| Budget Amount *help |
¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1987: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1986: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
It is generally found that the adsorptivity of an adsorbent observed in a flow operation is far less than that found in a test carried out in a batch system. This may be mainly due to the two: (1)granulation of powdery adsorbents appropriate for a flow operation, resulting in the decrease in the effective surface for the adsorption, and (2)some imperfect adsorbate/adsorbent contact such as channeling, elutriation, etc. in a flow system.
This project is directed to the two targets:one is concerning the development of new materials having excellent adsorptivity for PO_4^3-in wastewater (i.e., adsorbent tests in a batch system), and the other on the development of a new adsorbate/adsorbent contacting method for a continuous phosphorous-removal process (i.e., tests in a flow system). This method should be of course to realize the "excellent", batch-tested adsorptibity even in a flow system, almost perfectly.
For the first target, we found that fine-particulate, hydrous alumina gel has an exc
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ellent ability to adsorb phosphate ion in water. The adsorption capacity is about 4 to 20 times as great as that of usual alumina dry gel. On the dehydration of the hydrogel, the capacity remains almost unchanged (4 mmol-P/g-adsorbent) until the water content (based on the dry material) reaches about 150 %, and thereafter, the capacity sharply decreases with decreasing water content. It was suggested that this decrease in the adsorption capacity is caused by a pore-shrinkage of the hydrogel occurring along with the dehydration.
For the second target, we developed a new contacting method, i.e., floc-type fluidized contacting method (FFC). In the FFC, the fine-particulate hydrogel (water content 150%) is in situ flocculated by a flocculant (associated colloidal flocculant: ACF), and packed into the bottom-part of an adsorption tower. Phosphate-containing water is then passed into the tower through a nozzle which is situated at the bottom-part of the floc-packed bed and the tip of which is directed to the center of the tower bottom. The hydrogel flocles present near the nozzle tip is destroyed by the jet-flow of feed water into primary fine particles. The feed flow is reversed by the botton wall of the tower, flowing upward to induce the fluidization of the floc-type bed. The destroyed primary particles are reflocculated together along with the upstream to produce large enough flocles at the top of the bed to subside again to the bottom. Thus the FFC provides both an ideal contacting and a homogeneous mixing especially in the vertical direction of the bed. Application of this FFC method to the phosphorous removal process resulted in the following:
(1) Maximum loading capacity of the hydrogel reaches about 3 times that reported so far on dry alumina gels.
(2) When the feed flow rate is varied, this capacity remains almost unchanged within the present investigation, indicating a considerablly rapid adsorption reaction.
(3) As a result, a space velocity as high as about 40 h-l is possible without any adsorption capacity loss due to an insufficient adsorption rate. This space velocity corresponds to about 10 times that usually used in phosphorous removal operations. Less
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