Compound Removal Of Nutrients From River Polluted Water Using Various Types Of Clay Minerals

Clay mineral is a new type of eco-friendly material. Because of it’sexcellent absorbability, ion exchange and flocculating setting,it not onlycan mitigate eutrophication by adsorping nutritional components frompolluted water,but also can inhibit the growth of algae and prevent theoutbreak of algae.This paper studyed on the compound removal of ammonium andphosphate from polluted water by common clay minerals, such as zeolite,bentonite, activated clay and so on.The results showed that the maximum equilibrium adsorptioncapacity of activated clay on the phosphate,160mesh zeolite onammo-nium and Na-bentonite on ammo-nium was68.1,35.87and27.85mg/g respectively. We use six kind of grneral-purpose isotherms tocompare the effect, and found that the Redlich-Petersen adsorptionisotherm fited of the experimental data well, and the R²values are allgreater than0.96, the surface heterogeneity factors are also greater than1.0. These can tell us the three types of clay minerals have numerousadsorption centres and excellent adsorption properties.As the compound removal experiment, the combination of CaCO₃andPAC had high removal efficiency on phosphate, and this process has twostages:Ca²⁺andPO₄^3-combined together first and then the PAC flocculateto setting.The compound removal combination of160mesh zeolite,60mesh zeolite or Na-bentonite, CaCO₃and PAC had good removal efficiency onammonium and phosphate; the removal of phosphate was the synergies ofCaCO₃and PAC and they not affect the removal of ammonium, the clayminerals’ adsorption capacity and it’s ion exchange capacity act on theremoval of ammonium,and they not affect the removal of phosphate. Thecombination of160mesh zeolite, CaCO₃and PAC has nice removalefficiency especially. Before and after reaction,the pH value was reachedfrom6.30to8.33, the pH slightly increased, the pH value exchange wasalso in the scope of normal natural river. From the Orthogonal removalexperiment of160mesh zeolite, CaCO₃and PAC, the optimalcombination was160meshzeolite:CaCO₃^:PAC=50：5：1,this combinationhad98.83%,52.07%removal effcicency of phosphate and ammonium,respectively.The study has found a compound formula of simultaneousadsorption of ammonium and phosphate, that is160meshzeolite:CaCO₃:PAC=50：5：1. This experiment offered a more eco-friendly choice for theapplication of ecological restoration of river water.This not only can usedas a coagulant and covering the sediments, but also can used as a floatingisland medium, to provide a good condition for plant growth.