Clay Mineral Adsorption Of Phosphorus On Eutrophication

Water eutrophication is one of the environment problems we face nowadays. It is generally accepted that eutrophication may happen when the concentrations of total P and inorganic N in natural water are up to 20 mg/m~3 and 300 mg/m~3, respectively. Aquatic organisms are more sensitive to P than to N. Therefore, removal of P from water body has become one of the key measures to control eutrophication. Clay minerals are abundant in nature and have great appliance and high economic value due to their complicated, controllable and modifiable characters. At present, clay mineral is one of the most promising materials s to treat eutrophicated water.This experiment was conducted to investigate effect of clays minerals on the removal of P in eutrophicated water by clay minerals, in an attempt to understand the adsorption mechanism, and to find one or more modified clay minerals which should be in lower cost and more efficient in treating eutrophicated water.Bentonite(300),vermiculite(200), kaoline(200) and kaoline(800) , which were chosen in a preparatory experiment, could sorb P in simulated eutrophicated water. However, these unmodified mineral clays showed low efficiency in remval can removal of P in the water. The efficiency could be improved by adjusting pH to 5, elongating shaking time to 30 min. and increasing dosage,but these measures are unfeasible in practice. Then the selected natural clay minerals were modified to improve P adsorption. P removal rates of bentonite(300) heated at 600℃for 2 hours,Al-pillared bentonite(300), OH-Gr-pillared bentonite and OH- Al-pillared bentonite were all reached 100%.We also studied absorption mechanism of modified clay minerals by x-ray, and found that the space between adjacent layers in clay minerals increased after modification, which led to enhanced P adsorption. The P removal rate and the space between clay minerals layer changed in the same order: Al-pillared>OH-Gr-pillared>OH-Al-pillared. These results indicated that P adsorption efficiency could be improved if the space between adjacent layers in clay minerals were enlarged through modification.