Leaching washing

The barren liquors from the product separation or recovery sections, and the waste disposal facility may be recycled as wash liquor to the last stage of the leach-wash system after appropriate treatment. The process may include other streams such as an inlet of lixiviant or additional wash water, and a ficticious exit stream representing losses. 

Efficiencies of leaching, washing and the entire leach-wash system (optional). 

Fig. 16. Staged fluidized leaching/washing. [After Kwauk, 1973.]...

Leaching/washing/flushing of soil with water or surfactant (a surface-active substance) this is not very commonly practiced, and use is limited due to a need for large quantities of water. The results are also highly dependent upon the soil s physical parameters. 

The acid rain leaches (washes out) nutrients from the soil, and so prevents the healthy growth of plants. Not only that, the acid rain can attack the waxy layer on leaves. This increases water loss and makes the plant more susceptible to disease and pests. Trees that grow at high altitudes are especially vulnerable, as they are often in contact with the tiny droplets of water (sulfuric acid solution) in clouds. 

Many substances used in modem processing industries occur in a mixture of components dispersed through a soHd material. To separate the desired solute constituent or to remove an unwanted component from the soHd phase, the soHd is contacted with a Hquid phase in the process called Hquid—soHd extraction, or simply leaching. In leaching, when an undesirable component is removed from a soHd with water, the process is called washing. 

Fusion with caustic soda at 500—800°C in an iron cmcible is an effective method for opening pyrochlores and columbites (20). The reaction mixture is flaked and leached with water to yield an insoluble niobate which can be converted to niobic acid in yields >90 wt% by washing with hydrochloric acid. 

Performance assessments are predictions of radioactivity releases, the rate of transfer of contaminants through various media, and the potential for hazard to the pubHc. These are based on a combination of experimental data obtained in the process called site characterization and detaded computations about radionuchdes and their effects. The progressive attack on the metal or ceramic waste container, the diffusion of water into the waste form, the leaching of the radioactive compounds, diffusion out, and washing away of radionuchdes are all considered. 

Noodle washing is often inconvenient because of high gelatin content and the length of time required to leach by-products. 

This dissociated zircon is amenable to hot aqueous caustic leaching to remove the siHca in the form of soluble sodium siHcate. The remaining skeletal stmcture of zirconia is readily washed to remove residual caustic. Purity of this zirconia is direcdy related to the purity of the starting zircon since only siHca, phosphate, and trace alkaHes and alkaline earth are removed during the leach. This zirconia, and the untreated dissociated zircon, are both proposed for use in ceramic color glazes (36) (see Colorants for ceramics). 

Leaching is 90—95% complete as the soflds exit in the underflow of the first clarifier. Final washing of the soflds (mud) using fresh water takes place in a rotary filter from whence the mud, consisting of 65% H2O, 10—15% BaSO and siUcates, and 10—15% coke, is deflvered to landfill at an approved site. 

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