Study On The Adsorption Of Ammonia In The Aqueous Solution By The Active Filter

Ammonia pollution has become a main factor of our water quality at this stage,which was widely found in groundwater and surface water. It’s very urgent to solveammonia pollution problem. In this paper, the research object is a kind of specialactive filters in the long-term running pilot scale filter system used for treating thegroundwater polluted by ammonium, iron and manganese. According to a series ofphysical and chemical characterization of the active filter, we analyzed the surfacemorphology, surface area, pore volume, pore size, crystal type and elements.Combined with the experiments of adsorption isothermal and kinetic, the adsorptioncharacteristics of active filters and active filter membranes for ammonium in aqueoussolution were clarified. The main results are as follows:(1)Mature active filter has a more complex structure than the surface of the rawquartz sand filter. The surface of the active filters is coarse and porous. The membraneshave lots of slits and holes. Due to the increase of specific surface area, total porevolume and average pore diameter, the adsorption capacity for ammonium on activefilters was enhanced.(2)The active filter membrane is of amorphous structure, and its main material ismade of manganese oxide, which determines it has a certain chemical adsorptionproperties.(3)In single factor control conditions, their ammonium adsorption isotherms wereboth fitted well with Freundlich equation (R2=0.99/0.98) in active filters and activefilter membranes.1/n<2indicated that the ammonia adsorption can occur. Theadsorption processes fit well with the Freundlich equation, indicating it is the heterogeneous surface chemical absorption.(4) Pseudo second-order kinetic model can describe the ammonium adsorptionprocess both in active filters and active filter membranes very well. Their correlationcoefficient R2were both greater than0.99, and their theoretical equilibrium adsorptioncapacity is consistent with the experimental values. Ammonia adsorption equilibriumtimes are around640min, with the increase of the initial concentration of ammonia inwater adsorption capacity increases. The diffusion particles are not the only step ofcontrolling adsorption process.(5)Both in active filters and active filter membranes, positive linear correlationwas found between the initial concentration of ammonia and its equilibrium adsorptioncapacity. Both correlation coefficient R2were greater than0.99, so we could takeadvantage of the fitted linear equation to estimate the ammonia equilibrium adsorptioncapacity in the concentration range.