic Ion-Exchange Anti-Corrosion Pigments, ABRAFATl Congress Proceedings, Sao Paulo, Brasil, 1995, p. 770... 

The enriched acidity of the rain (mentioned above) means that when it falls on the ground it dissolves essential ions, including magnesium, out of the soil. Magnesium ions are essential for photosynthesis, and so plant growth is affected. Acid rain also dissolves some of the more toxic ions, such as aluminium, copper, lead and zinc, out of the soil. These metals under normal conditions remain fixed in the soil, but acid rain makes these toxic elements more available to plant life. These elements stunt the growth of plants. The water run-off from the soil into rivers and lakes means a build-up of toxic ions, and aquatic plants and fish are affected. 

This reaction would be ideal in the sense that two nontoxic gases are the sole products of the destruction of a toxic ion, and no dissolved solids build-up in the waste has occurred. Comparison of cyanides to cyanates shows that the former compounds are relatively stable the cyanates either hydrolyze to ammonium carbonate (I, 19) or rearrange to urea (1,16,24) ... 

Dissolution, if the NMs are soluble in the conditions of the test, and release of (toxic) ions... 

Fig-1 The final NM-induced toxic effect observed in vitro is the result of multiple processes (1) interaction with proteins (formation of the protein corona, activation/inactivation of enzymes) (2) dissolution and release of toxic ions (3) production of ROS at the NMs surface (4) aggregation/agglomeration (5) diffusion and sedimentation that influence NM transport to the cell layer and the final effective concentration (6) interaction with the cell membrane and membrane receptors (activation/inhibition) (7) cell uptake (including receptor-mediated endocytosis and other uptake mechanisms) (8) interaction with intracellular enzymes (activation/inhibition) (9) production of intracellular ROS (10) activation of transcription factors and (11) binding to nucleic acids and genotoxicity, among others. Processes (1)—(5) are closely interconnected. The resulting effect observed is the result of the composite rate of all these different reactions... 

Mishra, S.P, Dubey, S.S., and Tiwari, D., Inorganic particulates in removal of heavy metal toxic ions. IX. Rapid and efficient removal of Hg(II) by hydrous manganese and tin oxides, J. Colloid Interf. Sci., 219, 61, 2004. 

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