Research On Phosphate Removal Using Novel Fe-loaded Ceramic Adsorbents

In recent years, eutrophication has become one of the most serious environmentalproblems. Phosphorus is the dominant factor of the eutrophication, therefore, effectivecontrol of phosphorus is significant to deal with eutrophication. Among differentkinds of phosphorus removal methods, adsorption has attracted attention of scholarsdue to its advantages of low cost, simple operation, high treatment efficiency and nosecondary pollution.Most adsorbents are natural or synthetic materials, such as zeolite, steel slag and flyash. Some of these materials have a narrow application range, some are veryexpensive, so that they are not suitable for practical application. In addition, mostof the adsorbent are powders, which would be inconvenient to use and difficult torecovery.In this research, dolomite and montmorillonite were used as skeletonmaterial, FeSO4·7H2O was used as modifier and starch was used asporogen. Simplex-centroid mixture design and response surface analysis were used todetermine the optimum mixture proportions of the ceramic particles materials. Twokinds of ceramic materials (spherical and cylindrical) were made up in accordancewith the optimum mixture proportions and they would be used in static anddynamic conditions to study phosphate removal adsorption behavior from aqueoussolution.under static experimental conditions, the effect of reaction temperature, reactiontime and pH were investigated. The mixture design results shows that the optimumdosage of each component in the10g mixture was3.8777g of dolomite,2.9955g ofstarch,2.1269g of montmorillonite, and1.000g of FeSO4·7H2O. The adsorptionexperiment results show that the pseudo-second-order kinetic model and Langmuirisotherm equation are suitable for phosphate adsorption onto adsorbents, suggesting ithad monolayer adsorption on adsorbent surface. Negative values of G0and H0indicate that the adsorption of phosphate onto the material was spontaneous andexothermic. The spherical material can be efficient to remove phosphate when pH was between3and12, suggesting a wide application range of solution pH.Generally, the actual sewage are flowing state, in order to study phosphorusremoval effect of materials under dynamic conditions, this research preparedcolumnar ceramic on the basis of optimum mixture proportions and put itinto dynamic phosphorus waste water to determinate its phosphate removalefficiency. The effect of column height (adsorbent dosage), initial phosphorusconcentration and coexisting ions were investigated and the results suggest that themore sufficient the adsorption sites are, the more completely the phosphorusadsorption is. According to BDST model, the adsorption capacity of the column is1947mg/L. When initial phosphorus concentration is10mg/L,30mg/L and50mg/L,the equilibrium adsorption capacity based on Thormas model is3.8755mg/g,60.7150mg/g and58.8313mg/g, respectively. With the existence of different ions, thephosphorus adsorption rate according to the sequence as SO42-＞NO3-＞NH4+.Furthermore, the characterization of the two kinds of materials were tested, theresults of BET and EPMA suggesting that the high phosphate removal efficiency ofthe adsorbents is profit from their hierarchical porous structures. According to theSEM and EDS of pure adsorbents and adsorbed adsorbents, the adsorption process ofboth materials included chemical precipitation and electrostatic attraction.