Flotation sedimentation

If the ore consists of separate grains containing the desired material, it can be separated from undesired minerals by physical methods such as flotation, sedimentation, or magnetic separation. For metals this step can lead to 80 to 95 percent concentration of the value of the ore. Ceramic raw materials such as sand and clay can often be found pure enough in nature so that no concentration is needed. 

Most of the pollutants may be effectively removed by precipitation of metal hydroxides or carbonates using a reaction with lime, sodium hydroxide, or sodium carbonate. For some, improved removals are provided by the use of sodium sulfide or ferrous sulfide to precipitate the pollutants as sulfide compounds with very low solubilities. After soluble metals are precipitated as insoluble floes, one of the water-solid separators (such as dissolved air flotation, sedimentation, centrifugation, membrane filtration, and so on) can be used for floes removal.911 The effectiveness of pollutant removal by several different precipitation methods is summarized in Tables 5.15-5.17. 

We have considered the common non-solvent-based methods of separating postconsumer plastics. However, except for depolymerization, only selective dissolution is capable of purifying bonded, blended, and fill plastics effectively. Dissolution of the polymer releases the impurities which are then removed by filtration, adsorption, or flotation/sedimentation. This yields polymers of high purity for reuse in original applications. The major drawback of a solvent system is Ae increased expense due to the complexity of equipment and higher energy requirements. 

If a 2-liter bottle waste is assumed to be compose of 70 wt% PET and 30 wt% HDPE and this waste is exposed to NMP at 175°C for 30 minutes followed by flotation/sedimentation, filtration, and precipitation, the resulting polymer would be 99.91 wt% PET. If the NMP treatn nt had been preceded by a sink-float stage capable... 

Because of the varying composition of raw kaolin and different uses, raw kaolin generally requires processing (flotation, sedimentation, baking, etc.) to acquire characteristics suited to specific industrial uses. 

It is recommended to carry out miscibility tests to check that no separation (flotation, sedimentation, coagulation) will occur due to the preservation treatment. This is very important for coating slurries preservation where any rheological change in these complex formulations can destabilise the coating. These tests can include enduction ( draw down test ), brightness test, printability tests. 

Generally, Httle is known in advance concerning the degree of homogeneity of most sampled systems. Uniformity, rarely constant throughout bulk systems, is often nonrandom. During the production of thousands of tons of material, size and shape distribution, surface and bulk composition, density, moisture, etc, can vary. Thus, in any bulk container, the product may be stratified into zones of variable properties. In gas and Hquid systems, particulates segregate and concentrate in specific locations in the container as the result of sedimentation (qv) or flotation (qv) processes. 

Suspended Solids Removal. Depending on the concentration and characteristics of the suspended soflds, they can be removed by filtration, flotation, or sedimentation. Coarse soflds are removed by screening. Settleable suspended soflds are removed in a clarifier, which may be circular or rectangular. The efficiency of soflds removal is a function of the overflow rate (m /-d (gal/ft -d) as shown in Figure 5. 

Flocculation. Flocculation (qv) uses chemical precipitation to effect separation (54). It is used to increase the rate of sedimentation and flotation. The resulting material known as floe can be removed by filtration, sedimentation, or flotation. 

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