Re Adsorbent Micro-polluted Water Depth And Phosphorus Removal Study

The eutrophication situation of lakes is very severe all over the world, and the main reason which leads to the result is over surplus nitrogen and phosphorus into the water body. So many documents make clear that phosphorus quantity is the key role, and phosphorus removal is so urgent to eutrophication water body, such as lakes and reservoir.Biological and chemical techniques play important role. However, biological means is not steady for phosphate removal because of pollutants varying great with different, which result in operating badly, and at the same time temperature and pH value of influence play a great impact on removal ratio which leans on BOD in feed. To the chemical methods, there consume great amount of medical flocculants and coagulating. Contemporarily quantity of chemical sludge comes into being, and to be difficult to deal will it. Adsorption which takes up with the deficiency of biological and chemical measures, which is a high efficiency and low energy depletion, remove pollutants from low-concentration solution. Adsorbents with high specific-surface area separate phosphate from sewage by surface adsorption, ion exchange and precipitation. And farther phosphate can reclaim as resource, of course waste turn into use.The thesis research on phosphate removal from micro-polluted water, for improving quality of secondary effluent so as to satisfy with demand of surface water, some good results listed below.(1) On suspended bed test, the optimal result was getted when the sorbent's dosage is one gram per liter, and pH value extend from 4 to 7.5, and removal ratio up to 99 percent, but when rare earth adsorbent is used to suspended bed, the result is so bad that high turbidity, low effluent, high resistance which is diseconomic and suspended bed dose not suit to phosphate removal.(2) On fixed bed test, by means of immerged, dried, felted, baked, and molded, the sorbent is getted, 0.9 1.2mm in diameter and 2³mm in length that has good hydraulic condition, but capacity is reduced compared to powder-adsorbent, when the velocity of 6L/h, pH value of 7.3, and phosphate of 0.02mg/L in outlet, the capacity of sorbent is 4.12mg/g calculated by Origin 7.5 software, and satisfied with surface water's standard of third class;competing adsorption from other ions and anions does not exist, whatever samples is test such as distilled water, artificial groundwater, tap water and effluent of sewage treating plant.(3) On regeneration test, the best conditions are getted from single factor test and factorial experiment, including regenerating liquid of 12 liters, velocity of 0.5 m/h, the pH of 10.5 and auxiliary(i.e. MgCl₂) of 0.4%. such adsorption capacity decreased to 80% of primary capacity when the sorbent is reused 12 times.(4) On adsorption and desorption mechanism, in virtue of instrument analysis, such as SEM and XRD, we concluded that chemisorption is the key to phosphate removal, and other absorbability work on synchronously. At the same time, reaction-diffusion control isdynamic for phosphate removal, so that the less particle-size is, the shorter time to equilibrium is.(5) To model built, primary mathematical model is built, a theoretical model of 2nd.order adsorption dynamics was built up in this paper, and a new index of adsorption strength exponent b and k₁ conforming to single layer chemisorption.