Research On Mineral Powder Removing Phosphorus In Natural Water And From Sediment Releasing

Since the1990s, with the rapid development of modern industry, the main rivers and lakes in China had the eutrophication problem, such as Taihu lake, Chaohu lake, Dianchi and many small city river. Eutrophication maked many negative effects to natural water, and even serious pollute water seriously. The eutrophicated water smelled smelly, had poor sensory effects. Eutrophication coule reduce the water transparency, decrease the water dissolved oxygen obviously and release toxic substances to the water. Eutrophication in natural water not only affected water supply to the nearby town, but also harmed aquatic ecological system seriously.In addition to non-point source pollution, sediment releasing pollutants to the natural water in the condition of high temperature and low oxygen was a very important reason which could result in eutrophication. This phenomenon would cause cyanophyta explosion in short time. In view of these situations, the research selected stable and reliable mineral powder study and used the method of situ cover to control releasing phosphorus, so as to reduce eutrophication level and avoid cyanophyta bloom. The research contained two aspects of content:1、research on the mineral powders’capability of removing phosphorus in water. The research objects are nano-calcite powder, light-weight calcite powder, heavy-weight calcite powder, gesso for building, gesso for medical, aluminium sulfate residue.2、research on the technology of controlling phosphorus releasing by mineral powder situ cover. The study selected load materials and mixed it with mineral powders to become mixture material. Then put the mixture material on the interface to control phosphorus releasing. Finally, we could assess the effect and measure the safe level. The main research results are as follows.(1) The capacity of light-weight and heavy-weight calcite powder to remove phosphor-us fits Langmuir adsorption equation and the maximal capacity is0.387mg/g and0.351mg/g respectively. The capacity of nano-calcite powder to remove phosphorus fits Freundlich adsorption equation. These3kinds of calcite powder all had good capacity of removal phosphorus in tai lake water. The capacity of calcite powder to remove phosphorus increased with the increasing in pH and Ca2+concentration and alkalinity. Removing phosphorus in tai lake by calcite powder did not have negative effects on the water quality.(2) Gesso for building and gesso for medical all had good capacity of removal phosphorus in Tai lake water. Gesso for building and gesso for medical to remove phosphorus fits Langmuir adsorption equation, when solution pH ranged6-7. Gesso to remove phosphorus fits Freundlich adsorption equation, when solution pH ranged8-10. The gesso for building and gesso for medical to remove phosphorus increased with the increasing in pH and alkalinity. The changes of Ca2+concentration in solution had little influence on the capacity of gesso to remove phosphorus. Removing phosphorus in Tai lake by gesso for building and gesso for medical did not have negative effects on the water quality.(3) Nano-calcite powder had obvious effect on removal phosphorus. And gesso can dissolved a lot of benefit Ca+ions in the solution. So the research mixed nano-calcite powder and gesso together to become mixed powder to remove phosphorus in Tai lake water. When the two powders mixed with4:1and3:2, the capacity of mixed powder to remove phosphorus improved obviously by5%～20%.(4) Aluminum sulfate residue had good capacity of removal phosphorus in Tai lake water and distilled water. The capacity of aluminum sulfate residue to remove phosphorus descended with the increasing in pH. The maximum adsorption capacity decreased with the increasing of solution pH. When solution pH ranged6～8, the maximum phosphorus removal quantity in distilled water and Taihu lake water was2.92～3.41,2.41-3.08mg/g respectively. There was no Al3+detected in water after isothermal adsorption experiment, the SO42-dissolution quantity of aluminum sulfate residue in distilled water and Taihu lake water was0.09～0.37,0.24～0.37mmol/g. Aluminum sulfate residue could reduce the solution pH and consume the solution alkalinity.(5) The research selected volcano stone, coral, zeolite, ceramsite as load material to adhere nano-calcite powder by the way of water mix method. And load capacity could reach0.0116～0.0196g/g. By experiment, we know the load material had no ability of removal phosphorus in Tai lake water. So in the mixed material the effective component was nano-calcite powder.(6) The mixed material which makes volcano stone as load material had the best effect on controlling phosphorus releasing by situ cover. When the critical phosphorus concentration was0.02mg/L, the adsorption capacity of this mix material was1.801mg/g. The performance of these material to control the phosphorus releasing, by the order from good to bad was volcano stone mix material, coral mix material, zeolite mix material, ceramsite mix material.(7) Comparing with the single nano-calcite powder, the adsorption capacity of the mix material increased highly. Volcan stone mix material, coral mix material and zeolite mix material improved by84.86%,46.75%and47.47%respectively. The method of suit cover by mix material to control phosphorus releasing had on negative effects on the water quality. It was safe, reliable, and harmless.