| Phosphates are very important basic materials in agricultural and other industrial applications. Phosphorus is often present in wastewater, almost solely in the form of organic and inorganic phosphates. The removal of phosphates from surface waters is generally necessary to avoid problems, such as eutrophication. The usual methods of treatment are either biological or physicochemical by sedimentation. This thesis studies the removal of phosphorus by adsorption onto some natural adsorbents.Phosphorus adsorption isotherm and its kinetics were examined and effects of initial phosphorus concentration, adsorbent particle size, adsorbent dose, pH, organic materials, temperature and ion strengths were investigated to understand the characteristics of phosphorus adsorption onto zeolite, blast furnace slags, shale, gravel, dolomite and steel converter slags. In addition, Phosphorus adsorption mechanisms on different substrates were explored by the means of adsorption theromdynamics, the mean adsorption energy and the phosphorus fractionation of substrates saturated with phosphorus. Based on the obtained results, suitable substrates were selected and applied in concstructed wetlands. Unsuitable substrates were modified to improve their phosphorus adsorption capacity.Both Langmuir and Freundich isotherm were observed to fit the adsorption characteristics of zeolite, blast furnace slags, gravel and shale. Langmuir isotherm was more suitable to describe the phosphorus adsorption onto dolomite than Freundlich isotherm. The phosphorus adsorption onto steel converter slags can be described by Langmuir isotherm, but not by Freundlich isotherm. Two industrial by-products including steel converter slags and blast furnace slags had higher phosphorus adsorption capacities of 3.55 × 10~4 and 769.23mg/kg, respectively. Followed are shale, gravel and zeolite with phosphorus adsorption capacities of 232.56, 112.36 and 87.72mg/kg. The dolomite had the least phosphorus adsorption...
|
PDF Full Text Request